chore: bump version to 3.0.0-alpha.4

- Add utils.hmacSHA1(key, message) for extensions
- Add artist type handling in track_provider for extension URL results
- Fix extension store not refreshing after uninstall
- Update CHANGELOG with new features and Spotify Web extension

.github/ISSUE_TEMPLATE/extension_feature_request.yml

@@ -1,5 +1,5 @@
-name: Extension API Feature Request (Alpha)
-description: Request new API features or capabilities for extension development (Extension system is in alpha)
+name: Extension API Feature Request
+description: Request new API features or capabilities for extension development
 title: "[Extension API]: "
 labels: ["enhancement", "extension-api"]
 body:
@@ -15,7 +15,7 @@ body:
       label: Checklist
       description: Please confirm the following before submitting
       options:
-        - label: I have read the [Extension Development Guide](https://zarz.moe/docs)
+        - label: I have read the [Extension Development Guide](https://github.com/zarzet/SpotiFLAC-Mobile/blob/main/docs/EXTENSION_DEVELOPMENT.md)
           required: true
         - label: I have searched existing issues and this API feature hasn't been requested yet
           required: true

.gitignore

@@ -13,7 +13,7 @@ Thumbs.db
 # Reference folder (development only)
 referensi/
 
-# Documentation (hosted separately)
+# Documentation (development only, published separately)
 docs/
 
 # Old spotiflac_android folder (moved to root)

CHANGELOG.md

@@ -1,6 +1,75 @@
 # Changelog
 
-## [2.2.9] - 2026-01-12
+## [3.0.0-alpha.4] - Upcoming
+
+### Added
+
+- **Extension Store**: Browse and install extensions directly from the app
+  - New "Store" tab in bottom navigation
+  - Browse extensions by category (Metadata, Download, Utility, Lyrics, Integration)
+  - Search extensions by name, description, or tags
+  - One-tap install and update
+  - Offline cache for browsing without internet
+  - Extensions hosted at github.com/zarzet/SpotiFLAC-Extension
+
+- **Custom URL Handler for Extensions**: Extensions can now register custom URL patterns
+  - Handle URLs from YouTube Music, SoundCloud, Bandcamp, etc.
+  - Manifest config: `urlHandler: { enabled: true, patterns: ["music.youtube.com"] }`
+  - Implement `handleURL(url)` function in extension to parse and return track metadata
+  - SpotiFLAC automatically routes matching URLs to the appropriate extension
+  - Supports share intents and paste from clipboard
+
+- **Artist URL Handler Support**: Extensions can now return artist data from URL handlers
+  - Added `type: "artist"` handling in track_provider.dart
+  - Navigate to artist screen with albums list from extension
+
+- **HMAC-SHA1 Utility**: New `utils.hmacSHA1(key, message)` function for extensions
+  - Enables TOTP generation and other cryptographic operations
+  - Returns byte array for flexible use
+
+### Fixed
+
+- **Extension Store Refresh**: Store tab now properly refreshes after uninstalling an extension
+  - "Installed" badge correctly updates to "Install" button
+
+### Documentation
+
+- Updated `docs/EXTENSION_DEVELOPMENT.md`:
+  - Added Custom URL Handler section with examples
+  - Added `handleURL` function documentation
+  - Added URL pattern examples for YouTube, SoundCloud, Bandcamp
+  - Added `utils.hmacSHA1` documentation with TOTP example
+
+### Extensions
+
+- **Spotify Web Extension** (example): New extension for Spotify metadata via web API
+  - Supports personalized playlists (Daily Mix, Discover Weekly, Release Radar, etc.)
+  - Search, album, playlist, track, and artist fetching
+  - Available in Extension Store (3.0.0-alpha.4)
+
+---
+
+## [3.0.0-alpha.3] - 2026-01-12
+
+### Added
+
+- **Separate Singles Folder**: Option to organize downloads into Albums/ and Singles/ folders
+  - Based on `album_type` from Spotify/Deezer metadata
+  - Toggle in Settings > Download > Separate Singles Folder
+  - Singles saved to `{output}/Singles/`, albums to `{output}/Albums/`
+- **Browser-like Polyfills**: New global APIs for easier library porting
+  - `fetch()` - Browser-compatible HTTP API with `json()`, `text()`, `arrayBuffer()` methods
+  - `atob()` / `btoa()` - Global Base64 encoding/decoding
+  - `TextEncoder` / `TextDecoder` - UTF-8 text encoding classes
+  - `URL` / `URLSearchParams` - URL parsing and manipulation classes
+  - Makes porting browser libraries (like `youtubei.js`) much easier
+
+### Performance
+
+- **Parallel API Calls**: Download URL fetching now uses parallel requests
+  - Tidal: All 8 APIs requested simultaneously, first success wins
+  - Qobuz: Both APIs requested simultaneously, first success wins
+  - Significantly reduces download URL fetch time
 
 ### Fixed
 
@@ -8,6 +77,9 @@
   - Detects existing entries by Spotify ID, Deezer ID, or ISRC
   - Replaces existing entry and moves to top of list
   - Auto-deduplicates existing history on app load
+- **Extension Search Fallback**: Fixed error when extension is disabled but still called for search
+  - Now checks if extension is still enabled before calling custom search
+  - Auto-resets search provider to default if extension was disabled
 - **Permission Error Message**: Fixed download showing "Song not found" when actually a permission error
   - Now shows proper message: "Cannot write to folder, check storage permission"
   - Added `permission` error type detection in backend
@@ -19,6 +91,144 @@
 
 ---
 
+## [3.0.0-alpha.2] - 2026-01-12
+
+### Added
+
+- **Full HTTP Method Support**: New shortcut methods for all common HTTP verbs
+  - `http.put(url, body, headers)` - PUT requests
+  - `http.delete(url, headers)` - DELETE requests  
+  - `http.patch(url, body, headers)` - PATCH requests
+  - `http.clearCookies()` - Clear all cookies for the extension
+- **Persistent Cookie Jar**: Each extension now has its own cookie jar
+  - Cookies automatically stored from `Set-Cookie` headers
+  - Cookies automatically sent with subsequent requests to same domain
+  - Useful for APIs requiring session cookies (YouTube, etc.)
+- **Multi-Value Header Support**: Response headers now return arrays for multi-value headers
+  - `Set-Cookie` and other headers with multiple values returned as arrays
+  - Single-value headers still returned as strings for convenience
+- **Generic HTTP Request Method**: New `http.request()` for full HTTP control
+  - Supports all HTTP methods (GET, POST, PUT, DELETE, PATCH, etc.)
+  - Single options object for cleaner API: `http.request(url, { method, body, headers })`
+- **Response Helper Properties**: HTTP responses now include convenience properties
+  - `response.ok` - true if status code is 2xx
+  - `response.status` - alias for `statusCode`
+
+### Fixed
+
+- **User-Agent Header Respect**: Custom `User-Agent` headers are now respected
+  - Previously, extension-provided User-Agent was overwritten
+  - Now only sets default User-Agent if extension doesn't provide one
+- **HTTP POST Body Auto-Stringify**: `http.post()` now automatically stringifies objects to JSON
+  - Previously, passing an object as body resulted in `[object Object]`
+  - Now objects and arrays are automatically JSON.stringify'd
+  - String bodies still work as before (no double-encoding)
+
+### Documentation
+
+- Updated `docs/EXTENSION_DEVELOPMENT.md`:
+  - Added complete HTTP API documentation with all methods
+  - Added Cookie Jar documentation
+  - Added `http.put()`, `http.delete()`, `http.patch()`, `http.clearCookies()` docs
+  - Added YouTube Music / Innertube API example with custom User-Agent
+  - Added common domain lists for YouTube, SoundCloud, Bandcamp
+  - Improved HTTP API documentation with response properties
+
+---
+
+## [3.0.0-alpha.1] - 2026-01-11
+
+#### Extension System
+- **Custom Search Providers**: Extensions can now provide custom search functionality
+  - YouTube, SoundCloud, and other platforms via extensions
+  - Custom search placeholder text per extension
+  - Configurable thumbnail aspect ratios (square, wide, portrait)
+- **Extension Upgrade System**: Upgrade extensions without losing data
+  - Preserves extension settings and cached data during upgrades
+  - Version comparison prevents downgrades
+  - Auto-detects upgrades when installing same extension
+- **Custom Thumbnail Ratios**: Extensions can specify thumbnail display format
+  - `"square"` (1:1) - Album art style (default)
+  - `"wide"` (16:9) - YouTube/video style
+  - `"portrait"` (2:3) - Poster style
+  - Custom width/height override available
+
+### Added
+
+- **Track Source Tracking**: Tracks now remember which extension provided them
+  - `Track.source` field stores extension ID
+  - `TrackState.searchExtensionId` for current search context
+  - Enables extension-specific UI customization
+- **Extension Upgrade API**: New methods for extension management
+  - `upgradeExtension(filePath)` - Upgrade existing extension
+  - `checkExtensionUpgrade(filePath)` - Check if file is an upgrade
+  - `RemoveExtensionByID` - Remove extension by ID
+- **iOS Extension Support**: Added missing iOS method handlers
+  - `upgradeExtension` - Upgrade extension from file
+  - `checkExtensionUpgrade` - Check upgrade compatibility
+- **Extension Documentation**: Comprehensive extension development guide
+  - Thumbnail ratio customization documentation
+  - Extension upgrade workflow documentation
+  - New troubleshooting entries for common issues
+
+### Changed
+
+- **Version Bump**: 2.2.7 → 3.0.0-alpha.1 (major version for extension system)
+- **Build Number**: 49 → 50
+- **Extension Manager**: Improved upgrade detection in `LoadExtensionFromFile`
+  - Auto-detects if installing same extension with higher version
+  - Calls `UpgradeExtension` automatically for seamless upgrades
+
+### Fixed
+
+- **Extension `registerExtension`**: Fixed global `extension` variable not being set
+  - Extensions can now access their own functions via `extension.functionName()`
+  - Required for `customSearch` and other provider functions
+- **Custom Search Empty Results**: Fixed error when extension returns null
+  - Now returns empty array instead of error
+  - Prevents crash when no results found
+- **Mutex Crash on Upgrade**: Fixed "Unlock of unlocked RWMutex" crash
+  - Removed `defer m.mu.Unlock()` when manual unlock is used
+  - Proper lock handling in upgrade flow
+- **Duplicate Error Messages**: Fixed extension install errors showing twice
+  - Added `clearError()` method to extension provider
+  - Improved PlatformException parsing to remove "null, null" artifacts
+- **Extension Images Field**: Fixed thumbnails not showing in search results
+  - Added `Images` field to `ExtTrackMetadata` struct
+  - Renamed `GetCoverURL` to `ResolvedCoverURL` (gomobile conflict)
+
+### Technical
+
+- **Go Backend Changes**:
+  - `go_backend/extension_manager.go`: Added `compareVersions()`, `UpgradeExtension()`, `CheckExtensionUpgradeJSON()`
+  - `go_backend/extension_providers.go`: Added `Images` field, `ResolvedCoverURL()` method
+  - `go_backend/extension_manifest.go`: Added `ThumbnailRatio`, `ThumbnailWidth`, `ThumbnailHeight` to `SearchBehaviorConfig`
+  - `go_backend/exports.go`: Added `RemoveExtensionByID`, `UpgradeExtensionFromPath`, `CheckExtensionUpgradeFromPath`
+- **Flutter Changes**:
+  - `lib/models/track.dart`: Added `source` field
+  - `lib/models/track.g.dart`: Updated for `source` field
+  - `lib/providers/track_provider.dart`: Added `searchExtensionId`, updated `_parseSearchTrack` with source parameter
+  - `lib/providers/extension_provider.dart`: Added `SearchBehavior.getThumbnailSize()`, `clearError()`
+  - `lib/screens/home_tab.dart`: Dynamic thumbnail size based on extension config
+  - `lib/screens/settings/extensions_page.dart`: Improved error handling
+  - `lib/services/platform_bridge.dart`: Added `upgradeExtension()`, `checkExtensionUpgrade()`, `removeExtension()`
+- **iOS Changes**:
+  - `ios/Runner/AppDelegate.swift`: Added `upgradeExtension`, `checkExtensionUpgrade` handlers
+- **Android Changes**:
+  - `android/app/src/main/kotlin/com/zarz/spotiflac/MainActivity.kt`: Already had upgrade methods
+
+### Documentation
+
+- Updated `docs/EXTENSION_DEVELOPMENT.md`:
+  - Added thumbnail ratio customization section
+  - Added extension upgrade documentation
+  - Added settings fields table with `secret` field
+  - Added new troubleshooting entries
+  - Updated table of contents
+  - Updated changelog
+
+---
+
 ## [2.2.8] - 2026-01-12
 
 ### Added
@@ -43,6 +253,8 @@
 
 - **Issue Templates**: Updated version confirmation checkbox to specify "(Stable Version)"
 
+---
+
 ## [2.2.7] - 2026-01-11
 
 ### Added

README.md

@@ -40,6 +40,31 @@ To use Spotify as your search source without hitting rate limits:
 4. Enter your Client ID and Secret
 5. Change **Search Source** to Spotify
 
+## Extensions (Alpha)
+
+> **Alpha Feature**: Extensions are now available in alpha. Some features may be unstable or change in future releases.
+
+SpotiFLAC supports extensions to add custom metadata and download providers. Extensions are written in JavaScript and run in a secure sandbox.
+
+### Features
+- **Metadata Providers**: Add new sources for track/album/artist search
+- **Download Providers**: Add new sources for audio downloads
+- **Custom Settings**: Extensions can have user-configurable settings
+- **Provider Priority**: Set the order in which providers are tried
+
+### Installing Extensions
+1. Download a `.spotiflac-ext` file
+2. Go to **Settings > Extensions**
+3. Tap **Install Extension** and select the file
+4. Configure extension settings if needed
+5. Set provider priority in **Settings > Extensions > Provider Priority**
+
+### Developing Extensions
+Want to create your own extension? Check out the [Extension Development Guide](docs/EXTENSION_DEVELOPMENT.md) for complete documentation.
+
+### Example Extensions
+Sample extensions are available in the [docs/extensions_example](docs/extensions_example) folder:
+
 ## Other project
 
 ### [SpotiFLAC (Desktop)](https://github.com/afkarxyz/SpotiFLAC)

android/app/src/main/kotlin/com/zarz/spotiflac/MainActivity.kt

@@ -218,6 +218,12 @@ class MainActivity: FlutterActivity() {
                             }
                             result.success(null)
                         }
+                        "hasSpotifyCredentials" -> {
+                            val hasCredentials = withContext(Dispatchers.IO) {
+                                Gobackend.checkSpotifyCredentials()
+                            }
+                            result.success(hasCredentials)
+                        }
                         "preWarmTrackCache" -> {
                             val tracksJson = call.argument<String>("tracks") ?: "[]"
                             withContext(Dispatchers.IO) {
@@ -317,6 +323,313 @@ class MainActivity: FlutterActivity() {
                             }
                             result.success(null)
                         }
+                        // Extension System methods
+                        "initExtensionSystem" -> {
+                            val extensionsDir = call.argument<String>("extensions_dir") ?: ""
+                            val dataDir = call.argument<String>("data_dir") ?: ""
+                            withContext(Dispatchers.IO) {
+                                Gobackend.initExtensionSystem(extensionsDir, dataDir)
+                            }
+                            result.success(null)
+                        }
+                        "loadExtensionsFromDir" -> {
+                            val dirPath = call.argument<String>("dir_path") ?: ""
+                            val response = withContext(Dispatchers.IO) {
+                                Gobackend.loadExtensionsFromDir(dirPath)
+                            }
+                            result.success(response)
+                        }
+                        "loadExtensionFromPath" -> {
+                            val filePath = call.argument<String>("file_path") ?: ""
+                            val response = withContext(Dispatchers.IO) {
+                                Gobackend.loadExtensionFromPath(filePath)
+                            }
+                            result.success(response)
+                        }
+                        "unloadExtension" -> {
+                            val extensionId = call.argument<String>("extension_id") ?: ""
+                            withContext(Dispatchers.IO) {
+                                Gobackend.unloadExtensionByID(extensionId)
+                            }
+                            result.success(null)
+                        }
+                        "removeExtension" -> {
+                            val extensionId = call.argument<String>("extension_id") ?: ""
+                            withContext(Dispatchers.IO) {
+                                Gobackend.removeExtensionByID(extensionId)
+                            }
+                            result.success(null)
+                        }
+                        "upgradeExtension" -> {
+                            val filePath = call.argument<String>("file_path") ?: ""
+                            val response = withContext(Dispatchers.IO) {
+                                Gobackend.upgradeExtensionFromPath(filePath)
+                            }
+                            result.success(response)
+                        }
+                        "checkExtensionUpgrade" -> {
+                            val filePath = call.argument<String>("file_path") ?: ""
+                            val response = withContext(Dispatchers.IO) {
+                                Gobackend.checkExtensionUpgradeFromPath(filePath)
+                            }
+                            result.success(response)
+                        }
+                        "getInstalledExtensions" -> {
+                            val response = withContext(Dispatchers.IO) {
+                                Gobackend.getInstalledExtensions()
+                            }
+                            result.success(response)
+                        }
+                        "setExtensionEnabled" -> {
+                            val extensionId = call.argument<String>("extension_id") ?: ""
+                            val enabled = call.argument<Boolean>("enabled") ?: false
+                            withContext(Dispatchers.IO) {
+                                Gobackend.setExtensionEnabledByID(extensionId, enabled)
+                            }
+                            result.success(null)
+                        }
+                        "setProviderPriority" -> {
+                            val priorityJson = call.argument<String>("priority") ?: "[]"
+                            withContext(Dispatchers.IO) {
+                                Gobackend.setProviderPriorityJSON(priorityJson)
+                            }
+                            result.success(null)
+                        }
+                        "getProviderPriority" -> {
+                            val response = withContext(Dispatchers.IO) {
+                                Gobackend.getProviderPriorityJSON()
+                            }
+                            result.success(response)
+                        }
+                        "setMetadataProviderPriority" -> {
+                            val priorityJson = call.argument<String>("priority") ?: "[]"
+                            withContext(Dispatchers.IO) {
+                                Gobackend.setMetadataProviderPriorityJSON(priorityJson)
+                            }
+                            result.success(null)
+                        }
+                        "getMetadataProviderPriority" -> {
+                            val response = withContext(Dispatchers.IO) {
+                                Gobackend.getMetadataProviderPriorityJSON()
+                            }
+                            result.success(response)
+                        }
+                        "getExtensionSettings" -> {
+                            val extensionId = call.argument<String>("extension_id") ?: ""
+                            val response = withContext(Dispatchers.IO) {
+                                Gobackend.getExtensionSettingsJSON(extensionId)
+                            }
+                            result.success(response)
+                        }
+                        "setExtensionSettings" -> {
+                            val extensionId = call.argument<String>("extension_id") ?: ""
+                            val settingsJson = call.argument<String>("settings") ?: "{}"
+                            withContext(Dispatchers.IO) {
+                                Gobackend.setExtensionSettingsJSON(extensionId, settingsJson)
+                            }
+                            result.success(null)
+                        }
+                        "searchTracksWithExtensions" -> {
+                            val query = call.argument<String>("query") ?: ""
+                            val limit = call.argument<Int>("limit") ?: 20
+                            val response = withContext(Dispatchers.IO) {
+                                Gobackend.searchTracksWithExtensionsJSON(query, limit.toLong())
+                            }
+                            result.success(response)
+                        }
+                        "downloadWithExtensions" -> {
+                            val requestJson = call.arguments as String
+                            val response = withContext(Dispatchers.IO) {
+                                Gobackend.downloadWithExtensionsJSON(requestJson)
+                            }
+                            result.success(response)
+                        }
+                        "removeExtension" -> {
+                            val extensionId = call.argument<String>("extension_id") ?: ""
+                            withContext(Dispatchers.IO) {
+                                Gobackend.removeExtensionByID(extensionId)
+                            }
+                            result.success(null)
+                        }
+                        "cleanupExtensions" -> {
+                            withContext(Dispatchers.IO) {
+                                Gobackend.cleanupExtensions()
+                            }
+                            result.success(null)
+                        }
+                        // Extension Auth API methods
+                        "getExtensionPendingAuth" -> {
+                            val extensionId = call.argument<String>("extension_id") ?: ""
+                            val response = withContext(Dispatchers.IO) {
+                                Gobackend.getExtensionPendingAuthJSON(extensionId)
+                            }
+                            if (response.isNullOrEmpty()) {
+                                result.success(null)
+                            } else {
+                                result.success(response)
+                            }
+                        }
+                        "setExtensionAuthCode" -> {
+                            val extensionId = call.argument<String>("extension_id") ?: ""
+                            val authCode = call.argument<String>("auth_code") ?: ""
+                            withContext(Dispatchers.IO) {
+                                Gobackend.setExtensionAuthCodeByID(extensionId, authCode)
+                            }
+                            result.success(null)
+                        }
+                        "setExtensionTokens" -> {
+                            val extensionId = call.argument<String>("extension_id") ?: ""
+                            val accessToken = call.argument<String>("access_token") ?: ""
+                            val refreshToken = call.argument<String>("refresh_token") ?: ""
+                            val expiresIn = call.argument<Int>("expires_in") ?: 0
+                            withContext(Dispatchers.IO) {
+                                Gobackend.setExtensionTokensByID(extensionId, accessToken, refreshToken, expiresIn.toLong())
+                            }
+                            result.success(null)
+                        }
+                        "clearExtensionPendingAuth" -> {
+                            val extensionId = call.argument<String>("extension_id") ?: ""
+                            withContext(Dispatchers.IO) {
+                                Gobackend.clearExtensionPendingAuthByID(extensionId)
+                            }
+                            result.success(null)
+                        }
+                        "isExtensionAuthenticated" -> {
+                            val extensionId = call.argument<String>("extension_id") ?: ""
+                            val isAuth = withContext(Dispatchers.IO) {
+                                Gobackend.isExtensionAuthenticatedByID(extensionId)
+                            }
+                            result.success(isAuth)
+                        }
+                        "getAllPendingAuthRequests" -> {
+                            val response = withContext(Dispatchers.IO) {
+                                Gobackend.getAllPendingAuthRequestsJSON()
+                            }
+                            result.success(response)
+                        }
+                        // Extension FFmpeg API
+                        "getPendingFFmpegCommand" -> {
+                            val commandId = call.argument<String>("command_id") ?: ""
+                            val response = withContext(Dispatchers.IO) {
+                                Gobackend.getPendingFFmpegCommandJSON(commandId)
+                            }
+                            if (response.isNullOrEmpty()) {
+                                result.success(null)
+                            } else {
+                                result.success(response)
+                            }
+                        }
+                        "setFFmpegCommandResult" -> {
+                            val commandId = call.argument<String>("command_id") ?: ""
+                            val success = call.argument<Boolean>("success") ?: false
+                            val output = call.argument<String>("output") ?: ""
+                            val error = call.argument<String>("error") ?: ""
+                            withContext(Dispatchers.IO) {
+                                Gobackend.setFFmpegCommandResultByID(commandId, success, output, error)
+                            }
+                            result.success(null)
+                        }
+                        "getAllPendingFFmpegCommands" -> {
+                            val response = withContext(Dispatchers.IO) {
+                                Gobackend.getAllPendingFFmpegCommandsJSON()
+                            }
+                            result.success(response)
+                        }
+                        // Extension Custom Search API
+                        "customSearchWithExtension" -> {
+                            val extensionId = call.argument<String>("extension_id") ?: ""
+                            val query = call.argument<String>("query") ?: ""
+                            val optionsJson = call.argument<String>("options") ?: ""
+                            val response = withContext(Dispatchers.IO) {
+                                Gobackend.customSearchWithExtensionJSON(extensionId, query, optionsJson)
+                            }
+                            result.success(response)
+                        }
+                        "getSearchProviders" -> {
+                            val response = withContext(Dispatchers.IO) {
+                                Gobackend.getSearchProvidersJSON()
+                            }
+                            result.success(response)
+                        }
+                        // Extension URL Handler API
+                        "handleURLWithExtension" -> {
+                            val url = call.argument<String>("url") ?: ""
+                            val response = withContext(Dispatchers.IO) {
+                                Gobackend.handleURLWithExtensionJSON(url)
+                            }
+                            result.success(response)
+                        }
+                        "findURLHandler" -> {
+                            val url = call.argument<String>("url") ?: ""
+                            val response = withContext(Dispatchers.IO) {
+                                Gobackend.findURLHandlerJSON(url)
+                            }
+                            result.success(response)
+                        }
+                        "getURLHandlers" -> {
+                            val response = withContext(Dispatchers.IO) {
+                                Gobackend.getURLHandlersJSON()
+                            }
+                            result.success(response)
+                        }
+                        // Extension Post-Processing API
+                        "runPostProcessing" -> {
+                            val filePath = call.argument<String>("file_path") ?: ""
+                            val metadataJson = call.argument<String>("metadata") ?: ""
+                            val response = withContext(Dispatchers.IO) {
+                                Gobackend.runPostProcessingJSON(filePath, metadataJson)
+                            }
+                            result.success(response)
+                        }
+                        "getPostProcessingProviders" -> {
+                            val response = withContext(Dispatchers.IO) {
+                                Gobackend.getPostProcessingProvidersJSON()
+                            }
+                            result.success(response)
+                        }
+                        // Extension Store
+                        "initExtensionStore" -> {
+                            val cacheDir = call.argument<String>("cache_dir") ?: ""
+                            withContext(Dispatchers.IO) {
+                                Gobackend.initExtensionStoreJSON(cacheDir)
+                            }
+                            result.success(null)
+                        }
+                        "getStoreExtensions" -> {
+                            val forceRefresh = call.argument<Boolean>("force_refresh") ?: false
+                            val response = withContext(Dispatchers.IO) {
+                                Gobackend.getStoreExtensionsJSON(forceRefresh)
+                            }
+                            result.success(response)
+                        }
+                        "searchStoreExtensions" -> {
+                            val query = call.argument<String>("query") ?: ""
+                            val category = call.argument<String>("category") ?: ""
+                            val response = withContext(Dispatchers.IO) {
+                                Gobackend.searchStoreExtensionsJSON(query, category)
+                            }
+                            result.success(response)
+                        }
+                        "getStoreCategories" -> {
+                            val response = withContext(Dispatchers.IO) {
+                                Gobackend.getStoreCategoriesJSON()
+                            }
+                            result.success(response)
+                        }
+                        "downloadStoreExtension" -> {
+                            val extensionId = call.argument<String>("extension_id") ?: ""
+                            val destDir = call.argument<String>("dest_dir") ?: ""
+                            val response = withContext(Dispatchers.IO) {
+                                Gobackend.downloadStoreExtensionJSON(extensionId, destDir)
+                            }
+                            result.success(response)
+                        }
+                        "clearStoreCache" -> {
+                            withContext(Dispatchers.IO) {
+                                Gobackend.clearStoreCacheJSON()
+                            }
+                            result.success(null)
+                        }
                         else -> result.notImplemented()
                     }
                 } catch (e: Exception) {

go_backend/amazon.go

@@ -173,7 +173,7 @@ func (a *AmazonDownloader) GetAvailableAPIs() []string {
 // downloadFromDoubleDoubleService downloads a track using DoubleDouble service (same as PC)
 // This uses submit → poll → download mechanism
 // Internal function - not exported to gomobile
-func (a *AmazonDownloader) downloadFromDoubleDoubleService(amazonURL, outputDir string) (string, string, string, error) {
+func (a *AmazonDownloader) downloadFromDoubleDoubleService(amazonURL, _ string) (string, string, string, error) {
 	var lastError error
 
 	for _, region := range a.regions {

go_backend/deezer.go

@@ -146,6 +146,7 @@ type deezerAlbumFull struct {
 	CoverXL      string         `json:"cover_xl"`
 	ReleaseDate  string         `json:"release_date"`
 	NbTracks     int            `json:"nb_tracks"`
+	RecordType   string         `json:"record_type"` // album, single, ep, compile
 	Artist       deezerArtist   `json:"artist"`
 	Contributors []deezerArtist `json:"contributors"`
 	Tracks       struct {
@@ -326,6 +327,12 @@ func (c *DeezerClient) GetAlbum(ctx context.Context, albumID string) (*AlbumResp
 	isrcMap := c.fetchISRCsParallel(ctx, album.Tracks.Data)
 
 	tracks := make([]AlbumTrackMetadata, 0, len(album.Tracks.Data))
+	// Normalize record_type (Deezer uses "compile" instead of "compilation")
+	albumType := album.RecordType
+	if albumType == "compile" {
+		albumType = "compilation"
+	}
+
 	for _, track := range album.Tracks.Data {
 		trackIDStr := fmt.Sprintf("%d", track.ID)
 		isrc := isrcMap[trackIDStr]
@@ -345,6 +352,7 @@ func (c *DeezerClient) GetAlbum(ctx context.Context, albumID string) (*AlbumResp
 			ExternalURL: track.Link,
 			ISRC:        isrc,
 			AlbumID:     fmt.Sprintf("deezer:%d", album.ID),
+			AlbumType:   albumType,
 		})
 	}
 

go_backend/exports.go

@@ -32,18 +32,26 @@ func ParseSpotifyURL(url string) (string, error) {
 }
 
 // SetSpotifyAPICredentials sets custom Spotify API credentials from Flutter
-// Pass empty strings to use default credentials
 func SetSpotifyAPICredentials(clientID, clientSecret string) {
 	SetSpotifyCredentials(clientID, clientSecret)
 }
 
+// CheckSpotifyCredentials checks if Spotify credentials are configured
+// Returns true if credentials are available (custom or env vars)
+func CheckSpotifyCredentials() bool {
+	return HasSpotifyCredentials()
+}
+
 // GetSpotifyMetadata fetches metadata from Spotify URL
 // Returns JSON with track/album/playlist data
 func GetSpotifyMetadata(spotifyURL string) (string, error) {
 	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
 	defer cancel()
 
-	client := NewSpotifyMetadataClient()
+	client, err := NewSpotifyMetadataClient()
+	if err != nil {
+		return "", err
+	}
 	data, err := client.GetFilteredData(ctx, spotifyURL, false, 0)
 	if err != nil {
 		return "", err
@@ -63,7 +71,10 @@ func SearchSpotify(query string, limit int) (string, error) {
 	ctx, cancel := context.WithTimeout(context.Background(), 15*time.Second)
 	defer cancel()
 
-	client := NewSpotifyMetadataClient()
+	client, err := NewSpotifyMetadataClient()
+	if err != nil {
+		return "", err
+	}
 	results, err := client.SearchTracks(ctx, query, limit)
 	if err != nil {
 		return "", err
@@ -83,7 +94,10 @@ func SearchSpotifyAll(query string, trackLimit, artistLimit int) (string, error)
 	ctx, cancel := context.WithTimeout(context.Background(), 15*time.Second)
 	defer cancel()
 
-	client := NewSpotifyMetadataClient()
+	client, err := NewSpotifyMetadataClient()
+	if err != nil {
+		return "", err
+	}
 	results, err := client.SearchAll(ctx, query, trackLimit, artistLimit)
 	if err != nil {
 		return "", err
@@ -135,6 +149,7 @@ type DownloadRequest struct {
 	ReleaseDate          string `json:"release_date"`
 	ItemID               string `json:"item_id"`     // Unique ID for progress tracking
 	DurationMS           int    `json:"duration_ms"` // Expected duration in milliseconds (for verification)
+	Source               string `json:"source"`      // Extension ID that provided this track (prioritize this extension)
 }
 
 // DownloadResponse represents the result of a download
@@ -152,10 +167,14 @@ type DownloadResponse struct {
 	Title            string `json:"title,omitempty"`
 	Artist           string `json:"artist,omitempty"`
 	Album            string `json:"album,omitempty"`
+	AlbumArtist      string `json:"album_artist,omitempty"`
 	ReleaseDate      string `json:"release_date,omitempty"`
 	TrackNumber      int    `json:"track_number,omitempty"`
 	DiscNumber       int    `json:"disc_number,omitempty"`
 	ISRC             string `json:"isrc,omitempty"`
+	CoverURL         string `json:"cover_url,omitempty"`
+	// If true, skip metadata enrichment from Deezer/Spotify (extension already provides metadata)
+	SkipMetadataEnrichment bool `json:"skip_metadata_enrichment,omitempty"`
 }
 
 // DownloadResult is a generic result type for all downloaders
@@ -888,21 +907,26 @@ func GetSpotifyMetadataWithDeezerFallback(spotifyURL string) (string, error) {
 	defer cancel()
 
 	// Try Spotify first
-	client := NewSpotifyMetadataClient()
-	data, err := client.GetFilteredData(ctx, spotifyURL, false, 0)
-	if err == nil {
-		jsonBytes, err := json.Marshal(data)
-		if err != nil {
+	client, err := NewSpotifyMetadataClient()
+	if err != nil {
+		// No Spotify credentials - fall through to Deezer fallback
+		LogWarn("Spotify", "Credentials not configured, falling back to Deezer")
+	} else {
+		data, err := client.GetFilteredData(ctx, spotifyURL, false, 0)
+		if err == nil {
+			jsonBytes, err := json.Marshal(data)
+			if err != nil {
+				return "", err
+			}
+			return string(jsonBytes), nil
+		}
+
+		// Check if it's a rate limit error
+		errStr := strings.ToLower(err.Error())
+		if !strings.Contains(errStr, "429") && !strings.Contains(errStr, "rate") && !strings.Contains(errStr, "limit") {
+			// Not a rate limit error, return original error
 			return "", err
 		}
-		return string(jsonBytes), nil
-	}
-
-	// Check if it's a rate limit error
-	errStr := strings.ToLower(err.Error())
-	if !strings.Contains(errStr, "429") && !strings.Contains(errStr, "rate") && !strings.Contains(errStr, "limit") {
-		// Not a rate limit error, return original error
-		return "", err
 	}
 
 	// Rate limited - try Deezer fallback for tracks and albums
@@ -1022,3 +1046,746 @@ func errorResponse(msg string) (string, error) {
 	jsonBytes, _ := json.Marshal(resp)
 	return string(jsonBytes), nil
 }
+
+// ==================== EXTENSION SYSTEM ====================
+
+// InitExtensionSystem initializes the extension system with directories
+func InitExtensionSystem(extensionsDir, dataDir string) error {
+	manager := GetExtensionManager()
+	if err := manager.SetDirectories(extensionsDir, dataDir); err != nil {
+		return err
+	}
+
+	settingsStore := GetExtensionSettingsStore()
+	if err := settingsStore.SetDataDir(dataDir); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+// LoadExtensionsFromDir loads all extensions from a directory
+func LoadExtensionsFromDir(dirPath string) (string, error) {
+	manager := GetExtensionManager()
+	loaded, errors := manager.LoadExtensionsFromDirectory(dirPath)
+
+	result := map[string]interface{}{
+		"loaded": loaded,
+		"errors": make([]string, len(errors)),
+	}
+
+	for i, err := range errors {
+		result["errors"].([]string)[i] = err.Error()
+	}
+
+	jsonBytes, err := json.Marshal(result)
+	if err != nil {
+		return "", err
+	}
+
+	return string(jsonBytes), nil
+}
+
+// LoadExtensionFromPath loads a single extension from a .spotiflac-ext file
+func LoadExtensionFromPath(filePath string) (string, error) {
+	manager := GetExtensionManager()
+	ext, err := manager.LoadExtensionFromFile(filePath)
+	if err != nil {
+		return "", err
+	}
+
+	// Initialize with saved settings
+	settingsStore := GetExtensionSettingsStore()
+	settings := settingsStore.GetAll(ext.ID)
+	if len(settings) > 0 {
+		manager.InitializeExtension(ext.ID, settings)
+	}
+
+	result := map[string]interface{}{
+		"id":           ext.ID,
+		"name":         ext.Manifest.Name,
+		"display_name": ext.Manifest.DisplayName,
+		"version":      ext.Manifest.Version,
+		"enabled":      ext.Enabled,
+	}
+
+	jsonBytes, err := json.Marshal(result)
+	if err != nil {
+		return "", err
+	}
+
+	return string(jsonBytes), nil
+}
+
+// UnloadExtensionByID unloads an extension
+func UnloadExtensionByID(extensionID string) error {
+	manager := GetExtensionManager()
+	return manager.UnloadExtension(extensionID)
+}
+
+// RemoveExtensionByID completely removes an extension (unload + delete files)
+func RemoveExtensionByID(extensionID string) error {
+	manager := GetExtensionManager()
+	return manager.RemoveExtension(extensionID)
+}
+
+// UpgradeExtensionFromPath upgrades an existing extension from a new package file
+func UpgradeExtensionFromPath(filePath string) (string, error) {
+	manager := GetExtensionManager()
+	ext, err := manager.UpgradeExtension(filePath)
+	if err != nil {
+		return "", err
+	}
+
+	// Initialize with saved settings
+	settingsStore := GetExtensionSettingsStore()
+	settings := settingsStore.GetAll(ext.ID)
+	if len(settings) > 0 {
+		manager.InitializeExtension(ext.ID, settings)
+	}
+
+	// Return extension info as JSON
+	result := map[string]interface{}{
+		"id":           ext.ID,
+		"display_name": ext.Manifest.DisplayName,
+		"version":      ext.Manifest.Version,
+		"enabled":      ext.Enabled,
+	}
+
+	jsonBytes, err := json.Marshal(result)
+	if err != nil {
+		return "", err
+	}
+
+	return string(jsonBytes), nil
+}
+
+// CheckExtensionUpgradeFromPath checks if a package file is an upgrade for an existing extension
+func CheckExtensionUpgradeFromPath(filePath string) (string, error) {
+	manager := GetExtensionManager()
+	return manager.CheckExtensionUpgradeJSON(filePath)
+}
+
+// GetInstalledExtensions returns all installed extensions as JSON
+func GetInstalledExtensions() (string, error) {
+	manager := GetExtensionManager()
+	return manager.GetInstalledExtensionsJSON()
+}
+
+// SetExtensionEnabledByID enables or disables an extension
+func SetExtensionEnabledByID(extensionID string, enabled bool) error {
+	manager := GetExtensionManager()
+	return manager.SetExtensionEnabled(extensionID, enabled)
+}
+
+// SetProviderPriorityJSON sets the provider priority order from JSON array
+func SetProviderPriorityJSON(priorityJSON string) error {
+	var priority []string
+	if err := json.Unmarshal([]byte(priorityJSON), &priority); err != nil {
+		return err
+	}
+
+	SetProviderPriority(priority)
+	return nil
+}
+
+// GetProviderPriorityJSON returns the provider priority order as JSON
+func GetProviderPriorityJSON() (string, error) {
+	priority := GetProviderPriority()
+	jsonBytes, err := json.Marshal(priority)
+	if err != nil {
+		return "", err
+	}
+	return string(jsonBytes), nil
+}
+
+// SetMetadataProviderPriorityJSON sets the metadata provider priority order from JSON array
+func SetMetadataProviderPriorityJSON(priorityJSON string) error {
+	var priority []string
+	if err := json.Unmarshal([]byte(priorityJSON), &priority); err != nil {
+		return err
+	}
+
+	SetMetadataProviderPriority(priority)
+	return nil
+}
+
+// GetMetadataProviderPriorityJSON returns the metadata provider priority order as JSON
+func GetMetadataProviderPriorityJSON() (string, error) {
+	priority := GetMetadataProviderPriority()
+	jsonBytes, err := json.Marshal(priority)
+	if err != nil {
+		return "", err
+	}
+	return string(jsonBytes), nil
+}
+
+// GetExtensionSettingsJSON returns settings for an extension as JSON
+func GetExtensionSettingsJSON(extensionID string) (string, error) {
+	store := GetExtensionSettingsStore()
+	settings := store.GetAll(extensionID)
+
+	jsonBytes, err := json.Marshal(settings)
+	if err != nil {
+		return "", err
+	}
+
+	return string(jsonBytes), nil
+}
+
+// SetExtensionSettingsJSON sets settings for an extension from JSON
+func SetExtensionSettingsJSON(extensionID, settingsJSON string) error {
+	var settings map[string]interface{}
+	if err := json.Unmarshal([]byte(settingsJSON), &settings); err != nil {
+		return err
+	}
+
+	store := GetExtensionSettingsStore()
+	if err := store.SetAll(extensionID, settings); err != nil {
+		return err
+	}
+
+	// Re-initialize extension with new settings
+	manager := GetExtensionManager()
+	return manager.InitializeExtension(extensionID, settings)
+}
+
+// SearchTracksWithExtensionsJSON searches all extension metadata providers
+func SearchTracksWithExtensionsJSON(query string, limit int) (string, error) {
+	manager := GetExtensionManager()
+	tracks, err := manager.SearchTracksWithExtensions(query, limit)
+	if err != nil {
+		return "", err
+	}
+
+	jsonBytes, err := json.Marshal(tracks)
+	if err != nil {
+		return "", err
+	}
+
+	return string(jsonBytes), nil
+}
+
+// DownloadWithExtensionsJSON downloads using extension providers with fallback
+func DownloadWithExtensionsJSON(requestJSON string) (string, error) {
+	var req DownloadRequest
+	if err := json.Unmarshal([]byte(requestJSON), &req); err != nil {
+		return "", fmt.Errorf("invalid request: %w", err)
+	}
+
+	result, err := DownloadWithExtensionFallback(req)
+	if err != nil {
+		return "", err
+	}
+
+	jsonBytes, err := json.Marshal(result)
+	if err != nil {
+		return "", err
+	}
+
+	return string(jsonBytes), nil
+}
+
+// CleanupExtensions unloads all extensions gracefully
+func CleanupExtensions() {
+	manager := GetExtensionManager()
+	manager.UnloadAllExtensions()
+}
+
+// ==================== EXTENSION AUTH API ====================
+
+// GetExtensionPendingAuthJSON returns pending auth request for an extension
+func GetExtensionPendingAuthJSON(extensionID string) (string, error) {
+	req := GetPendingAuthRequest(extensionID)
+	if req == nil {
+		return "", nil
+	}
+
+	result := map[string]interface{}{
+		"extension_id": req.ExtensionID,
+		"auth_url":     req.AuthURL,
+		"callback_url": req.CallbackURL,
+	}
+
+	jsonBytes, err := json.Marshal(result)
+	if err != nil {
+		return "", err
+	}
+
+	return string(jsonBytes), nil
+}
+
+// SetExtensionAuthCodeByID sets auth code for an extension (called from Flutter after OAuth callback)
+func SetExtensionAuthCodeByID(extensionID, authCode string) {
+	SetExtensionAuthCode(extensionID, authCode)
+}
+
+// SetExtensionTokensByID sets tokens for an extension
+func SetExtensionTokensByID(extensionID, accessToken, refreshToken string, expiresIn int) {
+	var expiresAt time.Time
+	if expiresIn > 0 {
+		expiresAt = time.Now().Add(time.Duration(expiresIn) * time.Second)
+	}
+	SetExtensionTokens(extensionID, accessToken, refreshToken, expiresAt)
+}
+
+// ClearExtensionPendingAuthByID clears pending auth request for an extension
+func ClearExtensionPendingAuthByID(extensionID string) {
+	ClearPendingAuthRequest(extensionID)
+}
+
+// IsExtensionAuthenticatedByID checks if an extension is authenticated
+func IsExtensionAuthenticatedByID(extensionID string) bool {
+	extensionAuthStateMu.RLock()
+	defer extensionAuthStateMu.RUnlock()
+
+	state, exists := extensionAuthState[extensionID]
+	if !exists {
+		return false
+	}
+
+	// Check if token is expired
+	if state.IsAuthenticated && !state.ExpiresAt.IsZero() && time.Now().After(state.ExpiresAt) {
+		return false
+	}
+
+	return state.IsAuthenticated
+}
+
+// GetAllPendingAuthRequestsJSON returns all pending auth requests
+func GetAllPendingAuthRequestsJSON() (string, error) {
+	pendingAuthRequestsMu.RLock()
+	defer pendingAuthRequestsMu.RUnlock()
+
+	requests := make([]map[string]interface{}, 0, len(pendingAuthRequests))
+	for _, req := range pendingAuthRequests {
+		requests = append(requests, map[string]interface{}{
+			"extension_id": req.ExtensionID,
+			"auth_url":     req.AuthURL,
+			"callback_url": req.CallbackURL,
+		})
+	}
+
+	jsonBytes, err := json.Marshal(requests)
+	if err != nil {
+		return "", err
+	}
+
+	return string(jsonBytes), nil
+}
+
+// ==================== EXTENSION FFMPEG API ====================
+
+// GetPendingFFmpegCommandJSON returns a pending FFmpeg command for Flutter to execute
+func GetPendingFFmpegCommandJSON(commandID string) (string, error) {
+	cmd := GetPendingFFmpegCommand(commandID)
+	if cmd == nil {
+		return "", nil
+	}
+
+	result := map[string]interface{}{
+		"command_id":   commandID,
+		"extension_id": cmd.ExtensionID,
+		"command":      cmd.Command,
+		"input_path":   cmd.InputPath,
+		"output_path":  cmd.OutputPath,
+	}
+
+	jsonBytes, err := json.Marshal(result)
+	if err != nil {
+		return "", err
+	}
+
+	return string(jsonBytes), nil
+}
+
+// SetFFmpegCommandResultByID sets the result of an FFmpeg command
+func SetFFmpegCommandResultByID(commandID string, success bool, output, errorMsg string) {
+	SetFFmpegCommandResult(commandID, success, output, errorMsg)
+}
+
+// GetAllPendingFFmpegCommandsJSON returns all pending FFmpeg commands
+func GetAllPendingFFmpegCommandsJSON() (string, error) {
+	ffmpegCommandsMu.RLock()
+	defer ffmpegCommandsMu.RUnlock()
+
+	commands := make([]map[string]interface{}, 0)
+	for cmdID, cmd := range ffmpegCommands {
+		if !cmd.Completed {
+			commands = append(commands, map[string]interface{}{
+				"command_id":   cmdID,
+				"extension_id": cmd.ExtensionID,
+				"command":      cmd.Command,
+			})
+		}
+	}
+
+	jsonBytes, err := json.Marshal(commands)
+	if err != nil {
+		return "", err
+	}
+
+	return string(jsonBytes), nil
+}
+
+// ==================== EXTENSION CUSTOM SEARCH ====================
+
+// CustomSearchWithExtensionJSON performs custom search using an extension
+func CustomSearchWithExtensionJSON(extensionID, query string, optionsJSON string) (string, error) {
+	manager := GetExtensionManager()
+	ext, err := manager.GetExtension(extensionID)
+	if err != nil {
+		return "", err
+	}
+
+	if !ext.Manifest.HasCustomSearch() {
+		return "", fmt.Errorf("extension '%s' does not support custom search", extensionID)
+	}
+
+	var options map[string]interface{}
+	if optionsJSON != "" {
+		if err := json.Unmarshal([]byte(optionsJSON), &options); err != nil {
+			options = make(map[string]interface{})
+		}
+	}
+
+	provider := NewExtensionProviderWrapper(ext)
+	tracks, err := provider.CustomSearch(query, options)
+	if err != nil {
+		return "", err
+	}
+
+	// Convert to map format for Flutter, ensuring images field is set
+	result := make([]map[string]interface{}, len(tracks))
+	for i, track := range tracks {
+		result[i] = map[string]interface{}{
+			"id":           track.ID,
+			"name":         track.Name,
+			"artists":      track.Artists,
+			"album_name":   track.AlbumName,
+			"album_artist": track.AlbumArtist,
+			"duration_ms":  track.DurationMS,
+			"images":       track.ResolvedCoverURL(), // Use helper to get cover URL from either field
+			"release_date": track.ReleaseDate,
+			"track_number": track.TrackNumber,
+			"disc_number":  track.DiscNumber,
+			"isrc":         track.ISRC,
+			"provider_id":  track.ProviderID,
+		}
+	}
+
+	jsonBytes, err := json.Marshal(result)
+	if err != nil {
+		return "", err
+	}
+
+	return string(jsonBytes), nil
+}
+
+// GetSearchProvidersJSON returns all extensions that provide custom search
+func GetSearchProvidersJSON() (string, error) {
+	manager := GetExtensionManager()
+	providers := manager.GetSearchProviders()
+
+	result := make([]map[string]interface{}, 0, len(providers))
+	for _, p := range providers {
+		result = append(result, map[string]interface{}{
+			"id":           p.extension.ID,
+			"display_name": p.extension.Manifest.DisplayName,
+			"placeholder":  p.extension.Manifest.SearchBehavior.Placeholder,
+			"primary":      p.extension.Manifest.SearchBehavior.Primary,
+			"icon":         p.extension.Manifest.SearchBehavior.Icon,
+		})
+	}
+
+	jsonBytes, err := json.Marshal(result)
+	if err != nil {
+		return "", err
+	}
+
+	return string(jsonBytes), nil
+}
+
+// ==================== EXTENSION URL HANDLER ====================
+
+// HandleURLWithExtensionJSON tries to handle a URL with any matching extension
+// Returns JSON with type, tracks, album info, etc.
+func HandleURLWithExtensionJSON(url string) (string, error) {
+	manager := GetExtensionManager()
+	resultWithID, err := manager.HandleURLWithExtension(url)
+	if err != nil {
+		return "", err
+	}
+
+	result := resultWithID.Result
+	extensionID := resultWithID.ExtensionID
+
+	// Check if result is nil (handler found but returned error)
+	if result == nil {
+		return "", fmt.Errorf("extension %s failed to handle URL", extensionID)
+	}
+
+	// Build response
+	response := map[string]interface{}{
+		"type":         result.Type,
+		"extension_id": extensionID,
+		"name":         result.Name,
+		"cover_url":    result.CoverURL,
+	}
+
+	// Add track if single track
+	if result.Track != nil {
+		response["track"] = map[string]interface{}{
+			"id":           result.Track.ID,
+			"name":         result.Track.Name,
+			"artists":      result.Track.Artists,
+			"album_name":   result.Track.AlbumName,
+			"album_artist": result.Track.AlbumArtist,
+			"duration_ms":  result.Track.DurationMS,
+			"images":       result.Track.ResolvedCoverURL(),
+			"release_date": result.Track.ReleaseDate,
+			"track_number": result.Track.TrackNumber,
+			"disc_number":  result.Track.DiscNumber,
+			"isrc":         result.Track.ISRC,
+			"provider_id":  result.Track.ProviderID,
+		}
+	}
+
+	// Add tracks if multiple
+	if len(result.Tracks) > 0 {
+		tracks := make([]map[string]interface{}, len(result.Tracks))
+		for i, track := range result.Tracks {
+			tracks[i] = map[string]interface{}{
+				"id":           track.ID,
+				"name":         track.Name,
+				"artists":      track.Artists,
+				"album_name":   track.AlbumName,
+				"album_artist": track.AlbumArtist,
+				"duration_ms":  track.DurationMS,
+				"images":       track.ResolvedCoverURL(),
+				"release_date": track.ReleaseDate,
+				"track_number": track.TrackNumber,
+				"disc_number":  track.DiscNumber,
+				"isrc":         track.ISRC,
+				"provider_id":  track.ProviderID,
+			}
+		}
+		response["tracks"] = tracks
+	}
+
+	// Add album info if present
+	if result.Album != nil {
+		response["album"] = map[string]interface{}{
+			"id":           result.Album.ID,
+			"name":         result.Album.Name,
+			"artists":      result.Album.Artists,
+			"cover_url":    result.Album.CoverURL,
+			"release_date": result.Album.ReleaseDate,
+			"total_tracks": result.Album.TotalTracks,
+		}
+	}
+
+	// Add artist info if present
+	if result.Artist != nil {
+		response["artist"] = map[string]interface{}{
+			"id":        result.Artist.ID,
+			"name":      result.Artist.Name,
+			"image_url": result.Artist.ImageURL,
+		}
+	}
+
+	jsonBytes, err := json.Marshal(response)
+	if err != nil {
+		return "", err
+	}
+
+	return string(jsonBytes), nil
+}
+
+// FindURLHandlerJSON finds an extension that can handle the given URL
+// Returns extension ID or empty string if none found
+func FindURLHandlerJSON(url string) string {
+	manager := GetExtensionManager()
+	handler := manager.FindURLHandler(url)
+	if handler == nil {
+		return ""
+	}
+	return handler.extension.ID
+}
+
+// GetURLHandlersJSON returns all extensions that handle custom URLs
+func GetURLHandlersJSON() (string, error) {
+	manager := GetExtensionManager()
+	handlers := manager.GetURLHandlers()
+
+	result := make([]map[string]interface{}, 0, len(handlers))
+	for _, h := range handlers {
+		result = append(result, map[string]interface{}{
+			"id":           h.extension.ID,
+			"display_name": h.extension.Manifest.DisplayName,
+			"patterns":     h.extension.Manifest.URLHandler.Patterns,
+		})
+	}
+
+	jsonBytes, err := json.Marshal(result)
+	if err != nil {
+		return "", err
+	}
+
+	return string(jsonBytes), nil
+}
+
+// ==================== EXTENSION POST-PROCESSING ====================
+
+// RunPostProcessingJSON runs post-processing hooks on a file
+func RunPostProcessingJSON(filePath, metadataJSON string) (string, error) {
+	var metadata map[string]interface{}
+	if metadataJSON != "" {
+		if err := json.Unmarshal([]byte(metadataJSON), &metadata); err != nil {
+			metadata = make(map[string]interface{})
+		}
+	}
+
+	manager := GetExtensionManager()
+	result, err := manager.RunPostProcessing(filePath, metadata)
+	if err != nil {
+		return "", err
+	}
+
+	jsonBytes, err := json.Marshal(result)
+	if err != nil {
+		return "", err
+	}
+
+	return string(jsonBytes), nil
+}
+
+// GetPostProcessingProvidersJSON returns all extensions that provide post-processing
+func GetPostProcessingProvidersJSON() (string, error) {
+	manager := GetExtensionManager()
+	providers := manager.GetPostProcessingProviders()
+
+	result := make([]map[string]interface{}, 0, len(providers))
+	for _, p := range providers {
+		hooks := make([]map[string]interface{}, 0)
+		for _, h := range p.extension.Manifest.GetPostProcessingHooks() {
+			hooks = append(hooks, map[string]interface{}{
+				"id":                h.ID,
+				"name":              h.Name,
+				"description":       h.Description,
+				"default_enabled":   h.DefaultEnabled,
+				"supported_formats": h.SupportedFormats,
+			})
+		}
+
+		result = append(result, map[string]interface{}{
+			"id":           p.extension.ID,
+			"display_name": p.extension.Manifest.DisplayName,
+			"hooks":        hooks,
+		})
+	}
+
+	jsonBytes, err := json.Marshal(result)
+	if err != nil {
+		return "", err
+	}
+
+	return string(jsonBytes), nil
+}
+
+// ==================== EXTENSION STORE ====================
+
+// InitExtensionStoreJSON initializes the extension store with cache directory
+func InitExtensionStoreJSON(cacheDir string) error {
+	InitExtensionStore(cacheDir)
+	return nil
+}
+
+// GetStoreExtensionsJSON returns all extensions from the store with installation status
+func GetStoreExtensionsJSON(forceRefresh bool) (string, error) {
+	store := GetExtensionStore()
+	if store == nil {
+		return "", fmt.Errorf("extension store not initialized")
+	}
+
+	// Force refresh if requested
+	if forceRefresh {
+		store.FetchRegistry(true)
+	}
+
+	extensions, err := store.GetExtensionsWithStatus()
+	if err != nil {
+		return "", err
+	}
+
+	jsonBytes, err := json.Marshal(extensions)
+	if err != nil {
+		return "", err
+	}
+
+	return string(jsonBytes), nil
+}
+
+// SearchStoreExtensionsJSON searches extensions in the store
+func SearchStoreExtensionsJSON(query, category string) (string, error) {
+	store := GetExtensionStore()
+	if store == nil {
+		return "", fmt.Errorf("extension store not initialized")
+	}
+
+	extensions, err := store.SearchExtensions(query, category)
+	if err != nil {
+		return "", err
+	}
+
+	jsonBytes, err := json.Marshal(extensions)
+	if err != nil {
+		return "", err
+	}
+
+	return string(jsonBytes), nil
+}
+
+// GetStoreCategoriesJSON returns all available categories
+func GetStoreCategoriesJSON() (string, error) {
+	store := GetExtensionStore()
+	if store == nil {
+		return "", fmt.Errorf("extension store not initialized")
+	}
+
+	categories := store.GetCategories()
+	jsonBytes, err := json.Marshal(categories)
+	if err != nil {
+		return "", err
+	}
+
+	return string(jsonBytes), nil
+}
+
+// DownloadStoreExtensionJSON downloads an extension from the store
+// Returns the path to the downloaded file
+func DownloadStoreExtensionJSON(extensionID, destDir string) (string, error) {
+	store := GetExtensionStore()
+	if store == nil {
+		return "", fmt.Errorf("extension store not initialized")
+	}
+
+	destPath := fmt.Sprintf("%s/%s.spotiflac-ext", destDir, extensionID)
+	err := store.DownloadExtension(extensionID, destPath)
+	if err != nil {
+		return "", err
+	}
+
+	return destPath, nil
+}
+
+// ClearStoreCacheJSON clears the store cache
+func ClearStoreCacheJSON() error {
+	store := GetExtensionStore()
+	if store == nil {
+		return fmt.Errorf("extension store not initialized")
+	}
+
+	store.ClearCache()
+	return nil
+}

go_backend/extension_manager.go

@@ -0,0 +1,987 @@
+// Package gobackend provides extension management functionality
+package gobackend
+
+import (
+	"archive/zip"
+	"encoding/json"
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+	"strconv"
+	"strings"
+	"sync"
+
+	"github.com/dop251/goja"
+)
+
+// compareVersions compares two semantic version strings
+// Returns: -1 if v1 < v2, 0 if v1 == v2, 1 if v1 > v2
+func compareVersions(v1, v2 string) int {
+	// Parse version parts
+	parts1 := strings.Split(strings.TrimPrefix(v1, "v"), ".")
+	parts2 := strings.Split(strings.TrimPrefix(v2, "v"), ".")
+
+	// Pad shorter version with zeros
+	maxLen := len(parts1)
+	if len(parts2) > maxLen {
+		maxLen = len(parts2)
+	}
+
+	for i := 0; i < maxLen; i++ {
+		var n1, n2 int
+		if i < len(parts1) {
+			n1, _ = strconv.Atoi(parts1[i])
+		}
+		if i < len(parts2) {
+			n2, _ = strconv.Atoi(parts2[i])
+		}
+
+		if n1 < n2 {
+			return -1
+		}
+		if n1 > n2 {
+			return 1
+		}
+	}
+
+	return 0
+}
+
+// LoadedExtension represents an extension that has been loaded into memory
+type LoadedExtension struct {
+	ID        string             `json:"id"`
+	Manifest  *ExtensionManifest `json:"manifest"`
+	VM        *goja.Runtime      `json:"-"` // Goja VM instance (not serialized)
+	Enabled   bool               `json:"enabled"`
+	Error     string             `json:"error,omitempty"`
+	DataDir   string             `json:"data_dir"`   // Extension's data directory
+	SourceDir string             `json:"source_dir"` // Where extension files are extracted
+	IconPath  string             `json:"icon_path"`  // Full path to icon file (if exists)
+}
+
+// ExtensionManager manages all loaded extensions
+type ExtensionManager struct {
+	mu            sync.RWMutex
+	extensions    map[string]*LoadedExtension
+	extensionsDir string // Base directory for extensions
+	dataDir       string // Base directory for extension data
+}
+
+// Global extension manager instance
+var (
+	globalExtManager     *ExtensionManager
+	globalExtManagerOnce sync.Once
+)
+
+// GetExtensionManager returns the global extension manager instance
+func GetExtensionManager() *ExtensionManager {
+	globalExtManagerOnce.Do(func() {
+		globalExtManager = &ExtensionManager{
+			extensions: make(map[string]*LoadedExtension),
+		}
+	})
+	return globalExtManager
+}
+
+// SetDirectories sets the extensions and data directories
+func (m *ExtensionManager) SetDirectories(extensionsDir, dataDir string) error {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+
+	m.extensionsDir = extensionsDir
+	m.dataDir = dataDir
+
+	// Create directories if they don't exist
+	if err := os.MkdirAll(extensionsDir, 0755); err != nil {
+		return fmt.Errorf("failed to create extensions directory: %w", err)
+	}
+	if err := os.MkdirAll(dataDir, 0755); err != nil {
+		return fmt.Errorf("failed to create data directory: %w", err)
+	}
+
+	return nil
+}
+
+// LoadExtensionFromFile loads an extension from a .spotiflac-ext file
+func (m *ExtensionManager) LoadExtensionFromFile(filePath string) (*LoadedExtension, error) {
+	// Validate file extension
+	if !strings.HasSuffix(strings.ToLower(filePath), ".spotiflac-ext") {
+		return nil, fmt.Errorf("Invalid file format. Please select a .spotiflac-ext file")
+	}
+
+	// Open the zip file
+	zipReader, err := zip.OpenReader(filePath)
+	if err != nil {
+		return nil, fmt.Errorf("Cannot open extension file. The file may be corrupted or not a valid extension package")
+	}
+	defer zipReader.Close()
+
+	// Find and read manifest.json
+	var manifestData []byte
+	var hasIndexJS bool
+	for _, file := range zipReader.File {
+		name := filepath.Base(file.Name)
+		if name == "manifest.json" {
+			rc, err := file.Open()
+			if err != nil {
+				return nil, fmt.Errorf("failed to open manifest.json: %w", err)
+			}
+			manifestData, err = io.ReadAll(rc)
+			rc.Close()
+			if err != nil {
+				return nil, fmt.Errorf("failed to read manifest.json: %w", err)
+			}
+		}
+		if name == "index.js" {
+			hasIndexJS = true
+		}
+	}
+
+	if manifestData == nil {
+		return nil, fmt.Errorf("Invalid extension package: manifest.json not found")
+	}
+
+	if !hasIndexJS {
+		return nil, fmt.Errorf("Invalid extension package: index.js not found")
+	}
+
+	// Parse and validate manifest
+	manifest, err := ParseManifest(manifestData)
+	if err != nil {
+		return nil, fmt.Errorf("Invalid extension manifest: %w", err)
+	}
+
+	// Check if extension already loaded - if so, try upgrade (check without holding lock for long)
+	m.mu.RLock()
+	existing, exists := m.extensions[manifest.Name]
+	var existingVersion string
+	var existingDisplayName string
+	if exists {
+		existingVersion = existing.Manifest.Version
+		existingDisplayName = existing.Manifest.DisplayName
+	}
+	m.mu.RUnlock()
+
+	if exists {
+		// Check if this is an upgrade
+		versionCompare := compareVersions(manifest.Version, existingVersion)
+		if versionCompare > 0 {
+			// This is an upgrade - call UpgradeExtension
+			return m.UpgradeExtension(filePath)
+		} else if versionCompare == 0 {
+			return nil, fmt.Errorf("Extension '%s' v%s is already installed", existingDisplayName, existingVersion)
+		} else {
+			return nil, fmt.Errorf("Cannot downgrade '%s' from v%s to v%s", existingDisplayName, existingVersion, manifest.Version)
+		}
+	}
+
+	// Now acquire write lock for the rest of the operation
+	m.mu.Lock()
+	defer m.mu.Unlock()
+
+	// Double-check extension wasn't added while we were waiting for lock
+	if _, exists := m.extensions[manifest.Name]; exists {
+		return nil, fmt.Errorf("Extension '%s' was installed by another process", manifest.DisplayName)
+	}
+
+	// Create extension directory
+	extDir := filepath.Join(m.extensionsDir, manifest.Name)
+	if err := os.MkdirAll(extDir, 0755); err != nil {
+		return nil, fmt.Errorf("failed to create extension directory: %w", err)
+	}
+
+	// Extract all files
+	for _, file := range zipReader.File {
+		if file.FileInfo().IsDir() {
+			continue
+		}
+
+		// Get relative path within the zip
+		destPath := filepath.Join(extDir, filepath.Base(file.Name))
+
+		// Create destination file
+		destFile, err := os.Create(destPath)
+		if err != nil {
+			return nil, fmt.Errorf("failed to create file %s: %w", destPath, err)
+		}
+
+		// Copy content
+		srcFile, err := file.Open()
+		if err != nil {
+			destFile.Close()
+			return nil, fmt.Errorf("failed to open file in archive: %w", err)
+		}
+
+		_, err = io.Copy(destFile, srcFile)
+		srcFile.Close()
+		destFile.Close()
+		if err != nil {
+			return nil, fmt.Errorf("failed to extract file: %w", err)
+		}
+	}
+
+	// Create data directory for extension
+	extDataDir := filepath.Join(m.dataDir, manifest.Name)
+	if err := os.MkdirAll(extDataDir, 0755); err != nil {
+		return nil, fmt.Errorf("failed to create extension data directory: %w", err)
+	}
+
+	// Create loaded extension
+	ext := &LoadedExtension{
+		ID:        manifest.Name,
+		Manifest:  manifest,
+		Enabled:   false, // New extensions start disabled
+		DataDir:   extDataDir,
+		SourceDir: extDir,
+	}
+
+	// Initialize Goja VM
+	if err := m.initializeVM(ext); err != nil {
+		ext.Error = err.Error()
+		ext.Enabled = false
+		GoLog("[Extension] Failed to initialize VM for %s: %v\n", manifest.Name, err)
+	}
+
+	m.extensions[manifest.Name] = ext
+	GoLog("[Extension] Loaded extension: %s v%s\n", manifest.DisplayName, manifest.Version)
+
+	return ext, nil
+}
+
+// initializeVM creates and initializes the Goja VM for an extension
+func (m *ExtensionManager) initializeVM(ext *LoadedExtension) error {
+	// Create new Goja runtime
+	vm := goja.New()
+	ext.VM = vm
+
+	// Read index.js
+	indexPath := filepath.Join(ext.SourceDir, "index.js")
+	jsCode, err := os.ReadFile(indexPath)
+	if err != nil {
+		return fmt.Errorf("failed to read index.js: %w", err)
+	}
+
+	// Create extension runtime and register sandboxed APIs
+	runtime := NewExtensionRuntime(ext)
+	runtime.RegisterAPIs(vm)
+	runtime.RegisterGoBackendAPIs(vm)
+
+	// Set up console.log for debugging
+	console := vm.NewObject()
+	console.Set("log", func(call goja.FunctionCall) goja.Value {
+		args := make([]interface{}, len(call.Arguments))
+		for i, arg := range call.Arguments {
+			args[i] = arg.Export()
+		}
+		GoLog("[Extension:%s] %v\n", ext.ID, args)
+		return goja.Undefined()
+	})
+	vm.Set("console", console)
+
+	// Set up registerExtension function
+	var registeredExtension goja.Value
+	vm.Set("registerExtension", func(call goja.FunctionCall) goja.Value {
+		if len(call.Arguments) > 0 {
+			registeredExtension = call.Arguments[0]
+			// Also set it as global 'extension' variable for later access
+			vm.Set("extension", call.Arguments[0])
+		}
+		return goja.Undefined()
+	})
+
+	// Run the extension code
+	_, err = vm.RunString(string(jsCode))
+	if err != nil {
+		return fmt.Errorf("failed to execute extension code: %w", err)
+	}
+
+	// Verify extension was registered
+	if registeredExtension == nil || goja.IsUndefined(registeredExtension) {
+		return fmt.Errorf("extension did not call registerExtension()")
+	}
+
+	return nil
+}
+
+// UnloadExtension unloads an extension by ID
+func (m *ExtensionManager) UnloadExtension(extensionID string) error {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+
+	ext, exists := m.extensions[extensionID]
+	if !exists {
+		return fmt.Errorf("Extension not found")
+	}
+
+	// Call cleanup if VM is initialized
+	if ext.VM != nil {
+		// Try to call cleanup function
+		cleanup, err := ext.VM.RunString("typeof extension !== 'undefined' && typeof extension.cleanup === 'function' ? extension.cleanup() : null")
+		if err != nil {
+			GoLog("[Extension] Error calling cleanup for %s: %v\n", extensionID, err)
+		} else if cleanup != nil && !goja.IsUndefined(cleanup) && !goja.IsNull(cleanup) {
+			GoLog("[Extension] Cleanup called for %s\n", extensionID)
+		}
+	}
+
+	// Remove from registry
+	delete(m.extensions, extensionID)
+	GoLog("[Extension] Unloaded extension: %s\n", extensionID)
+
+	return nil
+}
+
+// GetExtension returns a loaded extension by ID
+// Returns error if extension not found (gomobile compatible)
+func (m *ExtensionManager) GetExtension(extensionID string) (*LoadedExtension, error) {
+	m.mu.RLock()
+	defer m.mu.RUnlock()
+
+	ext, exists := m.extensions[extensionID]
+	if !exists {
+		return nil, fmt.Errorf("Extension not found")
+	}
+	return ext, nil
+}
+
+// GetAllExtensions returns all loaded extensions
+func (m *ExtensionManager) GetAllExtensions() []*LoadedExtension {
+	m.mu.RLock()
+	defer m.mu.RUnlock()
+
+	result := make([]*LoadedExtension, 0, len(m.extensions))
+	for _, ext := range m.extensions {
+		result = append(result, ext)
+	}
+	return result
+}
+
+// SetExtensionEnabled enables or disables an extension
+func (m *ExtensionManager) SetExtensionEnabled(extensionID string, enabled bool) error {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+
+	ext, exists := m.extensions[extensionID]
+	if !exists {
+		return fmt.Errorf("Extension not found")
+	}
+
+	ext.Enabled = enabled
+	GoLog("[Extension] %s %s\n", extensionID, map[bool]string{true: "enabled", false: "disabled"}[enabled])
+
+	// Persist enabled state to settings store
+	store := GetExtensionSettingsStore()
+	if err := store.Set(extensionID, "_enabled", enabled); err != nil {
+		GoLog("[Extension] Failed to persist enabled state for %s: %v\n", extensionID, err)
+	}
+
+	return nil
+}
+
+// LoadExtensionsFromDirectory scans a directory and loads all valid extensions
+func (m *ExtensionManager) LoadExtensionsFromDirectory(dirPath string) ([]string, []error) {
+	var loaded []string
+	var errors []error
+
+	entries, err := os.ReadDir(dirPath)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return loaded, errors
+		}
+		return nil, []error{fmt.Errorf("failed to read extensions directory: %w", err)}
+	}
+
+	for _, entry := range entries {
+		if entry.IsDir() {
+			// Check if it's an extracted extension directory
+			manifestPath := filepath.Join(dirPath, entry.Name(), "manifest.json")
+			if _, err := os.Stat(manifestPath); err == nil {
+				ext, err := m.loadExtensionFromDirectory(filepath.Join(dirPath, entry.Name()))
+				if err != nil {
+					GoLog("[Extension] Failed to load %s: %v\n", entry.Name(), err)
+					errors = append(errors, fmt.Errorf("%s: %w", entry.Name(), err))
+				} else {
+					loaded = append(loaded, ext.ID)
+				}
+			}
+		} else if strings.HasSuffix(strings.ToLower(entry.Name()), ".spotiflac-ext") {
+			// Load from package file
+			ext, err := m.LoadExtensionFromFile(filepath.Join(dirPath, entry.Name()))
+			if err != nil {
+				GoLog("[Extension] Failed to load %s: %v\n", entry.Name(), err)
+				errors = append(errors, fmt.Errorf("%s: %w", entry.Name(), err))
+			} else {
+				loaded = append(loaded, ext.ID)
+			}
+		}
+	}
+
+	return loaded, errors
+}
+
+// loadExtensionFromDirectory loads an extension from an already extracted directory
+func (m *ExtensionManager) loadExtensionFromDirectory(dirPath string) (*LoadedExtension, error) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+
+	// Read manifest
+	manifestPath := filepath.Join(dirPath, "manifest.json")
+	manifestData, err := os.ReadFile(manifestPath)
+	if err != nil {
+		return nil, fmt.Errorf("failed to read manifest.json: %w", err)
+	}
+
+	// Parse and validate manifest
+	manifest, err := ParseManifest(manifestData)
+	if err != nil {
+		return nil, fmt.Errorf("Invalid extension manifest: %w", err)
+	}
+
+	// Check if index.js exists
+	indexPath := filepath.Join(dirPath, "index.js")
+	if _, err := os.Stat(indexPath); os.IsNotExist(err) {
+		return nil, fmt.Errorf("Extension is missing index.js file")
+	}
+
+	// Check if extension already loaded - skip if already exists (for directory loading on startup)
+	if _, exists := m.extensions[manifest.Name]; exists {
+		return nil, fmt.Errorf("Extension '%s' is already loaded", manifest.DisplayName)
+	}
+
+	// Create data directory for extension
+	extDataDir := filepath.Join(m.dataDir, manifest.Name)
+	if err := os.MkdirAll(extDataDir, 0755); err != nil {
+		return nil, fmt.Errorf("failed to create extension data directory: %w", err)
+	}
+
+	// Create loaded extension
+	ext := &LoadedExtension{
+		ID:        manifest.Name,
+		Manifest:  manifest,
+		Enabled:   false, // Will be restored from settings store
+		DataDir:   extDataDir,
+		SourceDir: dirPath,
+	}
+
+	// Restore enabled state from settings store
+	store := GetExtensionSettingsStore()
+	if enabledVal, err := store.Get(manifest.Name, "_enabled"); err == nil {
+		if enabled, ok := enabledVal.(bool); ok {
+			ext.Enabled = enabled
+			GoLog("[Extension] Restored enabled state for %s: %v\n", manifest.Name, enabled)
+		}
+	}
+
+	// Initialize Goja VM
+	if err := m.initializeVM(ext); err != nil {
+		ext.Error = err.Error()
+		ext.Enabled = false
+		GoLog("[Extension] Failed to initialize VM for %s: %v\n", manifest.Name, err)
+	}
+
+	m.extensions[manifest.Name] = ext
+	GoLog("[Extension] Loaded extension: %s v%s\n", manifest.DisplayName, manifest.Version)
+
+	return ext, nil
+}
+
+// RemoveExtension completely removes an extension (unload + delete files)
+func (m *ExtensionManager) RemoveExtension(extensionID string) error {
+	ext, err := m.GetExtension(extensionID)
+	if err != nil {
+		return err
+	}
+
+	// Unload first
+	if err := m.UnloadExtension(extensionID); err != nil {
+		return err
+	}
+
+	// Remove source directory
+	if ext.SourceDir != "" {
+		if err := os.RemoveAll(ext.SourceDir); err != nil {
+			GoLog("[Extension] Warning: failed to remove source dir: %v\n", err)
+		}
+	}
+
+	// Optionally remove data directory (keep for now to preserve settings)
+	// if ext.DataDir != "" {
+	//     os.RemoveAll(ext.DataDir)
+	// }
+
+	return nil
+}
+
+// UpgradeExtension upgrades an existing extension from a new package file
+// Only allows upgrades (new version > current version), not downgrades
+func (m *ExtensionManager) UpgradeExtension(filePath string) (*LoadedExtension, error) {
+	// Validate file extension
+	if !strings.HasSuffix(strings.ToLower(filePath), ".spotiflac-ext") {
+		return nil, fmt.Errorf("Invalid file format. Please select a .spotiflac-ext file")
+	}
+
+	// Open the zip file
+	zipReader, err := zip.OpenReader(filePath)
+	if err != nil {
+		return nil, fmt.Errorf("Cannot open extension file. The file may be corrupted or not a valid extension package")
+	}
+	defer zipReader.Close()
+
+	// Find and read manifest.json
+	var manifestData []byte
+	var hasIndexJS bool
+	for _, file := range zipReader.File {
+		name := filepath.Base(file.Name)
+		if name == "manifest.json" {
+			rc, err := file.Open()
+			if err != nil {
+				return nil, fmt.Errorf("failed to open manifest.json: %w", err)
+			}
+			manifestData, err = io.ReadAll(rc)
+			rc.Close()
+			if err != nil {
+				return nil, fmt.Errorf("failed to read manifest.json: %w", err)
+			}
+		}
+		if name == "index.js" {
+			hasIndexJS = true
+		}
+	}
+
+	if manifestData == nil {
+		return nil, fmt.Errorf("Invalid extension package: manifest.json not found")
+	}
+
+	if !hasIndexJS {
+		return nil, fmt.Errorf("Invalid extension package: index.js not found")
+	}
+
+	// Parse and validate manifest
+	newManifest, err := ParseManifest(manifestData)
+	if err != nil {
+		return nil, fmt.Errorf("Invalid extension manifest: %w", err)
+	}
+
+	// Check if extension exists
+	m.mu.RLock()
+	existing, exists := m.extensions[newManifest.Name]
+	m.mu.RUnlock()
+
+	if !exists {
+		return nil, fmt.Errorf("Extension '%s' is not installed. Use install instead of upgrade.", newManifest.DisplayName)
+	}
+
+	// Compare versions - only allow upgrade, not downgrade
+	versionCompare := compareVersions(newManifest.Version, existing.Manifest.Version)
+	if versionCompare < 0 {
+		return nil, fmt.Errorf("Cannot downgrade extension. Current version: %s, New version: %s", existing.Manifest.Version, newManifest.Version)
+	}
+	if versionCompare == 0 {
+		return nil, fmt.Errorf("Extension is already at version %s", existing.Manifest.Version)
+	}
+
+	GoLog("[Extension] Upgrading %s from v%s to v%s\n", newManifest.DisplayName, existing.Manifest.Version, newManifest.Version)
+
+	// Save data directory path and enabled state (we want to preserve them)
+	extDataDir := existing.DataDir
+	extDir := existing.SourceDir
+	wasEnabled := existing.Enabled
+
+	// Cleanup and unload existing extension
+	m.CleanupExtension(existing.ID)
+	m.UnloadExtension(existing.ID)
+
+	// Remove old source files but keep data directory
+	if extDir != "" {
+		if err := os.RemoveAll(extDir); err != nil {
+			GoLog("[Extension] Warning: failed to remove old source dir: %v\n", err)
+		}
+	}
+
+	// Recreate extension directory
+	if err := os.MkdirAll(extDir, 0755); err != nil {
+		return nil, fmt.Errorf("failed to create extension directory: %w", err)
+	}
+
+	// Extract all files from new package
+	for _, file := range zipReader.File {
+		if file.FileInfo().IsDir() {
+			continue
+		}
+
+		// Get relative path within the zip
+		destPath := filepath.Join(extDir, filepath.Base(file.Name))
+
+		// Create destination file
+		destFile, err := os.Create(destPath)
+		if err != nil {
+			return nil, fmt.Errorf("failed to create file %s: %w", destPath, err)
+		}
+
+		// Copy content
+		srcFile, err := file.Open()
+		if err != nil {
+			destFile.Close()
+			return nil, fmt.Errorf("failed to open file in archive: %w", err)
+		}
+
+		_, err = io.Copy(destFile, srcFile)
+		srcFile.Close()
+		destFile.Close()
+		if err != nil {
+			return nil, fmt.Errorf("failed to extract file: %w", err)
+		}
+	}
+
+	// Create new loaded extension (reusing data directory, preserving enabled state)
+	ext := &LoadedExtension{
+		ID:        newManifest.Name,
+		Manifest:  newManifest,
+		Enabled:   wasEnabled, // Preserve enabled state from before upgrade
+		DataDir:   extDataDir,
+		SourceDir: extDir,
+	}
+
+	// Initialize Goja VM
+	if err := m.initializeVM(ext); err != nil {
+		ext.Error = err.Error()
+		ext.Enabled = false
+		GoLog("[Extension] Failed to initialize VM for %s: %v\n", newManifest.Name, err)
+	}
+
+	m.mu.Lock()
+	m.extensions[newManifest.Name] = ext
+	m.mu.Unlock()
+
+	GoLog("[Extension] Upgraded extension: %s to v%s\n", newManifest.DisplayName, newManifest.Version)
+
+	return ext, nil
+}
+
+// ExtensionUpgradeInfo holds information about extension upgrade check
+type ExtensionUpgradeInfo struct {
+	ExtensionID    string `json:"extension_id"`
+	CurrentVersion string `json:"current_version"`
+	NewVersion     string `json:"new_version"`
+	CanUpgrade     bool   `json:"can_upgrade"`
+	IsInstalled    bool   `json:"is_installed"`
+}
+
+// checkExtensionUpgradeInternal checks if a package file is an upgrade for an existing extension
+// Internal function that returns struct
+func (m *ExtensionManager) checkExtensionUpgradeInternal(filePath string) (*ExtensionUpgradeInfo, error) {
+	// Validate file extension
+	if !strings.HasSuffix(strings.ToLower(filePath), ".spotiflac-ext") {
+		return nil, fmt.Errorf("Invalid file format")
+	}
+
+	// Open the zip file
+	zipReader, err := zip.OpenReader(filePath)
+	if err != nil {
+		return nil, fmt.Errorf("Cannot open extension file")
+	}
+	defer zipReader.Close()
+
+	// Find and read manifest.json
+	var manifestData []byte
+	for _, file := range zipReader.File {
+		name := filepath.Base(file.Name)
+		if name == "manifest.json" {
+			rc, err := file.Open()
+			if err != nil {
+				return nil, fmt.Errorf("failed to open manifest.json")
+			}
+			manifestData, err = io.ReadAll(rc)
+			rc.Close()
+			if err != nil {
+				return nil, fmt.Errorf("failed to read manifest.json")
+			}
+			break
+		}
+	}
+
+	if manifestData == nil {
+		return nil, fmt.Errorf("manifest.json not found")
+	}
+
+	// Parse manifest
+	newManifest, err := ParseManifest(manifestData)
+	if err != nil {
+		return nil, fmt.Errorf("Invalid manifest: %w", err)
+	}
+
+	// Check if extension exists
+	m.mu.RLock()
+	existing, exists := m.extensions[newManifest.Name]
+	m.mu.RUnlock()
+
+	info := &ExtensionUpgradeInfo{
+		ExtensionID: newManifest.Name,
+		NewVersion:  newManifest.Version,
+		IsInstalled: exists,
+	}
+
+	if !exists {
+		// Not installed - this is a new install, not upgrade
+		info.CurrentVersion = ""
+		info.CanUpgrade = false
+	} else {
+		// Compare versions
+		info.CurrentVersion = existing.Manifest.Version
+		info.CanUpgrade = compareVersions(newManifest.Version, existing.Manifest.Version) > 0
+	}
+
+	return info, nil
+}
+
+// CheckExtensionUpgradeJSON checks if a package file is an upgrade and returns JSON
+func (m *ExtensionManager) CheckExtensionUpgradeJSON(filePath string) (string, error) {
+	info, err := m.checkExtensionUpgradeInternal(filePath)
+	if err != nil {
+		return "", err
+	}
+
+	jsonBytes, err := json.Marshal(info)
+	if err != nil {
+		return "", err
+	}
+
+	return string(jsonBytes), nil
+}
+
+// GetInstalledExtensionsJSON returns all extensions as JSON for Flutter
+func (m *ExtensionManager) GetInstalledExtensionsJSON() (string, error) {
+	extensions := m.GetAllExtensions()
+
+	type ExtensionInfo struct {
+		ID                     string                `json:"id"`
+		Name                   string                `json:"name"`
+		DisplayName            string                `json:"display_name"`
+		Version                string                `json:"version"`
+		Author                 string                `json:"author"`
+		Description            string                `json:"description"`
+		Homepage               string                `json:"homepage,omitempty"`
+		IconPath               string                `json:"icon_path,omitempty"`
+		Types                  []ExtensionType       `json:"types"`
+		Enabled                bool                  `json:"enabled"`
+		Status                 string                `json:"status"`
+		Error                  string                `json:"error_message,omitempty"`
+		Settings               []ExtensionSetting    `json:"settings,omitempty"`
+		QualityOptions         []QualityOption       `json:"quality_options,omitempty"`
+		Permissions            []string              `json:"permissions"`
+		HasMetadataProvider    bool                  `json:"has_metadata_provider"`
+		HasDownloadProvider    bool                  `json:"has_download_provider"`
+		SkipMetadataEnrichment bool                  `json:"skip_metadata_enrichment"`
+		SearchBehavior         *SearchBehaviorConfig `json:"search_behavior,omitempty"`
+		TrackMatching          *TrackMatchingConfig  `json:"track_matching,omitempty"`
+		PostProcessing         *PostProcessingConfig `json:"post_processing,omitempty"`
+	}
+
+	infos := make([]ExtensionInfo, len(extensions))
+	for i, ext := range extensions {
+		// Build permissions list
+		permissions := []string{}
+		for _, domain := range ext.Manifest.Permissions.Network {
+			permissions = append(permissions, "network:"+domain)
+		}
+		if ext.Manifest.Permissions.Storage {
+			permissions = append(permissions, "storage:enabled")
+		}
+
+		// Determine status
+		status := "loaded"
+		if ext.Error != "" {
+			status = "error"
+		} else if !ext.Enabled {
+			status = "disabled"
+		}
+
+		// Check for icon file
+		iconPath := ""
+		if ext.Manifest.Icon != "" && ext.SourceDir != "" {
+			possibleIcon := filepath.Join(ext.SourceDir, ext.Manifest.Icon)
+			if _, err := os.Stat(possibleIcon); err == nil {
+				iconPath = possibleIcon
+			}
+		}
+		// Fallback: check for icon.png if not specified in manifest
+		if iconPath == "" && ext.SourceDir != "" {
+			possibleIcon := filepath.Join(ext.SourceDir, "icon.png")
+			if _, err := os.Stat(possibleIcon); err == nil {
+				iconPath = possibleIcon
+			}
+		}
+
+		infos[i] = ExtensionInfo{
+			ID:                     ext.ID,
+			Name:                   ext.Manifest.Name,
+			DisplayName:            ext.Manifest.DisplayName,
+			Version:                ext.Manifest.Version,
+			Author:                 ext.Manifest.Author,
+			Description:            ext.Manifest.Description,
+			Homepage:               ext.Manifest.Homepage,
+			IconPath:               iconPath,
+			Types:                  ext.Manifest.Types,
+			Enabled:                ext.Enabled,
+			Status:                 status,
+			Error:                  ext.Error,
+			Settings:               ext.Manifest.Settings,
+			QualityOptions:         ext.Manifest.QualityOptions,
+			Permissions:            permissions,
+			HasMetadataProvider:    ext.Manifest.IsMetadataProvider(),
+			HasDownloadProvider:    ext.Manifest.IsDownloadProvider(),
+			SkipMetadataEnrichment: ext.Manifest.SkipMetadataEnrichment,
+			SearchBehavior:         ext.Manifest.SearchBehavior,
+			TrackMatching:          ext.Manifest.TrackMatching,
+			PostProcessing:         ext.Manifest.PostProcessing,
+		}
+	}
+
+	jsonBytes, err := json.Marshal(infos)
+	if err != nil {
+		return "", err
+	}
+
+	return string(jsonBytes), nil
+}
+
+// ==================== Extension Lifecycle ====================
+
+// InitializeExtension calls the extension's initialize method with settings
+func (m *ExtensionManager) InitializeExtension(extensionID string, settings map[string]interface{}) error {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+
+	ext, exists := m.extensions[extensionID]
+	if !exists {
+		return fmt.Errorf("Extension not found")
+	}
+
+	if ext.VM == nil {
+		return fmt.Errorf("Extension failed to load. Please reinstall the extension")
+	}
+
+	// Convert settings to JSON for passing to JS
+	settingsJSON, err := json.Marshal(settings)
+	if err != nil {
+		return fmt.Errorf("Failed to save settings")
+	}
+
+	// Call initialize function
+	script := fmt.Sprintf(`
+		(function() {
+			var settings = %s;
+			if (typeof extension !== 'undefined' && typeof extension.initialize === 'function') {
+				try {
+					extension.initialize(settings);
+					return { success: true };
+				} catch (e) {
+					return { success: false, error: e.toString() };
+				}
+			}
+			return { success: true, message: 'no initialize function' };
+		})()
+	`, string(settingsJSON))
+
+	result, err := ext.VM.RunString(script)
+	if err != nil {
+		ext.Error = fmt.Sprintf("initialize failed: %v", err)
+		ext.Enabled = false
+		GoLog("[Extension] Initialize error for %s: %v\n", extensionID, err)
+		return err
+	}
+
+	// Check result
+	if result != nil && !goja.IsUndefined(result) {
+		exported := result.Export()
+		if resultMap, ok := exported.(map[string]interface{}); ok {
+			if success, ok := resultMap["success"].(bool); ok && !success {
+				errMsg := "unknown error"
+				if e, ok := resultMap["error"].(string); ok {
+					errMsg = e
+				}
+				ext.Error = errMsg
+				ext.Enabled = false
+				GoLog("[Extension] Initialize failed for %s: %s\n", extensionID, errMsg)
+				return fmt.Errorf("initialize failed: %s", errMsg)
+			}
+		}
+	}
+
+	GoLog("[Extension] Initialized %s\n", extensionID)
+	return nil
+}
+
+// CleanupExtension calls the extension's cleanup method
+func (m *ExtensionManager) CleanupExtension(extensionID string) error {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+
+	ext, exists := m.extensions[extensionID]
+	if !exists {
+		return fmt.Errorf("Extension not found")
+	}
+
+	if ext.VM == nil {
+		return nil // No VM, nothing to cleanup
+	}
+
+	// Call cleanup function
+	script := `
+		(function() {
+			if (typeof extension !== 'undefined' && typeof extension.cleanup === 'function') {
+				try {
+					extension.cleanup();
+					return { success: true };
+				} catch (e) {
+					return { success: false, error: e.toString() };
+				}
+			}
+			return { success: true, message: 'no cleanup function' };
+		})()
+	`
+
+	result, err := ext.VM.RunString(script)
+	if err != nil {
+		GoLog("[Extension] Cleanup error for %s: %v\n", extensionID, err)
+		return err
+	}
+
+	// Check result
+	if result != nil && !goja.IsUndefined(result) {
+		exported := result.Export()
+		if resultMap, ok := exported.(map[string]interface{}); ok {
+			if success, ok := resultMap["success"].(bool); ok && !success {
+				errMsg := "unknown error"
+				if e, ok := resultMap["error"].(string); ok {
+					errMsg = e
+				}
+				GoLog("[Extension] Cleanup failed for %s: %s\n", extensionID, errMsg)
+				return fmt.Errorf("cleanup failed: %s", errMsg)
+			}
+		}
+	}
+
+	GoLog("[Extension] Cleaned up %s\n", extensionID)
+	return nil
+}
+
+// UnloadAllExtensions unloads all extensions gracefully
+func (m *ExtensionManager) UnloadAllExtensions() {
+	m.mu.Lock()
+	extensionIDs := make([]string, 0, len(m.extensions))
+	for id := range m.extensions {
+		extensionIDs = append(extensionIDs, id)
+	}
+	m.mu.Unlock()
+
+	for _, id := range extensionIDs {
+		// Call cleanup first
+		m.CleanupExtension(id)
+		// Then unload
+		m.UnloadExtension(id)
+	}
+
+	GoLog("[Extension] All extensions unloaded\n")
+}

go_backend/extension_manifest.go

@@ -0,0 +1,314 @@
+// Package gobackend provides extension manifest parsing and validation
+package gobackend
+
+import (
+	"encoding/json"
+	"fmt"
+	"strings"
+)
+
+// ExtensionType represents the type of extension
+type ExtensionType string
+
+const (
+	ExtensionTypeMetadataProvider ExtensionType = "metadata_provider"
+	ExtensionTypeDownloadProvider ExtensionType = "download_provider"
+)
+
+// SettingType represents the type of a setting field
+type SettingType string
+
+const (
+	SettingTypeString SettingType = "string"
+	SettingTypeNumber SettingType = "number"
+	SettingTypeBool   SettingType = "boolean"
+	SettingTypeSelect SettingType = "select"
+)
+
+// ExtensionPermissions defines what resources an extension can access
+type ExtensionPermissions struct {
+	Network []string `json:"network"` // List of allowed domains
+	Storage bool     `json:"storage"` // Whether extension can use storage API
+}
+
+// ExtensionSetting defines a configurable setting for an extension
+type ExtensionSetting struct {
+	Key         string      `json:"key"`
+	Type        SettingType `json:"type"`
+	Label       string      `json:"label"`
+	Description string      `json:"description,omitempty"`
+	Required    bool        `json:"required,omitempty"`
+	Secret      bool        `json:"secret,omitempty"`
+	Default     interface{} `json:"default,omitempty"`
+	Options     []string    `json:"options,omitempty"` // For select type
+}
+
+// QualityOption represents a quality option for download providers
+type QualityOption struct {
+	ID          string                   `json:"id"`                 // Unique identifier (e.g., "mp3_320", "opus_128")
+	Label       string                   `json:"label"`              // Display name (e.g., "MP3 320kbps")
+	Description string                   `json:"description"`        // Optional description (e.g., "Best quality MP3")
+	Settings    []QualitySpecificSetting `json:"settings,omitempty"` // Quality-specific settings
+}
+
+// QualitySpecificSetting represents a setting that's specific to a quality option
+type QualitySpecificSetting struct {
+	Key         string      `json:"key"`
+	Type        SettingType `json:"type"`
+	Label       string      `json:"label"`
+	Description string      `json:"description,omitempty"`
+	Required    bool        `json:"required,omitempty"`
+	Secret      bool        `json:"secret,omitempty"`
+	Default     interface{} `json:"default,omitempty"`
+	Options     []string    `json:"options,omitempty"` // For select type
+}
+
+// SearchBehaviorConfig defines custom search behavior for an extension
+type SearchBehaviorConfig struct {
+	Enabled         bool   `json:"enabled"`                   // Whether extension provides custom search
+	Placeholder     string `json:"placeholder,omitempty"`     // Placeholder text for search box
+	Primary         bool   `json:"primary,omitempty"`         // If true, show as primary search tab
+	Icon            string `json:"icon,omitempty"`            // Icon for search tab
+	ThumbnailRatio  string `json:"thumbnailRatio,omitempty"`  // Thumbnail aspect ratio: "square" (1:1), "wide" (16:9), "portrait" (2:3)
+	ThumbnailWidth  int    `json:"thumbnailWidth,omitempty"`  // Custom thumbnail width in pixels
+	ThumbnailHeight int    `json:"thumbnailHeight,omitempty"` // Custom thumbnail height in pixels
+}
+
+// URLHandlerConfig defines custom URL handling for an extension
+type URLHandlerConfig struct {
+	Enabled  bool     `json:"enabled"`            // Whether extension handles URLs
+	Patterns []string `json:"patterns,omitempty"` // URL patterns to match (e.g., "music.youtube.com", "soundcloud.com")
+}
+
+// TrackMatchingConfig defines custom track matching behavior
+type TrackMatchingConfig struct {
+	CustomMatching    bool   `json:"customMatching"`              // Whether extension handles matching
+	Strategy          string `json:"strategy,omitempty"`          // "isrc", "name", "duration", "custom"
+	DurationTolerance int    `json:"durationTolerance,omitempty"` // Tolerance in seconds for duration matching
+}
+
+// PostProcessingHook defines a post-processing hook
+type PostProcessingHook struct {
+	ID               string   `json:"id"`                         // Unique identifier
+	Name             string   `json:"name"`                       // Display name
+	Description      string   `json:"description,omitempty"`      // Description
+	DefaultEnabled   bool     `json:"defaultEnabled,omitempty"`   // Whether enabled by default
+	SupportedFormats []string `json:"supportedFormats,omitempty"` // Supported file formats (e.g., ["flac", "mp3"])
+}
+
+// PostProcessingConfig defines post-processing capabilities
+type PostProcessingConfig struct {
+	Enabled bool                 `json:"enabled"`         // Whether extension provides post-processing
+	Hooks   []PostProcessingHook `json:"hooks,omitempty"` // Available hooks
+}
+
+// ExtensionManifest represents the manifest.json of an extension
+type ExtensionManifest struct {
+	Name                   string                `json:"name"`
+	DisplayName            string                `json:"displayName"`
+	Version                string                `json:"version"`
+	Author                 string                `json:"author"`
+	Description            string                `json:"description"`
+	Homepage               string                `json:"homepage,omitempty"`
+	Icon                   string                `json:"icon,omitempty"` // Icon filename (e.g., "icon.png")
+	Types                  []ExtensionType       `json:"type"`
+	Permissions            ExtensionPermissions  `json:"permissions"`
+	Settings               []ExtensionSetting    `json:"settings,omitempty"`
+	QualityOptions         []QualityOption       `json:"qualityOptions,omitempty"` // Custom quality options for download providers
+	MinAppVersion          string                `json:"minAppVersion,omitempty"`
+	SkipMetadataEnrichment bool                  `json:"skipMetadataEnrichment,omitempty"` // If true, don't enrich metadata from Deezer/Spotify
+	SkipBuiltInFallback    bool                  `json:"skipBuiltInFallback,omitempty"`    // If true, don't fallback to built-in providers (tidal/qobuz/amazon)
+	SearchBehavior         *SearchBehaviorConfig `json:"searchBehavior,omitempty"`         // Custom search behavior
+	URLHandler             *URLHandlerConfig     `json:"urlHandler,omitempty"`             // Custom URL handling
+	TrackMatching          *TrackMatchingConfig  `json:"trackMatching,omitempty"`          // Custom track matching
+	PostProcessing         *PostProcessingConfig `json:"postProcessing,omitempty"`         // Post-processing hooks
+}
+
+// ManifestValidationError represents a validation error in the manifest
+type ManifestValidationError struct {
+	Field   string
+	Message string
+}
+
+func (e *ManifestValidationError) Error() string {
+	return fmt.Sprintf("manifest validation error: %s - %s", e.Field, e.Message)
+}
+
+// ParseManifest parses and validates a manifest from JSON bytes
+func ParseManifest(data []byte) (*ExtensionManifest, error) {
+	var manifest ExtensionManifest
+	if err := json.Unmarshal(data, &manifest); err != nil {
+		return nil, fmt.Errorf("failed to parse manifest JSON: %w", err)
+	}
+
+	if err := manifest.Validate(); err != nil {
+		return nil, err
+	}
+
+	return &manifest, nil
+}
+
+// Validate checks if the manifest has all required fields and valid values
+func (m *ExtensionManifest) Validate() error {
+	// Check required fields
+	if strings.TrimSpace(m.Name) == "" {
+		return &ManifestValidationError{Field: "name", Message: "name is required"}
+	}
+
+	if strings.TrimSpace(m.Version) == "" {
+		return &ManifestValidationError{Field: "version", Message: "version is required"}
+	}
+
+	if strings.TrimSpace(m.Author) == "" {
+		return &ManifestValidationError{Field: "author", Message: "author is required"}
+	}
+
+	if strings.TrimSpace(m.Description) == "" {
+		return &ManifestValidationError{Field: "description", Message: "description is required"}
+	}
+
+	if len(m.Types) == 0 {
+		return &ManifestValidationError{Field: "type", Message: "at least one type is required"}
+	}
+
+	// Validate extension types
+	for _, t := range m.Types {
+		if t != ExtensionTypeMetadataProvider && t != ExtensionTypeDownloadProvider {
+			return &ManifestValidationError{
+				Field:   "type",
+				Message: fmt.Sprintf("invalid extension type: %s (must be 'metadata_provider' or 'download_provider')", t),
+			}
+		}
+	}
+
+	// Validate settings if present
+	for i, setting := range m.Settings {
+		if strings.TrimSpace(setting.Key) == "" {
+			return &ManifestValidationError{
+				Field:   fmt.Sprintf("settings[%d].key", i),
+				Message: "setting key is required",
+			}
+		}
+
+		if setting.Type == "" {
+			return &ManifestValidationError{
+				Field:   fmt.Sprintf("settings[%d].type", i),
+				Message: "setting type is required",
+			}
+		}
+
+		// Validate setting type
+		validTypes := map[SettingType]bool{
+			SettingTypeString: true,
+			SettingTypeNumber: true,
+			SettingTypeBool:   true,
+			SettingTypeSelect: true,
+		}
+		if !validTypes[setting.Type] {
+			return &ManifestValidationError{
+				Field:   fmt.Sprintf("settings[%d].type", i),
+				Message: fmt.Sprintf("invalid setting type: %s", setting.Type),
+			}
+		}
+
+		// Select type requires options
+		if setting.Type == SettingTypeSelect && len(setting.Options) == 0 {
+			return &ManifestValidationError{
+				Field:   fmt.Sprintf("settings[%d].options", i),
+				Message: "select type requires options",
+			}
+		}
+	}
+
+	return nil
+}
+
+// HasType checks if the extension has a specific type
+func (m *ExtensionManifest) HasType(t ExtensionType) bool {
+	for _, et := range m.Types {
+		if et == t {
+			return true
+		}
+	}
+	return false
+}
+
+// IsMetadataProvider returns true if extension provides metadata
+func (m *ExtensionManifest) IsMetadataProvider() bool {
+	return m.HasType(ExtensionTypeMetadataProvider)
+}
+
+// IsDownloadProvider returns true if extension provides downloads
+func (m *ExtensionManifest) IsDownloadProvider() bool {
+	return m.HasType(ExtensionTypeDownloadProvider)
+}
+
+// IsDomainAllowed checks if a domain is in the allowed network permissions
+func (m *ExtensionManifest) IsDomainAllowed(domain string) bool {
+	domain = strings.ToLower(strings.TrimSpace(domain))
+	for _, allowed := range m.Permissions.Network {
+		allowed = strings.ToLower(strings.TrimSpace(allowed))
+		if allowed == domain {
+			return true
+		}
+		// Support wildcard subdomains (e.g., *.example.com)
+		if strings.HasPrefix(allowed, "*.") {
+			suffix := allowed[1:] // Remove the *
+			if strings.HasSuffix(domain, suffix) {
+				return true
+			}
+		}
+	}
+	return false
+}
+
+// HasCustomSearch returns true if extension provides custom search
+func (m *ExtensionManifest) HasCustomSearch() bool {
+	return m.SearchBehavior != nil && m.SearchBehavior.Enabled
+}
+
+// HasCustomMatching returns true if extension provides custom track matching
+func (m *ExtensionManifest) HasCustomMatching() bool {
+	return m.TrackMatching != nil && m.TrackMatching.CustomMatching
+}
+
+// HasPostProcessing returns true if extension provides post-processing
+func (m *ExtensionManifest) HasPostProcessing() bool {
+	return m.PostProcessing != nil && m.PostProcessing.Enabled
+}
+
+// HasURLHandler returns true if extension handles custom URLs
+func (m *ExtensionManifest) HasURLHandler() bool {
+	return m.URLHandler != nil && m.URLHandler.Enabled && len(m.URLHandler.Patterns) > 0
+}
+
+// MatchesURL checks if a URL matches any of the extension's URL patterns
+func (m *ExtensionManifest) MatchesURL(urlStr string) bool {
+	if !m.HasURLHandler() {
+		return false
+	}
+
+	// Parse URL to get host
+	urlStr = strings.ToLower(strings.TrimSpace(urlStr))
+	for _, pattern := range m.URLHandler.Patterns {
+		pattern = strings.ToLower(strings.TrimSpace(pattern))
+		// Check if URL contains the pattern (host match)
+		if strings.Contains(urlStr, pattern) {
+			return true
+		}
+	}
+	return false
+}
+
+// GetPostProcessingHooks returns all post-processing hooks
+func (m *ExtensionManifest) GetPostProcessingHooks() []PostProcessingHook {
+	if m.PostProcessing == nil {
+		return nil
+	}
+	return m.PostProcessing.Hooks
+}
+
+// ToJSON serializes the manifest to JSON
+func (m *ExtensionManifest) ToJSON() ([]byte, error) {
+	return json.Marshal(m)
+}

go_backend/extension_runtime.go

@@ -0,0 +1,269 @@
+// Package gobackend provides extension runtime with sandboxed execution
+package gobackend
+
+import (
+	"net/http"
+	"net/url"
+	"sync"
+	"time"
+
+	"github.com/dop251/goja"
+)
+
+// Global auth state for extensions (stores pending auth codes)
+var (
+	extensionAuthState   = make(map[string]*ExtensionAuthState)
+	extensionAuthStateMu sync.RWMutex
+)
+
+// ExtensionAuthState holds auth state for an extension
+type ExtensionAuthState struct {
+	PendingAuthURL  string
+	AuthCode        string
+	AccessToken     string
+	RefreshToken    string
+	ExpiresAt       time.Time
+	IsAuthenticated bool
+	// PKCE support
+	PKCEVerifier  string
+	PKCEChallenge string
+}
+
+// PendingAuthRequest holds a pending OAuth request that needs Flutter to open URL
+type PendingAuthRequest struct {
+	ExtensionID string
+	AuthURL     string
+	CallbackURL string
+}
+
+// Global pending auth requests (Flutter polls this)
+var (
+	pendingAuthRequests   = make(map[string]*PendingAuthRequest)
+	pendingAuthRequestsMu sync.RWMutex
+)
+
+// GetPendingAuthRequest returns pending auth request for an extension (called from Flutter)
+func GetPendingAuthRequest(extensionID string) *PendingAuthRequest {
+	pendingAuthRequestsMu.RLock()
+	defer pendingAuthRequestsMu.RUnlock()
+	return pendingAuthRequests[extensionID]
+}
+
+// ClearPendingAuthRequest clears pending auth request (called from Flutter after opening URL)
+func ClearPendingAuthRequest(extensionID string) {
+	pendingAuthRequestsMu.Lock()
+	defer pendingAuthRequestsMu.Unlock()
+	delete(pendingAuthRequests, extensionID)
+}
+
+// SetExtensionAuthCode sets auth code for an extension (called from Flutter after OAuth callback)
+func SetExtensionAuthCode(extensionID string, authCode string) {
+	extensionAuthStateMu.Lock()
+	defer extensionAuthStateMu.Unlock()
+
+	state, exists := extensionAuthState[extensionID]
+	if !exists {
+		state = &ExtensionAuthState{}
+		extensionAuthState[extensionID] = state
+	}
+	state.AuthCode = authCode
+}
+
+// SetExtensionTokens sets access/refresh tokens for an extension
+func SetExtensionTokens(extensionID string, accessToken, refreshToken string, expiresAt time.Time) {
+	extensionAuthStateMu.Lock()
+	defer extensionAuthStateMu.Unlock()
+
+	state, exists := extensionAuthState[extensionID]
+	if !exists {
+		state = &ExtensionAuthState{}
+		extensionAuthState[extensionID] = state
+	}
+	state.AccessToken = accessToken
+	state.RefreshToken = refreshToken
+	state.ExpiresAt = expiresAt
+	state.IsAuthenticated = accessToken != ""
+}
+
+// ExtensionRuntime provides sandboxed APIs for extensions
+type ExtensionRuntime struct {
+	extensionID string
+	manifest    *ExtensionManifest
+	settings    map[string]interface{}
+	httpClient  *http.Client
+	cookieJar   http.CookieJar
+	dataDir     string
+	vm          *goja.Runtime
+}
+
+// NewExtensionRuntime creates a new runtime for an extension
+func NewExtensionRuntime(ext *LoadedExtension) *ExtensionRuntime {
+	// Create a cookie jar for this extension
+	jar, _ := newSimpleCookieJar()
+
+	client := &http.Client{
+		Timeout: 30 * time.Second,
+		Jar:     jar,
+	}
+
+	return &ExtensionRuntime{
+		extensionID: ext.ID,
+		manifest:    ext.Manifest,
+		settings:    make(map[string]interface{}),
+		httpClient:  client,
+		cookieJar:   jar,
+		dataDir:     ext.DataDir,
+		vm:          ext.VM,
+	}
+}
+
+// simpleCookieJar is a simple in-memory cookie jar
+type simpleCookieJar struct {
+	cookies map[string][]*http.Cookie
+	mu      sync.RWMutex
+}
+
+func newSimpleCookieJar() (*simpleCookieJar, error) {
+	return &simpleCookieJar{
+		cookies: make(map[string][]*http.Cookie),
+	}, nil
+}
+
+func (j *simpleCookieJar) SetCookies(u *url.URL, cookies []*http.Cookie) {
+	j.mu.Lock()
+	defer j.mu.Unlock()
+	key := u.Host
+	j.cookies[key] = append(j.cookies[key], cookies...)
+}
+
+func (j *simpleCookieJar) Cookies(u *url.URL) []*http.Cookie {
+	j.mu.RLock()
+	defer j.mu.RUnlock()
+	return j.cookies[u.Host]
+}
+
+// SetSettings updates the runtime settings
+func (r *ExtensionRuntime) SetSettings(settings map[string]interface{}) {
+	r.settings = settings
+}
+
+// RegisterAPIs registers all sandboxed APIs to the Goja VM
+func (r *ExtensionRuntime) RegisterAPIs(vm *goja.Runtime) {
+	r.vm = vm
+
+	// HTTP client (sandboxed to allowed domains)
+	httpObj := vm.NewObject()
+	httpObj.Set("get", r.httpGet)
+	httpObj.Set("post", r.httpPost)
+	httpObj.Set("put", r.httpPut)
+	httpObj.Set("delete", r.httpDelete)
+	httpObj.Set("patch", r.httpPatch)
+	httpObj.Set("request", r.httpRequest) // Generic HTTP request (GET, POST, PUT, DELETE, etc.)
+	httpObj.Set("clearCookies", r.httpClearCookies)
+	vm.Set("http", httpObj)
+
+	// Storage API
+	storageObj := vm.NewObject()
+	storageObj.Set("get", r.storageGet)
+	storageObj.Set("set", r.storageSet)
+	storageObj.Set("remove", r.storageRemove)
+	vm.Set("storage", storageObj)
+
+	// Secure Credentials API (encrypted storage for sensitive data)
+	credentialsObj := vm.NewObject()
+	credentialsObj.Set("store", r.credentialsStore)
+	credentialsObj.Set("get", r.credentialsGet)
+	credentialsObj.Set("remove", r.credentialsRemove)
+	credentialsObj.Set("has", r.credentialsHas)
+	vm.Set("credentials", credentialsObj)
+
+	// Auth API (for OAuth and other auth flows)
+	authObj := vm.NewObject()
+	authObj.Set("openAuthUrl", r.authOpenUrl)
+	authObj.Set("getAuthCode", r.authGetCode)
+	authObj.Set("setAuthCode", r.authSetCode)
+	authObj.Set("clearAuth", r.authClear)
+	authObj.Set("isAuthenticated", r.authIsAuthenticated)
+	authObj.Set("getTokens", r.authGetTokens)
+	// PKCE support
+	authObj.Set("generatePKCE", r.authGeneratePKCE)
+	authObj.Set("getPKCE", r.authGetPKCE)
+	authObj.Set("startOAuthWithPKCE", r.authStartOAuthWithPKCE)
+	authObj.Set("exchangeCodeWithPKCE", r.authExchangeCodeWithPKCE)
+	vm.Set("auth", authObj)
+
+	// File operations (sandboxed)
+	fileObj := vm.NewObject()
+	fileObj.Set("download", r.fileDownload)
+	fileObj.Set("exists", r.fileExists)
+	fileObj.Set("delete", r.fileDelete)
+	fileObj.Set("read", r.fileRead)
+	fileObj.Set("write", r.fileWrite)
+	fileObj.Set("copy", r.fileCopy)
+	fileObj.Set("move", r.fileMove)
+	fileObj.Set("getSize", r.fileGetSize)
+	vm.Set("file", fileObj)
+
+	// FFmpeg API (for post-processing)
+	ffmpegObj := vm.NewObject()
+	ffmpegObj.Set("execute", r.ffmpegExecute)
+	ffmpegObj.Set("getInfo", r.ffmpegGetInfo)
+	ffmpegObj.Set("convert", r.ffmpegConvert)
+	vm.Set("ffmpeg", ffmpegObj)
+
+	// Track matching API
+	matchingObj := vm.NewObject()
+	matchingObj.Set("compareStrings", r.matchingCompareStrings)
+	matchingObj.Set("compareDuration", r.matchingCompareDuration)
+	matchingObj.Set("normalizeString", r.matchingNormalizeString)
+	vm.Set("matching", matchingObj)
+
+	// Utilities
+	utilsObj := vm.NewObject()
+	utilsObj.Set("base64Encode", r.base64Encode)
+	utilsObj.Set("base64Decode", r.base64Decode)
+	utilsObj.Set("md5", r.md5Hash)
+	utilsObj.Set("sha256", r.sha256Hash)
+	utilsObj.Set("hmacSHA256", r.hmacSHA256)
+	utilsObj.Set("hmacSHA256Base64", r.hmacSHA256Base64)
+	utilsObj.Set("hmacSHA1", r.hmacSHA1)
+	utilsObj.Set("parseJSON", r.parseJSON)
+	utilsObj.Set("stringifyJSON", r.stringifyJSON)
+	// Crypto utilities for developers
+	utilsObj.Set("encrypt", r.cryptoEncrypt)
+	utilsObj.Set("decrypt", r.cryptoDecrypt)
+	utilsObj.Set("generateKey", r.cryptoGenerateKey)
+	vm.Set("utils", utilsObj)
+
+	// Log object (already set in extension_manager.go, but we can enhance it)
+	logObj := vm.NewObject()
+	logObj.Set("debug", r.logDebug)
+	logObj.Set("info", r.logInfo)
+	logObj.Set("warn", r.logWarn)
+	logObj.Set("error", r.logError)
+	vm.Set("log", logObj)
+
+	// Go backend functions
+	gobackendObj := vm.NewObject()
+	gobackendObj.Set("sanitizeFilename", r.sanitizeFilenameWrapper)
+	vm.Set("gobackend", gobackendObj)
+
+	// ==================== Browser-like Polyfills ====================
+	// These make porting browser/Node.js libraries easier
+
+	// Global fetch() - Promise-style HTTP API (browser-compatible)
+	vm.Set("fetch", r.fetchPolyfill)
+
+	// Global atob/btoa - Base64 encoding (browser-compatible)
+	vm.Set("atob", r.atobPolyfill)
+	vm.Set("btoa", r.btoaPolyfill)
+
+	// TextEncoder/TextDecoder constructors
+	r.registerTextEncoderDecoder(vm)
+
+	// URL class for URL parsing
+	r.registerURLClass(vm)
+
+	// JSON global (browser-compatible)
+	r.registerJSONGlobal(vm)
+}

go_backend/extension_runtime_auth.go

@@ -0,0 +1,547 @@
+// Package gobackend provides Auth API and PKCE support for extension runtime
+package gobackend
+
+import (
+	"crypto/rand"
+	"crypto/sha256"
+	"encoding/base64"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+	"strings"
+	"time"
+
+	"github.com/dop251/goja"
+)
+
+// ==================== Auth API (OAuth Support) ====================
+
+// authOpenUrl requests Flutter to open an OAuth URL
+func (r *ExtensionRuntime) authOpenUrl(call goja.FunctionCall) goja.Value {
+	if len(call.Arguments) < 1 {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   "auth URL is required",
+		})
+	}
+
+	authURL := call.Arguments[0].String()
+	callbackURL := ""
+	if len(call.Arguments) > 1 && !goja.IsUndefined(call.Arguments[1]) {
+		callbackURL = call.Arguments[1].String()
+	}
+
+	// Store pending auth request for Flutter to pick up
+	pendingAuthRequestsMu.Lock()
+	pendingAuthRequests[r.extensionID] = &PendingAuthRequest{
+		ExtensionID: r.extensionID,
+		AuthURL:     authURL,
+		CallbackURL: callbackURL,
+	}
+	pendingAuthRequestsMu.Unlock()
+
+	// Update auth state
+	extensionAuthStateMu.Lock()
+	state, exists := extensionAuthState[r.extensionID]
+	if !exists {
+		state = &ExtensionAuthState{}
+		extensionAuthState[r.extensionID] = state
+	}
+	state.PendingAuthURL = authURL
+	state.AuthCode = "" // Clear any previous auth code
+	extensionAuthStateMu.Unlock()
+
+	GoLog("[Extension:%s] Auth URL requested: %s\n", r.extensionID, authURL)
+
+	return r.vm.ToValue(map[string]interface{}{
+		"success": true,
+		"message": "Auth URL will be opened by the app",
+	})
+}
+
+// authGetCode gets the auth code (set by Flutter after OAuth callback)
+func (r *ExtensionRuntime) authGetCode(call goja.FunctionCall) goja.Value {
+	extensionAuthStateMu.RLock()
+	defer extensionAuthStateMu.RUnlock()
+
+	state, exists := extensionAuthState[r.extensionID]
+	if !exists || state.AuthCode == "" {
+		return goja.Undefined()
+	}
+
+	return r.vm.ToValue(state.AuthCode)
+}
+
+// authSetCode sets auth code and tokens (can be called by extension after token exchange)
+func (r *ExtensionRuntime) authSetCode(call goja.FunctionCall) goja.Value {
+	if len(call.Arguments) < 1 {
+		return r.vm.ToValue(false)
+	}
+
+	// Can accept either just auth code or an object with tokens
+	arg := call.Arguments[0].Export()
+
+	extensionAuthStateMu.Lock()
+	defer extensionAuthStateMu.Unlock()
+
+	state, exists := extensionAuthState[r.extensionID]
+	if !exists {
+		state = &ExtensionAuthState{}
+		extensionAuthState[r.extensionID] = state
+	}
+
+	switch v := arg.(type) {
+	case string:
+		state.AuthCode = v
+	case map[string]interface{}:
+		if code, ok := v["code"].(string); ok {
+			state.AuthCode = code
+		}
+		if accessToken, ok := v["access_token"].(string); ok {
+			state.AccessToken = accessToken
+			state.IsAuthenticated = true
+		}
+		if refreshToken, ok := v["refresh_token"].(string); ok {
+			state.RefreshToken = refreshToken
+		}
+		if expiresIn, ok := v["expires_in"].(float64); ok {
+			state.ExpiresAt = time.Now().Add(time.Duration(expiresIn) * time.Second)
+		}
+	}
+
+	return r.vm.ToValue(true)
+}
+
+// authClear clears all auth state for the extension
+func (r *ExtensionRuntime) authClear(call goja.FunctionCall) goja.Value {
+	extensionAuthStateMu.Lock()
+	delete(extensionAuthState, r.extensionID)
+	extensionAuthStateMu.Unlock()
+
+	pendingAuthRequestsMu.Lock()
+	delete(pendingAuthRequests, r.extensionID)
+	pendingAuthRequestsMu.Unlock()
+
+	GoLog("[Extension:%s] Auth state cleared\n", r.extensionID)
+	return r.vm.ToValue(true)
+}
+
+// authIsAuthenticated checks if extension has valid auth
+func (r *ExtensionRuntime) authIsAuthenticated(call goja.FunctionCall) goja.Value {
+	extensionAuthStateMu.RLock()
+	defer extensionAuthStateMu.RUnlock()
+
+	state, exists := extensionAuthState[r.extensionID]
+	if !exists {
+		return r.vm.ToValue(false)
+	}
+
+	// Check if token is expired
+	if state.IsAuthenticated && !state.ExpiresAt.IsZero() && time.Now().After(state.ExpiresAt) {
+		return r.vm.ToValue(false)
+	}
+
+	return r.vm.ToValue(state.IsAuthenticated)
+}
+
+// authGetTokens returns current tokens (for extension to use in API calls)
+func (r *ExtensionRuntime) authGetTokens(call goja.FunctionCall) goja.Value {
+	extensionAuthStateMu.RLock()
+	defer extensionAuthStateMu.RUnlock()
+
+	state, exists := extensionAuthState[r.extensionID]
+	if !exists {
+		return r.vm.ToValue(map[string]interface{}{})
+	}
+
+	result := map[string]interface{}{
+		"access_token":     state.AccessToken,
+		"refresh_token":    state.RefreshToken,
+		"is_authenticated": state.IsAuthenticated,
+	}
+
+	if !state.ExpiresAt.IsZero() {
+		result["expires_at"] = state.ExpiresAt.Unix()
+		result["is_expired"] = time.Now().After(state.ExpiresAt)
+	}
+
+	return r.vm.ToValue(result)
+}
+
+// ==================== PKCE Support ====================
+
+// generatePKCEVerifier generates a cryptographically random code verifier
+// Length should be between 43-128 characters (RFC 7636)
+func generatePKCEVerifier(length int) (string, error) {
+	if length < 43 {
+		length = 43
+	}
+	if length > 128 {
+		length = 128
+	}
+
+	// Generate random bytes
+	bytes := make([]byte, length)
+	if _, err := rand.Read(bytes); err != nil {
+		return "", err
+	}
+
+	// Use base64url encoding without padding (RFC 7636 compliant)
+	verifier := base64.RawURLEncoding.EncodeToString(bytes)
+
+	// Trim to exact length
+	if len(verifier) > length {
+		verifier = verifier[:length]
+	}
+
+	return verifier, nil
+}
+
+// generatePKCEChallenge generates a code challenge from verifier using S256 method
+func generatePKCEChallenge(verifier string) string {
+	hash := sha256.Sum256([]byte(verifier))
+	// Base64url encode without padding (RFC 7636)
+	return base64.RawURLEncoding.EncodeToString(hash[:])
+}
+
+// authGeneratePKCE generates a PKCE code verifier and challenge pair
+// Returns: { verifier: string, challenge: string, method: "S256" }
+func (r *ExtensionRuntime) authGeneratePKCE(call goja.FunctionCall) goja.Value {
+	// Default length is 64 characters
+	length := 64
+	if len(call.Arguments) > 0 && !goja.IsUndefined(call.Arguments[0]) {
+		if l, ok := call.Arguments[0].Export().(float64); ok && l >= 43 && l <= 128 {
+			length = int(l)
+		}
+	}
+
+	verifier, err := generatePKCEVerifier(length)
+	if err != nil {
+		GoLog("[Extension:%s] PKCE generation error: %v\n", r.extensionID, err)
+		return r.vm.ToValue(map[string]interface{}{
+			"error": err.Error(),
+		})
+	}
+
+	challenge := generatePKCEChallenge(verifier)
+
+	// Store in auth state for later use
+	extensionAuthStateMu.Lock()
+	state, exists := extensionAuthState[r.extensionID]
+	if !exists {
+		state = &ExtensionAuthState{}
+		extensionAuthState[r.extensionID] = state
+	}
+	state.PKCEVerifier = verifier
+	state.PKCEChallenge = challenge
+	extensionAuthStateMu.Unlock()
+
+	GoLog("[Extension:%s] PKCE generated (verifier length: %d)\n", r.extensionID, len(verifier))
+
+	return r.vm.ToValue(map[string]interface{}{
+		"verifier":  verifier,
+		"challenge": challenge,
+		"method":    "S256",
+	})
+}
+
+// authGetPKCE returns the current PKCE verifier and challenge (if generated)
+func (r *ExtensionRuntime) authGetPKCE(call goja.FunctionCall) goja.Value {
+	extensionAuthStateMu.RLock()
+	defer extensionAuthStateMu.RUnlock()
+
+	state, exists := extensionAuthState[r.extensionID]
+	if !exists || state.PKCEVerifier == "" {
+		return r.vm.ToValue(map[string]interface{}{})
+	}
+
+	return r.vm.ToValue(map[string]interface{}{
+		"verifier":  state.PKCEVerifier,
+		"challenge": state.PKCEChallenge,
+		"method":    "S256",
+	})
+}
+
+// authStartOAuthWithPKCE is a high-level helper that generates PKCE and opens OAuth URL
+// config: { authUrl, clientId, redirectUri, scope, extraParams }
+// Returns: { success, authUrl, pkce: { verifier, challenge } }
+func (r *ExtensionRuntime) authStartOAuthWithPKCE(call goja.FunctionCall) goja.Value {
+	if len(call.Arguments) < 1 {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   "config object is required",
+		})
+	}
+
+	configObj := call.Arguments[0].Export()
+	config, ok := configObj.(map[string]interface{})
+	if !ok {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   "config must be an object",
+		})
+	}
+
+	// Required fields
+	authURL, _ := config["authUrl"].(string)
+	clientID, _ := config["clientId"].(string)
+	redirectURI, _ := config["redirectUri"].(string)
+
+	if authURL == "" || clientID == "" || redirectURI == "" {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   "authUrl, clientId, and redirectUri are required",
+		})
+	}
+
+	// Optional fields
+	scope, _ := config["scope"].(string)
+	extraParams, _ := config["extraParams"].(map[string]interface{})
+
+	// Generate PKCE
+	verifier, err := generatePKCEVerifier(64)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   fmt.Sprintf("failed to generate PKCE: %v", err),
+		})
+	}
+	challenge := generatePKCEChallenge(verifier)
+
+	// Store PKCE in auth state
+	extensionAuthStateMu.Lock()
+	state, exists := extensionAuthState[r.extensionID]
+	if !exists {
+		state = &ExtensionAuthState{}
+		extensionAuthState[r.extensionID] = state
+	}
+	state.PKCEVerifier = verifier
+	state.PKCEChallenge = challenge
+	state.AuthCode = "" // Clear any previous auth code
+	extensionAuthStateMu.Unlock()
+
+	// Build OAuth URL with PKCE parameters
+	parsedURL, err := url.Parse(authURL)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   fmt.Sprintf("invalid authUrl: %v", err),
+		})
+	}
+
+	query := parsedURL.Query()
+	query.Set("client_id", clientID)
+	query.Set("redirect_uri", redirectURI)
+	query.Set("response_type", "code")
+	query.Set("code_challenge", challenge)
+	query.Set("code_challenge_method", "S256")
+
+	if scope != "" {
+		query.Set("scope", scope)
+	}
+
+	// Add extra params
+	for k, v := range extraParams {
+		query.Set(k, fmt.Sprintf("%v", v))
+	}
+
+	parsedURL.RawQuery = query.Encode()
+	fullAuthURL := parsedURL.String()
+
+	// Store pending auth request for Flutter
+	pendingAuthRequestsMu.Lock()
+	pendingAuthRequests[r.extensionID] = &PendingAuthRequest{
+		ExtensionID: r.extensionID,
+		AuthURL:     fullAuthURL,
+		CallbackURL: redirectURI,
+	}
+	pendingAuthRequestsMu.Unlock()
+
+	GoLog("[Extension:%s] PKCE OAuth started: %s\n", r.extensionID, fullAuthURL)
+
+	return r.vm.ToValue(map[string]interface{}{
+		"success": true,
+		"authUrl": fullAuthURL,
+		"pkce": map[string]interface{}{
+			"verifier":  verifier,
+			"challenge": challenge,
+			"method":    "S256",
+		},
+	})
+}
+
+// authExchangeCodeWithPKCE exchanges auth code for tokens using PKCE
+// config: { tokenUrl, clientId, redirectUri, code, extraParams }
+// Uses the stored PKCE verifier automatically
+func (r *ExtensionRuntime) authExchangeCodeWithPKCE(call goja.FunctionCall) goja.Value {
+	if len(call.Arguments) < 1 {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   "config object is required",
+		})
+	}
+
+	configObj := call.Arguments[0].Export()
+	config, ok := configObj.(map[string]interface{})
+	if !ok {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   "config must be an object",
+		})
+	}
+
+	// Required fields
+	tokenURL, _ := config["tokenUrl"].(string)
+	clientID, _ := config["clientId"].(string)
+	redirectURI, _ := config["redirectUri"].(string)
+	code, _ := config["code"].(string)
+
+	if tokenURL == "" || clientID == "" || code == "" {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   "tokenUrl, clientId, and code are required",
+		})
+	}
+
+	// Get stored PKCE verifier
+	extensionAuthStateMu.RLock()
+	state, exists := extensionAuthState[r.extensionID]
+	var verifier string
+	if exists {
+		verifier = state.PKCEVerifier
+	}
+	extensionAuthStateMu.RUnlock()
+
+	if verifier == "" {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   "no PKCE verifier found - call generatePKCE or startOAuthWithPKCE first",
+		})
+	}
+
+	// Validate domain
+	if err := r.validateDomain(tokenURL); err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+
+	// Build token request body
+	formData := url.Values{}
+	formData.Set("grant_type", "authorization_code")
+	formData.Set("client_id", clientID)
+	formData.Set("code", code)
+	formData.Set("code_verifier", verifier)
+	if redirectURI != "" {
+		formData.Set("redirect_uri", redirectURI)
+	}
+
+	// Add extra params
+	if extraParams, ok := config["extraParams"].(map[string]interface{}); ok {
+		for k, v := range extraParams {
+			formData.Set(k, fmt.Sprintf("%v", v))
+		}
+	}
+
+	// Make token request
+	req, err := http.NewRequest("POST", tokenURL, strings.NewReader(formData.Encode()))
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+
+	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
+	req.Header.Set("User-Agent", "SpotiFLAC-Extension/1.0")
+
+	resp, err := r.httpClient.Do(req)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+	defer resp.Body.Close()
+
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+
+	// Parse response
+	var tokenResp map[string]interface{}
+	if err := json.Unmarshal(body, &tokenResp); err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   fmt.Sprintf("failed to parse token response: %v", err),
+			"body":    string(body),
+		})
+	}
+
+	// Check for error in response
+	if errMsg, ok := tokenResp["error"].(string); ok {
+		errDesc, _ := tokenResp["error_description"].(string)
+		return r.vm.ToValue(map[string]interface{}{
+			"success":           false,
+			"error":             errMsg,
+			"error_description": errDesc,
+		})
+	}
+
+	// Extract tokens
+	accessToken, _ := tokenResp["access_token"].(string)
+	refreshToken, _ := tokenResp["refresh_token"].(string)
+	expiresIn, _ := tokenResp["expires_in"].(float64)
+
+	if accessToken == "" {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   "no access_token in response",
+			"body":    string(body),
+		})
+	}
+
+	// Store tokens in auth state
+	extensionAuthStateMu.Lock()
+	state, exists = extensionAuthState[r.extensionID]
+	if !exists {
+		state = &ExtensionAuthState{}
+		extensionAuthState[r.extensionID] = state
+	}
+	state.AccessToken = accessToken
+	state.RefreshToken = refreshToken
+	state.IsAuthenticated = true
+	if expiresIn > 0 {
+		state.ExpiresAt = time.Now().Add(time.Duration(expiresIn) * time.Second)
+	}
+	// Clear PKCE after successful exchange
+	state.PKCEVerifier = ""
+	state.PKCEChallenge = ""
+	extensionAuthStateMu.Unlock()
+
+	GoLog("[Extension:%s] PKCE token exchange successful\n", r.extensionID)
+
+	// Return full token response
+	result := map[string]interface{}{
+		"success":       true,
+		"access_token":  accessToken,
+		"refresh_token": refreshToken,
+		"token_type":    tokenResp["token_type"],
+	}
+	if expiresIn > 0 {
+		result["expires_in"] = expiresIn
+	}
+	// Include any additional fields from response
+	if scope, ok := tokenResp["scope"].(string); ok {
+		result["scope"] = scope
+	}
+
+	return r.vm.ToValue(result)
+}

go_backend/extension_runtime_ffmpeg.go

@@ -0,0 +1,204 @@
+// Package gobackend provides FFmpeg API for extension runtime
+package gobackend
+
+import (
+	"fmt"
+	"strings"
+	"sync"
+	"time"
+
+	"github.com/dop251/goja"
+)
+
+// ==================== FFmpeg API (Post-Processing) ====================
+
+// FFmpegCommand holds a pending FFmpeg command for Flutter to execute
+type FFmpegCommand struct {
+	ExtensionID string
+	Command     string
+	InputPath   string
+	OutputPath  string
+	Completed   bool
+	Success     bool
+	Error       string
+	Output      string
+}
+
+// Global FFmpeg command queue
+var (
+	ffmpegCommands   = make(map[string]*FFmpegCommand)
+	ffmpegCommandsMu sync.RWMutex
+	ffmpegCommandID  int64
+)
+
+// GetPendingFFmpegCommand returns a pending FFmpeg command (called from Flutter)
+func GetPendingFFmpegCommand(commandID string) *FFmpegCommand {
+	ffmpegCommandsMu.RLock()
+	defer ffmpegCommandsMu.RUnlock()
+	return ffmpegCommands[commandID]
+}
+
+// SetFFmpegCommandResult sets the result of an FFmpeg command (called from Flutter)
+func SetFFmpegCommandResult(commandID string, success bool, output, errorMsg string) {
+	ffmpegCommandsMu.Lock()
+	defer ffmpegCommandsMu.Unlock()
+	if cmd, exists := ffmpegCommands[commandID]; exists {
+		cmd.Completed = true
+		cmd.Success = success
+		cmd.Output = output
+		cmd.Error = errorMsg
+	}
+}
+
+// ClearFFmpegCommand removes a completed FFmpeg command
+func ClearFFmpegCommand(commandID string) {
+	ffmpegCommandsMu.Lock()
+	defer ffmpegCommandsMu.Unlock()
+	delete(ffmpegCommands, commandID)
+}
+
+// ffmpegExecute queues an FFmpeg command for execution by Flutter
+func (r *ExtensionRuntime) ffmpegExecute(call goja.FunctionCall) goja.Value {
+	if len(call.Arguments) < 1 {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   "command is required",
+		})
+	}
+
+	command := call.Arguments[0].String()
+
+	// Generate unique command ID
+	ffmpegCommandsMu.Lock()
+	ffmpegCommandID++
+	cmdID := fmt.Sprintf("%s_%d", r.extensionID, ffmpegCommandID)
+	ffmpegCommands[cmdID] = &FFmpegCommand{
+		ExtensionID: r.extensionID,
+		Command:     command,
+		Completed:   false,
+	}
+	ffmpegCommandsMu.Unlock()
+
+	GoLog("[Extension:%s] FFmpeg command queued: %s\n", r.extensionID, cmdID)
+
+	// Wait for completion (with timeout)
+	timeout := 5 * time.Minute
+	start := time.Now()
+	for {
+		ffmpegCommandsMu.RLock()
+		cmd := ffmpegCommands[cmdID]
+		completed := cmd != nil && cmd.Completed
+		ffmpegCommandsMu.RUnlock()
+
+		if completed {
+			ffmpegCommandsMu.RLock()
+			result := map[string]interface{}{
+				"success": cmd.Success,
+				"output":  cmd.Output,
+			}
+			if cmd.Error != "" {
+				result["error"] = cmd.Error
+			}
+			ffmpegCommandsMu.RUnlock()
+
+			// Cleanup
+			ClearFFmpegCommand(cmdID)
+			return r.vm.ToValue(result)
+		}
+
+		if time.Since(start) > timeout {
+			ClearFFmpegCommand(cmdID)
+			return r.vm.ToValue(map[string]interface{}{
+				"success": false,
+				"error":   "FFmpeg command timed out",
+			})
+		}
+
+		time.Sleep(100 * time.Millisecond)
+	}
+}
+
+// ffmpegGetInfo gets audio file information using FFprobe
+func (r *ExtensionRuntime) ffmpegGetInfo(call goja.FunctionCall) goja.Value {
+	if len(call.Arguments) < 1 {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   "file path is required",
+		})
+	}
+
+	filePath := call.Arguments[0].String()
+
+	// Use Go's built-in audio quality function
+	quality, err := GetAudioQuality(filePath)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+
+	return r.vm.ToValue(map[string]interface{}{
+		"success":       true,
+		"bit_depth":     quality.BitDepth,
+		"sample_rate":   quality.SampleRate,
+		"total_samples": quality.TotalSamples,
+		"duration":      float64(quality.TotalSamples) / float64(quality.SampleRate),
+	})
+}
+
+// ffmpegConvert is a helper for common conversion operations
+func (r *ExtensionRuntime) ffmpegConvert(call goja.FunctionCall) goja.Value {
+	if len(call.Arguments) < 2 {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   "input and output paths are required",
+		})
+	}
+
+	inputPath := call.Arguments[0].String()
+	outputPath := call.Arguments[1].String()
+
+	// Get options if provided
+	options := map[string]interface{}{}
+	if len(call.Arguments) > 2 && !goja.IsUndefined(call.Arguments[2]) && !goja.IsNull(call.Arguments[2]) {
+		if opts, ok := call.Arguments[2].Export().(map[string]interface{}); ok {
+			options = opts
+		}
+	}
+
+	// Build FFmpeg command
+	var cmdParts []string
+	cmdParts = append(cmdParts, "-i", fmt.Sprintf("%q", inputPath))
+
+	// Audio codec
+	if codec, ok := options["codec"].(string); ok {
+		cmdParts = append(cmdParts, "-c:a", codec)
+	}
+
+	// Bitrate
+	if bitrate, ok := options["bitrate"].(string); ok {
+		cmdParts = append(cmdParts, "-b:a", bitrate)
+	}
+
+	// Sample rate
+	if sampleRate, ok := options["sample_rate"].(float64); ok {
+		cmdParts = append(cmdParts, "-ar", fmt.Sprintf("%d", int(sampleRate)))
+	}
+
+	// Channels
+	if channels, ok := options["channels"].(float64); ok {
+		cmdParts = append(cmdParts, "-ac", fmt.Sprintf("%d", int(channels)))
+	}
+
+	// Overwrite output
+	cmdParts = append(cmdParts, "-y", fmt.Sprintf("%q", outputPath))
+
+	command := strings.Join(cmdParts, " ")
+
+	// Execute via ffmpegExecute
+	execCall := goja.FunctionCall{
+		Arguments: []goja.Value{r.vm.ToValue(command)},
+	}
+	return r.ffmpegExecute(execCall)
+}

go_backend/extension_runtime_file.go

@@ -0,0 +1,467 @@
+// Package gobackend provides File API for extension runtime
+package gobackend
+
+import (
+	"fmt"
+	"io"
+	"net/http"
+	"os"
+	"path/filepath"
+	"strings"
+
+	"github.com/dop251/goja"
+)
+
+// ==================== File API (Sandboxed) ====================
+
+// validatePath checks if the path is within the extension's data directory
+// For absolute paths (from download queue), it allows them if they're valid
+func (r *ExtensionRuntime) validatePath(path string) (string, error) {
+	// Clean and resolve the path
+	cleanPath := filepath.Clean(path)
+
+	// If path is absolute, allow it (for download queue paths)
+	// This is safe because the Go backend controls what paths are passed
+	if filepath.IsAbs(cleanPath) {
+		return cleanPath, nil
+	}
+
+	// For relative paths, join with data directory
+	fullPath := filepath.Join(r.dataDir, cleanPath)
+
+	// Resolve to absolute path
+	absPath, err := filepath.Abs(fullPath)
+	if err != nil {
+		return "", fmt.Errorf("invalid path: %w", err)
+	}
+
+	// Ensure path is within data directory
+	absDataDir, _ := filepath.Abs(r.dataDir)
+	if !strings.HasPrefix(absPath, absDataDir) {
+		return "", fmt.Errorf("file access denied: path '%s' is outside sandbox", path)
+	}
+
+	return absPath, nil
+}
+
+// fileDownload downloads a file from URL to the specified path
+// Supports progress callback via options.onProgress
+func (r *ExtensionRuntime) fileDownload(call goja.FunctionCall) goja.Value {
+	if len(call.Arguments) < 2 {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   "URL and output path are required",
+		})
+	}
+
+	urlStr := call.Arguments[0].String()
+	outputPath := call.Arguments[1].String()
+
+	// Validate domain
+	if err := r.validateDomain(urlStr); err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+
+	// Validate output path (allows absolute paths for download queue)
+	fullPath, err := r.validatePath(outputPath)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+
+	// Get options if provided
+	var onProgress goja.Callable
+	var headers map[string]string
+	if len(call.Arguments) > 2 && !goja.IsUndefined(call.Arguments[2]) && !goja.IsNull(call.Arguments[2]) {
+		optionsObj := call.Arguments[2].Export()
+		if opts, ok := optionsObj.(map[string]interface{}); ok {
+			// Extract headers
+			if h, ok := opts["headers"].(map[string]interface{}); ok {
+				headers = make(map[string]string)
+				for k, v := range h {
+					headers[k] = fmt.Sprintf("%v", v)
+				}
+			}
+			// Extract onProgress callback
+			if progressVal, ok := opts["onProgress"]; ok {
+				if callable, ok := goja.AssertFunction(r.vm.ToValue(progressVal)); ok {
+					onProgress = callable
+				}
+			}
+		}
+	}
+
+	// Create directory if needed
+	dir := filepath.Dir(fullPath)
+	if err := os.MkdirAll(dir, 0755); err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   fmt.Sprintf("failed to create directory: %v", err),
+		})
+	}
+
+	// Create HTTP request
+	req, err := http.NewRequest("GET", urlStr, nil)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+
+	// Set headers
+	for k, v := range headers {
+		req.Header.Set(k, v)
+	}
+	if req.Header.Get("User-Agent") == "" {
+		req.Header.Set("User-Agent", "SpotiFLAC-Extension/1.0")
+	}
+
+	// Download file
+	resp, err := r.httpClient.Do(req)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != 200 {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   fmt.Sprintf("HTTP error: %d", resp.StatusCode),
+		})
+	}
+
+	// Create output file
+	out, err := os.Create(fullPath)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   fmt.Sprintf("failed to create file: %v", err),
+		})
+	}
+	defer out.Close()
+
+	// Get content length for progress
+	contentLength := resp.ContentLength
+
+	// Copy content with progress reporting
+	var written int64
+	buf := make([]byte, 32*1024) // 32KB buffer
+	for {
+		nr, er := resp.Body.Read(buf)
+		if nr > 0 {
+			nw, ew := out.Write(buf[0:nr])
+			if nw < 0 || nr < nw {
+				nw = 0
+				if ew == nil {
+					ew = fmt.Errorf("invalid write result")
+				}
+			}
+			written += int64(nw)
+			if ew != nil {
+				return r.vm.ToValue(map[string]interface{}{
+					"success": false,
+					"error":   fmt.Sprintf("failed to write file: %v", ew),
+				})
+			}
+			if nr != nw {
+				return r.vm.ToValue(map[string]interface{}{
+					"success": false,
+					"error":   "short write",
+				})
+			}
+
+			// Report progress
+			if onProgress != nil && contentLength > 0 {
+				_, _ = onProgress(goja.Undefined(), r.vm.ToValue(written), r.vm.ToValue(contentLength))
+			}
+		}
+		if er != nil {
+			if er != io.EOF {
+				return r.vm.ToValue(map[string]interface{}{
+					"success": false,
+					"error":   fmt.Sprintf("failed to read response: %v", er),
+				})
+			}
+			break
+		}
+	}
+
+	GoLog("[Extension:%s] Downloaded %d bytes to %s\n", r.extensionID, written, fullPath)
+
+	return r.vm.ToValue(map[string]interface{}{
+		"success": true,
+		"path":    fullPath,
+		"size":    written,
+	})
+}
+
+// fileExists checks if a file exists in the sandbox
+func (r *ExtensionRuntime) fileExists(call goja.FunctionCall) goja.Value {
+	if len(call.Arguments) < 1 {
+		return r.vm.ToValue(false)
+	}
+
+	path := call.Arguments[0].String()
+	fullPath, err := r.validatePath(path)
+	if err != nil {
+		return r.vm.ToValue(false)
+	}
+
+	_, err = os.Stat(fullPath)
+	return r.vm.ToValue(err == nil)
+}
+
+// fileDelete deletes a file in the sandbox
+func (r *ExtensionRuntime) fileDelete(call goja.FunctionCall) goja.Value {
+	if len(call.Arguments) < 1 {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   "path is required",
+		})
+	}
+
+	path := call.Arguments[0].String()
+	fullPath, err := r.validatePath(path)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+
+	if err := os.Remove(fullPath); err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+
+	return r.vm.ToValue(map[string]interface{}{
+		"success": true,
+	})
+}
+
+// fileRead reads a file from the sandbox
+func (r *ExtensionRuntime) fileRead(call goja.FunctionCall) goja.Value {
+	if len(call.Arguments) < 1 {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   "path is required",
+		})
+	}
+
+	path := call.Arguments[0].String()
+	fullPath, err := r.validatePath(path)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+
+	data, err := os.ReadFile(fullPath)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+
+	return r.vm.ToValue(map[string]interface{}{
+		"success": true,
+		"data":    string(data),
+	})
+}
+
+// fileWrite writes data to a file in the sandbox
+func (r *ExtensionRuntime) fileWrite(call goja.FunctionCall) goja.Value {
+	if len(call.Arguments) < 2 {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   "path and data are required",
+		})
+	}
+
+	path := call.Arguments[0].String()
+	data := call.Arguments[1].String()
+
+	fullPath, err := r.validatePath(path)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+
+	// Create directory if needed
+	dir := filepath.Dir(fullPath)
+	if err := os.MkdirAll(dir, 0755); err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   fmt.Sprintf("failed to create directory: %v", err),
+		})
+	}
+
+	if err := os.WriteFile(fullPath, []byte(data), 0644); err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+
+	return r.vm.ToValue(map[string]interface{}{
+		"success": true,
+		"path":    fullPath,
+	})
+}
+
+// fileCopy copies a file within the sandbox
+func (r *ExtensionRuntime) fileCopy(call goja.FunctionCall) goja.Value {
+	if len(call.Arguments) < 2 {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   "source and destination paths are required",
+		})
+	}
+
+	srcPath := call.Arguments[0].String()
+	dstPath := call.Arguments[1].String()
+
+	fullSrc, err := r.validatePath(srcPath)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+
+	fullDst, err := r.validatePath(dstPath)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+
+	// Read source file
+	data, err := os.ReadFile(fullSrc)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   fmt.Sprintf("failed to read source: %v", err),
+		})
+	}
+
+	// Create destination directory if needed
+	dir := filepath.Dir(fullDst)
+	if err := os.MkdirAll(dir, 0755); err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   fmt.Sprintf("failed to create directory: %v", err),
+		})
+	}
+
+	// Write to destination
+	if err := os.WriteFile(fullDst, data, 0644); err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   fmt.Sprintf("failed to write destination: %v", err),
+		})
+	}
+
+	return r.vm.ToValue(map[string]interface{}{
+		"success": true,
+		"path":    fullDst,
+	})
+}
+
+// fileMove moves/renames a file within the sandbox
+func (r *ExtensionRuntime) fileMove(call goja.FunctionCall) goja.Value {
+	if len(call.Arguments) < 2 {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   "source and destination paths are required",
+		})
+	}
+
+	srcPath := call.Arguments[0].String()
+	dstPath := call.Arguments[1].String()
+
+	fullSrc, err := r.validatePath(srcPath)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+
+	fullDst, err := r.validatePath(dstPath)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+
+	// Create destination directory if needed
+	dir := filepath.Dir(fullDst)
+	if err := os.MkdirAll(dir, 0755); err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   fmt.Sprintf("failed to create directory: %v", err),
+		})
+	}
+
+	if err := os.Rename(fullSrc, fullDst); err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   fmt.Sprintf("failed to move file: %v", err),
+		})
+	}
+
+	return r.vm.ToValue(map[string]interface{}{
+		"success": true,
+		"path":    fullDst,
+	})
+}
+
+// fileGetSize returns the size of a file in bytes
+func (r *ExtensionRuntime) fileGetSize(call goja.FunctionCall) goja.Value {
+	if len(call.Arguments) < 1 {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   "path is required",
+		})
+	}
+
+	path := call.Arguments[0].String()
+	fullPath, err := r.validatePath(path)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+
+	info, err := os.Stat(fullPath)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+
+	return r.vm.ToValue(map[string]interface{}{
+		"success": true,
+		"size":    info.Size(),
+	})
+}

go_backend/extension_runtime_http.go

@@ -0,0 +1,499 @@
+// Package gobackend provides HTTP API for extension runtime
+package gobackend
+
+import (
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+	"strings"
+
+	"github.com/dop251/goja"
+)
+
+// ==================== HTTP API (Sandboxed) ====================
+
+// HTTPResponse represents the response from an HTTP request
+type HTTPResponse struct {
+	StatusCode int               `json:"statusCode"`
+	Body       string            `json:"body"`
+	Headers    map[string]string `json:"headers"`
+}
+
+// validateDomain checks if the domain is allowed by the extension's permissions
+func (r *ExtensionRuntime) validateDomain(urlStr string) error {
+	parsed, err := url.Parse(urlStr)
+	if err != nil {
+		return fmt.Errorf("invalid URL: %w", err)
+	}
+
+	domain := parsed.Hostname()
+	if !r.manifest.IsDomainAllowed(domain) {
+		return fmt.Errorf("network access denied: domain '%s' not in allowed list", domain)
+	}
+
+	return nil
+}
+
+// httpGet performs a GET request (sandboxed)
+func (r *ExtensionRuntime) httpGet(call goja.FunctionCall) goja.Value {
+	if len(call.Arguments) < 1 {
+		return r.vm.ToValue(map[string]interface{}{
+			"error": "URL is required",
+		})
+	}
+
+	urlStr := call.Arguments[0].String()
+
+	// Validate domain
+	if err := r.validateDomain(urlStr); err != nil {
+		GoLog("[Extension:%s] HTTP blocked: %v\n", r.extensionID, err)
+		return r.vm.ToValue(map[string]interface{}{
+			"error": err.Error(),
+		})
+	}
+
+	// Get headers if provided
+	headers := make(map[string]string)
+	if len(call.Arguments) > 1 && !goja.IsUndefined(call.Arguments[1]) && !goja.IsNull(call.Arguments[1]) {
+		headersObj := call.Arguments[1].Export()
+		if h, ok := headersObj.(map[string]interface{}); ok {
+			for k, v := range h {
+				headers[k] = fmt.Sprintf("%v", v)
+			}
+		}
+	}
+
+	// Create request
+	req, err := http.NewRequest("GET", urlStr, nil)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"error": err.Error(),
+		})
+	}
+
+	// Set headers - user headers first
+	for k, v := range headers {
+		req.Header.Set(k, v)
+	}
+	// Only set default User-Agent if not provided by extension
+	if req.Header.Get("User-Agent") == "" {
+		req.Header.Set("User-Agent", "Spotiflac-Extension/1.0")
+	}
+
+	// Execute request
+	resp, err := r.httpClient.Do(req)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"error": err.Error(),
+		})
+	}
+	defer resp.Body.Close()
+
+	// Read body
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"error": err.Error(),
+		})
+	}
+
+	// Extract response headers - return all values as arrays for multi-value headers (cookies, etc.)
+	respHeaders := make(map[string]interface{})
+	for k, v := range resp.Header {
+		if len(v) == 1 {
+			respHeaders[k] = v[0]
+		} else {
+			respHeaders[k] = v // Return as array if multiple values
+		}
+	}
+
+	return r.vm.ToValue(map[string]interface{}{
+		"statusCode": resp.StatusCode,
+		"status":     resp.StatusCode, // Alias for convenience
+		"ok":         resp.StatusCode >= 200 && resp.StatusCode < 300,
+		"body":       string(body),
+		"headers":    respHeaders,
+	})
+}
+
+// httpPost performs a POST request (sandboxed)
+func (r *ExtensionRuntime) httpPost(call goja.FunctionCall) goja.Value {
+	if len(call.Arguments) < 1 {
+		return r.vm.ToValue(map[string]interface{}{
+			"error": "URL is required",
+		})
+	}
+
+	urlStr := call.Arguments[0].String()
+
+	// Validate domain
+	if err := r.validateDomain(urlStr); err != nil {
+		GoLog("[Extension:%s] HTTP blocked: %v\n", r.extensionID, err)
+		return r.vm.ToValue(map[string]interface{}{
+			"error": err.Error(),
+		})
+	}
+
+	// Get body if provided - support both string and object
+	var bodyStr string
+	if len(call.Arguments) > 1 && !goja.IsUndefined(call.Arguments[1]) && !goja.IsNull(call.Arguments[1]) {
+		bodyArg := call.Arguments[1].Export()
+		switch v := bodyArg.(type) {
+		case string:
+			bodyStr = v
+		case map[string]interface{}, []interface{}:
+			// Auto-stringify objects and arrays to JSON
+			jsonBytes, err := json.Marshal(v)
+			if err != nil {
+				return r.vm.ToValue(map[string]interface{}{
+					"error": fmt.Sprintf("failed to stringify body: %v", err),
+				})
+			}
+			bodyStr = string(jsonBytes)
+		default:
+			// Fallback to string conversion
+			bodyStr = call.Arguments[1].String()
+		}
+	}
+
+	// Get headers if provided
+	headers := make(map[string]string)
+	if len(call.Arguments) > 2 && !goja.IsUndefined(call.Arguments[2]) && !goja.IsNull(call.Arguments[2]) {
+		headersObj := call.Arguments[2].Export()
+		if h, ok := headersObj.(map[string]interface{}); ok {
+			for k, v := range h {
+				headers[k] = fmt.Sprintf("%v", v)
+			}
+		}
+	}
+
+	// Create request
+	req, err := http.NewRequest("POST", urlStr, strings.NewReader(bodyStr))
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"error": err.Error(),
+		})
+	}
+
+	// Set headers - user headers first
+	for k, v := range headers {
+		req.Header.Set(k, v)
+	}
+	// Only set defaults if not provided by extension
+	if req.Header.Get("User-Agent") == "" {
+		req.Header.Set("User-Agent", "Spotiflac-Extension/1.0")
+	}
+	if req.Header.Get("Content-Type") == "" {
+		req.Header.Set("Content-Type", "application/json")
+	}
+
+	// Execute request
+	resp, err := r.httpClient.Do(req)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"error": err.Error(),
+		})
+	}
+	defer resp.Body.Close()
+
+	// Read body
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"error": err.Error(),
+		})
+	}
+
+	// Extract response headers - return all values as arrays for multi-value headers
+	respHeaders := make(map[string]interface{})
+	for k, v := range resp.Header {
+		if len(v) == 1 {
+			respHeaders[k] = v[0]
+		} else {
+			respHeaders[k] = v // Return as array if multiple values
+		}
+	}
+
+	return r.vm.ToValue(map[string]interface{}{
+		"statusCode": resp.StatusCode,
+		"status":     resp.StatusCode, // Alias for convenience
+		"ok":         resp.StatusCode >= 200 && resp.StatusCode < 300,
+		"body":       string(body),
+		"headers":    respHeaders,
+	})
+}
+
+// httpRequest performs a generic HTTP request (GET, POST, PUT, DELETE, etc.)
+// Usage: http.request(url, options) where options = { method, body, headers }
+func (r *ExtensionRuntime) httpRequest(call goja.FunctionCall) goja.Value {
+	if len(call.Arguments) < 1 {
+		return r.vm.ToValue(map[string]interface{}{
+			"error": "URL is required",
+		})
+	}
+
+	urlStr := call.Arguments[0].String()
+
+	// Validate domain
+	if err := r.validateDomain(urlStr); err != nil {
+		GoLog("[Extension:%s] HTTP blocked: %v\n", r.extensionID, err)
+		return r.vm.ToValue(map[string]interface{}{
+			"error": err.Error(),
+		})
+	}
+
+	// Default options
+	method := "GET"
+	var bodyStr string
+	headers := make(map[string]string)
+
+	// Parse options if provided
+	if len(call.Arguments) > 1 && !goja.IsUndefined(call.Arguments[1]) && !goja.IsNull(call.Arguments[1]) {
+		optionsObj := call.Arguments[1].Export()
+		if opts, ok := optionsObj.(map[string]interface{}); ok {
+			// Get method
+			if m, ok := opts["method"].(string); ok {
+				method = strings.ToUpper(m)
+			}
+
+			// Get body - support both string and object
+			if bodyArg, ok := opts["body"]; ok && bodyArg != nil {
+				switch v := bodyArg.(type) {
+				case string:
+					bodyStr = v
+				case map[string]interface{}, []interface{}:
+					// Auto-stringify objects and arrays to JSON
+					jsonBytes, err := json.Marshal(v)
+					if err != nil {
+						return r.vm.ToValue(map[string]interface{}{
+							"error": fmt.Sprintf("failed to stringify body: %v", err),
+						})
+					}
+					bodyStr = string(jsonBytes)
+				default:
+					bodyStr = fmt.Sprintf("%v", v)
+				}
+			}
+
+			// Get headers
+			if h, ok := opts["headers"].(map[string]interface{}); ok {
+				for k, v := range h {
+					headers[k] = fmt.Sprintf("%v", v)
+				}
+			}
+		}
+	}
+
+	// Create request
+	var reqBody io.Reader
+	if bodyStr != "" {
+		reqBody = strings.NewReader(bodyStr)
+	}
+
+	req, err := http.NewRequest(method, urlStr, reqBody)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"error": err.Error(),
+		})
+	}
+
+	// Set headers - user headers first
+	for k, v := range headers {
+		req.Header.Set(k, v)
+	}
+	// Only set defaults if not provided by extension
+	if req.Header.Get("User-Agent") == "" {
+		req.Header.Set("User-Agent", "Spotiflac-Extension/1.0")
+	}
+	if bodyStr != "" && req.Header.Get("Content-Type") == "" {
+		req.Header.Set("Content-Type", "application/json")
+	}
+
+	// Execute request
+	resp, err := r.httpClient.Do(req)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"error": err.Error(),
+		})
+	}
+	defer resp.Body.Close()
+
+	// Read body
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"error": err.Error(),
+		})
+	}
+
+	// Extract response headers - return all values as arrays for multi-value headers
+	respHeaders := make(map[string]interface{})
+	for k, v := range resp.Header {
+		if len(v) == 1 {
+			respHeaders[k] = v[0]
+		} else {
+			respHeaders[k] = v // Return as array if multiple values
+		}
+	}
+
+	// Return response with helper properties
+	return r.vm.ToValue(map[string]interface{}{
+		"statusCode": resp.StatusCode,
+		"status":     resp.StatusCode, // Alias for convenience
+		"ok":         resp.StatusCode >= 200 && resp.StatusCode < 300,
+		"body":       string(body),
+		"headers":    respHeaders,
+	})
+}
+
+// httpPut performs a PUT request (shortcut for http.request with method: "PUT")
+func (r *ExtensionRuntime) httpPut(call goja.FunctionCall) goja.Value {
+	return r.httpMethodShortcut("PUT", call)
+}
+
+// httpDelete performs a DELETE request (shortcut for http.request with method: "DELETE")
+func (r *ExtensionRuntime) httpDelete(call goja.FunctionCall) goja.Value {
+	return r.httpMethodShortcut("DELETE", call)
+}
+
+// httpPatch performs a PATCH request (shortcut for http.request with method: "PATCH")
+func (r *ExtensionRuntime) httpPatch(call goja.FunctionCall) goja.Value {
+	return r.httpMethodShortcut("PATCH", call)
+}
+
+// httpMethodShortcut is a helper for PUT/DELETE/PATCH shortcuts
+// Signature: http.put(url, body, headers) / http.delete(url, headers) / http.patch(url, body, headers)
+func (r *ExtensionRuntime) httpMethodShortcut(method string, call goja.FunctionCall) goja.Value {
+	if len(call.Arguments) < 1 {
+		return r.vm.ToValue(map[string]interface{}{
+			"error": "URL is required",
+		})
+	}
+
+	urlStr := call.Arguments[0].String()
+
+	// Validate domain
+	if err := r.validateDomain(urlStr); err != nil {
+		GoLog("[Extension:%s] HTTP blocked: %v\n", r.extensionID, err)
+		return r.vm.ToValue(map[string]interface{}{
+			"error": err.Error(),
+		})
+	}
+
+	var bodyStr string
+	headers := make(map[string]string)
+
+	// For DELETE, second arg is headers; for PUT/PATCH, second arg is body
+	if method == "DELETE" {
+		// http.delete(url, headers)
+		if len(call.Arguments) > 1 && !goja.IsUndefined(call.Arguments[1]) && !goja.IsNull(call.Arguments[1]) {
+			headersObj := call.Arguments[1].Export()
+			if h, ok := headersObj.(map[string]interface{}); ok {
+				for k, v := range h {
+					headers[k] = fmt.Sprintf("%v", v)
+				}
+			}
+		}
+	} else {
+		// http.put(url, body, headers) / http.patch(url, body, headers)
+		if len(call.Arguments) > 1 && !goja.IsUndefined(call.Arguments[1]) && !goja.IsNull(call.Arguments[1]) {
+			bodyArg := call.Arguments[1].Export()
+			switch v := bodyArg.(type) {
+			case string:
+				bodyStr = v
+			case map[string]interface{}, []interface{}:
+				jsonBytes, err := json.Marshal(v)
+				if err != nil {
+					return r.vm.ToValue(map[string]interface{}{
+						"error": fmt.Sprintf("failed to stringify body: %v", err),
+					})
+				}
+				bodyStr = string(jsonBytes)
+			default:
+				bodyStr = call.Arguments[1].String()
+			}
+		}
+
+		if len(call.Arguments) > 2 && !goja.IsUndefined(call.Arguments[2]) && !goja.IsNull(call.Arguments[2]) {
+			headersObj := call.Arguments[2].Export()
+			if h, ok := headersObj.(map[string]interface{}); ok {
+				for k, v := range h {
+					headers[k] = fmt.Sprintf("%v", v)
+				}
+			}
+		}
+	}
+
+	// Create request
+	var reqBody io.Reader
+	if bodyStr != "" {
+		reqBody = strings.NewReader(bodyStr)
+	}
+
+	req, err := http.NewRequest(method, urlStr, reqBody)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"error": err.Error(),
+		})
+	}
+
+	// Set headers - user headers first
+	for k, v := range headers {
+		req.Header.Set(k, v)
+	}
+	if req.Header.Get("User-Agent") == "" {
+		req.Header.Set("User-Agent", "Spotiflac-Extension/1.0")
+	}
+	if bodyStr != "" && req.Header.Get("Content-Type") == "" {
+		req.Header.Set("Content-Type", "application/json")
+	}
+
+	// Execute request
+	resp, err := r.httpClient.Do(req)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"error": err.Error(),
+		})
+	}
+	defer resp.Body.Close()
+
+	// Read body
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"error": err.Error(),
+		})
+	}
+
+	// Extract response headers
+	respHeaders := make(map[string]interface{})
+	for k, v := range resp.Header {
+		if len(v) == 1 {
+			respHeaders[k] = v[0]
+		} else {
+			respHeaders[k] = v
+		}
+	}
+
+	return r.vm.ToValue(map[string]interface{}{
+		"statusCode": resp.StatusCode,
+		"status":     resp.StatusCode,
+		"ok":         resp.StatusCode >= 200 && resp.StatusCode < 300,
+		"body":       string(body),
+		"headers":    respHeaders,
+	})
+}
+
+// httpClearCookies clears all cookies for this extension
+func (r *ExtensionRuntime) httpClearCookies(call goja.FunctionCall) goja.Value {
+	if jar, ok := r.cookieJar.(*simpleCookieJar); ok {
+		jar.mu.Lock()
+		jar.cookies = make(map[string][]*http.Cookie)
+		jar.mu.Unlock()
+		GoLog("[Extension:%s] Cookies cleared\n", r.extensionID)
+		return r.vm.ToValue(true)
+	}
+	return r.vm.ToValue(false)
+}

go_backend/extension_runtime_matching.go

@@ -0,0 +1,151 @@
+// Package gobackend provides Track Matching API for extension runtime
+package gobackend
+
+import (
+	"strings"
+
+	"github.com/dop251/goja"
+)
+
+// ==================== Track Matching API ====================
+
+// matchingCompareStrings compares two strings with fuzzy matching
+func (r *ExtensionRuntime) matchingCompareStrings(call goja.FunctionCall) goja.Value {
+	if len(call.Arguments) < 2 {
+		return r.vm.ToValue(0.0)
+	}
+
+	str1 := strings.ToLower(strings.TrimSpace(call.Arguments[0].String()))
+	str2 := strings.ToLower(strings.TrimSpace(call.Arguments[1].String()))
+
+	if str1 == str2 {
+		return r.vm.ToValue(1.0)
+	}
+
+	// Calculate Levenshtein distance-based similarity
+	similarity := calculateStringSimilarity(str1, str2)
+	return r.vm.ToValue(similarity)
+}
+
+// matchingCompareDuration compares two durations with tolerance
+func (r *ExtensionRuntime) matchingCompareDuration(call goja.FunctionCall) goja.Value {
+	if len(call.Arguments) < 2 {
+		return r.vm.ToValue(false)
+	}
+
+	dur1 := int(call.Arguments[0].ToInteger())
+	dur2 := int(call.Arguments[1].ToInteger())
+
+	// Default tolerance: 3 seconds
+	tolerance := 3000 // milliseconds
+	if len(call.Arguments) > 2 && !goja.IsUndefined(call.Arguments[2]) {
+		tolerance = int(call.Arguments[2].ToInteger())
+	}
+
+	diff := dur1 - dur2
+	if diff < 0 {
+		diff = -diff
+	}
+
+	return r.vm.ToValue(diff <= tolerance)
+}
+
+// matchingNormalizeString normalizes a string for comparison
+func (r *ExtensionRuntime) matchingNormalizeString(call goja.FunctionCall) goja.Value {
+	if len(call.Arguments) < 1 {
+		return r.vm.ToValue("")
+	}
+
+	str := call.Arguments[0].String()
+	normalized := normalizeStringForMatching(str)
+	return r.vm.ToValue(normalized)
+}
+
+// calculateStringSimilarity calculates similarity between two strings (0-1)
+func calculateStringSimilarity(s1, s2 string) float64 {
+	if len(s1) == 0 && len(s2) == 0 {
+		return 1.0
+	}
+	if len(s1) == 0 || len(s2) == 0 {
+		return 0.0
+	}
+
+	// Use Levenshtein distance
+	distance := levenshteinDistance(s1, s2)
+	maxLen := len(s1)
+	if len(s2) > maxLen {
+		maxLen = len(s2)
+	}
+
+	return 1.0 - float64(distance)/float64(maxLen)
+}
+
+// levenshteinDistance calculates the Levenshtein distance between two strings
+func levenshteinDistance(s1, s2 string) int {
+	if len(s1) == 0 {
+		return len(s2)
+	}
+	if len(s2) == 0 {
+		return len(s1)
+	}
+
+	// Create matrix
+	matrix := make([][]int, len(s1)+1)
+	for i := range matrix {
+		matrix[i] = make([]int, len(s2)+1)
+		matrix[i][0] = i
+	}
+	for j := range matrix[0] {
+		matrix[0][j] = j
+	}
+
+	// Fill matrix
+	for i := 1; i <= len(s1); i++ {
+		for j := 1; j <= len(s2); j++ {
+			cost := 1
+			if s1[i-1] == s2[j-1] {
+				cost = 0
+			}
+			matrix[i][j] = min(
+				matrix[i-1][j]+1,      // deletion
+				matrix[i][j-1]+1,      // insertion
+				matrix[i-1][j-1]+cost, // substitution
+			)
+		}
+	}
+
+	return matrix[len(s1)][len(s2)]
+}
+
+// normalizeStringForMatching normalizes a string for comparison
+func normalizeStringForMatching(s string) string {
+	// Convert to lowercase
+	s = strings.ToLower(s)
+
+	// Remove common suffixes/prefixes
+	suffixes := []string{
+		" (remastered)", " (remaster)", " - remastered", " - remaster",
+		" (deluxe)", " (deluxe edition)", " - deluxe", " - deluxe edition",
+		" (explicit)", " (clean)", " [explicit]", " [clean]",
+		" (album version)", " (single version)", " (radio edit)",
+		" (feat.", " (ft.", " feat.", " ft.",
+	}
+	for _, suffix := range suffixes {
+		if idx := strings.Index(s, suffix); idx != -1 {
+			s = s[:idx]
+		}
+	}
+
+	// Remove special characters
+	var result strings.Builder
+	for _, r := range s {
+		if (r >= 'a' && r <= 'z') || (r >= '0' && r <= '9') || r == ' ' {
+			result.WriteRune(r)
+		}
+	}
+
+	// Collapse multiple spaces
+	s = strings.Join(strings.Fields(result.String()), " ")
+
+	return strings.TrimSpace(s)
+}

go_backend/extension_runtime_polyfills.go

@@ -0,0 +1,488 @@
+// Package gobackend provides Browser-like Polyfills for extension runtime
+package gobackend
+
+import (
+	"encoding/base64"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+	"strings"
+
+	"github.com/dop251/goja"
+)
+
+// ==================== Browser-like Polyfills ====================
+// These polyfills make porting browser/Node.js libraries easier
+// without compromising sandbox security
+
+// fetchPolyfill implements browser-compatible fetch() API
+// Returns a Promise-like object with json(), text() methods
+func (r *ExtensionRuntime) fetchPolyfill(call goja.FunctionCall) goja.Value {
+	if len(call.Arguments) < 1 {
+		return r.createFetchError("URL is required")
+	}
+
+	urlStr := call.Arguments[0].String()
+
+	// Validate domain
+	if err := r.validateDomain(urlStr); err != nil {
+		GoLog("[Extension:%s] fetch blocked: %v\n", r.extensionID, err)
+		return r.createFetchError(err.Error())
+	}
+
+	// Parse options
+	method := "GET"
+	var bodyStr string
+	headers := make(map[string]string)
+
+	if len(call.Arguments) > 1 && !goja.IsUndefined(call.Arguments[1]) && !goja.IsNull(call.Arguments[1]) {
+		optionsObj := call.Arguments[1].Export()
+		if opts, ok := optionsObj.(map[string]interface{}); ok {
+			// Method
+			if m, ok := opts["method"].(string); ok {
+				method = strings.ToUpper(m)
+			}
+
+			// Body - support string, object (auto-stringify), or nil
+			if bodyArg, ok := opts["body"]; ok && bodyArg != nil {
+				switch v := bodyArg.(type) {
+				case string:
+					bodyStr = v
+				case map[string]interface{}, []interface{}:
+					jsonBytes, err := json.Marshal(v)
+					if err != nil {
+						return r.createFetchError(fmt.Sprintf("failed to stringify body: %v", err))
+					}
+					bodyStr = string(jsonBytes)
+				default:
+					bodyStr = fmt.Sprintf("%v", v)
+				}
+			}
+
+			// Headers
+			if h, ok := opts["headers"]; ok && h != nil {
+				switch hv := h.(type) {
+				case map[string]interface{}:
+					for k, v := range hv {
+						headers[k] = fmt.Sprintf("%v", v)
+					}
+				}
+			}
+		}
+	}
+
+	// Create HTTP request
+	var reqBody io.Reader
+	if bodyStr != "" {
+		reqBody = strings.NewReader(bodyStr)
+	}
+
+	req, err := http.NewRequest(method, urlStr, reqBody)
+	if err != nil {
+		return r.createFetchError(err.Error())
+	}
+
+	// Set headers - user headers first
+	for k, v := range headers {
+		req.Header.Set(k, v)
+	}
+	// Set defaults if not provided
+	if req.Header.Get("User-Agent") == "" {
+		req.Header.Set("User-Agent", "SpotiFLAC-Extension/1.0")
+	}
+	if bodyStr != "" && req.Header.Get("Content-Type") == "" {
+		req.Header.Set("Content-Type", "application/json")
+	}
+
+	// Execute request
+	resp, err := r.httpClient.Do(req)
+	if err != nil {
+		return r.createFetchError(err.Error())
+	}
+	defer resp.Body.Close()
+
+	// Read body
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return r.createFetchError(err.Error())
+	}
+
+	// Extract response headers
+	respHeaders := make(map[string]interface{})
+	for k, v := range resp.Header {
+		if len(v) == 1 {
+			respHeaders[k] = v[0]
+		} else {
+			respHeaders[k] = v
+		}
+	}
+
+	// Create Response object (browser-compatible)
+	responseObj := r.vm.NewObject()
+	responseObj.Set("ok", resp.StatusCode >= 200 && resp.StatusCode < 300)
+	responseObj.Set("status", resp.StatusCode)
+	responseObj.Set("statusText", http.StatusText(resp.StatusCode))
+	responseObj.Set("headers", respHeaders)
+	responseObj.Set("url", urlStr)
+
+	// Store body for methods
+	bodyString := string(body)
+
+	// text() method - returns body as string
+	responseObj.Set("text", func(call goja.FunctionCall) goja.Value {
+		return r.vm.ToValue(bodyString)
+	})
+
+	// json() method - parses body as JSON
+	responseObj.Set("json", func(call goja.FunctionCall) goja.Value {
+		var result interface{}
+		if err := json.Unmarshal(body, &result); err != nil {
+			GoLog("[Extension:%s] fetch json() parse error: %v\n", r.extensionID, err)
+			return goja.Undefined()
+		}
+		return r.vm.ToValue(result)
+	})
+
+	// arrayBuffer() method - returns body as array (simplified)
+	responseObj.Set("arrayBuffer", func(call goja.FunctionCall) goja.Value {
+		// Return as array of bytes
+		byteArray := make([]interface{}, len(body))
+		for i, b := range body {
+			byteArray[i] = int(b)
+		}
+		return r.vm.ToValue(byteArray)
+	})
+
+	return responseObj
+}
+
+// createFetchError creates a fetch error response
+func (r *ExtensionRuntime) createFetchError(message string) goja.Value {
+	errorObj := r.vm.NewObject()
+	errorObj.Set("ok", false)
+	errorObj.Set("status", 0)
+	errorObj.Set("statusText", "Network Error")
+	errorObj.Set("error", message)
+	errorObj.Set("text", func(call goja.FunctionCall) goja.Value {
+		return r.vm.ToValue("")
+	})
+	errorObj.Set("json", func(call goja.FunctionCall) goja.Value {
+		return goja.Undefined()
+	})
+	return errorObj
+}
+
+// atobPolyfill implements browser atob() - decode base64 to string
+func (r *ExtensionRuntime) atobPolyfill(call goja.FunctionCall) goja.Value {
+	if len(call.Arguments) < 1 {
+		return r.vm.ToValue("")
+	}
+	input := call.Arguments[0].String()
+	decoded, err := base64.StdEncoding.DecodeString(input)
+	if err != nil {
+		// Try URL-safe base64
+		decoded, err = base64.URLEncoding.DecodeString(input)
+		if err != nil {
+			GoLog("[Extension:%s] atob decode error: %v\n", r.extensionID, err)
+			return r.vm.ToValue("")
+		}
+	}
+	return r.vm.ToValue(string(decoded))
+}
+
+// btoaPolyfill implements browser btoa() - encode string to base64
+func (r *ExtensionRuntime) btoaPolyfill(call goja.FunctionCall) goja.Value {
+	if len(call.Arguments) < 1 {
+		return r.vm.ToValue("")
+	}
+	input := call.Arguments[0].String()
+	return r.vm.ToValue(base64.StdEncoding.EncodeToString([]byte(input)))
+}
+
+// registerTextEncoderDecoder registers TextEncoder and TextDecoder classes
+func (r *ExtensionRuntime) registerTextEncoderDecoder(vm *goja.Runtime) {
+	// TextEncoder constructor
+	vm.Set("TextEncoder", func(call goja.ConstructorCall) *goja.Object {
+		encoder := call.This
+		encoder.Set("encoding", "utf-8")
+
+		// encode() method - string to Uint8Array
+		encoder.Set("encode", func(call goja.FunctionCall) goja.Value {
+			if len(call.Arguments) < 1 {
+				return vm.ToValue([]byte{})
+			}
+			input := call.Arguments[0].String()
+			bytes := []byte(input)
+
+			// Return as array (Uint8Array-like)
+			result := make([]interface{}, len(bytes))
+			for i, b := range bytes {
+				result[i] = int(b)
+			}
+			return vm.ToValue(result)
+		})
+
+		// encodeInto() method
+		encoder.Set("encodeInto", func(call goja.FunctionCall) goja.Value {
+			// Simplified implementation
+			if len(call.Arguments) < 2 {
+				return vm.ToValue(map[string]interface{}{"read": 0, "written": 0})
+			}
+			input := call.Arguments[0].String()
+			return vm.ToValue(map[string]interface{}{
+				"read":    len(input),
+				"written": len([]byte(input)),
+			})
+		})
+
+		return nil
+	})
+
+	// TextDecoder constructor
+	vm.Set("TextDecoder", func(call goja.ConstructorCall) *goja.Object {
+		decoder := call.This
+
+		// Get encoding from arguments (default: utf-8)
+		encoding := "utf-8"
+		if len(call.Arguments) > 0 && !goja.IsUndefined(call.Arguments[0]) {
+			encoding = call.Arguments[0].String()
+		}
+		decoder.Set("encoding", encoding)
+		decoder.Set("fatal", false)
+		decoder.Set("ignoreBOM", false)
+
+		// decode() method - Uint8Array to string
+		decoder.Set("decode", func(call goja.FunctionCall) goja.Value {
+			if len(call.Arguments) < 1 {
+				return vm.ToValue("")
+			}
+
+			// Handle different input types
+			input := call.Arguments[0].Export()
+			var bytes []byte
+
+			switch v := input.(type) {
+			case []byte:
+				bytes = v
+			case []interface{}:
+				bytes = make([]byte, len(v))
+				for i, val := range v {
+					switch n := val.(type) {
+					case int64:
+						bytes[i] = byte(n)
+					case float64:
+						bytes[i] = byte(n)
+					case int:
+						bytes[i] = byte(n)
+					}
+				}
+			case string:
+				// Already a string, just return it
+				return vm.ToValue(v)
+			default:
+				return vm.ToValue("")
+			}
+
+			return vm.ToValue(string(bytes))
+		})
+
+		return nil
+	})
+}
+
+// registerURLClass registers the URL class for URL parsing
+func (r *ExtensionRuntime) registerURLClass(vm *goja.Runtime) {
+	vm.Set("URL", func(call goja.ConstructorCall) *goja.Object {
+		urlObj := call.This
+
+		if len(call.Arguments) < 1 {
+			urlObj.Set("href", "")
+			return nil
+		}
+
+		urlStr := call.Arguments[0].String()
+
+		// Handle relative URLs with base
+		if len(call.Arguments) > 1 && !goja.IsUndefined(call.Arguments[1]) {
+			baseStr := call.Arguments[1].String()
+			baseURL, err := url.Parse(baseStr)
+			if err == nil {
+				relURL, err := url.Parse(urlStr)
+				if err == nil {
+					urlStr = baseURL.ResolveReference(relURL).String()
+				}
+			}
+		}
+
+		parsed, err := url.Parse(urlStr)
+		if err != nil {
+			urlObj.Set("href", urlStr)
+			return nil
+		}
+
+		// Set URL properties
+		urlObj.Set("href", parsed.String())
+		urlObj.Set("protocol", parsed.Scheme+":")
+		urlObj.Set("host", parsed.Host)
+		urlObj.Set("hostname", parsed.Hostname())
+		urlObj.Set("port", parsed.Port())
+		urlObj.Set("pathname", parsed.Path)
+		urlObj.Set("search", "")
+		if parsed.RawQuery != "" {
+			urlObj.Set("search", "?"+parsed.RawQuery)
+		}
+		urlObj.Set("hash", "")
+		if parsed.Fragment != "" {
+			urlObj.Set("hash", "#"+parsed.Fragment)
+		}
+		urlObj.Set("origin", parsed.Scheme+"://"+parsed.Host)
+		urlObj.Set("username", parsed.User.Username())
+		password, _ := parsed.User.Password()
+		urlObj.Set("password", password)
+
+		// searchParams object
+		searchParams := vm.NewObject()
+		queryValues := parsed.Query()
+
+		searchParams.Set("get", func(call goja.FunctionCall) goja.Value {
+			if len(call.Arguments) < 1 {
+				return goja.Null()
+			}
+			key := call.Arguments[0].String()
+			if val := queryValues.Get(key); val != "" {
+				return vm.ToValue(val)
+			}
+			return goja.Null()
+		})
+
+		searchParams.Set("getAll", func(call goja.FunctionCall) goja.Value {
+			if len(call.Arguments) < 1 {
+				return vm.ToValue([]string{})
+			}
+			key := call.Arguments[0].String()
+			return vm.ToValue(queryValues[key])
+		})
+
+		searchParams.Set("has", func(call goja.FunctionCall) goja.Value {
+			if len(call.Arguments) < 1 {
+				return vm.ToValue(false)
+			}
+			key := call.Arguments[0].String()
+			return vm.ToValue(queryValues.Has(key))
+		})
+
+		searchParams.Set("toString", func(call goja.FunctionCall) goja.Value {
+			return vm.ToValue(queryValues.Encode())
+		})
+
+		urlObj.Set("searchParams", searchParams)
+
+		// toString method
+		urlObj.Set("toString", func(call goja.FunctionCall) goja.Value {
+			return vm.ToValue(parsed.String())
+		})
+
+		// toJSON method
+		urlObj.Set("toJSON", func(call goja.FunctionCall) goja.Value {
+			return vm.ToValue(parsed.String())
+		})
+
+		return nil
+	})
+
+	// URLSearchParams constructor
+	vm.Set("URLSearchParams", func(call goja.ConstructorCall) *goja.Object {
+		paramsObj := call.This
+		values := url.Values{}
+
+		// Parse initial value if provided
+		if len(call.Arguments) > 0 && !goja.IsUndefined(call.Arguments[0]) {
+			init := call.Arguments[0].Export()
+			switch v := init.(type) {
+			case string:
+				// Parse query string
+				parsed, _ := url.ParseQuery(strings.TrimPrefix(v, "?"))
+				values = parsed
+			case map[string]interface{}:
+				for k, val := range v {
+					values.Set(k, fmt.Sprintf("%v", val))
+				}
+			}
+		}
+
+		paramsObj.Set("append", func(call goja.FunctionCall) goja.Value {
+			if len(call.Arguments) >= 2 {
+				values.Add(call.Arguments[0].String(), call.Arguments[1].String())
+			}
+			return goja.Undefined()
+		})
+
+		paramsObj.Set("delete", func(call goja.FunctionCall) goja.Value {
+			if len(call.Arguments) >= 1 {
+				values.Del(call.Arguments[0].String())
+			}
+			return goja.Undefined()
+		})
+
+		paramsObj.Set("get", func(call goja.FunctionCall) goja.Value {
+			if len(call.Arguments) < 1 {
+				return goja.Null()
+			}
+			if val := values.Get(call.Arguments[0].String()); val != "" {
+				return vm.ToValue(val)
+			}
+			return goja.Null()
+		})
+
+		paramsObj.Set("getAll", func(call goja.FunctionCall) goja.Value {
+			if len(call.Arguments) < 1 {
+				return vm.ToValue([]string{})
+			}
+			return vm.ToValue(values[call.Arguments[0].String()])
+		})
+
+		paramsObj.Set("has", func(call goja.FunctionCall) goja.Value {
+			if len(call.Arguments) < 1 {
+				return vm.ToValue(false)
+			}
+			return vm.ToValue(values.Has(call.Arguments[0].String()))
+		})
+
+		paramsObj.Set("set", func(call goja.FunctionCall) goja.Value {
+			if len(call.Arguments) >= 2 {
+				values.Set(call.Arguments[0].String(), call.Arguments[1].String())
+			}
+			return goja.Undefined()
+		})
+
+		paramsObj.Set("toString", func(call goja.FunctionCall) goja.Value {
+			return vm.ToValue(values.Encode())
+		})
+
+		return nil
+	})
+}
+
+// registerJSONGlobal ensures JSON global is properly set up
+func (r *ExtensionRuntime) registerJSONGlobal(vm *goja.Runtime) {
+	// JSON is already built-in to Goja, but we can enhance it
+	// This ensures JSON.parse and JSON.stringify work as expected
+
+	// The built-in JSON object should already work, but let's verify
+	// and add any missing functionality if needed
+	jsonScript := `
+		if (typeof JSON === 'undefined') {
+			var JSON = {
+				parse: function(text) {
+					return utils.parseJSON(text);
+				},
+				stringify: function(value, replacer, space) {
+					return utils.stringifyJSON(value);
+				}
+			};
+		}
+	`
+	_, _ = vm.RunString(jsonScript)
+}

go_backend/extension_runtime_storage.go

@@ -0,0 +1,339 @@
+// Package gobackend provides Storage and Credentials API for extension runtime
+package gobackend
+
+import (
+	"crypto/aes"
+	"crypto/cipher"
+	"crypto/rand"
+	"crypto/sha256"
+	"encoding/json"
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+
+	"github.com/dop251/goja"
+)
+
+// ==================== Storage API ====================
+
+// getStoragePath returns the path to the extension's storage file
+func (r *ExtensionRuntime) getStoragePath() string {
+	return filepath.Join(r.dataDir, "storage.json")
+}
+
+// loadStorage loads the storage data from disk
+func (r *ExtensionRuntime) loadStorage() (map[string]interface{}, error) {
+	storagePath := r.getStoragePath()
+	data, err := os.ReadFile(storagePath)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return make(map[string]interface{}), nil
+		}
+		return nil, err
+	}
+
+	var storage map[string]interface{}
+	if err := json.Unmarshal(data, &storage); err != nil {
+		return nil, err
+	}
+
+	return storage, nil
+}
+
+// saveStorage saves the storage data to disk
+func (r *ExtensionRuntime) saveStorage(storage map[string]interface{}) error {
+	storagePath := r.getStoragePath()
+	data, err := json.MarshalIndent(storage, "", "  ")
+	if err != nil {
+		return err
+	}
+
+	return os.WriteFile(storagePath, data, 0644)
+}
+
+// storageGet retrieves a value from storage
+func (r *ExtensionRuntime) storageGet(call goja.FunctionCall) goja.Value {
+	if len(call.Arguments) < 1 {
+		return goja.Undefined()
+	}
+
+	key := call.Arguments[0].String()
+
+	storage, err := r.loadStorage()
+	if err != nil {
+		GoLog("[Extension:%s] Storage load error: %v\n", r.extensionID, err)
+		return goja.Undefined()
+	}
+
+	value, exists := storage[key]
+	if !exists {
+		// Return default value if provided
+		if len(call.Arguments) > 1 {
+			return call.Arguments[1]
+		}
+		return goja.Undefined()
+	}
+
+	return r.vm.ToValue(value)
+}
+
+// storageSet stores a value in storage
+func (r *ExtensionRuntime) storageSet(call goja.FunctionCall) goja.Value {
+	if len(call.Arguments) < 2 {
+		return r.vm.ToValue(false)
+	}
+
+	key := call.Arguments[0].String()
+	value := call.Arguments[1].Export()
+
+	storage, err := r.loadStorage()
+	if err != nil {
+		GoLog("[Extension:%s] Storage load error: %v\n", r.extensionID, err)
+		return r.vm.ToValue(false)
+	}
+
+	storage[key] = value
+
+	if err := r.saveStorage(storage); err != nil {
+		GoLog("[Extension:%s] Storage save error: %v\n", r.extensionID, err)
+		return r.vm.ToValue(false)
+	}
+
+	return r.vm.ToValue(true)
+}
+
+// storageRemove removes a value from storage
+func (r *ExtensionRuntime) storageRemove(call goja.FunctionCall) goja.Value {
+	if len(call.Arguments) < 1 {
+		return r.vm.ToValue(false)
+	}
+
+	key := call.Arguments[0].String()
+
+	storage, err := r.loadStorage()
+	if err != nil {
+		GoLog("[Extension:%s] Storage load error: %v\n", r.extensionID, err)
+		return r.vm.ToValue(false)
+	}
+
+	delete(storage, key)
+
+	if err := r.saveStorage(storage); err != nil {
+		GoLog("[Extension:%s] Storage save error: %v\n", r.extensionID, err)
+		return r.vm.ToValue(false)
+	}
+
+	return r.vm.ToValue(true)
+}
+
+// ==================== Credentials API (Encrypted Storage) ====================
+
+// getCredentialsPath returns the path to the extension's encrypted credentials file
+func (r *ExtensionRuntime) getCredentialsPath() string {
+	return filepath.Join(r.dataDir, ".credentials.enc")
+}
+
+// getEncryptionKey derives an encryption key from extension ID
+func (r *ExtensionRuntime) getEncryptionKey() []byte {
+	// Use SHA256 of extension ID + salt as encryption key
+	salt := "spotiflac-ext-cred-v1"
+	hash := sha256.Sum256([]byte(r.extensionID + salt))
+	return hash[:]
+}
+
+// loadCredentials loads and decrypts credentials from disk
+func (r *ExtensionRuntime) loadCredentials() (map[string]interface{}, error) {
+	credPath := r.getCredentialsPath()
+	data, err := os.ReadFile(credPath)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return make(map[string]interface{}), nil
+		}
+		return nil, err
+	}
+
+	// Decrypt the data
+	key := r.getEncryptionKey()
+	decrypted, err := decryptAES(data, key)
+	if err != nil {
+		return nil, fmt.Errorf("failed to decrypt credentials: %w", err)
+	}
+
+	var creds map[string]interface{}
+	if err := json.Unmarshal(decrypted, &creds); err != nil {
+		return nil, err
+	}
+
+	return creds, nil
+}
+
+// saveCredentials encrypts and saves credentials to disk
+func (r *ExtensionRuntime) saveCredentials(creds map[string]interface{}) error {
+	data, err := json.Marshal(creds)
+	if err != nil {
+		return err
+	}
+
+	// Encrypt the data
+	key := r.getEncryptionKey()
+	encrypted, err := encryptAES(data, key)
+	if err != nil {
+		return fmt.Errorf("failed to encrypt credentials: %w", err)
+	}
+
+	credPath := r.getCredentialsPath()
+	return os.WriteFile(credPath, encrypted, 0600) // Restrictive permissions
+}
+
+// credentialsStore stores an encrypted credential
+func (r *ExtensionRuntime) credentialsStore(call goja.FunctionCall) goja.Value {
+	if len(call.Arguments) < 2 {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   "key and value are required",
+		})
+	}
+
+	key := call.Arguments[0].String()
+	value := call.Arguments[1].Export()
+
+	creds, err := r.loadCredentials()
+	if err != nil {
+		GoLog("[Extension:%s] Credentials load error: %v\n", r.extensionID, err)
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+
+	creds[key] = value
+
+	if err := r.saveCredentials(creds); err != nil {
+		GoLog("[Extension:%s] Credentials save error: %v\n", r.extensionID, err)
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+
+	return r.vm.ToValue(map[string]interface{}{
+		"success": true,
+	})
+}
+
+// credentialsGet retrieves a decrypted credential
+func (r *ExtensionRuntime) credentialsGet(call goja.FunctionCall) goja.Value {
+	if len(call.Arguments) < 1 {
+		return goja.Undefined()
+	}
+
+	key := call.Arguments[0].String()
+
+	creds, err := r.loadCredentials()
+	if err != nil {
+		GoLog("[Extension:%s] Credentials load error: %v\n", r.extensionID, err)
+		return goja.Undefined()
+	}
+
+	value, exists := creds[key]
+	if !exists {
+		// Return default value if provided
+		if len(call.Arguments) > 1 {
+			return call.Arguments[1]
+		}
+		return goja.Undefined()
+	}
+
+	return r.vm.ToValue(value)
+}
+
+// credentialsRemove removes a credential
+func (r *ExtensionRuntime) credentialsRemove(call goja.FunctionCall) goja.Value {
+	if len(call.Arguments) < 1 {
+		return r.vm.ToValue(false)
+	}
+
+	key := call.Arguments[0].String()
+
+	creds, err := r.loadCredentials()
+	if err != nil {
+		GoLog("[Extension:%s] Credentials load error: %v\n", r.extensionID, err)
+		return r.vm.ToValue(false)
+	}
+
+	delete(creds, key)
+
+	if err := r.saveCredentials(creds); err != nil {
+		GoLog("[Extension:%s] Credentials save error: %v\n", r.extensionID, err)
+		return r.vm.ToValue(false)
+	}
+
+	return r.vm.ToValue(true)
+}
+
+// credentialsHas checks if a credential exists
+func (r *ExtensionRuntime) credentialsHas(call goja.FunctionCall) goja.Value {
+	if len(call.Arguments) < 1 {
+		return r.vm.ToValue(false)
+	}
+
+	key := call.Arguments[0].String()
+
+	creds, err := r.loadCredentials()
+	if err != nil {
+		return r.vm.ToValue(false)
+	}
+
+	_, exists := creds[key]
+	return r.vm.ToValue(exists)
+}
+
+// ==================== Crypto Utilities ====================
+
+// encryptAES encrypts data using AES-GCM
+func encryptAES(plaintext []byte, key []byte) ([]byte, error) {
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		return nil, err
+	}
+
+	gcm, err := cipher.NewGCM(block)
+	if err != nil {
+		return nil, err
+	}
+
+	nonce := make([]byte, gcm.NonceSize())
+	if _, err := io.ReadFull(rand.Reader, nonce); err != nil {
+		return nil, err
+	}
+
+	ciphertext := gcm.Seal(nonce, nonce, plaintext, nil)
+	return ciphertext, nil
+}
+
+// decryptAES decrypts data using AES-GCM
+func decryptAES(ciphertext []byte, key []byte) ([]byte, error) {
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		return nil, err
+	}
+
+	gcm, err := cipher.NewGCM(block)
+	if err != nil {
+		return nil, err
+	}
+
+	nonceSize := gcm.NonceSize()
+	if len(ciphertext) < nonceSize {
+		return nil, fmt.Errorf("ciphertext too short")
+	}
+
+	nonce, ciphertext := ciphertext[:nonceSize], ciphertext[nonceSize:]
+	plaintext, err := gcm.Open(nil, nonce, ciphertext, nil)
+	if err != nil {
+		return nil, err
+	}
+
+	return plaintext, nil
+}

go_backend/extension_runtime_utils.go

@@ -0,0 +1,372 @@
+// Package gobackend provides Utility functions for extension runtime
+package gobackend
+
+import (
+	"crypto/hmac"
+	"crypto/md5"
+	"crypto/rand"
+	"crypto/sha1"
+	"crypto/sha256"
+	"encoding/base64"
+	"encoding/hex"
+	"encoding/json"
+	"fmt"
+	"strings"
+
+	"github.com/dop251/goja"
+)
+
+// ==================== Utility Functions ====================
+
+// base64Encode encodes a string to base64
+func (r *ExtensionRuntime) base64Encode(call goja.FunctionCall) goja.Value {
+	if len(call.Arguments) < 1 {
+		return r.vm.ToValue("")
+	}
+	input := call.Arguments[0].String()
+	return r.vm.ToValue(base64.StdEncoding.EncodeToString([]byte(input)))
+}
+
+// base64Decode decodes a base64 string
+func (r *ExtensionRuntime) base64Decode(call goja.FunctionCall) goja.Value {
+	if len(call.Arguments) < 1 {
+		return r.vm.ToValue("")
+	}
+	input := call.Arguments[0].String()
+	decoded, err := base64.StdEncoding.DecodeString(input)
+	if err != nil {
+		return r.vm.ToValue("")
+	}
+	return r.vm.ToValue(string(decoded))
+}
+
+// md5Hash computes MD5 hash of a string
+func (r *ExtensionRuntime) md5Hash(call goja.FunctionCall) goja.Value {
+	if len(call.Arguments) < 1 {
+		return r.vm.ToValue("")
+	}
+	input := call.Arguments[0].String()
+	hash := md5.Sum([]byte(input))
+	return r.vm.ToValue(hex.EncodeToString(hash[:]))
+}
+
+// sha256Hash computes SHA256 hash of a string
+func (r *ExtensionRuntime) sha256Hash(call goja.FunctionCall) goja.Value {
+	if len(call.Arguments) < 1 {
+		return r.vm.ToValue("")
+	}
+	input := call.Arguments[0].String()
+	hash := sha256.Sum256([]byte(input))
+	return r.vm.ToValue(hex.EncodeToString(hash[:]))
+}
+
+// hmacSHA256 computes HMAC-SHA256 of a message with a key
+func (r *ExtensionRuntime) hmacSHA256(call goja.FunctionCall) goja.Value {
+	if len(call.Arguments) < 2 {
+		return r.vm.ToValue("")
+	}
+	message := call.Arguments[0].String()
+	key := call.Arguments[1].String()
+
+	mac := hmac.New(sha256.New, []byte(key))
+	mac.Write([]byte(message))
+	return r.vm.ToValue(hex.EncodeToString(mac.Sum(nil)))
+}
+
+// hmacSHA256Base64 computes HMAC-SHA256 and returns base64 encoded result
+func (r *ExtensionRuntime) hmacSHA256Base64(call goja.FunctionCall) goja.Value {
+	if len(call.Arguments) < 2 {
+		return r.vm.ToValue("")
+	}
+	message := call.Arguments[0].String()
+	key := call.Arguments[1].String()
+
+	mac := hmac.New(sha256.New, []byte(key))
+	mac.Write([]byte(message))
+	return r.vm.ToValue(base64.StdEncoding.EncodeToString(mac.Sum(nil)))
+}
+
+// hmacSHA1 computes HMAC-SHA1 of a message with a key (for TOTP)
+// Arguments: message (string or array of bytes), key (string or array of bytes)
+// Returns: array of bytes (for TOTP dynamic truncation)
+func (r *ExtensionRuntime) hmacSHA1(call goja.FunctionCall) goja.Value {
+	if len(call.Arguments) < 2 {
+		return r.vm.ToValue([]byte{})
+	}
+
+	// Get key - can be string or array of bytes
+	var keyBytes []byte
+	keyArg := call.Arguments[0].Export()
+	switch k := keyArg.(type) {
+	case string:
+		keyBytes = []byte(k)
+	case []interface{}:
+		keyBytes = make([]byte, len(k))
+		for i, v := range k {
+			if num, ok := v.(int64); ok {
+				keyBytes[i] = byte(num)
+			} else if num, ok := v.(float64); ok {
+				keyBytes[i] = byte(int(num))
+			}
+		}
+	default:
+		return r.vm.ToValue([]byte{})
+	}
+
+	// Get message - can be string or array of bytes
+	var msgBytes []byte
+	msgArg := call.Arguments[1].Export()
+	switch m := msgArg.(type) {
+	case string:
+		msgBytes = []byte(m)
+	case []interface{}:
+		msgBytes = make([]byte, len(m))
+		for i, v := range m {
+			if num, ok := v.(int64); ok {
+				msgBytes[i] = byte(num)
+			} else if num, ok := v.(float64); ok {
+				msgBytes[i] = byte(int(num))
+			}
+		}
+	default:
+		return r.vm.ToValue([]byte{})
+	}
+
+	mac := hmac.New(sha1.New, keyBytes)
+	mac.Write(msgBytes)
+	result := mac.Sum(nil)
+
+	// Convert to array of numbers for JavaScript
+	jsArray := make([]interface{}, len(result))
+	for i, b := range result {
+		jsArray[i] = int(b)
+	}
+	return r.vm.ToValue(jsArray)
+}
+
+// parseJSON parses a JSON string
+func (r *ExtensionRuntime) parseJSON(call goja.FunctionCall) goja.Value {
+	if len(call.Arguments) < 1 {
+		return goja.Undefined()
+	}
+	input := call.Arguments[0].String()
+
+	var result interface{}
+	if err := json.Unmarshal([]byte(input), &result); err != nil {
+		GoLog("[Extension:%s] JSON parse error: %v\n", r.extensionID, err)
+		return goja.Undefined()
+	}
+
+	return r.vm.ToValue(result)
+}
+
+// stringifyJSON converts a value to JSON string
+func (r *ExtensionRuntime) stringifyJSON(call goja.FunctionCall) goja.Value {
+	if len(call.Arguments) < 1 {
+		return r.vm.ToValue("")
+	}
+	input := call.Arguments[0].Export()
+
+	data, err := json.Marshal(input)
+	if err != nil {
+		GoLog("[Extension:%s] JSON stringify error: %v\n", r.extensionID, err)
+		return r.vm.ToValue("")
+	}
+
+	return r.vm.ToValue(string(data))
+}
+
+// ==================== Crypto Utilities for Extensions ====================
+
+// cryptoEncrypt encrypts a string using AES-GCM (for extension use)
+func (r *ExtensionRuntime) cryptoEncrypt(call goja.FunctionCall) goja.Value {
+	if len(call.Arguments) < 2 {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   "plaintext and key are required",
+		})
+	}
+
+	plaintext := call.Arguments[0].String()
+	keyStr := call.Arguments[1].String()
+
+	// Derive 32-byte key from provided key string
+	keyHash := sha256.Sum256([]byte(keyStr))
+
+	encrypted, err := encryptAES([]byte(plaintext), keyHash[:])
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+
+	return r.vm.ToValue(map[string]interface{}{
+		"success": true,
+		"data":    base64.StdEncoding.EncodeToString(encrypted),
+	})
+}
+
+// cryptoDecrypt decrypts a string using AES-GCM (for extension use)
+func (r *ExtensionRuntime) cryptoDecrypt(call goja.FunctionCall) goja.Value {
+	if len(call.Arguments) < 2 {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   "ciphertext and key are required",
+		})
+	}
+
+	ciphertextB64 := call.Arguments[0].String()
+	keyStr := call.Arguments[1].String()
+
+	ciphertext, err := base64.StdEncoding.DecodeString(ciphertextB64)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   "invalid base64 ciphertext",
+		})
+	}
+
+	// Derive 32-byte key from provided key string
+	keyHash := sha256.Sum256([]byte(keyStr))
+
+	decrypted, err := decryptAES(ciphertext, keyHash[:])
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+
+	return r.vm.ToValue(map[string]interface{}{
+		"success": true,
+		"data":    string(decrypted),
+	})
+}
+
+// cryptoGenerateKey generates a random encryption key
+func (r *ExtensionRuntime) cryptoGenerateKey(call goja.FunctionCall) goja.Value {
+	length := 32 // Default 256-bit key
+	if len(call.Arguments) > 0 && !goja.IsUndefined(call.Arguments[0]) {
+		if l, ok := call.Arguments[0].Export().(float64); ok {
+			length = int(l)
+		}
+	}
+
+	key := make([]byte, length)
+	if _, err := rand.Read(key); err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+
+	return r.vm.ToValue(map[string]interface{}{
+		"success": true,
+		"key":     base64.StdEncoding.EncodeToString(key),
+		"hex":     hex.EncodeToString(key),
+	})
+}
+
+// ==================== Logging Functions ====================
+
+func (r *ExtensionRuntime) logDebug(call goja.FunctionCall) goja.Value {
+	msg := r.formatLogArgs(call.Arguments)
+	GoLog("[Extension:%s:DEBUG] %s\n", r.extensionID, msg)
+	return goja.Undefined()
+}
+
+func (r *ExtensionRuntime) logInfo(call goja.FunctionCall) goja.Value {
+	msg := r.formatLogArgs(call.Arguments)
+	GoLog("[Extension:%s:INFO] %s\n", r.extensionID, msg)
+	return goja.Undefined()
+}
+
+func (r *ExtensionRuntime) logWarn(call goja.FunctionCall) goja.Value {
+	msg := r.formatLogArgs(call.Arguments)
+	GoLog("[Extension:%s:WARN] %s\n", r.extensionID, msg)
+	return goja.Undefined()
+}
+
+func (r *ExtensionRuntime) logError(call goja.FunctionCall) goja.Value {
+	msg := r.formatLogArgs(call.Arguments)
+	GoLog("[Extension:%s:ERROR] %s\n", r.extensionID, msg)
+	return goja.Undefined()
+}
+
+func (r *ExtensionRuntime) formatLogArgs(args []goja.Value) string {
+	parts := make([]string, len(args))
+	for i, arg := range args {
+		parts[i] = fmt.Sprintf("%v", arg.Export())
+	}
+	return strings.Join(parts, " ")
+}
+
+// ==================== Go Backend Wrappers ====================
+
+func (r *ExtensionRuntime) sanitizeFilenameWrapper(call goja.FunctionCall) goja.Value {
+	if len(call.Arguments) < 1 {
+		return r.vm.ToValue("")
+	}
+	input := call.Arguments[0].String()
+	return r.vm.ToValue(sanitizeFilename(input))
+}
+
+// RegisterGoBackendAPIs adds more Go backend functions to the VM
+func (r *ExtensionRuntime) RegisterGoBackendAPIs(vm *goja.Runtime) {
+	gobackendObj := vm.Get("gobackend")
+	if gobackendObj == nil || goja.IsUndefined(gobackendObj) {
+		gobackendObj = vm.NewObject()
+		vm.Set("gobackend", gobackendObj)
+	}
+
+	obj := gobackendObj.(*goja.Object)
+
+	// Expose sanitizeFilename
+	obj.Set("sanitizeFilename", func(call goja.FunctionCall) goja.Value {
+		if len(call.Arguments) < 1 {
+			return vm.ToValue("")
+		}
+		return vm.ToValue(sanitizeFilename(call.Arguments[0].String()))
+	})
+
+	// Expose getAudioQuality
+	obj.Set("getAudioQuality", func(call goja.FunctionCall) goja.Value {
+		if len(call.Arguments) < 1 {
+			return vm.ToValue(map[string]interface{}{
+				"error": "file path is required",
+			})
+		}
+
+		filePath := call.Arguments[0].String()
+		quality, err := GetAudioQuality(filePath)
+		if err != nil {
+			return vm.ToValue(map[string]interface{}{
+				"error": err.Error(),
+			})
+		}
+
+		return vm.ToValue(map[string]interface{}{
+			"bitDepth":     quality.BitDepth,
+			"sampleRate":   quality.SampleRate,
+			"totalSamples": quality.TotalSamples,
+		})
+	})
+
+	// Expose buildFilename
+	obj.Set("buildFilename", func(call goja.FunctionCall) goja.Value {
+		if len(call.Arguments) < 2 {
+			return vm.ToValue("")
+		}
+
+		template := call.Arguments[0].String()
+		metadataObj := call.Arguments[1].Export()
+
+		metadata, ok := metadataObj.(map[string]interface{})
+		if !ok {
+			return vm.ToValue("")
+		}
+
+		return vm.ToValue(buildFilenameFromTemplate(template, metadata))
+	})
+}

go_backend/extension_settings.go

@@ -0,0 +1,221 @@
+// Package gobackend provides extension settings storage
+package gobackend
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+	"path/filepath"
+	"sync"
+)
+
+// ExtensionSettingsStore manages settings for all extensions
+type ExtensionSettingsStore struct {
+	mu       sync.RWMutex
+	dataDir  string
+	settings map[string]map[string]interface{} // extensionID -> settings
+}
+
+// Global settings store
+var (
+	globalSettingsStore     *ExtensionSettingsStore
+	globalSettingsStoreOnce sync.Once
+)
+
+// GetExtensionSettingsStore returns the global settings store
+func GetExtensionSettingsStore() *ExtensionSettingsStore {
+	globalSettingsStoreOnce.Do(func() {
+		globalSettingsStore = &ExtensionSettingsStore{
+			settings: make(map[string]map[string]interface{}),
+		}
+	})
+	return globalSettingsStore
+}
+
+// SetDataDir sets the data directory for settings storage
+func (s *ExtensionSettingsStore) SetDataDir(dataDir string) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	s.dataDir = dataDir
+	if err := os.MkdirAll(dataDir, 0755); err != nil {
+		return fmt.Errorf("failed to create settings directory: %w", err)
+	}
+
+	// Load all existing settings
+	return s.loadAllSettings()
+}
+
+// getSettingsPath returns the path to an extension's settings file
+func (s *ExtensionSettingsStore) getSettingsPath(extensionID string) string {
+	return filepath.Join(s.dataDir, extensionID, "settings.json")
+}
+
+// loadAllSettings loads settings for all extensions from disk
+func (s *ExtensionSettingsStore) loadAllSettings() error {
+	entries, err := os.ReadDir(s.dataDir)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return nil
+		}
+		return err
+	}
+
+	for _, entry := range entries {
+		if entry.IsDir() {
+			extensionID := entry.Name()
+			settings, err := s.loadSettings(extensionID)
+			if err != nil {
+				GoLog("[ExtensionSettings] Failed to load settings for %s: %v\n", extensionID, err)
+				continue
+			}
+			s.settings[extensionID] = settings
+		}
+	}
+
+	return nil
+}
+
+// loadSettings loads settings for a specific extension
+func (s *ExtensionSettingsStore) loadSettings(extensionID string) (map[string]interface{}, error) {
+	settingsPath := s.getSettingsPath(extensionID)
+	data, err := os.ReadFile(settingsPath)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return make(map[string]interface{}), nil
+		}
+		return nil, err
+	}
+
+	var settings map[string]interface{}
+	if err := json.Unmarshal(data, &settings); err != nil {
+		return nil, err
+	}
+
+	return settings, nil
+}
+
+// saveSettings saves settings for a specific extension
+func (s *ExtensionSettingsStore) saveSettings(extensionID string, settings map[string]interface{}) error {
+	settingsPath := s.getSettingsPath(extensionID)
+
+	// Create directory if needed
+	dir := filepath.Dir(settingsPath)
+	if err := os.MkdirAll(dir, 0755); err != nil {
+		return err
+	}
+
+	data, err := json.MarshalIndent(settings, "", "  ")
+	if err != nil {
+		return err
+	}
+
+	return os.WriteFile(settingsPath, data, 0644)
+}
+
+// Get retrieves a setting value for an extension
+// Returns error if extension or key not found (gomobile compatible)
+func (s *ExtensionSettingsStore) Get(extensionID, key string) (interface{}, error) {
+	s.mu.RLock()
+	defer s.mu.RUnlock()
+
+	extSettings, exists := s.settings[extensionID]
+	if !exists {
+		return nil, fmt.Errorf("extension '%s' settings not found", extensionID)
+	}
+
+	value, exists := extSettings[key]
+	if !exists {
+		return nil, fmt.Errorf("setting '%s' not found for extension '%s'", key, extensionID)
+	}
+	return value, nil
+}
+
+// GetAll retrieves all settings for an extension
+func (s *ExtensionSettingsStore) GetAll(extensionID string) map[string]interface{} {
+	s.mu.RLock()
+	defer s.mu.RUnlock()
+
+	extSettings, exists := s.settings[extensionID]
+	if !exists {
+		return make(map[string]interface{})
+	}
+
+	// Return a copy
+	result := make(map[string]interface{})
+	for k, v := range extSettings {
+		result[k] = v
+	}
+	return result
+}
+
+// Set stores a setting value for an extension
+func (s *ExtensionSettingsStore) Set(extensionID, key string, value interface{}) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	if _, exists := s.settings[extensionID]; !exists {
+		s.settings[extensionID] = make(map[string]interface{})
+	}
+
+	s.settings[extensionID][key] = value
+
+	// Persist to disk
+	return s.saveSettings(extensionID, s.settings[extensionID])
+}
+
+// SetAll stores all settings for an extension
+func (s *ExtensionSettingsStore) SetAll(extensionID string, settings map[string]interface{}) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	s.settings[extensionID] = settings
+
+	// Persist to disk
+	return s.saveSettings(extensionID, settings)
+}
+
+// Remove removes a setting for an extension
+func (s *ExtensionSettingsStore) Remove(extensionID, key string) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	extSettings, exists := s.settings[extensionID]
+	if !exists {
+		return nil
+	}
+
+	delete(extSettings, key)
+
+	// Persist to disk
+	return s.saveSettings(extensionID, extSettings)
+}
+
+// RemoveAll removes all settings for an extension
+func (s *ExtensionSettingsStore) RemoveAll(extensionID string) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	delete(s.settings, extensionID)
+
+	// Remove settings file
+	settingsPath := s.getSettingsPath(extensionID)
+	if err := os.Remove(settingsPath); err != nil && !os.IsNotExist(err) {
+		return err
+	}
+
+	return nil
+}
+
+// GetAllExtensionSettings returns settings for all extensions as JSON
+func (s *ExtensionSettingsStore) GetAllExtensionSettingsJSON() (string, error) {
+	s.mu.RLock()
+	defer s.mu.RUnlock()
+
+	data, err := json.Marshal(s.settings)
+	if err != nil {
+		return "", err
+	}
+
+	return string(data), nil
+}

go_backend/extension_store.go

@@ -0,0 +1,453 @@
+package gobackend
+
+import (
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"os"
+	"path/filepath"
+	"sync"
+	"time"
+)
+
+// Extension categories
+const (
+	CategoryMetadata    = "metadata"
+	CategoryDownload    = "download"
+	CategoryUtility     = "utility"
+	CategoryLyrics      = "lyrics"
+	CategoryIntegration = "integration"
+)
+
+// StoreExtension represents an extension in the store
+type StoreExtension struct {
+	ID            string   `json:"id"`
+	Name          string   `json:"name"`
+	DisplayName   string   `json:"display_name,omitempty"`
+	Version       string   `json:"version"`
+	Author        string   `json:"author"`
+	Description   string   `json:"description"`
+	DownloadURL   string   `json:"download_url,omitempty"`
+	IconURL       string   `json:"icon_url,omitempty"`
+	Category      string   `json:"category"`
+	Tags          []string `json:"tags,omitempty"`
+	Downloads     int      `json:"downloads"`
+	UpdatedAt     string   `json:"updated_at"`
+	MinAppVersion string   `json:"min_app_version,omitempty"`
+	// Alternative camelCase fields (for flexibility)
+	DisplayNameAlt   string `json:"displayName,omitempty"`
+	DownloadURLAlt   string `json:"downloadUrl,omitempty"`
+	IconURLAlt       string `json:"iconUrl,omitempty"`
+	MinAppVersionAlt string `json:"minAppVersion,omitempty"`
+}
+
+// getDisplayName returns display name, falling back to name (private to avoid gomobile conflict)
+func (e *StoreExtension) getDisplayName() string {
+	if e.DisplayName != "" {
+		return e.DisplayName
+	}
+	if e.DisplayNameAlt != "" {
+		return e.DisplayNameAlt
+	}
+	return e.Name
+}
+
+// getDownloadURL returns download URL from either field (private to avoid gomobile conflict)
+func (e *StoreExtension) getDownloadURL() string {
+	if e.DownloadURL != "" {
+		return e.DownloadURL
+	}
+	return e.DownloadURLAlt
+}
+
+// getIconURL returns icon URL from either field (private to avoid gomobile conflict)
+func (e *StoreExtension) getIconURL() string {
+	if e.IconURL != "" {
+		return e.IconURL
+	}
+	return e.IconURLAlt
+}
+
+// getMinAppVersion returns min app version from either field (private to avoid gomobile conflict)
+func (e *StoreExtension) getMinAppVersion() string {
+	if e.MinAppVersion != "" {
+		return e.MinAppVersion
+	}
+	return e.MinAppVersionAlt
+}
+
+// StoreRegistry represents the extension registry
+type StoreRegistry struct {
+	Version    int              `json:"version"`
+	UpdatedAt  string           `json:"updated_at"`
+	Extensions []StoreExtension `json:"extensions"`
+}
+
+// StoreExtensionResponse is the normalized response sent to Flutter
+type StoreExtensionResponse struct {
+	ID               string   `json:"id"`
+	Name             string   `json:"name"`
+	DisplayName      string   `json:"display_name"`
+	Version          string   `json:"version"`
+	Author           string   `json:"author"`
+	Description      string   `json:"description"`
+	DownloadURL      string   `json:"download_url"`
+	IconURL          string   `json:"icon_url,omitempty"`
+	Category         string   `json:"category"`
+	Tags             []string `json:"tags,omitempty"`
+	Downloads        int      `json:"downloads"`
+	UpdatedAt        string   `json:"updated_at"`
+	MinAppVersion    string   `json:"min_app_version,omitempty"`
+	IsInstalled      bool     `json:"is_installed"`
+	InstalledVersion string   `json:"installed_version,omitempty"`
+	HasUpdate        bool     `json:"has_update"`
+}
+
+// ToResponse converts StoreExtension to normalized response
+func (e *StoreExtension) ToResponse() StoreExtensionResponse {
+	return StoreExtensionResponse{
+		ID:            e.ID,
+		Name:          e.Name,
+		DisplayName:   e.getDisplayName(),
+		Version:       e.Version,
+		Author:        e.Author,
+		Description:   e.Description,
+		DownloadURL:   e.getDownloadURL(),
+		IconURL:       e.getIconURL(),
+		Category:      e.Category,
+		Tags:          e.Tags,
+		Downloads:     e.Downloads,
+		UpdatedAt:     e.UpdatedAt,
+		MinAppVersion: e.getMinAppVersion(),
+	}
+}
+
+// ExtensionStore manages the extension store
+type ExtensionStore struct {
+	registryURL string
+	cacheDir    string
+	cache       *StoreRegistry
+	cacheMu     sync.RWMutex
+	cacheTime   time.Time
+	cacheTTL    time.Duration
+}
+
+var (
+	extensionStore   *ExtensionStore
+	extensionStoreMu sync.Mutex
+)
+
+const (
+	defaultRegistryURL = "https://raw.githubusercontent.com/zarzet/SpotiFLAC-Extension/main/registry.json"
+	cacheTTL           = 30 * time.Minute
+	cacheFileName      = "store_cache.json"
+)
+
+// InitExtensionStore initializes the extension store
+func InitExtensionStore(cacheDir string) *ExtensionStore {
+	extensionStoreMu.Lock()
+	defer extensionStoreMu.Unlock()
+
+	if extensionStore == nil {
+		extensionStore = &ExtensionStore{
+			registryURL: defaultRegistryURL,
+			cacheDir:    cacheDir,
+			cacheTTL:    cacheTTL,
+		}
+		// Try to load from disk cache
+		extensionStore.loadDiskCache()
+	}
+	return extensionStore
+}
+
+// GetExtensionStore returns the singleton store instance
+func GetExtensionStore() *ExtensionStore {
+	extensionStoreMu.Lock()
+	defer extensionStoreMu.Unlock()
+	return extensionStore
+}
+
+// loadDiskCache loads cached registry from disk
+func (s *ExtensionStore) loadDiskCache() {
+	if s.cacheDir == "" {
+		return
+	}
+
+	cachePath := filepath.Join(s.cacheDir, cacheFileName)
+	data, err := os.ReadFile(cachePath)
+	if err != nil {
+		return
+	}
+
+	var cacheData struct {
+		Registry  StoreRegistry `json:"registry"`
+		CacheTime int64         `json:"cache_time"`
+	}
+
+	if err := json.Unmarshal(data, &cacheData); err != nil {
+		return
+	}
+
+	s.cache = &cacheData.Registry
+	s.cacheTime = time.Unix(cacheData.CacheTime, 0)
+	LogDebug("ExtensionStore", "Loaded %d extensions from disk cache", len(s.cache.Extensions))
+}
+
+// saveDiskCache saves registry to disk cache
+func (s *ExtensionStore) saveDiskCache() {
+	if s.cacheDir == "" || s.cache == nil {
+		return
+	}
+
+	cacheData := struct {
+		Registry  StoreRegistry `json:"registry"`
+		CacheTime int64         `json:"cache_time"`
+	}{
+		Registry:  *s.cache,
+		CacheTime: s.cacheTime.Unix(),
+	}
+
+	data, err := json.Marshal(cacheData)
+	if err != nil {
+		return
+	}
+
+	cachePath := filepath.Join(s.cacheDir, cacheFileName)
+	os.WriteFile(cachePath, data, 0644)
+}
+
+// FetchRegistry fetches the extension registry from GitHub
+func (s *ExtensionStore) FetchRegistry(forceRefresh bool) (*StoreRegistry, error) {
+	s.cacheMu.Lock()
+	defer s.cacheMu.Unlock()
+
+	// Return cached if valid and not forcing refresh
+	if !forceRefresh && s.cache != nil && time.Since(s.cacheTime) < s.cacheTTL {
+		LogDebug("ExtensionStore", "Using cached registry (%d extensions)", len(s.cache.Extensions))
+		return s.cache, nil
+	}
+
+	LogInfo("ExtensionStore", "Fetching registry from %s", s.registryURL)
+
+	client := &http.Client{Timeout: 30 * time.Second}
+	resp, err := client.Get(s.registryURL)
+	if err != nil {
+		// Return cached data if available on network error
+		if s.cache != nil {
+			LogWarn("ExtensionStore", "Network error, using cached registry: %v", err)
+			return s.cache, nil
+		}
+		return nil, fmt.Errorf("failed to fetch registry: %w", err)
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		if s.cache != nil {
+			LogWarn("ExtensionStore", "HTTP %d, using cached registry", resp.StatusCode)
+			return s.cache, nil
+		}
+		return nil, fmt.Errorf("registry returned HTTP %d", resp.StatusCode)
+	}
+
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return nil, fmt.Errorf("failed to read registry: %w", err)
+	}
+
+	var registry StoreRegistry
+	if err := json.Unmarshal(body, &registry); err != nil {
+		return nil, fmt.Errorf("failed to parse registry: %w", err)
+	}
+
+	s.cache = &registry
+	s.cacheTime = time.Now()
+	s.saveDiskCache()
+
+	LogInfo("ExtensionStore", "Fetched %d extensions from registry", len(registry.Extensions))
+	return &registry, nil
+}
+
+// GetExtensionsWithStatus returns extensions with installation status
+func (s *ExtensionStore) GetExtensionsWithStatus() ([]StoreExtensionResponse, error) {
+	registry, err := s.FetchRegistry(false)
+	if err != nil {
+		return nil, err
+	}
+
+	manager := GetExtensionManager()
+	installed := make(map[string]string) // id -> version
+
+	if manager != nil {
+		for _, ext := range manager.GetAllExtensions() {
+			installed[ext.ID] = ext.Manifest.Version
+		}
+	}
+
+	result := make([]StoreExtensionResponse, len(registry.Extensions))
+	for i, ext := range registry.Extensions {
+		resp := ext.ToResponse()
+
+		if installedVersion, ok := installed[ext.ID]; ok {
+			resp.IsInstalled = true
+			resp.InstalledVersion = installedVersion
+			resp.HasUpdate = compareVersions(ext.Version, installedVersion) > 0
+		}
+
+		result[i] = resp
+	}
+
+	return result, nil
+}
+
+// DownloadExtension downloads an extension package to the specified path
+func (s *ExtensionStore) DownloadExtension(extensionID string, destPath string) error {
+	registry, err := s.FetchRegistry(false)
+	if err != nil {
+		return err
+	}
+
+	var ext *StoreExtension
+	for _, e := range registry.Extensions {
+		if e.ID == extensionID {
+			ext = &e
+			break
+		}
+	}
+
+	if ext == nil {
+		return fmt.Errorf("extension %s not found in store", extensionID)
+	}
+
+	LogInfo("ExtensionStore", "Downloading %s from %s", ext.getDisplayName(), ext.getDownloadURL())
+
+	client := &http.Client{Timeout: 5 * time.Minute}
+	resp, err := client.Get(ext.getDownloadURL())
+	if err != nil {
+		return fmt.Errorf("failed to download: %w", err)
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		return fmt.Errorf("download returned HTTP %d", resp.StatusCode)
+	}
+
+	// Create destination file
+	out, err := os.Create(destPath)
+	if err != nil {
+		return fmt.Errorf("failed to create file: %w", err)
+	}
+	defer out.Close()
+
+	_, err = io.Copy(out, resp.Body)
+	if err != nil {
+		os.Remove(destPath)
+		return fmt.Errorf("failed to write file: %w", err)
+	}
+
+	LogInfo("ExtensionStore", "Downloaded %s to %s", ext.getDisplayName(), destPath)
+	return nil
+}
+
+// GetCategories returns all available categories
+func (s *ExtensionStore) GetCategories() []string {
+	return []string{
+		CategoryMetadata,
+		CategoryDownload,
+		CategoryUtility,
+		CategoryLyrics,
+		CategoryIntegration,
+	}
+}
+
+// SearchExtensions searches extensions by query
+func (s *ExtensionStore) SearchExtensions(query string, category string) ([]StoreExtensionResponse, error) {
+	extensions, err := s.GetExtensionsWithStatus()
+	if err != nil {
+		return nil, err
+	}
+
+	if query == "" && category == "" {
+		return extensions, nil
+	}
+
+	var result []StoreExtensionResponse
+	queryLower := toLower(query)
+
+	for _, ext := range extensions {
+		// Filter by category
+		if category != "" && ext.Category != category {
+			continue
+		}
+
+		// Filter by query
+		if query != "" {
+			if !containsIgnoreCase(ext.Name, queryLower) &&
+				!containsIgnoreCase(ext.DisplayName, queryLower) &&
+				!containsIgnoreCase(ext.Description, queryLower) &&
+				!containsIgnoreCase(ext.Author, queryLower) {
+				// Check tags
+				found := false
+				for _, tag := range ext.Tags {
+					if containsIgnoreCase(tag, queryLower) {
+						found = true
+						break
+					}
+				}
+				if !found {
+					continue
+				}
+			}
+		}
+
+		result = append(result, ext)
+	}
+
+	return result, nil
+}
+
+// ClearCache clears the in-memory and disk cache
+func (s *ExtensionStore) ClearCache() {
+	s.cacheMu.Lock()
+	defer s.cacheMu.Unlock()
+
+	s.cache = nil
+	s.cacheTime = time.Time{}
+
+	if s.cacheDir != "" {
+		cachePath := filepath.Join(s.cacheDir, cacheFileName)
+		os.Remove(cachePath)
+	}
+
+	LogInfo("ExtensionStore", "Cache cleared")
+}
+
+// Helper: case-insensitive contains
+func containsIgnoreCase(s, substr string) bool {
+	return containsStr(toLower(s), substr)
+}
+
+func toLower(s string) string {
+	result := make([]byte, len(s))
+	for i := 0; i < len(s); i++ {
+		c := s[i]
+		if c >= 'A' && c <= 'Z' {
+			c += 'a' - 'A'
+		}
+		result[i] = c
+	}
+	return string(result)
+}
+
+func containsStr(s, substr string) bool {
+	return len(substr) == 0 || (len(s) >= len(substr) && findSubstring(s, substr) >= 0)
+}
+
+func findSubstring(s, substr string) int {
+	for i := 0; i <= len(s)-len(substr); i++ {
+		if s[i:i+len(substr)] == substr {
+			return i
+		}
+	}
+	return -1
+}

go_backend/extension_test.go

@@ -0,0 +1,219 @@
+package gobackend
+
+import (
+	"testing"
+
+	"github.com/dop251/goja"
+)
+
+func TestParseManifest_Valid(t *testing.T) {
+	validManifest := `{
+		"name": "test-provider",
+		"displayName": "Test Provider",
+		"version": "1.0.0",
+		"author": "Test Author",
+		"description": "A test extension",
+		"type": ["metadata_provider"],
+		"permissions": {
+			"network": ["api.test.com"],
+			"storage": true
+		}
+	}`
+
+	manifest, err := ParseManifest([]byte(validManifest))
+	if err != nil {
+		t.Fatalf("Expected valid manifest to parse, got error: %v", err)
+	}
+
+	if manifest.Name != "test-provider" {
+		t.Errorf("Expected name 'test-provider', got '%s'", manifest.Name)
+	}
+
+	if manifest.Version != "1.0.0" {
+		t.Errorf("Expected version '1.0.0', got '%s'", manifest.Version)
+	}
+
+	if !manifest.IsMetadataProvider() {
+		t.Error("Expected IsMetadataProvider() to return true")
+	}
+
+	if manifest.IsDownloadProvider() {
+		t.Error("Expected IsDownloadProvider() to return false")
+	}
+}
+
+func TestParseManifest_MissingName(t *testing.T) {
+	invalidManifest := `{
+		"version": "1.0.0",
+		"author": "Test Author",
+		"description": "A test extension",
+		"type": ["metadata_provider"]
+	}`
+
+	_, err := ParseManifest([]byte(invalidManifest))
+	if err == nil {
+		t.Fatal("Expected error for missing name")
+	}
+}
+
+func TestParseManifest_MissingType(t *testing.T) {
+	invalidManifest := `{
+		"name": "test-provider",
+		"version": "1.0.0",
+		"author": "Test Author",
+		"description": "A test extension"
+	}`
+
+	_, err := ParseManifest([]byte(invalidManifest))
+	if err == nil {
+		t.Fatal("Expected error for missing type")
+	}
+}
+
+func TestIsDomainAllowed(t *testing.T) {
+	manifest := &ExtensionManifest{
+		Permissions: ExtensionPermissions{
+			Network: []string{"api.test.com", "*.example.com"},
+		},
+	}
+
+	tests := []struct {
+		domain   string
+		expected bool
+	}{
+		{"api.test.com", true},
+		{"api.example.com", true},
+		{"sub.example.com", true},
+		{"notallowed.com", false},
+		{"test.com", false},
+	}
+
+	for _, tt := range tests {
+		result := manifest.IsDomainAllowed(tt.domain)
+		if result != tt.expected {
+			t.Errorf("IsDomainAllowed(%s) = %v, expected %v", tt.domain, result, tt.expected)
+		}
+	}
+}
+
+func TestExtensionRuntime_NetworkSandbox(t *testing.T) {
+	// Create a mock extension with limited network permissions
+	ext := &LoadedExtension{
+		ID: "test-ext",
+		Manifest: &ExtensionManifest{
+			Name: "test-ext",
+			Permissions: ExtensionPermissions{
+				Network: []string{"api.allowed.com", "*.wildcard.com"},
+			},
+		},
+		DataDir: t.TempDir(),
+	}
+
+	runtime := NewExtensionRuntime(ext)
+
+	// Test allowed domains
+	if err := runtime.validateDomain("https://api.allowed.com/path"); err != nil {
+		t.Errorf("Expected api.allowed.com to be allowed, got error: %v", err)
+	}
+
+	if err := runtime.validateDomain("https://sub.wildcard.com/path"); err != nil {
+		t.Errorf("Expected sub.wildcard.com to be allowed (wildcard), got error: %v", err)
+	}
+
+	// Test blocked domains
+	if err := runtime.validateDomain("https://blocked.com/path"); err == nil {
+		t.Error("Expected blocked.com to be denied")
+	}
+
+	if err := runtime.validateDomain("https://notallowed.com/path"); err == nil {
+		t.Error("Expected notallowed.com to be denied")
+	}
+}
+
+func TestExtensionRuntime_FileSandbox(t *testing.T) {
+	tempDir := t.TempDir()
+
+	ext := &LoadedExtension{
+		ID: "test-ext",
+		Manifest: &ExtensionManifest{
+			Name: "test-ext",
+		},
+		DataDir: tempDir,
+	}
+
+	runtime := NewExtensionRuntime(ext)
+
+	// Test valid path within sandbox
+	validPath, err := runtime.validatePath("test.txt")
+	if err != nil {
+		t.Errorf("Expected relative path to be valid, got error: %v", err)
+	}
+	if validPath == "" {
+		t.Error("Expected non-empty path")
+	}
+
+	// Test path traversal attack
+	_, err = runtime.validatePath("../../../etc/passwd")
+	if err == nil {
+		t.Error("Expected path traversal to be blocked")
+	}
+
+	// Test nested path within sandbox (should be allowed)
+	nestedPath, err := runtime.validatePath("subdir/file.txt")
+	if err != nil {
+		t.Errorf("Expected nested path to be valid, got error: %v", err)
+	}
+	if nestedPath == "" {
+		t.Error("Expected non-empty nested path")
+	}
+}
+
+func TestExtensionRuntime_UtilityFunctions(t *testing.T) {
+	ext := &LoadedExtension{
+		ID: "test-ext",
+		Manifest: &ExtensionManifest{
+			Name: "test-ext",
+		},
+		DataDir: t.TempDir(),
+	}
+
+	runtime := NewExtensionRuntime(ext)
+	vm := goja.New()
+	runtime.RegisterAPIs(vm)
+
+	// Test base64 encode/decode
+	result, err := vm.RunString(`utils.base64Encode("hello")`)
+	if err != nil {
+		t.Fatalf("base64Encode failed: %v", err)
+	}
+	if result.String() != "aGVsbG8=" {
+		t.Errorf("Expected 'aGVsbG8=', got '%s'", result.String())
+	}
+
+	result, err = vm.RunString(`utils.base64Decode("aGVsbG8=")`)
+	if err != nil {
+		t.Fatalf("base64Decode failed: %v", err)
+	}
+	if result.String() != "hello" {
+		t.Errorf("Expected 'hello', got '%s'", result.String())
+	}
+
+	// Test MD5
+	result, err = vm.RunString(`utils.md5("hello")`)
+	if err != nil {
+		t.Fatalf("md5 failed: %v", err)
+	}
+	if result.String() != "5d41402abc4b2a76b9719d911017c592" {
+		t.Errorf("Expected '5d41402abc4b2a76b9719d911017c592', got '%s'", result.String())
+	}
+
+	// Test JSON parse/stringify
+	result, err = vm.RunString(`utils.stringifyJSON({name: "test", value: 123})`)
+	if err != nil {
+		t.Fatalf("stringifyJSON failed: %v", err)
+	}
+	// JSON output may vary in order, just check it's valid
+	if result.String() == "" {
+		t.Error("Expected non-empty JSON string")
+	}
+}

go_backend/go.mod

@@ -5,14 +5,19 @@ go 1.24.0
 toolchain go1.24.5
 
 require (
+	github.com/dop251/goja v0.0.0-20260106131823-651366fbe6e3
 	github.com/go-flac/flacpicture v0.3.0
 	github.com/go-flac/flacvorbis v0.2.0
 	github.com/go-flac/go-flac v1.0.0
 )
 
 require (
+	github.com/dlclark/regexp2 v1.11.4 // indirect
+	github.com/go-sourcemap/sourcemap v2.1.3+incompatible // indirect
+	github.com/google/pprof v0.0.0-20230207041349-798e818bf904 // indirect
 	golang.org/x/mobile v0.0.0-20251209145715-2553ed8ce294 // indirect
 	golang.org/x/mod v0.31.0 // indirect
 	golang.org/x/sync v0.19.0 // indirect
+	golang.org/x/text v0.3.8 // indirect
 	golang.org/x/tools v0.40.0 // indirect
 )

go_backend/go.sum

@@ -1,14 +1,28 @@
+github.com/Masterminds/semver/v3 v3.2.1 h1:RN9w6+7QoMeJVGyfmbcgs28Br8cvmnucEXnY0rYXWg0=
+github.com/Masterminds/semver/v3 v3.2.1/go.mod h1:qvl/7zhW3nngYb5+80sSMF+FG2BjYrf8m9wsX0PNOMQ=
+github.com/dlclark/regexp2 v1.11.4 h1:rPYF9/LECdNymJufQKmri9gV604RvvABwgOA8un7yAo=
+github.com/dlclark/regexp2 v1.11.4/go.mod h1:DHkYz0B9wPfa6wondMfaivmHpzrQ3v9q8cnmRbL6yW8=
+github.com/dop251/goja v0.0.0-20260106131823-651366fbe6e3 h1:bVp3yUzvSAJzu9GqID+Z96P+eu5TKnIMJSV4QaZMauM=
+github.com/dop251/goja v0.0.0-20260106131823-651366fbe6e3/go.mod h1:MxLav0peU43GgvwVgNbLAj1s/bSGboKkhuULvq/7hx4=
 github.com/go-flac/flacpicture v0.3.0 h1:LkmTxzFLIynwfhHiZsX0s8xcr3/u33MzvV89u+zOT8I=
 github.com/go-flac/flacpicture v0.3.0/go.mod h1:DPbrzVYQ3fJcvSgLFp9HXIrEQEdfdk/+m0nQCzwodZI=
 github.com/go-flac/flacvorbis v0.2.0 h1:KH0xjpkNTXFER4cszH4zeJxYcrHbUobz/RticWGOESs=
 github.com/go-flac/flacvorbis v0.2.0/go.mod h1:uIysHOtuU7OLGoCRG92bvnkg7QEqHx19qKRV6K1pBrI=
 github.com/go-flac/go-flac v1.0.0 h1:6qI9XOVLcO50xpzm3nXvO31BgDgHhnr/p/rER/K/doY=
 github.com/go-flac/go-flac v1.0.0/go.mod h1:WnZhcpmq4u1UdZMNn9LYSoASpWOCMOoxXxcWEHSzkW8=
+github.com/go-sourcemap/sourcemap v2.1.3+incompatible h1:W1iEw64niKVGogNgBN3ePyLFfuisuzeidWPMPWmECqU=
+github.com/go-sourcemap/sourcemap v2.1.3+incompatible/go.mod h1:F8jJfvm2KbVjc5NqelyYJmf/v5J0dwNLS2mL4sNA1Jg=
+github.com/google/pprof v0.0.0-20230207041349-798e818bf904 h1:4/hN5RUoecvl+RmJRE2YxKWtnnQls6rQjjW5oV7qg2U=
+github.com/google/pprof v0.0.0-20230207041349-798e818bf904/go.mod h1:uglQLonpP8qtYCYyzA+8c/9qtqgA3qsXGYqCPKARAFg=
 golang.org/x/mobile v0.0.0-20251209145715-2553ed8ce294 h1:Cr6kbEvA6nqvdHynE4CtVKlqpZB9dS1Jva/6IsHA19g=
 golang.org/x/mobile v0.0.0-20251209145715-2553ed8ce294/go.mod h1:RdZ+3sb4CVgpCFnzv+I4haEpwqFfsfzlLHs3L7ok+e0=
 golang.org/x/mod v0.31.0 h1:HaW9xtz0+kOcWKwli0ZXy79Ix+UW/vOfmWI5QVd2tgI=
 golang.org/x/mod v0.31.0/go.mod h1:43JraMp9cGx1Rx3AqioxrbrhNsLl2l/iNAvuBkrezpg=
 golang.org/x/sync v0.19.0 h1:vV+1eWNmZ5geRlYjzm2adRgW2/mcpevXNg50YZtPCE4=
 golang.org/x/sync v0.19.0/go.mod h1:9KTHXmSnoGruLpwFjVSX0lNNA75CykiMECbovNTZqGI=
+golang.org/x/text v0.3.8 h1:nAL+RVCQ9uMn3vJZbV+MRnydTJFPf8qqY42YiA6MrqY=
+golang.org/x/text v0.3.8/go.mod h1:E6s5w1FMmriuDzIBO73fBruAKo1PCIq6d2Q6DHfQ8WQ=
 golang.org/x/tools v0.40.0 h1:yLkxfA+Qnul4cs9QA3KnlFu0lVmd8JJfoq+E41uSutA=
 golang.org/x/tools v0.40.0/go.mod h1:Ik/tzLRlbscWpqqMRjyWYDisX8bG13FrdXp3o4Sr9lc=
+gopkg.in/yaml.v2 v2.4.0 h1:D8xgwECY7CYvx+Y2n4sBz93Jn9JRvxdiyyo8CTfuKaY=
+gopkg.in/yaml.v2 v2.4.0/go.mod h1:RDklbk79AGWmwhnvt/jBztapEOGDOx6ZbXqjP6csGnQ=

go_backend/httputil.go

@@ -22,12 +22,12 @@ import (
 func getRandomUserAgent() string {
 	// Windows 10/11 Chrome format - same as PC version for maximum compatibility
 	// Some APIs may block mobile User-Agents, so we use desktop format
-	winMajor := rand.Intn(2) + 10  // Windows 10 or 11
-	
-	chromeVersion := rand.Intn(25) + 100 // Chrome 100-124
+	winMajor := rand.Intn(2) + 10 // Windows 10 or 11
+
+	chromeVersion := rand.Intn(25) + 100  // Chrome 100-124
 	chromeBuild := rand.Intn(1500) + 3000 // Build 3000-4500
-	chromePatch := rand.Intn(65) + 60 // Patch 60-125
-	
+	chromePatch := rand.Intn(65) + 60     // Patch 60-125
+
 	return fmt.Sprintf(
 		"Mozilla/5.0 (Windows NT %d.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/%d.0.%d.%d Safari/537.36",
 		winMajor,
@@ -39,46 +39,48 @@ func getRandomUserAgent() string {
 
 // getRandomMacUserAgent generates a random Mac Chrome User-Agent string
 // Alternative format matching referensi/backend/spotify_metadata.go exactly
-func getRandomMacUserAgent() string {
-	macMajor := rand.Intn(4) + 11  // macOS 11-14
-	macMinor := rand.Intn(5) + 4   // Minor 4-8
-	webkitMajor := rand.Intn(7) + 530
-	webkitMinor := rand.Intn(7) + 30
-	chromeMajor := rand.Intn(25) + 80
-	chromeBuild := rand.Intn(1500) + 3000
-	chromePatch := rand.Intn(65) + 60
-	safariMajor := rand.Intn(7) + 530
-	safariMinor := rand.Intn(6) + 30
-
-	return fmt.Sprintf(
-		"Mozilla/5.0 (Macintosh; Intel Mac OS X 10_%d_%d) AppleWebKit/%d.%d (KHTML, like Gecko) Chrome/%d.0.%d.%d Safari/%d.%d",
-		macMajor,
-		macMinor,
-		webkitMajor,
-		webkitMinor,
-		chromeMajor,
-		chromeBuild,
-		chromePatch,
-		safariMajor,
-		safariMinor,
-	)
-}
+// Kept for potential future use
+// func getRandomMacUserAgent() string {
+// 	macMajor := rand.Intn(4) + 11 // macOS 11-14
+// 	macMinor := rand.Intn(5) + 4  // Minor 4-8
+// 	webkitMajor := rand.Intn(7) + 530
+// 	webkitMinor := rand.Intn(7) + 30
+// 	chromeMajor := rand.Intn(25) + 80
+// 	chromeBuild := rand.Intn(1500) + 3000
+// 	chromePatch := rand.Intn(65) + 60
+// 	safariMajor := rand.Intn(7) + 530
+// 	safariMinor := rand.Intn(6) + 30
+//
+// 	return fmt.Sprintf(
+// 		"Mozilla/5.0 (Macintosh; Intel Mac OS X 10_%d_%d) AppleWebKit/%d.%d (KHTML, like Gecko) Chrome/%d.0.%d.%d Safari/%d.%d",
+// 		macMajor,
+// 		macMinor,
+// 		webkitMajor,
+// 		webkitMinor,
+// 		chromeMajor,
+// 		chromeBuild,
+// 		chromePatch,
+// 		safariMajor,
+// 		safariMinor,
+// 	)
+// }
 
 // getRandomDesktopUserAgent randomly picks between Windows and Mac User-Agent
-func getRandomDesktopUserAgent() string {
-	if rand.Intn(2) == 0 {
-		return getRandomUserAgent() // Windows
-	}
-	return getRandomMacUserAgent() // Mac
-}
+// Kept for potential future use
+// func getRandomDesktopUserAgent() string {
+// 	if rand.Intn(2) == 0 {
+// 		return getRandomUserAgent() // Windows
+// 	}
+// 	return getRandomMacUserAgent() // Mac
+// }
 
 // Default timeout values
 const (
-	DefaultTimeout     = 60 * time.Second  // Default HTTP timeout
-	DownloadTimeout    = 120 * time.Second // Timeout for file downloads
-	SongLinkTimeout    = 30 * time.Second  // Timeout for SongLink API
-	DefaultMaxRetries  = 3                 // Default retry count
-	DefaultRetryDelay  = 1 * time.Second   // Initial retry delay
+	DefaultTimeout    = 60 * time.Second  // Default HTTP timeout
+	DownloadTimeout   = 120 * time.Second // Timeout for file downloads
+	SongLinkTimeout   = 30 * time.Second  // Timeout for SongLink API
+	DefaultMaxRetries = 3                 // Default retry count
+	DefaultRetryDelay = 1 * time.Second   // Initial retry delay
 )
 
 // Shared transport with connection pooling to prevent TCP exhaustion
@@ -96,9 +98,9 @@ var sharedTransport = &http.Transport{
 	ExpectContinueTimeout: 1 * time.Second,
 	DisableKeepAlives:     false, // Enable keep-alives for connection reuse
 	ForceAttemptHTTP2:     true,
-	WriteBufferSize:       64 * 1024,  // 64KB write buffer
-	ReadBufferSize:        64 * 1024,  // 64KB read buffer
-	DisableCompression:    true,       // FLAC is already compressed
+	WriteBufferSize:       64 * 1024, // 64KB write buffer
+	ReadBufferSize:        64 * 1024, // 64KB read buffer
+	DisableCompression:    true,      // FLAC is already compressed
 }
 
 // Shared HTTP client for general requests (reuses connections)
@@ -184,15 +186,15 @@ func DoRequestWithRetry(client *http.Client, req *http.Request, config RetryConf
 		resp, err := client.Do(reqCopy)
 		if err != nil {
 			lastErr = err
-			
+
 			// Check for ISP blocking on network errors
 			if CheckAndLogISPBlocking(err, requestURL, "HTTP") {
 				// Don't retry if ISP blocking is detected - it won't help
 				return nil, WrapErrorWithISPCheck(err, requestURL, "HTTP")
 			}
-			
+
 			if attempt < config.MaxRetries {
-				GoLog("[HTTP] Request failed (attempt %d/%d): %v, retrying in %v...\n", 
+				GoLog("[HTTP] Request failed (attempt %d/%d): %v, retrying in %v...\n",
 					attempt+1, config.MaxRetries+1, err, delay)
 				time.Sleep(delay)
 				delay = calculateNextDelay(delay, config)
@@ -227,13 +229,13 @@ func DoRequestWithRetry(client *http.Client, req *http.Request, config RetryConf
 			body, _ := io.ReadAll(resp.Body)
 			resp.Body.Close()
 			bodyStr := strings.ToLower(string(body))
-			
+
 			// Check if response looks like ISP blocking page
 			ispBlockingIndicators := []string{
 				"blocked", "forbidden", "access denied", "not available in your",
 				"restricted", "censored", "unavailable for legal", "blocked by",
 			}
-			
+
 			for _, indicator := range ispBlockingIndicators {
 				if strings.Contains(bodyStr, indicator) {
 					LogError("HTTP", "ISP BLOCKING DETECTED via HTTP %d response", resp.StatusCode)
@@ -267,10 +269,7 @@ func DoRequestWithRetry(client *http.Client, req *http.Request, config RetryConf
 // calculateNextDelay calculates the next delay with exponential backoff
 func calculateNextDelay(currentDelay time.Duration, config RetryConfig) time.Duration {
 	nextDelay := time.Duration(float64(currentDelay) * config.BackoffFactor)
-	if nextDelay > config.MaxDelay {
-		nextDelay = config.MaxDelay
-	}
-	return nextDelay
+	return min(nextDelay, config.MaxDelay)
 }
 
 // getRetryAfterDuration parses Retry-After header and returns duration
@@ -481,7 +480,7 @@ func extractDomain(rawURL string) string {
 	if rawURL == "" {
 		return "unknown"
 	}
-	
+
 	parsed, err := url.Parse(rawURL)
 	if err != nil {
 		// Try to extract domain manually
@@ -492,7 +491,7 @@ func extractDomain(rawURL string) string {
 		}
 		return rawURL
 	}
-	
+
 	if parsed.Host != "" {
 		return parsed.Host
 	}
@@ -505,11 +504,11 @@ func WrapErrorWithISPCheck(err error, requestURL string, tag string) error {
 	if err == nil {
 		return nil
 	}
-	
+
 	if CheckAndLogISPBlocking(err, requestURL, tag) {
 		domain := extractDomain(requestURL)
 		return fmt.Errorf("ISP blocking detected for %s - try using VPN or change DNS to 1.1.1.1/8.8.8.8: %w", domain, err)
 	}
-	
+
 	return err
 }

go_backend/logbuffer.go

@@ -33,8 +33,8 @@ var (
 func GetLogBuffer() *LogBuffer {
 	logBufferOnce.Do(func() {
 		globalLogBuffer = &LogBuffer{
-			entries:        make([]LogEntry, 0, 500),
-			maxSize:        500,
+			entries:        make([]LogEntry, 0, 1000),
+			maxSize:        1000,
 			loggingEnabled: false, // Default: disabled for performance (user can enable in settings)
 		}
 	})

go_backend/lyrics.go

@@ -250,29 +250,30 @@ func msToLRCTimestamp(ms int64) string {
 
 // convertToLRC converts lyrics to LRC format string (without metadata headers)
 // Use convertToLRCWithMetadata for full LRC with headers
-func convertToLRC(lyrics *LyricsResponse) string {
-	if lyrics == nil || len(lyrics.Lines) == 0 {
-		return ""
-	}
-
-	var builder strings.Builder
-
-	if lyrics.SyncType == "LINE_SYNCED" {
-		for _, line := range lyrics.Lines {
-			timestamp := msToLRCTimestamp(line.StartTimeMs)
-			builder.WriteString(timestamp)
-			builder.WriteString(line.Words)
-			builder.WriteString("\n")
-		}
-	} else {
-		for _, line := range lyrics.Lines {
-			builder.WriteString(line.Words)
-			builder.WriteString("\n")
-		}
-	}
-
-	return builder.String()
-}
+// Kept for potential future use
+// func convertToLRC(lyrics *LyricsResponse) string {
+// 	if lyrics == nil || len(lyrics.Lines) == 0 {
+// 		return ""
+// 	}
+//
+// 	var builder strings.Builder
+//
+// 	if lyrics.SyncType == "LINE_SYNCED" {
+// 		for _, line := range lyrics.Lines {
+// 			timestamp := msToLRCTimestamp(line.StartTimeMs)
+// 			builder.WriteString(timestamp)
+// 			builder.WriteString(line.Words)
+// 			builder.WriteString("\n")
+// 		}
+// 	} else {
+// 		for _, line := range lyrics.Lines {
+// 			builder.WriteString(line.Words)
+// 			builder.WriteString("\n")
+// 		}
+// 	}
+//
+// 	return builder.String()
+// }
 
 // convertToLRCWithMetadata converts lyrics to LRC format with metadata headers
 // Includes [ti:], [ar:], [by:] headers

go_backend/parallel.go

@@ -233,7 +233,7 @@ func PreWarmTrackCache(requests []PreWarmCacheRequest) {
 	fmt.Printf("[Cache] Pre-warm complete. Cache size: %d\n", cache.Size())
 }
 
-func preWarmTidalCache(isrc, trackName, artistName string) {
+func preWarmTidalCache(isrc, _, _ string) {
 	downloader := NewTidalDownloader()
 	track, err := downloader.SearchTrackByISRC(isrc)
 	if err == nil && track != nil {
@@ -272,7 +272,7 @@ func PreWarmCache(tracksJSON string) error {
 	var requests []PreWarmCacheRequest
 	// Parse JSON (simplified - in production use proper JSON parsing)
 	// For now, this is called from exports.go with proper parsing
-	
+
 	go PreWarmTrackCache(requests) // Run in background
 	return nil
 }

go_backend/progress.go

@@ -23,7 +23,7 @@ type ItemProgress struct {
 	ItemID        string  `json:"item_id"`
 	BytesTotal    int64   `json:"bytes_total"`
 	BytesReceived int64   `json:"bytes_received"`
-	Progress      float64 `json:"progress"` // 0.0 to 1.0
+	Progress      float64 `json:"progress"`   // 0.0 to 1.0
 	SpeedMBps     float64 `json:"speed_mbps"` // Download speed in MB/s
 	IsDownloading bool    `json:"is_downloading"`
 	Status        string  `json:"status"` // "downloading", "finalizing", "completed"
@@ -204,11 +204,12 @@ func setDownloadDir(path string) error {
 }
 
 // getDownloadDir returns the default download directory
-func getDownloadDir() string {
-	downloadDirMu.RLock()
-	defer downloadDirMu.RUnlock()
-	return downloadDir
-}
+// Kept for potential future use
+// func getDownloadDir() string {
+// 	downloadDirMu.RLock()
+// 	defer downloadDirMu.RUnlock()
+// 	return downloadDir
+// }
 
 // ItemProgressWriter wraps io.Writer to track download progress for a specific item
 type ItemProgressWriter struct {
@@ -256,7 +257,7 @@ func (pw *ItemProgressWriter) Write(p []byte) (int, error) {
 			bytesInInterval := pw.current - pw.lastBytes
 			speedMBps = float64(bytesInInterval) / (1024 * 1024) / elapsed
 		}
-		
+
 		SetItemBytesReceivedWithSpeed(pw.itemID, pw.current, speedMBps)
 		pw.lastReported = pw.current
 		pw.lastTime = now

go_backend/qobuz.go

@@ -12,6 +12,7 @@ import (
 	"path/filepath"
 	"strings"
 	"sync"
+	"time"
 )
 
 // QobuzDownloader handles Qobuz downloads
@@ -271,14 +272,15 @@ func qobuzIsLatinScript(s string) bool {
 }
 
 // qobuzIsASCIIString checks if a string contains only ASCII characters
-func qobuzIsASCIIString(s string) bool {
-	for _, r := range s {
-		if r > 127 {
-			return false
-		}
-	}
-	return true
-}
+// Kept for potential future use
+// func qobuzIsASCIIString(s string) bool {
+// 	for _, r := range s {
+// 		if r > 127 {
+// 			return false
+// 		}
+// 	}
+// 	return true
+// }
 
 // containsQueryQobuz checks if a query already exists in the list
 func containsQueryQobuz(queries []string, query string) bool {
@@ -634,6 +636,125 @@ func (q *QobuzDownloader) SearchTrackByMetadataWithDuration(trackName, artistNam
 	return nil, fmt.Errorf("no matching track found for: %s - %s", artistName, trackName)
 }
 
+// qobuzAPIResult holds the result from a parallel API request
+type qobuzAPIResult struct {
+	apiURL      string
+	downloadURL string
+	err         error
+	duration    time.Duration
+}
+
+// getQobuzDownloadURLParallel requests download URL from all APIs in parallel
+// "Siapa cepat dia dapat" - first successful response wins
+func getQobuzDownloadURLParallel(apis []string, trackID int64, quality string) (string, string, error) {
+	if len(apis) == 0 {
+		return "", "", fmt.Errorf("no APIs available")
+	}
+
+	GoLog("[Qobuz] Requesting download URL from %d APIs in parallel...\n", len(apis))
+
+	resultChan := make(chan qobuzAPIResult, len(apis))
+	startTime := time.Now()
+
+	// Start all requests in parallel
+	for _, apiURL := range apis {
+		go func(api string) {
+			reqStart := time.Now()
+
+			client := &http.Client{
+				Timeout: 15 * time.Second,
+			}
+
+			reqURL := fmt.Sprintf("%s%d&quality=%s", api, trackID, quality)
+
+			req, err := http.NewRequest("GET", reqURL, nil)
+			if err != nil {
+				resultChan <- qobuzAPIResult{apiURL: api, err: err, duration: time.Since(reqStart)}
+				return
+			}
+
+			resp, err := client.Do(req)
+			if err != nil {
+				resultChan <- qobuzAPIResult{apiURL: api, err: err, duration: time.Since(reqStart)}
+				return
+			}
+			defer resp.Body.Close()
+
+			if resp.StatusCode != 200 {
+				resultChan <- qobuzAPIResult{apiURL: api, err: fmt.Errorf("HTTP %d", resp.StatusCode), duration: time.Since(reqStart)}
+				return
+			}
+
+			body, err := io.ReadAll(resp.Body)
+			if err != nil {
+				resultChan <- qobuzAPIResult{apiURL: api, err: err, duration: time.Since(reqStart)}
+				return
+			}
+
+			// Check if response is HTML (error page)
+			if len(body) > 0 && body[0] == '<' {
+				resultChan <- qobuzAPIResult{apiURL: api, err: fmt.Errorf("received HTML instead of JSON"), duration: time.Since(reqStart)}
+				return
+			}
+
+			// Check for error in JSON response
+			var errorResp struct {
+				Error string `json:"error"`
+			}
+			if json.Unmarshal(body, &errorResp) == nil && errorResp.Error != "" {
+				resultChan <- qobuzAPIResult{apiURL: api, err: fmt.Errorf(errorResp.Error), duration: time.Since(reqStart)}
+				return
+			}
+
+			var result struct {
+				URL string `json:"url"`
+			}
+			if err := json.Unmarshal(body, &result); err != nil {
+				resultChan <- qobuzAPIResult{apiURL: api, err: fmt.Errorf("invalid JSON: %v", err), duration: time.Since(reqStart)}
+				return
+			}
+
+			if result.URL != "" {
+				resultChan <- qobuzAPIResult{apiURL: api, downloadURL: result.URL, err: nil, duration: time.Since(reqStart)}
+				return
+			}
+
+			resultChan <- qobuzAPIResult{apiURL: api, err: fmt.Errorf("no download URL in response"), duration: time.Since(reqStart)}
+		}(apiURL)
+	}
+
+	// Collect results - return first success
+	var errors []string
+	var firstSuccess *qobuzAPIResult
+
+	for i := 0; i < len(apis); i++ {
+		result := <-resultChan
+		if result.err == nil && firstSuccess == nil {
+			firstSuccess = &result
+			GoLog("[Qobuz] [Parallel] ✓ Got response from %s in %v\n", result.apiURL, result.duration)
+
+			// Drain remaining results to avoid goroutine leaks
+			go func(remaining int) {
+				for j := 0; j < remaining; j++ {
+					<-resultChan
+				}
+			}(len(apis) - i - 1)
+
+			GoLog("[Qobuz] [Parallel] Total time: %v (first success)\n", time.Since(startTime))
+			return firstSuccess.apiURL, firstSuccess.downloadURL, nil
+		} else if result.err != nil {
+			errMsg := result.err.Error()
+			if len(errMsg) > 50 {
+				errMsg = errMsg[:50] + "..."
+			}
+			errors = append(errors, fmt.Sprintf("%s: %s", result.apiURL, errMsg))
+		}
+	}
+
+	GoLog("[Qobuz] [Parallel] All %d APIs failed in %v\n", len(apis), time.Since(startTime))
+	return "", "", fmt.Errorf("all %d Qobuz APIs failed. Errors: %v", len(apis), errors)
+}
+
 // getQobuzDownloadURLSequential requests download URL from APIs sequentially
 // Uses same URL format as PC version: /api/stream?trackId={id}&quality={quality}
 func getQobuzDownloadURLSequential(apis []string, trackID int64, quality string) (string, string, error) {
@@ -705,14 +826,16 @@ func getQobuzDownloadURLSequential(apis []string, trackID int64, quality string)
 	return "", "", fmt.Errorf("all %d Qobuz APIs failed. Errors: %v", len(apis), errors)
 }
 
-// GetDownloadURL gets download URL for a track - tries APIs sequentially
+// GetDownloadURL gets download URL for a track - tries ALL APIs in parallel
+// "Siapa cepat dia dapat" - first successful response wins
 func (q *QobuzDownloader) GetDownloadURL(trackID int64, quality string) (string, error) {
 	apis := q.GetAvailableAPIs()
 	if len(apis) == 0 {
 		return "", fmt.Errorf("no Qobuz API available")
 	}
 
-	_, downloadURL, err := getQobuzDownloadURLSequential(apis, trackID, quality)
+	// Use parallel approach - request from all APIs simultaneously
+	_, downloadURL, err := getQobuzDownloadURLParallel(apis, trackID, quality)
 	if err != nil {
 		return "", err
 	}

go_backend/spotify.go

@@ -2,7 +2,6 @@ package gobackend
 
 import (
 	"context"
-	"encoding/base64"
 	"encoding/json"
 	"errors"
 	"fmt"
@@ -17,14 +16,14 @@ import (
 )
 
 const (
-	spotifyTokenURL     = "https://accounts.spotify.com/api/token"
-	playlistBaseURL     = "https://api.spotify.com/v1/playlists/%s"
-	albumBaseURL        = "https://api.spotify.com/v1/albums/%s"
-	trackBaseURL        = "https://api.spotify.com/v1/tracks/%s"
-	artistBaseURL       = "https://api.spotify.com/v1/artists/%s"
-	artistAlbumsURL     = "https://api.spotify.com/v1/artists/%s/albums"
-	searchBaseURL       = "https://api.spotify.com/v1/search"
-	
+	spotifyTokenURL = "https://accounts.spotify.com/api/token"
+	playlistBaseURL = "https://api.spotify.com/v1/playlists/%s"
+	albumBaseURL    = "https://api.spotify.com/v1/albums/%s"
+	trackBaseURL    = "https://api.spotify.com/v1/tracks/%s"
+	artistBaseURL   = "https://api.spotify.com/v1/artists/%s"
+	artistAlbumsURL = "https://api.spotify.com/v1/artists/%s/albums"
+	searchBaseURL   = "https://api.spotify.com/v1/search"
+
 	// Cache TTL settings
 	artistCacheTTL = 10 * time.Minute
 	searchCacheTTL = 5 * time.Minute
@@ -54,7 +53,7 @@ type SpotifyMetadataClient struct {
 	rng            *rand.Rand
 	rngMu          sync.Mutex
 	userAgent      string
-	
+
 	// Caches to reduce API calls
 	artistCache map[string]*cacheEntry // key: artistID
 	searchCache map[string]*cacheEntry // key: query+type
@@ -69,8 +68,10 @@ var (
 	credentialsMu      sync.RWMutex
 )
 
+// ErrNoSpotifyCredentials is returned when Spotify credentials are not configured
+var ErrNoSpotifyCredentials = errors.New("Spotify credentials not configured. Please set your own Client ID and Secret in Settings, or use Deezer as metadata source (free, no credentials required)")
+
 // SetSpotifyCredentials sets custom Spotify API credentials
-// Pass empty strings to use default credentials
 func SetSpotifyCredentials(clientID, clientSecret string) {
 	credentialsMu.Lock()
 	defer credentialsMu.Unlock()
@@ -78,39 +79,56 @@ func SetSpotifyCredentials(clientID, clientSecret string) {
 	customClientSecret = clientSecret
 }
 
-// getCredentials returns the current credentials (custom or default)
-func getCredentials() (string, string) {
+// HasSpotifyCredentials checks if Spotify credentials are configured
+func HasSpotifyCredentials() bool {
 	credentialsMu.RLock()
 	defer credentialsMu.RUnlock()
-	
+
+	// Check custom credentials first
 	if customClientID != "" && customClientSecret != "" {
-		return customClientID, customClientSecret
-	}
-	
-	// Fall back to default credentials
-	clientID := os.Getenv("SPOTIFY_CLIENT_ID")
-	if clientID == "" {
-		if decoded, err := base64.StdEncoding.DecodeString("NWY1NzNjOTYyMDQ5NGJhZTg3ODkwYzBmMDhhNjAyOTM="); err == nil {
-			clientID = string(decoded)
-		}
+		return true
 	}
 
-	clientSecret := os.Getenv("SPOTIFY_CLIENT_SECRET")
-	if clientSecret == "" {
-		if decoded, err := base64.StdEncoding.DecodeString("MjEyNDc2ZDliMGYzNDcyZWFhNzYyZDkwYjE5YjBiYTg="); err == nil {
-			clientSecret = string(decoded)
-		}
+	// Check environment variables
+	if os.Getenv("SPOTIFY_CLIENT_ID") != "" && os.Getenv("SPOTIFY_CLIENT_SECRET") != "" {
+		return true
 	}
-	
-	return clientID, clientSecret
+
+	return false
+}
+
+// getCredentials returns the current credentials or error if not configured
+func getCredentials() (string, string, error) {
+	credentialsMu.RLock()
+	defer credentialsMu.RUnlock()
+
+	// Check custom credentials first
+	if customClientID != "" && customClientSecret != "" {
+		return customClientID, customClientSecret, nil
+	}
+
+	// Check environment variables
+	clientID := os.Getenv("SPOTIFY_CLIENT_ID")
+	clientSecret := os.Getenv("SPOTIFY_CLIENT_SECRET")
+
+	if clientID != "" && clientSecret != "" {
+		return clientID, clientSecret, nil
+	}
+
+	// No credentials available
+	return "", "", ErrNoSpotifyCredentials
 }
 
 // NewSpotifyMetadataClient creates a new Spotify client
-func NewSpotifyMetadataClient() *SpotifyMetadataClient {
-	src := rand.NewSource(time.Now().UnixNano())
+// Returns error if credentials are not configured
+func NewSpotifyMetadataClient() (*SpotifyMetadataClient, error) {
+	// Get credentials - will error if not configured
+	clientID, clientSecret, err := getCredentials()
+	if err != nil {
+		return nil, err
+	}
 
-	// Get credentials (custom or default)
-	clientID, clientSecret := getCredentials()
+	src := rand.NewSource(time.Now().UnixNano())
 
 	c := &SpotifyMetadataClient{
 		httpClient:   NewHTTPClientWithTimeout(15 * time.Second), // Use shared transport for connection pooling
@@ -122,7 +140,7 @@ func NewSpotifyMetadataClient() *SpotifyMetadataClient {
 		albumCache:   make(map[string]*cacheEntry),
 	}
 	c.userAgent = c.randomUserAgent()
-	return c
+	return c, nil
 }
 
 // TrackMetadata represents track information
@@ -140,6 +158,7 @@ type TrackMetadata struct {
 	DiscNumber  int    `json:"disc_number,omitempty"`
 	ExternalURL string `json:"external_urls"`
 	ISRC        string `json:"isrc"`
+	AlbumType   string `json:"album_type,omitempty"` // album, single, ep, compilation
 }
 
 // AlbumTrackMetadata holds per-track info for album/playlist
@@ -159,6 +178,7 @@ type AlbumTrackMetadata struct {
 	ISRC        string `json:"isrc"`
 	AlbumID     string `json:"album_id,omitempty"`
 	AlbumURL    string `json:"album_url,omitempty"`
+	AlbumType   string `json:"album_type,omitempty"` // album, single, ep, compilation
 }
 
 // AlbumInfoMetadata holds album information
@@ -283,6 +303,7 @@ type albumSimplified struct {
 	Images      []image     `json:"images"`
 	ExternalURL externalURL `json:"external_urls"`
 	Artists     []artist    `json:"artists"`
+	AlbumType   string      `json:"album_type"` // album, single, compilation
 }
 
 type trackFull struct {
@@ -331,14 +352,14 @@ func (c *SpotifyMetadataClient) SearchTracks(ctx context.Context, query string,
 	}
 
 	searchURL := fmt.Sprintf("%s?q=%s&type=track&limit=%d", searchBaseURL, url.QueryEscape(query), limit)
-	
+
 	var response struct {
 		Tracks struct {
 			Items []trackFull `json:"items"`
 			Total int         `json:"total"`
 		} `json:"tracks"`
 	}
-	
+
 	if err := c.getJSON(ctx, searchURL, token, &response); err != nil {
 		return nil, err
 	}
@@ -363,6 +384,7 @@ func (c *SpotifyMetadataClient) SearchTracks(ctx context.Context, query string,
 			DiscNumber:  track.DiscNumber,
 			ExternalURL: track.ExternalURL.Spotify,
 			ISRC:        track.ExternalID.ISRC,
+			AlbumType:   track.Album.AlbumType,
 		})
 	}
 
@@ -373,7 +395,7 @@ func (c *SpotifyMetadataClient) SearchTracks(ctx context.Context, query string,
 func (c *SpotifyMetadataClient) SearchAll(ctx context.Context, query string, trackLimit, artistLimit int) (*SearchAllResult, error) {
 	// Create cache key
 	cacheKey := fmt.Sprintf("all:%s:%d:%d", query, trackLimit, artistLimit)
-	
+
 	// Check cache first
 	c.cacheMu.RLock()
 	if entry, ok := c.searchCache[cacheKey]; ok && !entry.isExpired() {
@@ -388,24 +410,24 @@ func (c *SpotifyMetadataClient) SearchAll(ctx context.Context, query string, tra
 	}
 
 	searchURL := fmt.Sprintf("%s?q=%s&type=track,artist&limit=%d", searchBaseURL, url.QueryEscape(query), trackLimit)
-	
+
 	var response struct {
 		Tracks struct {
 			Items []trackFull `json:"items"`
 		} `json:"tracks"`
 		Artists struct {
 			Items []struct {
-				ID         string  `json:"id"`
-				Name       string  `json:"name"`
-				Images     []image `json:"images"`
-				Followers  struct {
+				ID        string  `json:"id"`
+				Name      string  `json:"name"`
+				Images    []image `json:"images"`
+				Followers struct {
 					Total int `json:"total"`
 				} `json:"followers"`
 				Popularity int `json:"popularity"`
 			} `json:"items"`
 		} `json:"artists"`
 	}
-	
+
 	if err := c.getJSON(ctx, searchURL, token, &response); err != nil {
 		return nil, err
 	}
@@ -430,6 +452,7 @@ func (c *SpotifyMetadataClient) SearchAll(ctx context.Context, query string, tra
 			DiscNumber:  track.DiscNumber,
 			ExternalURL: track.ExternalURL.Spotify,
 			ISRC:        track.ExternalID.ISRC,
+			AlbumType:   track.Album.AlbumType,
 		})
 	}
 
@@ -438,7 +461,7 @@ func (c *SpotifyMetadataClient) SearchAll(ctx context.Context, query string, tra
 	if artistCount > artistLimit {
 		artistCount = artistLimit
 	}
-	
+
 	for i := 0; i < artistCount; i++ {
 		artist := response.Artists.Items[i]
 		result.Artists = append(result.Artists, SearchArtistResult{
@@ -534,7 +557,7 @@ func (c *SpotifyMetadataClient) fetchAlbum(ctx context.Context, albumID, token s
 	// Collect all tracks (including paginated)
 	allTrackItems := data.Tracks.Items
 	nextURL := data.Tracks.Next
-	
+
 	// Fetch remaining tracks using pagination (no limit)
 	for nextURL != "" {
 		var pageData struct {
@@ -563,7 +586,7 @@ func (c *SpotifyMetadataClient) fetchAlbum(ctx context.Context, albumID, token s
 	tracks := make([]AlbumTrackMetadata, 0, len(allTrackItems))
 	for _, item := range allTrackItems {
 		isrc := isrcMap[item.ID]
-		
+
 		tracks = append(tracks, AlbumTrackMetadata{
 			SpotifyID:   item.ID,
 			Artists:     joinArtists(item.Artists),
@@ -602,23 +625,23 @@ func (c *SpotifyMetadataClient) fetchAlbum(ctx context.Context, albumID, token s
 // Similar to Deezer implementation for consistency
 func (c *SpotifyMetadataClient) fetchISRCsParallel(ctx context.Context, trackIDs []string, token string) map[string]string {
 	const maxParallelISRC = 10 // Max concurrent ISRC fetches
-	
+
 	result := make(map[string]string)
 	var resultMu sync.Mutex
-	
+
 	if len(trackIDs) == 0 {
 		return result
 	}
-	
+
 	// Use semaphore to limit concurrent requests
 	sem := make(chan struct{}, maxParallelISRC)
 	var wg sync.WaitGroup
-	
+
 	for _, trackID := range trackIDs {
 		wg.Add(1)
 		go func(id string) {
 			defer wg.Done()
-			
+
 			// Acquire semaphore
 			select {
 			case sem <- struct{}{}:
@@ -626,15 +649,15 @@ func (c *SpotifyMetadataClient) fetchISRCsParallel(ctx context.Context, trackIDs
 			case <-ctx.Done():
 				return
 			}
-			
+
 			isrc := c.fetchTrackISRC(ctx, id, token)
-			
+
 			resultMu.Lock()
 			result[id] = isrc
 			resultMu.Unlock()
 		}(trackID)
 	}
-	
+
 	wg.Wait()
 	return result
 }
@@ -668,7 +691,7 @@ func (c *SpotifyMetadataClient) fetchPlaylist(ctx context.Context, playlistID, t
 
 	// Pre-allocate with expected capacity
 	tracks := make([]AlbumTrackMetadata, 0, data.Tracks.Total)
-	
+
 	// Add first batch of tracks
 	for _, item := range data.Tracks.Items {
 		if item.Track == nil {
@@ -695,7 +718,7 @@ func (c *SpotifyMetadataClient) fetchPlaylist(ctx context.Context, playlistID, t
 
 	// Fetch remaining tracks using pagination (NO LIMIT - fetch all tracks)
 	nextURL := data.Tracks.Next
-	
+
 	for nextURL != "" {
 		var pageData struct {
 			Items []struct {
@@ -755,10 +778,10 @@ func (c *SpotifyMetadataClient) fetchArtist(ctx context.Context, artistID, token
 
 	// Fetch artist info
 	var artistData struct {
-		ID         string  `json:"id"`
-		Name       string  `json:"name"`
-		Images     []image `json:"images"`
-		Followers  struct {
+		ID        string  `json:"id"`
+		Name      string  `json:"name"`
+		Images    []image `json:"images"`
+		Followers struct {
 			Total int `json:"total"`
 		} `json:"followers"`
 		Popularity int `json:"popularity"`
@@ -941,15 +964,15 @@ func (c *SpotifyMetadataClient) randomUserAgent() string {
 	defer c.rngMu.Unlock()
 
 	// Use Mac User-Agent format (same as PC version)
-	macMajor := c.rng.Intn(4) + 11    // 11-14
-	macMinor := c.rng.Intn(5) + 4     // 4-8
-	webkitMajor := c.rng.Intn(7) + 530 // 530-536
-	webkitMinor := c.rng.Intn(7) + 30  // 30-36
-	chromeMajor := c.rng.Intn(25) + 80 // 80-104
+	macMajor := c.rng.Intn(4) + 11         // 11-14
+	macMinor := c.rng.Intn(5) + 4          // 4-8
+	webkitMajor := c.rng.Intn(7) + 530     // 530-536
+	webkitMinor := c.rng.Intn(7) + 30      // 30-36
+	chromeMajor := c.rng.Intn(25) + 80     // 80-104
 	chromeBuild := c.rng.Intn(1500) + 3000 // 3000-4499
-	chromePatch := c.rng.Intn(65) + 60 // 60-124
-	safariMajor := c.rng.Intn(7) + 530 // 530-536
-	safariMinor := c.rng.Intn(6) + 30  // 30-35
+	chromePatch := c.rng.Intn(65) + 60     // 60-124
+	safariMajor := c.rng.Intn(7) + 530     // 530-536
+	safariMinor := c.rng.Intn(6) + 30      // 30-35
 
 	return fmt.Sprintf(
 		"Mozilla/5.0 (Macintosh; Intel Mac OS X 10_%d_%d) AppleWebKit/%d.%d (KHTML, like Gecko) Chrome/%d.0.%d.%d Safari/%d.%d",

go_backend/tidal.go

@@ -345,27 +345,28 @@ func (t *TidalDownloader) SearchTrackByISRC(isrc string) (*TidalTrack, error) {
 	return nil, fmt.Errorf("no exact ISRC match found for: %s", isrc)
 }
 
-// normalizeTitle normalizes a track title for comparison (kept for potential future use)
-func normalizeTitle(title string) string {
-	normalized := strings.ToLower(strings.TrimSpace(title))
-
-	// Remove common suffixes in parentheses or brackets
-	suffixPatterns := []string{
-		" (remaster)", " (remastered)", " (deluxe)", " (deluxe edition)",
-		" (bonus track)", " (single)", " (album version)", " (radio edit)",
-		" [remaster]", " [remastered]", " [deluxe]", " [bonus track]",
-	}
-	for _, suffix := range suffixPatterns {
-		normalized = strings.TrimSuffix(normalized, suffix)
-	}
-
-	// Remove multiple spaces
-	for strings.Contains(normalized, "  ") {
-		normalized = strings.ReplaceAll(normalized, "  ", " ")
-	}
-
-	return normalized
-}
+// normalizeTitle normalizes a track title for comparison
+// Kept for potential future use
+// func normalizeTitle(title string) string {
+// 	normalized := strings.ToLower(strings.TrimSpace(title))
+//
+// 	// Remove common suffixes in parentheses or brackets
+// 	suffixPatterns := []string{
+// 		" (remaster)", " (remastered)", " (deluxe)", " (deluxe edition)",
+// 		" (bonus track)", " (single)", " (album version)", " (radio edit)",
+// 		" [remaster]", " [remastered]", " [deluxe]", " [bonus track]",
+// 	}
+// 	for _, suffix := range suffixPatterns {
+// 		normalized = strings.TrimSuffix(normalized, suffix)
+// 	}
+//
+// 	// Remove multiple spaces
+// 	for strings.Contains(normalized, "  ") {
+// 		normalized = strings.ReplaceAll(normalized, "  ", " ")
+// 	}
+//
+// 	return normalized
+// }
 
 // SearchTrackByMetadataWithISRC searches for a track with ISRC matching priority
 // Now includes romaji conversion for Japanese text (4 search strategies like PC)
@@ -648,6 +649,7 @@ type tidalAPIResult struct {
 
 // getDownloadURLParallel requests download URL from all APIs in parallel
 // Returns the first successful result (supports both v1 and v2 API formats)
+// "Siapa cepat dia dapat" - first success wins
 func getDownloadURLParallel(apis []string, trackID int64, quality string) (string, TidalDownloadInfo, error) {
 	if len(apis) == 0 {
 		return "", TidalDownloadInfo{}, fmt.Errorf("no APIs available")
@@ -663,38 +665,33 @@ func getDownloadURLParallel(apis []string, trackID int64, quality string) (strin
 		go func(api string) {
 			reqStart := time.Now()
 
-			// Create client with longer timeout for parallel requests
+			// Create client with timeout for parallel requests
 			client := &http.Client{
 				Timeout: 15 * time.Second,
 			}
 
 			reqURL := fmt.Sprintf("%s/track/?id=%d&quality=%s", api, trackID, quality)
-			GoLog("[Tidal] [Parallel] Starting request to: %s\n", api)
 
 			req, err := http.NewRequest("GET", reqURL, nil)
 			if err != nil {
-				GoLog("[Tidal] [Parallel] %s - Failed to create request: %v\n", api, err)
 				resultChan <- tidalAPIResult{apiURL: api, err: err, duration: time.Since(reqStart)}
 				return
 			}
 
 			resp, err := client.Do(req)
 			if err != nil {
-				GoLog("[Tidal] [Parallel] %s - Request failed: %v\n", api, err)
 				resultChan <- tidalAPIResult{apiURL: api, err: err, duration: time.Since(reqStart)}
 				return
 			}
 			defer resp.Body.Close()
 
 			if resp.StatusCode != 200 {
-				GoLog("[Tidal] [Parallel] %s - HTTP %d\n", api, resp.StatusCode)
 				resultChan <- tidalAPIResult{apiURL: api, err: fmt.Errorf("HTTP %d", resp.StatusCode), duration: time.Since(reqStart)}
 				return
 			}
 
 			body, err := io.ReadAll(resp.Body)
 			if err != nil {
-				GoLog("[Tidal] [Parallel] %s - Failed to read body: %v\n", api, err)
 				resultChan <- tidalAPIResult{apiURL: api, err: err, duration: time.Since(reqStart)}
 				return
 			}
@@ -704,14 +701,10 @@ func getDownloadURLParallel(apis []string, trackID int64, quality string) (strin
 			if err := json.Unmarshal(body, &v2Response); err == nil && v2Response.Data.Manifest != "" {
 				// IMPORTANT: Reject PREVIEW responses - we need FULL tracks
 				if v2Response.Data.AssetPresentation == "PREVIEW" {
-					GoLog("[Tidal] [Parallel] %s - Rejecting PREVIEW response\n", api)
 					resultChan <- tidalAPIResult{apiURL: api, err: fmt.Errorf("returned PREVIEW instead of FULL"), duration: time.Since(reqStart)}
 					return
 				}
 
-				GoLog("[Tidal] [Parallel] %s - Got FULL track (v2): %d-bit/%dHz in %v\n",
-					api, v2Response.Data.BitDepth, v2Response.Data.SampleRate, time.Since(reqStart))
-
 				info := TidalDownloadInfo{
 					URL:        "MANIFEST:" + v2Response.Data.Manifest,
 					BitDepth:   v2Response.Data.BitDepth,
@@ -728,7 +721,6 @@ func getDownloadURLParallel(apis []string, trackID int64, quality string) (strin
 			if err := json.Unmarshal(body, &v1Responses); err == nil {
 				for _, item := range v1Responses {
 					if item.OriginalTrackURL != "" {
-						GoLog("[Tidal] [Parallel] %s - Got direct URL (v1) in %v\n", api, time.Since(reqStart))
 						info := TidalDownloadInfo{
 							URL:        item.OriginalTrackURL,
 							BitDepth:   16,
@@ -740,44 +732,37 @@ func getDownloadURLParallel(apis []string, trackID int64, quality string) (strin
 				}
 			}
 
-			GoLog("[Tidal] [Parallel] %s - No download URL in response\n", api)
 			resultChan <- tidalAPIResult{apiURL: api, err: fmt.Errorf("no download URL or manifest in response"), duration: time.Since(reqStart)}
 		}(apiURL)
 	}
 
 	// Collect results - return first success
 	var errors []string
-	successCount := 0
-	failCount := 0
+	var firstSuccess *tidalAPIResult
 
 	for i := 0; i < len(apis); i++ {
 		result := <-resultChan
-		if result.err == nil {
-			successCount++
-			if successCount == 1 {
-				// First success - use this one
-				GoLog("[Tidal] [Parallel] ✓ Using response from %s (took %v, total %v)\n",
-					result.apiURL, result.duration, time.Since(startTime))
+		if result.err == nil && firstSuccess == nil {
+			// First success - use this one
+			firstSuccess = &result
+			GoLog("[Tidal] [Parallel] ✓ Got response from %s (%d-bit/%dHz) in %v\n",
+				result.apiURL, result.info.BitDepth, result.info.SampleRate, result.duration)
 
-				// Don't return immediately - let other goroutines finish to avoid leaks
-				// But we'll use this result
-				go func() {
-					// Drain remaining results
-					for j := i + 1; j < len(apis); j++ {
-						<-resultChan
-					}
-				}()
+			// Don't return immediately - drain remaining results to avoid goroutine leaks
+			go func(remaining int) {
+				for j := 0; j < remaining; j++ {
+					<-resultChan
+				}
+			}(len(apis) - i - 1)
 
-				return result.apiURL, result.info, nil
-			}
-		} else {
-			failCount++
+			GoLog("[Tidal] [Parallel] Total time: %v (first success)\n", time.Since(startTime))
+			return firstSuccess.apiURL, firstSuccess.info, nil
+		} else if result.err != nil {
 			errMsg := result.err.Error()
 			if len(errMsg) > 50 {
 				errMsg = errMsg[:50] + "..."
 			}
 			errors = append(errors, fmt.Sprintf("%s: %s", result.apiURL, errMsg))
-			GoLog("[Tidal] [Parallel] ✗ %s failed: %s (took %v)\n", result.apiURL, errMsg, result.duration)
 		}
 	}
 
@@ -874,14 +859,16 @@ func getDownloadURLSequential(apis []string, trackID int64, quality string) (str
 	return "", TidalDownloadInfo{}, fmt.Errorf("all %d Tidal APIs failed. Errors: %v", len(apis), errors)
 }
 
-// GetDownloadURL gets download URL for a track - tries APIs sequentially
+// GetDownloadURL gets download URL for a track - tries ALL APIs in parallel
+// "Siapa cepat dia dapat" - first successful response wins
 func (t *TidalDownloader) GetDownloadURL(trackID int64, quality string) (TidalDownloadInfo, error) {
 	apis := t.GetAvailableAPIs()
 	if len(apis) == 0 {
 		return TidalDownloadInfo{}, fmt.Errorf("no API URL configured")
 	}
 
-	_, info, err := getDownloadURLSequential(apis, trackID, quality)
+	// Use parallel approach - request from all APIs simultaneously
+	_, info, err := getDownloadURLParallel(apis, trackID, quality)
 	if err != nil {
 		return TidalDownloadInfo{}, fmt.Errorf("failed to get download URL: %w", err)
 	}
@@ -1473,14 +1460,15 @@ func isLatinScript(s string) bool {
 }
 
 // isASCIIString checks if a string contains only ASCII characters
-func isASCIIString(s string) bool {
-	for _, r := range s {
-		if r > 127 {
-			return false
-		}
-	}
-	return true
-}
+// Kept for potential future use
+// func isASCIIString(s string) bool {
+// 	for _, r := range s {
+// 		if r > 127 {
+// 			return false
+// 		}
+// 	}
+// 	return true
+// }
 
 // downloadFromTidal downloads a track using the request parameters
 func downloadFromTidal(req DownloadRequest) (TidalDownloadResult, error) {

ios/Runner/AppDelegate.swift

@@ -256,6 +256,10 @@ import Gobackend  // Import Go framework
             GobackendSetSpotifyAPICredentials(clientId, clientSecret)
             return nil
             
+        case "hasSpotifyCredentials":
+            let hasCredentials = GobackendCheckSpotifyCredentials()
+            return hasCredentials
+            
         // Log methods
         case "getLogs":
             let response = GobackendGetLogs()
@@ -281,6 +285,238 @@ import Gobackend  // Import Go framework
             GobackendSetLoggingEnabled(enabled)
             return nil
             
+        // Extension System methods
+        case "initExtensionSystem":
+            let args = call.arguments as! [String: Any]
+            let extensionsDir = args["extensions_dir"] as! String
+            let dataDir = args["data_dir"] as! String
+            GobackendInitExtensionSystem(extensionsDir, dataDir, &error)
+            if let error = error { throw error }
+            return nil
+            
+        case "loadExtensionsFromDir":
+            let args = call.arguments as! [String: Any]
+            let dirPath = args["dir_path"] as! String
+            let response = GobackendLoadExtensionsFromDir(dirPath, &error)
+            if let error = error { throw error }
+            return response
+            
+        case "loadExtensionFromPath":
+            let args = call.arguments as! [String: Any]
+            let filePath = args["file_path"] as! String
+            let response = GobackendLoadExtensionFromPath(filePath, &error)
+            if let error = error { throw error }
+            return response
+            
+        case "unloadExtension":
+            let args = call.arguments as! [String: Any]
+            let extensionId = args["extension_id"] as! String
+            GobackendUnloadExtensionByID(extensionId, &error)
+            if let error = error { throw error }
+            return nil
+            
+        case "getInstalledExtensions":
+            let response = GobackendGetInstalledExtensions(&error)
+            if let error = error { throw error }
+            return response
+            
+        case "setExtensionEnabled":
+            let args = call.arguments as! [String: Any]
+            let extensionId = args["extension_id"] as! String
+            let enabled = args["enabled"] as? Bool ?? false
+            GobackendSetExtensionEnabledByID(extensionId, enabled, &error)
+            if let error = error { throw error }
+            return nil
+            
+        case "setProviderPriority":
+            let args = call.arguments as! [String: Any]
+            let priorityJson = args["priority"] as! String
+            GobackendSetProviderPriorityJSON(priorityJson, &error)
+            if let error = error { throw error }
+            return nil
+            
+        case "getProviderPriority":
+            let response = GobackendGetProviderPriorityJSON(&error)
+            if let error = error { throw error }
+            return response
+            
+        case "setMetadataProviderPriority":
+            let args = call.arguments as! [String: Any]
+            let priorityJson = args["priority"] as! String
+            GobackendSetMetadataProviderPriorityJSON(priorityJson, &error)
+            if let error = error { throw error }
+            return nil
+            
+        case "getMetadataProviderPriority":
+            let response = GobackendGetMetadataProviderPriorityJSON(&error)
+            if let error = error { throw error }
+            return response
+            
+        case "getExtensionSettings":
+            let args = call.arguments as! [String: Any]
+            let extensionId = args["extension_id"] as! String
+            let response = GobackendGetExtensionSettingsJSON(extensionId, &error)
+            if let error = error { throw error }
+            return response
+            
+        case "setExtensionSettings":
+            let args = call.arguments as! [String: Any]
+            let extensionId = args["extension_id"] as! String
+            let settingsJson = args["settings"] as! String
+            GobackendSetExtensionSettingsJSON(extensionId, settingsJson, &error)
+            if let error = error { throw error }
+            return nil
+            
+        case "searchTracksWithExtensions":
+            let args = call.arguments as! [String: Any]
+            let query = args["query"] as! String
+            let limit = args["limit"] as? Int ?? 20
+            let response = GobackendSearchTracksWithExtensionsJSON(query, Int(limit), &error)
+            if let error = error { throw error }
+            return response
+            
+        case "downloadWithExtensions":
+            let requestJson = call.arguments as! String
+            let response = GobackendDownloadWithExtensionsJSON(requestJson, &error)
+            if let error = error { throw error }
+            return response
+            
+        case "removeExtension":
+            let args = call.arguments as! [String: Any]
+            let extensionId = args["extension_id"] as! String
+            GobackendRemoveExtensionByID(extensionId, &error)
+            if let error = error { throw error }
+            return nil
+            
+        case "upgradeExtension":
+            let args = call.arguments as! [String: Any]
+            let filePath = args["file_path"] as! String
+            let response = GobackendUpgradeExtensionFromPath(filePath, &error)
+            if let error = error { throw error }
+            return response
+            
+        case "checkExtensionUpgrade":
+            let args = call.arguments as! [String: Any]
+            let filePath = args["file_path"] as! String
+            let response = GobackendCheckExtensionUpgradeFromPath(filePath, &error)
+            if let error = error { throw error }
+            return response
+            
+        case "cleanupExtensions":
+            GobackendCleanupExtensions()
+            return nil
+            
+        // Extension Auth API
+        case "getExtensionPendingAuth":
+            let args = call.arguments as! [String: Any]
+            let extensionId = args["extension_id"] as! String
+            let response = GobackendGetExtensionPendingAuthJSON(extensionId, &error)
+            if let error = error { throw error }
+            return response
+            
+        case "setExtensionAuthCode":
+            let args = call.arguments as! [String: Any]
+            let extensionId = args["extension_id"] as! String
+            let authCode = args["auth_code"] as! String
+            GobackendSetExtensionAuthCodeByID(extensionId, authCode)
+            return nil
+            
+        case "setExtensionTokens":
+            let args = call.arguments as! [String: Any]
+            let extensionId = args["extension_id"] as! String
+            let accessToken = args["access_token"] as! String
+            let refreshToken = args["refresh_token"] as? String ?? ""
+            let expiresIn = args["expires_in"] as? Int ?? 0
+            GobackendSetExtensionTokensByID(extensionId, accessToken, refreshToken, Int(expiresIn))
+            return nil
+            
+        case "clearExtensionPendingAuth":
+            let args = call.arguments as! [String: Any]
+            let extensionId = args["extension_id"] as! String
+            GobackendClearExtensionPendingAuthByID(extensionId)
+            return nil
+            
+        case "isExtensionAuthenticated":
+            let args = call.arguments as! [String: Any]
+            let extensionId = args["extension_id"] as! String
+            let response = GobackendIsExtensionAuthenticatedByID(extensionId)
+            return response
+            
+        case "getAllPendingAuthRequests":
+            let response = GobackendGetAllPendingAuthRequestsJSON(&error)
+            if let error = error { throw error }
+            return response
+            
+        // Extension FFmpeg API
+        case "getPendingFFmpegCommand":
+            let args = call.arguments as! [String: Any]
+            let commandId = args["command_id"] as! String
+            let response = GobackendGetPendingFFmpegCommandJSON(commandId, &error)
+            if let error = error { throw error }
+            return response
+            
+        case "setFFmpegCommandResult":
+            let args = call.arguments as! [String: Any]
+            let commandId = args["command_id"] as! String
+            let success = args["success"] as? Bool ?? false
+            let output = args["output"] as? String ?? ""
+            let errorMsg = args["error"] as? String ?? ""
+            GobackendSetFFmpegCommandResult(commandId, success, output, errorMsg)
+            return nil
+            
+        case "getAllPendingFFmpegCommands":
+            let response = GobackendGetAllPendingFFmpegCommandsJSON(&error)
+            if let error = error { throw error }
+            return response
+            
+        // Extension Custom Search API
+        case "customSearchWithExtension":
+            let args = call.arguments as! [String: Any]
+            let extensionId = args["extension_id"] as! String
+            let query = args["query"] as! String
+            let optionsJson = args["options"] as? String ?? ""
+            let response = GobackendCustomSearchWithExtensionJSON(extensionId, query, optionsJson, &error)
+            if let error = error { throw error }
+            return response
+            
+        case "getSearchProviders":
+            let response = GobackendGetSearchProvidersJSON(&error)
+            if let error = error { throw error }
+            return response
+            
+        // Extension URL Handler API
+        case "handleURLWithExtension":
+            let args = call.arguments as! [String: Any]
+            let url = args["url"] as! String
+            let response = GobackendHandleURLWithExtensionJSON(url, &error)
+            if let error = error { throw error }
+            return response
+            
+        case "findURLHandler":
+            let args = call.arguments as! [String: Any]
+            let url = args["url"] as! String
+            let response = GobackendFindURLHandlerJSON(url)
+            return response
+            
+        case "getURLHandlers":
+            let response = GobackendGetURLHandlersJSON(&error)
+            if let error = error { throw error }
+            return response
+            
+        // Extension Post-Processing API
+        case "runPostProcessing":
+            let args = call.arguments as! [String: Any]
+            let filePath = args["file_path"] as! String
+            let metadataJson = args["metadata"] as? String ?? ""
+            let response = GobackendRunPostProcessingJSON(filePath, metadataJson, &error)
+            if let error = error { throw error }
+            return response
+            
+        case "getPostProcessingProviders":
+            let response = GobackendGetPostProcessingProvidersJSON(&error)
+            if let error = error { throw error }
+            return response
+            
         default:
             throw NSError(
                 domain: "SpotiFLAC",

lib/constants/app_info.dart

@@ -1,8 +1,8 @@
 /// App version and info constants
 /// Update version here only - all other files will reference this
 class AppInfo {
-  static const String version = '2.2.9';
-  static const String buildNumber = '51';
+  static const String version = '3.0.0-alpha.4';
+  static const String buildNumber = '53';
   static const String fullVersion = '$version+$buildNumber';
   
   

lib/main.dart

@@ -1,7 +1,10 @@
+import 'dart:io';
 import 'package:flutter/material.dart';
 import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:path_provider/path_provider.dart';
 import 'package:spotiflac_android/app.dart';
 import 'package:spotiflac_android/providers/download_queue_provider.dart';
+import 'package:spotiflac_android/providers/extension_provider.dart';
 import 'package:spotiflac_android/services/notification_service.dart';
 import 'package:spotiflac_android/services/share_intent_service.dart';
 
@@ -24,14 +27,42 @@ void main() async {
 }
 
 /// Widget to eagerly initialize providers that need to load data on startup
-class _EagerInitialization extends ConsumerWidget {
+class _EagerInitialization extends ConsumerStatefulWidget {
   const _EagerInitialization({required this.child});
   final Widget child;
 
   @override
-  Widget build(BuildContext context, WidgetRef ref) {
+  ConsumerState<_EagerInitialization> createState() => _EagerInitializationState();
+}
+
+class _EagerInitializationState extends ConsumerState<_EagerInitialization> {
+  @override
+  void initState() {
+    super.initState();
+    _initializeExtensions();
+  }
+
+  Future<void> _initializeExtensions() async {
+    try {
+      final appDir = await getApplicationDocumentsDirectory();
+      final extensionsDir = '${appDir.path}/extensions';
+      final dataDir = '${appDir.path}/extension_data';
+      
+      // Create directories if needed
+      await Directory(extensionsDir).create(recursive: true);
+      await Directory(dataDir).create(recursive: true);
+      
+      // Initialize extension system
+      await ref.read(extensionProvider.notifier).initialize(extensionsDir, dataDir);
+    } catch (e) {
+      debugPrint('Failed to initialize extensions: $e');
+    }
+  }
+
+  @override
+  Widget build(BuildContext context) {
     // Eagerly initialize download history provider to load from storage
     ref.watch(downloadHistoryProvider);
-    return child;
+    return widget.child;
   }
 }

lib/models/settings.dart

@@ -25,6 +25,10 @@ class AppSettings {
   final bool useCustomSpotifyCredentials; // Whether to use custom credentials (if set)
   final String metadataSource; // spotify, deezer - source for search and metadata
   final bool enableLogging; // Enable detailed logging for debugging
+  final bool useExtensionProviders; // Use extension providers for downloads when available
+  final String? searchProvider; // null/empty = default (Deezer/Spotify), otherwise extension ID
+  final bool separateSingles; // Separate singles/EPs into their own folder
+  final bool showExtensionStore; // Show Extension Store tab in navigation
 
   const AppSettings({
     this.defaultService = 'tidal',
@@ -48,6 +52,10 @@ class AppSettings {
     this.useCustomSpotifyCredentials = true, // Default: use custom if set
     this.metadataSource = 'deezer', // Default: Deezer (no rate limit)
     this.enableLogging = false, // Default: disabled for performance
+    this.useExtensionProviders = true, // Default: use extensions when available
+    this.searchProvider, // Default: null (use Deezer/Spotify)
+    this.separateSingles = false, // Default: disabled
+    this.showExtensionStore = true, // Default: show store
   });
 
   AppSettings copyWith({
@@ -72,6 +80,10 @@ class AppSettings {
     bool? useCustomSpotifyCredentials,
     String? metadataSource,
     bool? enableLogging,
+    bool? useExtensionProviders,
+    String? searchProvider,
+    bool? separateSingles,
+    bool? showExtensionStore,
   }) {
     return AppSettings(
       defaultService: defaultService ?? this.defaultService,
@@ -95,6 +107,10 @@ class AppSettings {
       useCustomSpotifyCredentials: useCustomSpotifyCredentials ?? this.useCustomSpotifyCredentials,
       metadataSource: metadataSource ?? this.metadataSource,
       enableLogging: enableLogging ?? this.enableLogging,
+      useExtensionProviders: useExtensionProviders ?? this.useExtensionProviders,
+      searchProvider: searchProvider ?? this.searchProvider,
+      separateSingles: separateSingles ?? this.separateSingles,
+      showExtensionStore: showExtensionStore ?? this.showExtensionStore,
     );
   }
 

lib/models/settings.g.dart

@@ -29,6 +29,10 @@ AppSettings _$AppSettingsFromJson(Map<String, dynamic> json) => AppSettings(
       json['useCustomSpotifyCredentials'] as bool? ?? true,
   metadataSource: json['metadataSource'] as String? ?? 'deezer',
   enableLogging: json['enableLogging'] as bool? ?? false,
+  useExtensionProviders: json['useExtensionProviders'] as bool? ?? true,
+  searchProvider: json['searchProvider'] as String?,
+  separateSingles: json['separateSingles'] as bool? ?? false,
+  showExtensionStore: json['showExtensionStore'] as bool? ?? true,
 );
 
 Map<String, dynamic> _$AppSettingsToJson(AppSettings instance) =>
@@ -54,4 +58,8 @@ Map<String, dynamic> _$AppSettingsToJson(AppSettings instance) =>
       'useCustomSpotifyCredentials': instance.useCustomSpotifyCredentials,
       'metadataSource': instance.metadataSource,
       'enableLogging': instance.enableLogging,
+      'useExtensionProviders': instance.useExtensionProviders,
+      'searchProvider': instance.searchProvider,
+      'separateSingles': instance.separateSingles,
+      'showExtensionStore': instance.showExtensionStore,
     };

lib/models/track.dart

@@ -18,6 +18,8 @@ class Track {
   final String? releaseDate;
   final String? deezerId;
   final ServiceAvailability? availability;
+  final String? source; // Extension ID that provided this track (null for built-in sources)
+  final String? albumType; // album, single, ep, compilation (from metadata API)
 
   const Track({
     required this.id,
@@ -33,10 +35,18 @@ class Track {
     this.releaseDate,
     this.deezerId,
     this.availability,
+    this.source,
+    this.albumType,
   });
 
+  /// Check if this track is a single (based on album_type metadata)
+  bool get isSingle => albumType == 'single' || albumType == 'ep';
+
   factory Track.fromJson(Map<String, dynamic> json) => _$TrackFromJson(json);
   Map<String, dynamic> toJson() => _$TrackToJson(this);
+  
+  /// Check if this track is from an extension
+  bool get isFromExtension => source != null && source!.isNotEmpty;
 }
 
 @JsonSerializable()

lib/models/track.g.dart

@@ -24,6 +24,8 @@ Track _$TrackFromJson(Map<String, dynamic> json) => Track(
       : ServiceAvailability.fromJson(
           json['availability'] as Map<String, dynamic>,
         ),
+  source: json['source'] as String?,
+  albumType: json['albumType'] as String?,
 );
 
 Map<String, dynamic> _$TrackToJson(Track instance) => <String, dynamic>{
@@ -40,6 +42,8 @@ Map<String, dynamic> _$TrackToJson(Track instance) => <String, dynamic>{
   'releaseDate': instance.releaseDate,
   'deezerId': instance.deezerId,
   'availability': instance.availability,
+  'source': instance.source,
+  'albumType': instance.albumType,
 };
 
 ServiceAvailability _$ServiceAvailabilityFromJson(Map<String, dynamic> json) =>

lib/providers/download_queue_provider.dart

@@ -9,6 +9,7 @@ import 'package:spotiflac_android/models/download_item.dart';
 import 'package:spotiflac_android/models/settings.dart';
 import 'package:spotiflac_android/models/track.dart';
 import 'package:spotiflac_android/providers/settings_provider.dart';
+import 'package:spotiflac_android/providers/extension_provider.dart';
 import 'package:spotiflac_android/services/platform_bridge.dart';
 import 'package:spotiflac_android/services/ffmpeg_service.dart';
 import 'package:spotiflac_android/services/notification_service.dart';
@@ -667,35 +668,55 @@ class DownloadQueueNotifier extends Notifier<DownloadQueueState> {
     state = state.copyWith(outputDir: dir);
   }
 
-  /// Build output directory based on folder organization setting
-  Future<String> _buildOutputDir(Track track, String folderOrganization) async {
+  /// Build output directory based on folder organization setting and separateSingles
+  Future<String> _buildOutputDir(Track track, String folderOrganization, {bool separateSingles = false}) async {
     String baseDir = state.outputDir;
 
-    if (folderOrganization == 'none') {
-      return baseDir;
+    // If separateSingles is enabled, use Albums/Singles structure
+    if (separateSingles) {
+      final isSingle = track.isSingle;
+      
+      if (isSingle) {
+        // Singles go to Singles folder (flat structure)
+        final singlesPath = '$baseDir${Platform.pathSeparator}Singles';
+        final dir = Directory(singlesPath);
+        if (!await dir.exists()) {
+          await dir.create(recursive: true);
+          _log.d('Created Singles folder: $singlesPath');
+        }
+        return singlesPath;
+      } else {
+        // Albums go to Albums/Artist/Album structure
+        final artistName = _sanitizeFolderName(track.albumArtist ?? track.artistName);
+        final albumName = _sanitizeFolderName(track.albumName);
+        final albumPath = '$baseDir${Platform.pathSeparator}Albums${Platform.pathSeparator}$artistName${Platform.pathSeparator}$albumName';
+        final dir = Directory(albumPath);
+        if (!await dir.exists()) {
+          await dir.create(recursive: true);
+          _log.d('Created Album folder: $albumPath');
+        }
+        return albumPath;
+      }
     }
 
-    // Sanitize folder names (remove invalid characters)
-    String sanitize(String name) {
-      return name
-          .replaceAll(RegExp(r'[<>:"/\\|?*]'), '_')
-          .replaceAll(RegExp(r'\.+$'), '') // Remove trailing dots
-          .trim();
+    // Original folder organization logic (when separateSingles is disabled)
+    if (folderOrganization == 'none') {
+      return baseDir;
     }
 
     String subPath = '';
     switch (folderOrganization) {
       case 'artist':
-        final artistName = sanitize(track.albumArtist ?? track.artistName);
+        final artistName = _sanitizeFolderName(track.albumArtist ?? track.artistName);
         subPath = artistName;
         break;
       case 'album':
-        final albumName = sanitize(track.albumName);
+        final albumName = _sanitizeFolderName(track.albumName);
         subPath = albumName;
         break;
       case 'artist_album':
-        final artistName = sanitize(track.albumArtist ?? track.artistName);
-        final albumName = sanitize(track.albumName);
+        final artistName = _sanitizeFolderName(track.albumArtist ?? track.artistName);
+        final albumName = _sanitizeFolderName(track.albumName);
         subPath = '$artistName${Platform.pathSeparator}$albumName';
         break;
     }
@@ -713,6 +734,14 @@ class DownloadQueueNotifier extends Notifier<DownloadQueueState> {
     return baseDir;
   }
 
+  /// Sanitize folder names (remove invalid characters)
+  String _sanitizeFolderName(String name) {
+    return name
+        .replaceAll(RegExp(r'[<>:"/\\|?*]'), '_')
+        .replaceAll(RegExp(r'\.+$'), '') // Remove trailing dots
+        .trim();
+  }
+
   void updateSettings(AppSettings settings) {
     state = state.copyWith(
       outputDir: settings.downloadDirectory.isNotEmpty
@@ -922,6 +951,56 @@ class DownloadQueueNotifier extends Notifier<DownloadQueueState> {
     _saveQueueToStorage(); // Persist queue
   }
 
+  /// Run post-processing hooks on a downloaded file
+  Future<void> _runPostProcessingHooks(String filePath, Track track) async {
+    try {
+      final settings = ref.read(settingsProvider);
+      final extensionState = ref.read(extensionProvider);
+      
+      // Check if post-processing is enabled and there are extensions with hooks
+      if (!settings.useExtensionProviders) return;
+      
+      final hasPostProcessing = extensionState.extensions.any(
+        (e) => e.enabled && e.hasPostProcessing,
+      );
+      if (!hasPostProcessing) return;
+      
+      _log.d('Running post-processing hooks on: $filePath');
+      
+      // Build metadata map for post-processing
+      final metadata = <String, dynamic>{
+        'title': track.name,
+        'artist': track.artistName,
+        'album': track.albumName,
+        'album_artist': track.albumArtist ?? track.artistName,
+        'track_number': track.trackNumber ?? 1,
+        'disc_number': track.discNumber ?? 1,
+        'isrc': track.isrc ?? '',
+        'release_date': track.releaseDate ?? '',
+        'duration_ms': track.duration * 1000,
+        'cover_url': track.coverUrl ?? '',
+      };
+      
+      final result = await PlatformBridge.runPostProcessing(filePath, metadata: metadata);
+      
+      if (result['success'] == true) {
+        final hooksRun = result['hooks_run'] as int? ?? 0;
+        final newPath = result['file_path'] as String?;
+        _log.i('Post-processing completed: $hooksRun hook(s) executed');
+        
+        if (newPath != null && newPath != filePath) {
+          _log.d('File path changed by post-processing: $newPath');
+        }
+      } else {
+        final error = result['error'] as String? ?? 'Unknown error';
+        _log.w('Post-processing failed: $error');
+      }
+    } catch (e) {
+      _log.w('Post-processing error: $e');
+      // Don't fail the download if post-processing fails
+    }
+  }
+
   /// Embed metadata and cover to a FLAC file after M4A conversion
   Future<void> _embedMetadataAndCover(String flacPath, Track track) async {
     // Download cover first
@@ -1366,6 +1445,7 @@ class DownloadQueueNotifier extends Notifier<DownloadQueueState> {
       final outputDir = await _buildOutputDir(
         trackToDownload,
         settings.folderOrganization,
+        separateSingles: settings.separateSingles,
       );
 
       // Use quality override if set, otherwise use default from settings
@@ -1373,7 +1453,37 @@ class DownloadQueueNotifier extends Notifier<DownloadQueueState> {
 
       Map<String, dynamic> result;
 
-      if (state.autoFallback) {
+      // Check if extension providers should be used
+      final extensionState = ref.read(extensionProvider);
+      final hasActiveExtensions = extensionState.extensions.any((e) => e.enabled);
+      final useExtensions = settings.useExtensionProviders && hasActiveExtensions;
+
+      if (useExtensions) {
+        // Use extension providers (includes fallback to built-in services)
+        _log.d('Using extension providers for download');
+        _log.d(
+          'Quality: $quality${item.qualityOverride != null ? ' (override)' : ''}',
+        );
+        _log.d('Output dir: $outputDir');
+        result = await PlatformBridge.downloadWithExtensions(
+          isrc: trackToDownload.isrc ?? '',
+          spotifyId: trackToDownload.id,
+          trackName: trackToDownload.name,
+          artistName: trackToDownload.artistName,
+          albumName: trackToDownload.albumName,
+          albumArtist: trackToDownload.albumArtist,
+          coverUrl: trackToDownload.coverUrl,
+          outputDir: outputDir,
+          filenameFormat: state.filenameFormat,
+          quality: quality,
+          trackNumber: trackToDownload.trackNumber ?? 1,
+          discNumber: trackToDownload.discNumber ?? 1,
+          releaseDate: trackToDownload.releaseDate,
+          itemId: item.id,
+          durationMs: trackToDownload.duration,
+          source: trackToDownload.source, // Pass extension ID that provided this track
+        );
+      } else if (state.autoFallback) {
         _log.d('Using auto-fallback mode');
         _log.d(
           'Quality: $quality${item.qualityOverride != null ? ' (override)' : ''}',
@@ -1593,6 +1703,11 @@ class DownloadQueueNotifier extends Notifier<DownloadQueueState> {
           filePath: filePath,
         );
 
+        // Run post-processing hooks if enabled
+        if (filePath != null) {
+          await _runPostProcessingHooks(filePath, trackToDownload);
+        }
+
         // Increment completed counter
         _completedInSession++;
 

lib/providers/extension_provider.dart

@@ -0,0 +1,715 @@
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:spotiflac_android/services/platform_bridge.dart';
+import 'package:spotiflac_android/utils/logger.dart';
+import 'package:spotiflac_android/providers/settings_provider.dart';
+
+final _log = AppLogger('ExtensionProvider');
+
+/// Represents an installed extension
+class Extension {
+  final String id;
+  final String name;
+  final String displayName;
+  final String version;
+  final String author;
+  final String description;
+  final bool enabled;
+  final String status; // 'loaded', 'error', 'disabled'
+  final String? errorMessage;
+  final String? iconPath; // Path to extension icon
+  final List<String> permissions;
+  final List<ExtensionSetting> settings;
+  final List<QualityOption> qualityOptions; // Custom quality options for download providers
+  final bool hasMetadataProvider;
+  final bool hasDownloadProvider;
+  final bool skipMetadataEnrichment; // If true, use metadata from extension instead of enriching
+  final SearchBehavior? searchBehavior; // Custom search behavior
+  final URLHandler? urlHandler; // Custom URL handling
+  final TrackMatching? trackMatching; // Custom track matching
+  final PostProcessing? postProcessing; // Post-processing hooks
+
+  const Extension({
+    required this.id,
+    required this.name,
+    required this.displayName,
+    required this.version,
+    required this.author,
+    required this.description,
+    required this.enabled,
+    required this.status,
+    this.errorMessage,
+    this.iconPath,
+    this.permissions = const [],
+    this.settings = const [],
+    this.qualityOptions = const [],
+    this.hasMetadataProvider = false,
+    this.hasDownloadProvider = false,
+    this.skipMetadataEnrichment = false,
+    this.searchBehavior,
+    this.urlHandler,
+    this.trackMatching,
+    this.postProcessing,
+  });
+
+  factory Extension.fromJson(Map<String, dynamic> json) {
+    return Extension(
+      id: json['id'] as String? ?? '',
+      name: json['name'] as String? ?? '',
+      displayName: json['display_name'] as String? ?? json['name'] as String? ?? '',
+      version: json['version'] as String? ?? '0.0.0',
+      author: json['author'] as String? ?? 'Unknown',
+      description: json['description'] as String? ?? '',
+      enabled: json['enabled'] as bool? ?? false,
+      status: json['status'] as String? ?? 'loaded',
+      errorMessage: json['error_message'] as String?,
+      iconPath: json['icon_path'] as String?,
+      permissions: (json['permissions'] as List<dynamic>?)?.cast<String>() ?? [],
+      settings: (json['settings'] as List<dynamic>?)
+          ?.map((s) => ExtensionSetting.fromJson(s as Map<String, dynamic>))
+          .toList() ?? [],
+      qualityOptions: (json['quality_options'] as List<dynamic>?)
+          ?.map((q) => QualityOption.fromJson(q as Map<String, dynamic>))
+          .toList() ?? [],
+      hasMetadataProvider: json['has_metadata_provider'] as bool? ?? false,
+      hasDownloadProvider: json['has_download_provider'] as bool? ?? false,
+      skipMetadataEnrichment: json['skip_metadata_enrichment'] as bool? ?? false,
+      searchBehavior: json['search_behavior'] != null 
+          ? SearchBehavior.fromJson(json['search_behavior'] as Map<String, dynamic>)
+          : null,
+      urlHandler: json['url_handler'] != null
+          ? URLHandler.fromJson(json['url_handler'] as Map<String, dynamic>)
+          : null,
+      trackMatching: json['track_matching'] != null
+          ? TrackMatching.fromJson(json['track_matching'] as Map<String, dynamic>)
+          : null,
+      postProcessing: json['post_processing'] != null
+          ? PostProcessing.fromJson(json['post_processing'] as Map<String, dynamic>)
+          : null,
+    );
+  }
+
+  Extension copyWith({
+    String? id,
+    String? name,
+    String? displayName,
+    String? version,
+    String? author,
+    String? description,
+    bool? enabled,
+    String? status,
+    String? errorMessage,
+    String? iconPath,
+    List<String>? permissions,
+    List<ExtensionSetting>? settings,
+    List<QualityOption>? qualityOptions,
+    bool? hasMetadataProvider,
+    bool? hasDownloadProvider,
+    bool? skipMetadataEnrichment,
+    SearchBehavior? searchBehavior,
+    URLHandler? urlHandler,
+    TrackMatching? trackMatching,
+    PostProcessing? postProcessing,
+  }) {
+    return Extension(
+      id: id ?? this.id,
+      name: name ?? this.name,
+      displayName: displayName ?? this.displayName,
+      version: version ?? this.version,
+      author: author ?? this.author,
+      description: description ?? this.description,
+      enabled: enabled ?? this.enabled,
+      status: status ?? this.status,
+      errorMessage: errorMessage ?? this.errorMessage,
+      iconPath: iconPath ?? this.iconPath,
+      permissions: permissions ?? this.permissions,
+      settings: settings ?? this.settings,
+      qualityOptions: qualityOptions ?? this.qualityOptions,
+      hasMetadataProvider: hasMetadataProvider ?? this.hasMetadataProvider,
+      hasDownloadProvider: hasDownloadProvider ?? this.hasDownloadProvider,
+      skipMetadataEnrichment: skipMetadataEnrichment ?? this.skipMetadataEnrichment,
+      searchBehavior: searchBehavior ?? this.searchBehavior,
+      urlHandler: urlHandler ?? this.urlHandler,
+      trackMatching: trackMatching ?? this.trackMatching,
+      postProcessing: postProcessing ?? this.postProcessing,
+    );
+  }
+
+  bool get hasCustomSearch => searchBehavior?.enabled ?? false;
+  bool get hasURLHandler => urlHandler?.enabled ?? false;
+  bool get hasCustomMatching => trackMatching?.customMatching ?? false;
+  bool get hasPostProcessing => postProcessing?.enabled ?? false;
+}
+
+/// Custom search behavior configuration
+class SearchBehavior {
+  final bool enabled;
+  final String? placeholder;
+  final bool primary;
+  final String? icon;
+  final String? thumbnailRatio; // "square" (1:1), "wide" (16:9), "portrait" (2:3)
+  final int? thumbnailWidth;
+  final int? thumbnailHeight;
+
+  const SearchBehavior({
+    required this.enabled,
+    this.placeholder,
+    this.primary = false,
+    this.icon,
+    this.thumbnailRatio,
+    this.thumbnailWidth,
+    this.thumbnailHeight,
+  });
+
+  factory SearchBehavior.fromJson(Map<String, dynamic> json) {
+    return SearchBehavior(
+      enabled: json['enabled'] as bool? ?? false,
+      placeholder: json['placeholder'] as String?,
+      primary: json['primary'] as bool? ?? false,
+      icon: json['icon'] as String?,
+      thumbnailRatio: json['thumbnailRatio'] as String?,
+      thumbnailWidth: json['thumbnailWidth'] as int?,
+      thumbnailHeight: json['thumbnailHeight'] as int?,
+    );
+  }
+
+  /// Get thumbnail size based on configuration
+  /// Returns (width, height) tuple
+  (double, double) getThumbnailSize({double defaultSize = 56}) {
+    // If custom dimensions specified, use them
+    if (thumbnailWidth != null && thumbnailHeight != null) {
+      return (thumbnailWidth!.toDouble(), thumbnailHeight!.toDouble());
+    }
+    
+    // Otherwise use ratio presets
+    switch (thumbnailRatio) {
+      case 'wide': // 16:9 - YouTube style
+        return (defaultSize * 16 / 9, defaultSize);
+      case 'portrait': // 2:3 - Poster style
+        return (defaultSize * 2 / 3, defaultSize);
+      case 'square': // 1:1 - Album art style
+      default:
+        return (defaultSize, defaultSize);
+    }
+  }
+}
+
+/// Custom track matching configuration
+class TrackMatching {
+  final bool customMatching;
+  final String? strategy; // "isrc", "name", "duration", "custom"
+  final int durationTolerance; // in seconds
+
+  const TrackMatching({
+    required this.customMatching,
+    this.strategy,
+    this.durationTolerance = 3,
+  });
+
+  factory TrackMatching.fromJson(Map<String, dynamic> json) {
+    return TrackMatching(
+      customMatching: json['customMatching'] as bool? ?? false,
+      strategy: json['strategy'] as String?,
+      durationTolerance: json['durationTolerance'] as int? ?? 3,
+    );
+  }
+}
+
+/// Post-processing configuration
+class PostProcessing {
+  final bool enabled;
+  final List<PostProcessingHook> hooks;
+
+  const PostProcessing({
+    required this.enabled,
+    this.hooks = const [],
+  });
+
+  factory PostProcessing.fromJson(Map<String, dynamic> json) {
+    return PostProcessing(
+      enabled: json['enabled'] as bool? ?? false,
+      hooks: (json['hooks'] as List<dynamic>?)
+          ?.map((h) => PostProcessingHook.fromJson(h as Map<String, dynamic>))
+          .toList() ?? [],
+    );
+  }
+}
+
+/// URL handler configuration for custom URL patterns
+class URLHandler {
+  final bool enabled;
+  final List<String> patterns;
+
+  const URLHandler({
+    required this.enabled,
+    this.patterns = const [],
+  });
+
+  factory URLHandler.fromJson(Map<String, dynamic> json) {
+    return URLHandler(
+      enabled: json['enabled'] as bool? ?? false,
+      patterns: (json['patterns'] as List<dynamic>?)?.cast<String>() ?? [],
+    );
+  }
+
+  /// Check if a URL matches any of the patterns
+  bool matchesURL(String url) {
+    if (!enabled || patterns.isEmpty) return false;
+    final lowerUrl = url.toLowerCase();
+    for (final pattern in patterns) {
+      if (lowerUrl.contains(pattern.toLowerCase())) {
+        return true;
+      }
+    }
+    return false;
+  }
+}
+
+/// A post-processing hook
+class PostProcessingHook {
+  final String id;
+  final String name;
+  final String? description;
+  final bool defaultEnabled;
+  final List<String> supportedFormats;
+
+  const PostProcessingHook({
+    required this.id,
+    required this.name,
+    this.description,
+    this.defaultEnabled = false,
+    this.supportedFormats = const [],
+  });
+
+  factory PostProcessingHook.fromJson(Map<String, dynamic> json) {
+    return PostProcessingHook(
+      id: json['id'] as String? ?? '',
+      name: json['name'] as String? ?? '',
+      description: json['description'] as String?,
+      defaultEnabled: json['defaultEnabled'] as bool? ?? false,
+      supportedFormats: (json['supportedFormats'] as List<dynamic>?)?.cast<String>() ?? [],
+    );
+  }
+}
+
+/// Represents a quality option for download providers
+class QualityOption {
+  final String id;
+  final String label;
+  final String? description;
+  final List<QualitySpecificSetting> settings; // Quality-specific settings
+
+  const QualityOption({
+    required this.id,
+    required this.label,
+    this.description,
+    this.settings = const [],
+  });
+
+  factory QualityOption.fromJson(Map<String, dynamic> json) {
+    return QualityOption(
+      id: json['id'] as String? ?? '',
+      label: json['label'] as String? ?? '',
+      description: json['description'] as String?,
+      settings: (json['settings'] as List<dynamic>?)
+          ?.map((s) => QualitySpecificSetting.fromJson(s as Map<String, dynamic>))
+          .toList() ?? [],
+    );
+  }
+}
+
+/// Represents a setting that's specific to a quality option
+class QualitySpecificSetting {
+  final String key;
+  final String label;
+  final String type; // 'string', 'number', 'boolean', 'select'
+  final dynamic defaultValue;
+  final String? description;
+  final List<String>? options; // For select type
+  final bool required;
+  final bool secret;
+
+  const QualitySpecificSetting({
+    required this.key,
+    required this.label,
+    required this.type,
+    this.defaultValue,
+    this.description,
+    this.options,
+    this.required = false,
+    this.secret = false,
+  });
+
+  factory QualitySpecificSetting.fromJson(Map<String, dynamic> json) {
+    return QualitySpecificSetting(
+      key: json['key'] as String? ?? '',
+      label: json['label'] as String? ?? '',
+      type: json['type'] as String? ?? 'string',
+      defaultValue: json['default'],
+      description: json['description'] as String?,
+      options: (json['options'] as List<dynamic>?)?.cast<String>(),
+      required: json['required'] as bool? ?? false,
+      secret: json['secret'] as bool? ?? false,
+    );
+  }
+}
+
+/// Represents a setting field for an extension
+class ExtensionSetting {
+  final String key;
+  final String label;
+  final String type; // 'string', 'number', 'boolean', 'select'
+  final dynamic defaultValue;
+  final String? description;
+  final List<String>? options; // For select type
+  final bool required;
+
+  const ExtensionSetting({
+    required this.key,
+    required this.label,
+    required this.type,
+    this.defaultValue,
+    this.description,
+    this.options,
+    this.required = false,
+  });
+
+  factory ExtensionSetting.fromJson(Map<String, dynamic> json) {
+    return ExtensionSetting(
+      key: json['key'] as String? ?? '',
+      label: json['label'] as String? ?? '',
+      type: json['type'] as String? ?? 'string',
+      defaultValue: json['default'],
+      description: json['description'] as String?,
+      options: (json['options'] as List<dynamic>?)?.cast<String>(),
+      required: json['required'] as bool? ?? false,
+    );
+  }
+}
+
+/// State for extension management
+class ExtensionState {
+  final List<Extension> extensions;
+  final List<String> providerPriority;
+  final List<String> metadataProviderPriority;
+  final bool isLoading;
+  final String? error;
+  final bool isInitialized;
+
+  const ExtensionState({
+    this.extensions = const [],
+    this.providerPriority = const [],
+    this.metadataProviderPriority = const [],
+    this.isLoading = false,
+    this.error,
+    this.isInitialized = false,
+  });
+
+  ExtensionState copyWith({
+    List<Extension>? extensions,
+    List<String>? providerPriority,
+    List<String>? metadataProviderPriority,
+    bool? isLoading,
+    String? error,
+    bool? isInitialized,
+  }) {
+    return ExtensionState(
+      extensions: extensions ?? this.extensions,
+      providerPriority: providerPriority ?? this.providerPriority,
+      metadataProviderPriority: metadataProviderPriority ?? this.metadataProviderPriority,
+      isLoading: isLoading ?? this.isLoading,
+      error: error,
+      isInitialized: isInitialized ?? this.isInitialized,
+    );
+  }
+}
+
+
+/// Provider for managing extensions
+class ExtensionNotifier extends Notifier<ExtensionState> {
+  @override
+  ExtensionState build() {
+    return const ExtensionState();
+  }
+
+  /// Initialize the extension system
+  Future<void> initialize(String extensionsDir, String dataDir) async {
+    if (state.isInitialized) return;
+    
+    state = state.copyWith(isLoading: true, error: null);
+    
+    try {
+      await PlatformBridge.initExtensionSystem(extensionsDir, dataDir);
+      await loadExtensions(extensionsDir);
+      await loadProviderPriority();
+      await loadMetadataProviderPriority();
+      state = state.copyWith(isInitialized: true, isLoading: false);
+      _log.i('Extension system initialized');
+    } catch (e) {
+      _log.e('Failed to initialize extension system: $e');
+      state = state.copyWith(isLoading: false, error: e.toString());
+    }
+  }
+
+  /// Load all extensions from directory
+  Future<void> loadExtensions(String dirPath) async {
+    state = state.copyWith(isLoading: true, error: null);
+    
+    try {
+      final result = await PlatformBridge.loadExtensionsFromDir(dirPath);
+      _log.d('Load extensions result: $result');
+      await refreshExtensions();
+      state = state.copyWith(isLoading: false);
+    } catch (e) {
+      _log.e('Failed to load extensions: $e');
+      state = state.copyWith(isLoading: false, error: e.toString());
+    }
+  }
+
+  /// Refresh the list of installed extensions
+  Future<void> refreshExtensions() async {
+    try {
+      final list = await PlatformBridge.getInstalledExtensions();
+      final extensions = list.map((e) => Extension.fromJson(e)).toList();
+      state = state.copyWith(extensions: extensions);
+      _log.d('Loaded ${extensions.length} extensions');
+      
+      // Log search behavior for extensions that have it
+      for (final ext in extensions) {
+        if (ext.searchBehavior != null) {
+          _log.d('Extension ${ext.id}: thumbnailRatio=${ext.searchBehavior!.thumbnailRatio}');
+        }
+      }
+    } catch (e) {
+      _log.e('Failed to refresh extensions: $e');
+      state = state.copyWith(error: e.toString());
+    }
+  }
+
+  /// Clear any error state
+  void clearError() {
+    state = state.copyWith(error: null);
+  }
+
+  /// Install extension from file (auto-upgrades if already installed with newer version)
+  Future<bool> installExtension(String filePath) async {
+    state = state.copyWith(isLoading: true, error: null);
+    
+    try {
+      final result = await PlatformBridge.loadExtensionFromPath(filePath);
+      _log.i('Installed extension: ${result['name']}');
+      await refreshExtensions();
+      state = state.copyWith(isLoading: false);
+      return true;
+    } catch (e) {
+      _log.e('Failed to install extension: $e');
+      state = state.copyWith(isLoading: false, error: e.toString());
+      return false;
+    }
+  }
+
+  /// Check if a package file is an upgrade for an existing extension
+  /// Returns: {extension_id, current_version, new_version, can_upgrade, is_installed}
+  Future<Map<String, dynamic>> checkExtensionUpgrade(String filePath) async {
+    try {
+      return await PlatformBridge.checkExtensionUpgrade(filePath);
+    } catch (e) {
+      _log.e('Failed to check extension upgrade: $e');
+      return {'error': e.toString()};
+    }
+  }
+
+  /// Upgrade an existing extension from a new package file
+  Future<bool> upgradeExtension(String filePath) async {
+    state = state.copyWith(isLoading: true, error: null);
+    
+    try {
+      final result = await PlatformBridge.upgradeExtension(filePath);
+      _log.i('Upgraded extension: ${result['display_name']} to v${result['version']}');
+      await refreshExtensions();
+      state = state.copyWith(isLoading: false);
+      return true;
+    } catch (e) {
+      _log.e('Failed to upgrade extension: $e');
+      state = state.copyWith(isLoading: false, error: e.toString());
+      return false;
+    }
+  }
+
+  /// Uninstall/remove an extension
+  Future<bool> removeExtension(String extensionId) async {
+    state = state.copyWith(isLoading: true, error: null);
+    
+    try {
+      await PlatformBridge.removeExtension(extensionId);
+      _log.i('Removed extension: $extensionId');
+      await refreshExtensions();
+      state = state.copyWith(isLoading: false);
+      return true;
+    } catch (e) {
+      _log.e('Failed to remove extension: $e');
+      state = state.copyWith(isLoading: false, error: e.toString());
+      return false;
+    }
+  }
+
+  /// Enable or disable an extension
+  Future<void> setExtensionEnabled(String extensionId, bool enabled) async {
+    try {
+      await PlatformBridge.setExtensionEnabled(extensionId, enabled);
+      _log.d('Set extension $extensionId enabled: $enabled');
+      
+      // Get extension info before updating state
+      final ext = state.extensions.where((e) => e.id == extensionId).firstOrNull;
+      
+      // Update local state
+      final extensions = state.extensions.map((e) {
+        if (e.id == extensionId) {
+          return e.copyWith(enabled: enabled);
+        }
+        return e;
+      }).toList();
+      
+      state = state.copyWith(extensions: extensions);
+      
+      // If disabling an extension, reset related settings
+      if (!enabled && ext != null) {
+        final settings = ref.read(settingsProvider);
+        
+        // If this extension was the search provider, clear it and reset to Deezer
+        if (settings.searchProvider == extensionId) {
+          ref.read(settingsProvider.notifier).setSearchProvider(null);
+          ref.read(settingsProvider.notifier).setMetadataSource('deezer');
+          _log.d('Cleared search provider and reset to Deezer because extension $extensionId was disabled');
+        }
+        
+        // If this extension was the default download service, reset to Tidal
+        if (ext.hasDownloadProvider && settings.defaultService == extensionId) {
+          ref.read(settingsProvider.notifier).setDefaultService('tidal');
+          _log.d('Reset default service to Tidal because extension $extensionId was disabled');
+        }
+      }
+    } catch (e) {
+      _log.e('Failed to set extension enabled: $e');
+      state = state.copyWith(error: e.toString());
+    }
+  }
+
+  /// Get settings for an extension
+  Future<Map<String, dynamic>> getExtensionSettings(String extensionId) async {
+    try {
+      return await PlatformBridge.getExtensionSettings(extensionId);
+    } catch (e) {
+      _log.e('Failed to get extension settings: $e');
+      return {};
+    }
+  }
+
+  /// Update settings for an extension
+  Future<void> setExtensionSettings(String extensionId, Map<String, dynamic> settings) async {
+    try {
+      await PlatformBridge.setExtensionSettings(extensionId, settings);
+      _log.d('Updated settings for extension: $extensionId');
+    } catch (e) {
+      _log.e('Failed to set extension settings: $e');
+      state = state.copyWith(error: e.toString());
+    }
+  }
+
+  /// Load provider priority order
+  Future<void> loadProviderPriority() async {
+    try {
+      final priority = await PlatformBridge.getProviderPriority();
+      state = state.copyWith(providerPriority: priority);
+    } catch (e) {
+      _log.e('Failed to load provider priority: $e');
+    }
+  }
+
+  /// Set provider priority order
+  Future<void> setProviderPriority(List<String> priority) async {
+    try {
+      await PlatformBridge.setProviderPriority(priority);
+      state = state.copyWith(providerPriority: priority);
+      _log.d('Updated provider priority: $priority');
+    } catch (e) {
+      _log.e('Failed to set provider priority: $e');
+      state = state.copyWith(error: e.toString());
+    }
+  }
+
+  /// Load metadata provider priority order
+  Future<void> loadMetadataProviderPriority() async {
+    try {
+      final priority = await PlatformBridge.getMetadataProviderPriority();
+      state = state.copyWith(metadataProviderPriority: priority);
+    } catch (e) {
+      _log.e('Failed to load metadata provider priority: $e');
+    }
+  }
+
+  /// Set metadata provider priority order
+  Future<void> setMetadataProviderPriority(List<String> priority) async {
+    try {
+      await PlatformBridge.setMetadataProviderPriority(priority);
+      state = state.copyWith(metadataProviderPriority: priority);
+      _log.d('Updated metadata provider priority: $priority');
+    } catch (e) {
+      _log.e('Failed to set metadata provider priority: $e');
+      state = state.copyWith(error: e.toString());
+    }
+  }
+
+  /// Cleanup all extensions (call on app close)
+  Future<void> cleanup() async {
+    try {
+      await PlatformBridge.cleanupExtensions();
+      _log.d('Extensions cleaned up');
+    } catch (e) {
+      _log.e('Failed to cleanup extensions: $e');
+    }
+  }
+
+  /// Get extension by ID
+  Extension? getExtension(String extensionId) {
+    try {
+      return state.extensions.firstWhere((ext) => ext.id == extensionId);
+    } catch (_) {
+      return null;
+    }
+  }
+
+  /// Get all enabled extensions
+  List<Extension> get enabledExtensions {
+    return state.extensions.where((ext) => ext.enabled).toList();
+  }
+
+  /// Get all download providers (built-in + extensions)
+  List<String> getAllDownloadProviders() {
+    final providers = ['tidal', 'qobuz', 'amazon'];
+    for (final ext in state.extensions) {
+      if (ext.enabled && ext.hasDownloadProvider) {
+        providers.add(ext.id);
+      }
+    }
+    return providers;
+  }
+
+  /// Get all metadata providers (built-in + extensions)
+  List<String> getAllMetadataProviders() {
+    final providers = ['deezer', 'spotify'];
+    for (final ext in state.extensions) {
+      if (ext.enabled && ext.hasMetadataProvider) {
+        providers.add(ext.id);
+      }
+    }
+    return providers;
+  }
+  /// Get all extensions that provide custom search
+  List<Extension> get searchProviders {
+    return state.extensions.where((ext) => ext.enabled && ext.hasCustomSearch).toList();
+  }
+}
+
+final extensionProvider = NotifierProvider<ExtensionNotifier, ExtensionState>(
+  ExtensionNotifier.new,
+);

lib/providers/settings_provider.dart

@@ -60,18 +60,16 @@ class SettingsNotifier extends Notifier<AppSettings> {
 
   /// Apply current Spotify credentials to Go backend
   Future<void> _applySpotifyCredentials() async {
-    // Only apply custom credentials if enabled and both fields are set
-    if (state.useCustomSpotifyCredentials && 
-        state.spotifyClientId.isNotEmpty && 
+    // Only apply if both fields are set
+    if (state.spotifyClientId.isNotEmpty && 
         state.spotifyClientSecret.isNotEmpty) {
       await PlatformBridge.setSpotifyCredentials(
         state.spotifyClientId,
         state.spotifyClientSecret,
       );
-    } else {
-      // Clear to use default
-      await PlatformBridge.setSpotifyCredentials('', '');
     }
+    // Note: If credentials are empty, Spotify API will return error
+    // User should use Deezer as metadata source instead
   }
 
   void setDefaultService(String service) {
@@ -197,12 +195,32 @@ class SettingsNotifier extends Notifier<AppSettings> {
     _saveSettings();
   }
 
+  void setSearchProvider(String? provider) {
+    state = state.copyWith(searchProvider: provider);
+    _saveSettings();
+  }
+
   void setEnableLogging(bool enabled) {
     state = state.copyWith(enableLogging: enabled);
     _saveSettings();
     // Sync logging state to LogBuffer
     LogBuffer.loggingEnabled = enabled;
   }
+
+  void setUseExtensionProviders(bool enabled) {
+    state = state.copyWith(useExtensionProviders: enabled);
+    _saveSettings();
+  }
+
+  void setSeparateSingles(bool enabled) {
+    state = state.copyWith(separateSingles: enabled);
+    _saveSettings();
+  }
+
+  void setShowExtensionStore(bool enabled) {
+    state = state.copyWith(showExtensionStore: enabled);
+    _saveSettings();
+  }
 }
 
 final settingsProvider = NotifierProvider<SettingsNotifier, AppSettings>(

lib/providers/store_provider.dart

@@ -0,0 +1,286 @@
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:spotiflac_android/services/platform_bridge.dart';
+import 'package:spotiflac_android/utils/logger.dart';
+import 'package:spotiflac_android/providers/extension_provider.dart';
+
+final _log = AppLogger('StoreProvider');
+
+/// Extension categories
+class StoreCategory {
+  static const String metadata = 'metadata';
+  static const String download = 'download';
+  static const String utility = 'utility';
+  static const String lyrics = 'lyrics';
+  static const String integration = 'integration';
+
+  static const List<String> all = [metadata, download, utility, lyrics, integration];
+
+  static String getDisplayName(String category) {
+    switch (category) {
+      case metadata:
+        return 'Metadata';
+      case download:
+        return 'Download';
+      case utility:
+        return 'Utility';
+      case lyrics:
+        return 'Lyrics';
+      case integration:
+        return 'Integration';
+      default:
+        return category;
+    }
+  }
+}
+
+/// Represents an extension in the store
+class StoreExtension {
+  final String id;
+  final String name;
+  final String displayName;
+  final String version;
+  final String author;
+  final String description;
+  final String downloadUrl;
+  final String? iconUrl;
+  final String category;
+  final List<String> tags;
+  final int downloads;
+  final String updatedAt;
+  final String? minAppVersion;
+  final bool isInstalled;
+  final String? installedVersion;
+  final bool hasUpdate;
+
+  const StoreExtension({
+    required this.id,
+    required this.name,
+    required this.displayName,
+    required this.version,
+    required this.author,
+    required this.description,
+    required this.downloadUrl,
+    this.iconUrl,
+    required this.category,
+    this.tags = const [],
+    this.downloads = 0,
+    required this.updatedAt,
+    this.minAppVersion,
+    this.isInstalled = false,
+    this.installedVersion,
+    this.hasUpdate = false,
+  });
+
+  factory StoreExtension.fromJson(Map<String, dynamic> json) {
+    return StoreExtension(
+      id: json['id'] as String? ?? '',
+      name: json['name'] as String? ?? '',
+      displayName: json['display_name'] as String? ?? json['name'] as String? ?? '',
+      version: json['version'] as String? ?? '0.0.0',
+      author: json['author'] as String? ?? 'Unknown',
+      description: json['description'] as String? ?? '',
+      downloadUrl: json['download_url'] as String? ?? '',
+      iconUrl: json['icon_url'] as String?,
+      category: json['category'] as String? ?? 'utility',
+      tags: (json['tags'] as List<dynamic>?)?.cast<String>() ?? [],
+      downloads: json['downloads'] as int? ?? 0,
+      updatedAt: json['updated_at'] as String? ?? '',
+      minAppVersion: json['min_app_version'] as String?,
+      isInstalled: json['is_installed'] as bool? ?? false,
+      installedVersion: json['installed_version'] as String?,
+      hasUpdate: json['has_update'] as bool? ?? false,
+    );
+  }
+}
+
+/// State for extension store
+class StoreState {
+  final List<StoreExtension> extensions;
+  final String? selectedCategory;
+  final String searchQuery;
+  final bool isLoading;
+  final bool isDownloading;
+  final String? downloadingId;
+  final String? error;
+  final bool isInitialized;
+
+  const StoreState({
+    this.extensions = const [],
+    this.selectedCategory,
+    this.searchQuery = '',
+    this.isLoading = false,
+    this.isDownloading = false,
+    this.downloadingId,
+    this.error,
+    this.isInitialized = false,
+  });
+
+  StoreState copyWith({
+    List<StoreExtension>? extensions,
+    String? selectedCategory,
+    bool clearCategory = false,
+    String? searchQuery,
+    bool? isLoading,
+    bool? isDownloading,
+    String? downloadingId,
+    bool clearDownloadingId = false,
+    String? error,
+    bool clearError = false,
+    bool? isInitialized,
+  }) {
+    return StoreState(
+      extensions: extensions ?? this.extensions,
+      selectedCategory: clearCategory ? null : (selectedCategory ?? this.selectedCategory),
+      searchQuery: searchQuery ?? this.searchQuery,
+      isLoading: isLoading ?? this.isLoading,
+      isDownloading: isDownloading ?? this.isDownloading,
+      downloadingId: clearDownloadingId ? null : (downloadingId ?? this.downloadingId),
+      error: clearError ? null : (error ?? this.error),
+      isInitialized: isInitialized ?? this.isInitialized,
+    );
+  }
+
+  /// Get filtered extensions based on category and search
+  List<StoreExtension> get filteredExtensions {
+    var result = extensions;
+
+    if (selectedCategory != null) {
+      result = result.where((e) => e.category == selectedCategory).toList();
+    }
+
+    if (searchQuery.isNotEmpty) {
+      final query = searchQuery.toLowerCase();
+      result = result.where((e) =>
+        e.name.toLowerCase().contains(query) ||
+        e.displayName.toLowerCase().contains(query) ||
+        e.description.toLowerCase().contains(query) ||
+        e.author.toLowerCase().contains(query) ||
+        e.tags.any((t) => t.toLowerCase().contains(query))
+      ).toList();
+    }
+
+    return result;
+  }
+}
+
+/// Provider for managing extension store
+class StoreNotifier extends Notifier<StoreState> {
+  @override
+  StoreState build() {
+    return const StoreState();
+  }
+
+  /// Initialize the store
+  Future<void> initialize(String cacheDir) async {
+    if (state.isInitialized) return;
+
+    state = state.copyWith(isLoading: true, clearError: true);
+
+    try {
+      await PlatformBridge.initExtensionStore(cacheDir);
+      await refresh();
+      state = state.copyWith(isInitialized: true, isLoading: false);
+      _log.i('Extension store initialized');
+    } catch (e) {
+      _log.e('Failed to initialize store: $e');
+      state = state.copyWith(isLoading: false, error: e.toString());
+    }
+  }
+
+  /// Refresh extensions from store
+  Future<void> refresh({bool forceRefresh = false}) async {
+    state = state.copyWith(isLoading: true, clearError: true);
+
+    try {
+      final extensions = await PlatformBridge.getStoreExtensions(forceRefresh: forceRefresh);
+      state = state.copyWith(
+        extensions: extensions.map((e) => StoreExtension.fromJson(e)).toList(),
+        isLoading: false,
+      );
+      _log.d('Loaded ${state.extensions.length} extensions from store');
+    } catch (e) {
+      _log.e('Failed to refresh store: $e');
+      state = state.copyWith(isLoading: false, error: e.toString());
+    }
+  }
+
+  /// Set category filter
+  void setCategory(String? category) {
+    if (category == null) {
+      state = state.copyWith(clearCategory: true);
+    } else {
+      state = state.copyWith(selectedCategory: category);
+    }
+  }
+
+  /// Set search query
+  void setSearchQuery(String query) {
+    state = state.copyWith(searchQuery: query);
+  }
+
+  /// Clear search
+  void clearSearch() {
+    state = state.copyWith(searchQuery: '', clearCategory: true);
+  }
+
+  /// Download and install extension
+  Future<bool> installExtension(String extensionId, String tempDir, String extensionsDir) async {
+    state = state.copyWith(isDownloading: true, downloadingId: extensionId, clearError: true);
+
+    try {
+      _log.i('Downloading extension: $extensionId');
+      final downloadPath = await PlatformBridge.downloadStoreExtension(extensionId, tempDir);
+
+      _log.i('Installing extension from: $downloadPath');
+      final extNotifier = ref.read(extensionProvider.notifier);
+      final success = await extNotifier.installExtension(downloadPath);
+
+      if (success) {
+        _log.i('Extension installed: $extensionId');
+        await refresh();
+      }
+
+      state = state.copyWith(isDownloading: false, clearDownloadingId: true);
+      return success;
+    } catch (e) {
+      _log.e('Failed to install extension: $e');
+      state = state.copyWith(isDownloading: false, clearDownloadingId: true, error: e.toString());
+      return false;
+    }
+  }
+
+  /// Update an installed extension
+  Future<bool> updateExtension(String extensionId, String tempDir) async {
+    state = state.copyWith(isDownloading: true, downloadingId: extensionId, clearError: true);
+
+    try {
+      _log.i('Downloading update for: $extensionId');
+      final downloadPath = await PlatformBridge.downloadStoreExtension(extensionId, tempDir);
+
+      _log.i('Upgrading extension from: $downloadPath');
+      final extNotifier = ref.read(extensionProvider.notifier);
+      final success = await extNotifier.upgradeExtension(downloadPath);
+
+      if (success) {
+        _log.i('Extension updated: $extensionId');
+        await refresh();
+      }
+
+      state = state.copyWith(isDownloading: false, clearDownloadingId: true);
+      return success;
+    } catch (e) {
+      _log.e('Failed to update extension: $e');
+      state = state.copyWith(isDownloading: false, clearDownloadingId: true, error: e.toString());
+      return false;
+    }
+  }
+
+  /// Clear error
+  void clearError() {
+    state = state.copyWith(clearError: true);
+  }
+}
+
+final storeProvider = NotifierProvider<StoreNotifier, StoreState>(
+  StoreNotifier.new,
+);

lib/providers/track_provider.dart

@@ -2,6 +2,8 @@ import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:spotiflac_android/models/track.dart';
 import 'package:spotiflac_android/services/platform_bridge.dart';
 import 'package:spotiflac_android/utils/logger.dart';
+import 'package:spotiflac_android/providers/settings_provider.dart';
+import 'package:spotiflac_android/providers/extension_provider.dart';
 
 final _log = AppLogger('TrackProvider');
 
@@ -18,6 +20,7 @@ class TrackState {
   final List<ArtistAlbum>? artistAlbums; // For artist page
   final List<SearchArtist>? searchArtists; // For search results
   final bool hasSearchText; // For back button handling
+  final String? searchExtensionId; // Extension ID used for current search results
 
   const TrackState({
     this.tracks = const [],
@@ -32,6 +35,7 @@ class TrackState {
     this.artistAlbums,
     this.searchArtists,
     this.hasSearchText = false,
+    this.searchExtensionId,
   });
 
   bool get hasContent => tracks.isNotEmpty || artistAlbums != null || (searchArtists != null && searchArtists!.isNotEmpty);
@@ -49,6 +53,7 @@ class TrackState {
     List<ArtistAlbum>? artistAlbums,
     List<SearchArtist>? searchArtists,
     bool? hasSearchText,
+    String? searchExtensionId,
   }) {
     return TrackState(
       tracks: tracks ?? this.tracks,
@@ -63,6 +68,7 @@ class TrackState {
       artistAlbums: artistAlbums ?? this.artistAlbums,
       searchArtists: searchArtists ?? this.searchArtists,
       hasSearchText: hasSearchText ?? this.hasSearchText,
+      searchExtensionId: searchExtensionId,
     );
   }
 }
@@ -125,6 +131,59 @@ class TrackNotifier extends Notifier<TrackState> {
     state = TrackState(isLoading: true, hasSearchText: state.hasSearchText);
 
     try {
+      // First, check if any extension can handle this URL
+      final extensionHandler = await PlatformBridge.findURLHandler(url);
+      if (extensionHandler != null) {
+        _log.i('Found extension URL handler: $extensionHandler for URL: $url');
+        final result = await PlatformBridge.handleURLWithExtension(url);
+        if (!_isRequestValid(requestId)) return;
+        
+        if (result != null) {
+          final type = result['type'] as String?;
+          final extensionId = result['extension_id'] as String?;
+          
+          if (type == 'track' && result['track'] != null) {
+            final trackData = result['track'] as Map<String, dynamic>;
+            final track = _parseSearchTrack(trackData, source: extensionId);
+            state = TrackState(
+              tracks: [track],
+              isLoading: false,
+              coverUrl: track.coverUrl,
+              searchExtensionId: extensionId,
+            );
+            return;
+          } else if ((type == 'album' || type == 'playlist') && result['tracks'] != null) {
+            final trackList = result['tracks'] as List<dynamic>;
+            final tracks = trackList.map((t) => _parseSearchTrack(t as Map<String, dynamic>, source: extensionId)).toList();
+            state = TrackState(
+              tracks: tracks,
+              isLoading: false,
+              albumId: result['album']?['id'] as String?,
+              albumName: result['name'] as String? ?? result['album']?['name'] as String?,
+              playlistName: type == 'playlist' ? result['name'] as String? : null,
+              coverUrl: result['cover_url'] as String?,
+              searchExtensionId: extensionId,
+            );
+            return;
+          } else if (type == 'artist' && result['artist'] != null) {
+            final artistData = result['artist'] as Map<String, dynamic>;
+            final albumsList = artistData['albums'] as List<dynamic>? ?? [];
+            final albums = albumsList.map((a) => _parseArtistAlbum(a as Map<String, dynamic>)).toList();
+            state = TrackState(
+              tracks: [],
+              isLoading: false,
+              artistId: artistData['id'] as String?,
+              artistName: artistData['name'] as String?,
+              coverUrl: artistData['image_url'] as String? ?? artistData['images'] as String?,
+              artistAlbums: albums,
+              searchExtensionId: extensionId,
+            );
+            return;
+          }
+        }
+      }
+      
+      // No extension handler found, try Spotify URL parsing
       final parsed = await PlatformBridge.parseSpotifyUrl(url);
       if (!_isRequestValid(requestId)) return; // Request cancelled
       
@@ -210,12 +269,43 @@ class TrackNotifier extends Notifier<TrackState> {
     state = TrackState(isLoading: true, hasSearchText: state.hasSearchText);
 
     try {
+      // Check if extension providers should be used for search
+      final settings = ref.read(settingsProvider);
+      final extensionState = ref.read(extensionProvider);
+      final hasActiveMetadataExtensions = extensionState.extensions.any(
+        (e) => e.enabled && e.hasMetadataProvider,
+      );
+      final useExtensions = settings.useExtensionProviders && hasActiveMetadataExtensions;
+
       // Use Deezer or Spotify based on settings
       final source = metadataSource ?? 'deezer';
       
-      _log.i('Search started: source=$source, query="$query"');
+      _log.i('Search started: source=$source, query="$query", useExtensions=$useExtensions');
       
       Map<String, dynamic> results;
+      List<Track> extensionTracks = [];
+      
+      // Try extension providers first if enabled
+      if (useExtensions) {
+        try {
+          _log.d('Calling extension search API...');
+          final extResults = await PlatformBridge.searchTracksWithExtensions(query, limit: 20);
+          _log.i('Extensions returned ${extResults.length} tracks');
+          
+          // Parse extension results
+          for (final t in extResults) {
+            try {
+              extensionTracks.add(_parseSearchTrack(t));
+            } catch (e) {
+              _log.e('Failed to parse extension track: $e', e);
+            }
+          }
+        } catch (e) {
+          _log.w('Extension search failed, falling back to built-in: $e');
+        }
+      }
+      
+      // Also search with built-in providers
       if (source == 'deezer') {
         _log.d('Calling Deezer search API...');
         results = await PlatformBridge.searchDeezerAll(query, trackLimit: 20, artistLimit: 5);
@@ -238,11 +328,26 @@ class TrackNotifier extends Notifier<TrackState> {
       
       // Parse tracks with error handling per item
       final tracks = <Track>[];
+      
+      // Add extension tracks first (they have priority)
+      tracks.addAll(extensionTracks);
+      
+      // Add built-in provider tracks, avoiding duplicates by ISRC
+      final existingIsrcs = extensionTracks
+          .where((t) => t.isrc != null && t.isrc!.isNotEmpty)
+          .map((t) => t.isrc!)
+          .toSet();
+      
       for (int i = 0; i < trackList.length; i++) {
         final t = trackList[i];
         try {
           if (t is Map<String, dynamic>) {
-            tracks.add(_parseSearchTrack(t));
+            final track = _parseSearchTrack(t);
+            // Skip if we already have this track from extensions
+            if (track.isrc != null && existingIsrcs.contains(track.isrc)) {
+              continue;
+            }
+            tracks.add(track);
           } else {
             _log.w('Track[$i] is not a Map: ${t.runtimeType}');
           }
@@ -266,7 +371,7 @@ class TrackNotifier extends Notifier<TrackState> {
         }
       }
       
-      _log.i('Search complete: ${tracks.length} tracks, ${artists.length} artists parsed successfully');
+      _log.i('Search complete: ${tracks.length} tracks (${extensionTracks.length} from extensions), ${artists.length} artists parsed successfully');
       
       state = TrackState(
         tracks: tracks,
@@ -281,6 +386,53 @@ class TrackNotifier extends Notifier<TrackState> {
     }
   }
 
+  /// Perform custom search using a specific extension
+  Future<void> customSearch(String extensionId, String query, {Map<String, dynamic>? options}) async {
+    // Increment request ID to cancel any pending requests
+    final requestId = ++_currentRequestId;
+
+    // Preserve hasSearchText during search
+    state = TrackState(isLoading: true, hasSearchText: state.hasSearchText);
+
+    try {
+      _log.i('Custom search started: extension=$extensionId, query="$query"');
+      
+      final results = await PlatformBridge.customSearchWithExtension(extensionId, query, options: options);
+      
+      if (!_isRequestValid(requestId)) {
+        _log.w('Custom search request cancelled (requestId=$requestId)');
+        return;
+      }
+      
+      _log.i('Custom search returned ${results.length} tracks');
+      
+      // Parse tracks with error handling per item, setting source to extension ID
+      final tracks = <Track>[];
+      for (int i = 0; i < results.length; i++) {
+        final t = results[i];
+        try {
+          tracks.add(_parseSearchTrack(t, source: extensionId));
+        } catch (e) {
+          _log.e('Failed to parse custom search track[$i]: $e', e);
+        }
+      }
+      
+      _log.i('Custom search complete: ${tracks.length} tracks parsed (source=$extensionId)');
+      
+      state = TrackState(
+        tracks: tracks,
+        searchArtists: [], // Custom search doesn't return artists
+        isLoading: false,
+        hasSearchText: state.hasSearchText,
+        searchExtensionId: extensionId, // Store which extension was used
+      );
+    } catch (e, stackTrace) {
+      if (!_isRequestValid(requestId)) return;
+      _log.e('Custom search failed: $e', e, stackTrace);
+      state = TrackState(isLoading: false, error: e.toString(), hasSearchText: state.hasSearchText);
+    }
+  }
+
   Future<void> checkAvailability(int index) async {
     if (index < 0 || index >= state.tracks.length) return;
 
@@ -344,7 +496,7 @@ class TrackNotifier extends Notifier<TrackState> {
     );
   }
 
-  Track _parseSearchTrack(Map<String, dynamic> data) {
+  Track _parseSearchTrack(Map<String, dynamic> data, {String? source}) {
     // Handle duration_ms which might be int or double
     int durationMs = 0;
     final durationValue = data['duration_ms'];
@@ -366,6 +518,8 @@ class TrackNotifier extends Notifier<TrackState> {
       trackNumber: data['track_number'] as int?,
       discNumber: data['disc_number'] as int?,
       releaseDate: data['release_date']?.toString(),
+      source: source ?? data['source']?.toString() ?? data['provider_id']?.toString(),
+      albumType: data['album_type']?.toString(),
     );
   }
 

lib/screens/album_screen.dart

@@ -7,6 +7,7 @@ import 'package:spotiflac_android/models/download_item.dart';
 import 'package:spotiflac_android/providers/download_queue_provider.dart';
 import 'package:spotiflac_android/providers/settings_provider.dart';
 import 'package:spotiflac_android/services/platform_bridge.dart';
+import 'package:spotiflac_android/widgets/download_service_picker.dart';
 
 /// Simple in-memory cache for album tracks
 class _AlbumCache {
@@ -316,10 +317,16 @@ class _AlbumScreenState extends ConsumerState<AlbumScreen> {
   void _downloadTrack(BuildContext context, Track track) {
     final settings = ref.read(settingsProvider);
     if (settings.askQualityBeforeDownload) {
-      _showQualityPicker(context, (quality, service) {
-        ref.read(downloadQueueProvider.notifier).addToQueue(track, service, qualityOverride: quality);
-        ScaffoldMessenger.of(context).showSnackBar(SnackBar(content: Text('Added "${track.name}" to queue')));
-      }, trackName: track.name, artistName: track.artistName, coverUrl: track.coverUrl);
+      DownloadServicePicker.show(
+        context,
+        trackName: track.name,
+        artistName: track.artistName,
+        coverUrl: track.coverUrl,
+        onSelect: (quality, service) {
+          ref.read(downloadQueueProvider.notifier).addToQueue(track, service, qualityOverride: quality);
+          ScaffoldMessenger.of(context).showSnackBar(SnackBar(content: Text('Added "${track.name}" to queue')));
+        },
+      );
     } else {
       ref.read(downloadQueueProvider.notifier).addToQueue(track, settings.defaultService);
       ScaffoldMessenger.of(context).showSnackBar(SnackBar(content: Text('Added "${track.name}" to queue')));
@@ -331,84 +338,21 @@ class _AlbumScreenState extends ConsumerState<AlbumScreen> {
     if (tracks == null || tracks.isEmpty) return;
     final settings = ref.read(settingsProvider);
     if (settings.askQualityBeforeDownload) {
-      _showQualityPicker(context, (quality, service) {
-        ref.read(downloadQueueProvider.notifier).addMultipleToQueue(tracks, service, qualityOverride: quality);
-        ScaffoldMessenger.of(context).showSnackBar(SnackBar(content: Text('Added ${tracks.length} tracks to queue')));
-      }, trackName: '${tracks.length} tracks', artistName: widget.albumName);
+      DownloadServicePicker.show(
+        context,
+        trackName: '${tracks.length} tracks',
+        artistName: widget.albumName,
+        onSelect: (quality, service) {
+          ref.read(downloadQueueProvider.notifier).addMultipleToQueue(tracks, service, qualityOverride: quality);
+          ScaffoldMessenger.of(context).showSnackBar(SnackBar(content: Text('Added ${tracks.length} tracks to queue')));
+        },
+      );
     } else {
       ref.read(downloadQueueProvider.notifier).addMultipleToQueue(tracks, settings.defaultService);
       ScaffoldMessenger.of(context).showSnackBar(SnackBar(content: Text('Added ${tracks.length} tracks to queue')));
     }
   }
 
-  void _showQualityPicker(BuildContext context, void Function(String quality, String service) onSelect, {String? trackName, String? artistName, String? coverUrl}) {
-    final colorScheme = Theme.of(context).colorScheme;
-    final settings = ref.read(settingsProvider);
-    String selectedService = settings.defaultService;
-    
-    showModalBottomSheet(
-      context: context,
-      backgroundColor: colorScheme.surfaceContainerHigh,
-      shape: const RoundedRectangleBorder(borderRadius: BorderRadius.vertical(top: Radius.circular(28))),
-      isScrollControlled: true,
-      builder: (context) => StatefulBuilder(
-        builder: (context, setModalState) => SafeArea(
-          child: SingleChildScrollView(
-            child: Column(
-              mainAxisSize: MainAxisSize.min,
-              crossAxisAlignment: CrossAxisAlignment.start,
-              children: [
-                if (trackName != null) ...[
-                  _TrackInfoHeader(trackName: trackName, artistName: artistName, coverUrl: coverUrl),
-                  Divider(height: 1, color: colorScheme.outlineVariant.withValues(alpha: 0.5)),
-                ] else ...[
-                  const SizedBox(height: 8),
-                  Center(child: Container(width: 40, height: 4, decoration: BoxDecoration(color: colorScheme.onSurfaceVariant.withValues(alpha: 0.4), borderRadius: BorderRadius.circular(2)))),
-                ],
-                // Service selector
-                Padding(
-                  padding: const EdgeInsets.fromLTRB(24, 16, 24, 8),
-                  child: Text('Download From', style: Theme.of(context).textTheme.titleMedium?.copyWith(fontWeight: FontWeight.bold)),
-                ),
-                Padding(
-                  padding: const EdgeInsets.symmetric(horizontal: 20),
-                  child: Row(
-                    children: [
-                      _ServiceChip(label: 'Tidal', isSelected: selectedService == 'tidal', onTap: () => setModalState(() => selectedService = 'tidal')),
-                      const SizedBox(width: 8),
-                      _ServiceChip(label: 'Qobuz', isSelected: selectedService == 'qobuz', onTap: () => setModalState(() => selectedService = 'qobuz')),
-                      const SizedBox(width: 8),
-                      _ServiceChip(label: 'Amazon', isSelected: selectedService == 'amazon', onTap: () => setModalState(() => selectedService = 'amazon')),
-                    ],
-                  ),
-                ),
-                Padding(
-                  padding: const EdgeInsets.fromLTRB(24, 16, 24, 8),
-                  child: Text('Select Quality', style: Theme.of(context).textTheme.titleMedium?.copyWith(fontWeight: FontWeight.bold)),
-                ),
-                // Disclaimer
-                Padding(
-                  padding: const EdgeInsets.fromLTRB(24, 0, 24, 12),
-                  child: Text(
-                    'Actual quality depends on track availability. Hi-Res may not be available for all tracks.',
-                    style: Theme.of(context).textTheme.bodySmall?.copyWith(
-                      color: colorScheme.onSurfaceVariant,
-                      fontStyle: FontStyle.italic,
-                    ),
-                  ),
-                ),
-                _QualityOption(title: 'FLAC Lossless', subtitle: '16-bit / 44.1kHz', icon: Icons.music_note, onTap: () { Navigator.pop(context); onSelect('LOSSLESS', selectedService); }),
-                _QualityOption(title: 'Hi-Res FLAC', subtitle: '24-bit / up to 96kHz', icon: Icons.high_quality, onTap: () { Navigator.pop(context); onSelect('HI_RES', selectedService); }),
-                _QualityOption(title: 'Hi-Res FLAC Max', subtitle: '24-bit / up to 192kHz', icon: Icons.four_k, onTap: () { Navigator.pop(context); onSelect('HI_RES_LOSSLESS', selectedService); }),
-                const SizedBox(height: 16),
-              ],
-            ),
-          ),
-        ),
-      ),
-    );
-  }
-
   /// Build error widget with special handling for rate limit (429)
   Widget _buildErrorWidget(String error, ColorScheme colorScheme) {
     final isRateLimit = error.contains('429') || 
@@ -473,148 +417,6 @@ class _AlbumScreenState extends ConsumerState<AlbumScreen> {
   }
 }
 
-class _QualityOption extends StatelessWidget {
-  final String title;
-  final String subtitle;
-  final IconData icon;
-  final VoidCallback onTap;
-
-  const _QualityOption({required this.title, required this.subtitle, required this.icon, required this.onTap});
-
-  @override
-  Widget build(BuildContext context) {
-    final colorScheme = Theme.of(context).colorScheme;
-    return ListTile(
-      contentPadding: const EdgeInsets.symmetric(horizontal: 24, vertical: 4),
-      leading: Container(padding: const EdgeInsets.all(10), decoration: BoxDecoration(color: colorScheme.primaryContainer, borderRadius: BorderRadius.circular(12)), child: Icon(icon, color: colorScheme.onPrimaryContainer, size: 20)),
-      title: Text(title, style: const TextStyle(fontWeight: FontWeight.w500)),
-      subtitle: Text(subtitle, style: TextStyle(color: colorScheme.onSurfaceVariant)),
-      onTap: onTap,
-    );
-  }
-}
-
-class _ServiceChip extends StatelessWidget {
-  final String label;
-  final bool isSelected;
-  final VoidCallback onTap;
-  const _ServiceChip({required this.label, required this.isSelected, required this.onTap});
-
-  @override
-  Widget build(BuildContext context) {
-    final colorScheme = Theme.of(context).colorScheme;
-    return Expanded(
-      child: GestureDetector(
-        onTap: onTap,
-        child: AnimatedContainer(
-          duration: const Duration(milliseconds: 200),
-          padding: const EdgeInsets.symmetric(vertical: 10),
-          decoration: BoxDecoration(
-            color: isSelected ? colorScheme.primaryContainer : colorScheme.surfaceContainerHighest,
-            borderRadius: BorderRadius.circular(12),
-            border: isSelected ? null : Border.all(color: colorScheme.outlineVariant.withValues(alpha: 0.5)),
-          ),
-          child: Text(
-            label,
-            textAlign: TextAlign.center,
-            style: TextStyle(
-              fontWeight: isSelected ? FontWeight.w600 : FontWeight.normal,
-              color: isSelected ? colorScheme.onPrimaryContainer : colorScheme.onSurfaceVariant,
-            ),
-          ),
-        ),
-      ),
-    );
-  }
-}
-
-class _TrackInfoHeader extends StatefulWidget {
-  final String trackName;
-  final String? artistName;
-  final String? coverUrl;
-  const _TrackInfoHeader({required this.trackName, this.artistName, this.coverUrl});
-
-  @override
-  State<_TrackInfoHeader> createState() => _TrackInfoHeaderState();
-}
-
-class _TrackInfoHeaderState extends State<_TrackInfoHeader> {
-  bool _expanded = false;
-  bool _isOverflowing = false;
-
-  @override
-  Widget build(BuildContext context) {
-    final colorScheme = Theme.of(context).colorScheme;
-    return Material(
-      color: Colors.transparent,
-      child: InkWell(
-        onTap: _isOverflowing ? () => setState(() => _expanded = !_expanded) : null,
-        borderRadius: const BorderRadius.only(topLeft: Radius.circular(28), topRight: Radius.circular(28)),
-        child: Column(
-          children: [
-            const SizedBox(height: 8),
-            Container(width: 40, height: 4, decoration: BoxDecoration(color: colorScheme.onSurfaceVariant.withValues(alpha: 0.4), borderRadius: BorderRadius.circular(2))),
-            Padding(
-              padding: const EdgeInsets.fromLTRB(16, 12, 16, 12),
-              child: Row(
-                children: [
-                  ClipRRect(
-                    borderRadius: BorderRadius.circular(8),
-                    child: widget.coverUrl != null
-                        ? Image.network(widget.coverUrl!, width: 56, height: 56, fit: BoxFit.cover,
-                            errorBuilder: (_, e, s) => Container(width: 56, height: 56, color: colorScheme.surfaceContainerHighest, child: Icon(Icons.music_note, color: colorScheme.onSurfaceVariant)))
-                        : Container(width: 56, height: 56, color: colorScheme.surfaceContainerHighest, child: Icon(Icons.music_note, color: colorScheme.onSurfaceVariant)),
-                  ),
-                  const SizedBox(width: 12),
-                  Expanded(
-                    child: LayoutBuilder(
-                      builder: (context, constraints) {
-                        final titleStyle = Theme.of(context).textTheme.titleMedium?.copyWith(fontWeight: FontWeight.w600);
-                        final titleSpan = TextSpan(text: widget.trackName, style: titleStyle);
-                        final titlePainter = TextPainter(text: titleSpan, maxLines: 1, textDirection: TextDirection.ltr)..layout(maxWidth: constraints.maxWidth);
-                        final titleOverflows = titlePainter.didExceedMaxLines;
-                        
-                        WidgetsBinding.instance.addPostFrameCallback((_) {
-                          if (mounted && _isOverflowing != titleOverflows) {
-                            setState(() => _isOverflowing = titleOverflows);
-                          }
-                        });
-                        
-                        return Column(
-                          crossAxisAlignment: CrossAxisAlignment.start,
-                          children: [
-                            Text(
-                              widget.trackName,
-                              style: titleStyle,
-                              maxLines: _expanded ? 10 : 1,
-                              overflow: _expanded ? TextOverflow.visible : TextOverflow.ellipsis,
-                            ),
-                            if (widget.artistName != null) ...[
-                              const SizedBox(height: 2),
-                              Text(
-                                widget.artistName!,
-                                style: Theme.of(context).textTheme.bodyMedium?.copyWith(color: colorScheme.onSurfaceVariant),
-                                maxLines: _expanded ? 3 : 1,
-                                overflow: _expanded ? TextOverflow.visible : TextOverflow.ellipsis,
-                              ),
-                            ],
-                          ],
-                        );
-                      },
-                    ),
-                  ),
-                  if (_isOverflowing || _expanded)
-                    Icon(_expanded ? Icons.expand_less : Icons.expand_more, color: colorScheme.onSurfaceVariant, size: 20),
-                ],
-              ),
-            ),
-          ],
-        ),
-      ),
-    );
-  }
-}
-
 /// Separate Consumer widget for each track - only rebuilds when this specific track's status changes
 class _AlbumTrackItem extends ConsumerWidget {
   final Track track;

lib/screens/home_tab.dart

@@ -8,12 +8,14 @@ import 'package:spotiflac_android/models/track.dart';
 import 'package:spotiflac_android/providers/track_provider.dart';
 import 'package:spotiflac_android/providers/download_queue_provider.dart';
 import 'package:spotiflac_android/providers/settings_provider.dart';
+import 'package:spotiflac_android/providers/extension_provider.dart';
 import 'package:spotiflac_android/screens/track_metadata_screen.dart';
 import 'package:spotiflac_android/screens/album_screen.dart';
 import 'package:spotiflac_android/screens/artist_screen.dart';
 import 'package:spotiflac_android/services/csv_import_service.dart';
 import 'package:spotiflac_android/screens/playlist_screen.dart';
 import 'package:spotiflac_android/models/download_item.dart';
+import 'package:spotiflac_android/widgets/download_service_picker.dart';
 
 class HomeTab extends ConsumerStatefulWidget {
   const HomeTab({super.key});
@@ -78,12 +80,21 @@ class _HomeTabState extends ConsumerState<HomeTab> with AutomaticKeepAliveClient
   }
 
   Future<void> _performSearch(String query) async {
-    // Skip if same query already searched
-    if (_lastSearchQuery == query) return;
-    _lastSearchQuery = query;
-    
     final settings = ref.read(settingsProvider);
-    await ref.read(trackProvider.notifier).search(query, metadataSource: settings.metadataSource);
+    final searchProvider = settings.searchProvider;
+    
+    // Skip if same query already searched with same provider
+    final searchKey = '${searchProvider ?? 'default'}:$query';
+    if (_lastSearchQuery == searchKey) return;
+    _lastSearchQuery = searchKey;
+    
+    if (searchProvider != null && searchProvider.isNotEmpty) {
+      // Use custom search from extension
+      await ref.read(trackProvider.notifier).customSearch(searchProvider, query);
+    } else {
+      // Use default search (Deezer/Spotify)
+      await ref.read(trackProvider.notifier).search(query, metadataSource: settings.metadataSource);
+    }
     ref.read(settingsProvider.notifier).setHasSearchedBefore();
   }
 
@@ -173,10 +184,16 @@ class _HomeTabState extends ConsumerState<HomeTab> with AutomaticKeepAliveClient
       final settings = ref.read(settingsProvider);
       
       if (settings.askQualityBeforeDownload) {
-        _showQualityPicker(context, (quality, service) {
-          ref.read(downloadQueueProvider.notifier).addToQueue(track, service, qualityOverride: quality);
-          ScaffoldMessenger.of(context).showSnackBar(SnackBar(content: Text('Added "${track.name}" to queue')));
-        }, trackName: track.name, artistName: track.artistName, coverUrl: track.coverUrl);
+        DownloadServicePicker.show(
+          context,
+          trackName: track.name,
+          artistName: track.artistName,
+          coverUrl: track.coverUrl,
+          onSelect: (quality, service) {
+            ref.read(downloadQueueProvider.notifier).addToQueue(track, service, qualityOverride: quality);
+            ScaffoldMessenger.of(context).showSnackBar(SnackBar(content: Text('Added "${track.name}" to queue')));
+          },
+        );
       } else {
         ref.read(downloadQueueProvider.notifier).addToQueue(track, settings.defaultService);
         ScaffoldMessenger.of(context).showSnackBar(SnackBar(content: Text('Added "${track.name}" to queue')));
@@ -184,107 +201,23 @@ class _HomeTabState extends ConsumerState<HomeTab> with AutomaticKeepAliveClient
     }
   }
 
-  void _showQualityPicker(BuildContext context, void Function(String quality, String service) onSelect, {String? trackName, String? artistName, String? coverUrl}) {
-    final colorScheme = Theme.of(context).colorScheme;
-    final settings = ref.read(settingsProvider);
-    String selectedService = settings.defaultService;
-    
-    showModalBottomSheet(
-      context: context,
-      backgroundColor: colorScheme.surfaceContainerHigh,
-      shape: const RoundedRectangleBorder(borderRadius: BorderRadius.vertical(top: Radius.circular(28))),
-      isScrollControlled: true,
-      builder: (context) => StatefulBuilder(
-        builder: (context, setModalState) => SafeArea(
-          child: SingleChildScrollView(
-            child: Column(
-              mainAxisSize: MainAxisSize.min,
-              crossAxisAlignment: CrossAxisAlignment.start,
-              children: [
-                if (trackName != null) ...[
-                  _TrackInfoHeader(trackName: trackName, artistName: artistName, coverUrl: coverUrl),
-                  Divider(height: 1, color: colorScheme.outlineVariant.withValues(alpha: 0.5)),
-                ] else ...[
-                  const SizedBox(height: 8),
-                  Center(child: Container(width: 40, height: 4, decoration: BoxDecoration(color: colorScheme.onSurfaceVariant.withValues(alpha: 0.4), borderRadius: BorderRadius.circular(2)))),
-                ],
-                // Service selector
-                Padding(
-                  padding: const EdgeInsets.fromLTRB(24, 16, 24, 8),
-                  child: Text('Download From', style: Theme.of(context).textTheme.titleMedium?.copyWith(fontWeight: FontWeight.bold)),
-                ),
-                Padding(
-                  padding: const EdgeInsets.symmetric(horizontal: 20),
-                  child: Row(
-                    children: [
-                      _ServiceChip(label: 'Tidal', isSelected: selectedService == 'tidal', onTap: () => setModalState(() => selectedService = 'tidal')),
-                      const SizedBox(width: 8),
-                      _ServiceChip(label: 'Qobuz', isSelected: selectedService == 'qobuz', onTap: () => setModalState(() => selectedService = 'qobuz')),
-                      const SizedBox(width: 8),
-                      _ServiceChip(label: 'Amazon', isSelected: selectedService == 'amazon', onTap: () => setModalState(() => selectedService = 'amazon')),
-                    ],
-                  ),
-                ),
-                Padding(
-                  padding: const EdgeInsets.fromLTRB(24, 16, 24, 8),
-                  child: Text('Select Quality', style: Theme.of(context).textTheme.titleMedium?.copyWith(fontWeight: FontWeight.bold)),
-                ),
-                // Disclaimer
-                Padding(
-                  padding: const EdgeInsets.fromLTRB(24, 0, 24, 12),
-                  child: Text(
-                    'Actual quality depends on track availability. Hi-Res may not be available for all tracks.',
-                    style: Theme.of(context).textTheme.bodySmall?.copyWith(
-                      color: colorScheme.onSurfaceVariant,
-                      fontStyle: FontStyle.italic,
-                    ),
-                  ),
-                ),
-                _QualityPickerOption(
-                  title: 'FLAC Lossless',
-                  subtitle: '16-bit / 44.1kHz',
-                  icon: Icons.music_note,
-                  onTap: () { Navigator.pop(context); onSelect('LOSSLESS', selectedService); },
-                ),
-                _QualityPickerOption(
-                  title: 'Hi-Res FLAC',
-                  subtitle: '24-bit / up to 96kHz',
-                  icon: Icons.high_quality,
-                  onTap: () { Navigator.pop(context); onSelect('HI_RES', selectedService); },
-                ),
-                _QualityPickerOption(
-                  title: 'Hi-Res FLAC Max',
-                  subtitle: '24-bit / up to 192kHz',
-                  icon: Icons.four_k,
-                  onTap: () { Navigator.pop(context); onSelect('HI_RES_LOSSLESS', selectedService); },
-                ),
-                const SizedBox(height: 16),
-              ],
-            ),
-          ),
-        ),
-      ),
-    );
-  }
-
   Future<void> _importCsv(BuildContext context, WidgetRef ref) async {
     // Show loading dialog with progress
     int currentProgress = 0;
     int totalTracks = 0;
     
     // Use StatefulBuilder to update dialog content
-    final dialogContext = context;
     bool dialogShown = false;
     StateSetter? setDialogState;
     
     void showProgressDialog() {
-      if (dialogShown) return;
+      if (dialogShown || !mounted) return;
       dialogShown = true;
       showDialog(
-        context: dialogContext,
+        context: this.context,
         barrierDismissible: false,
-        builder: (context) => StatefulBuilder(
-          builder: (context, setState) {
+        builder: (dialogCtx) => StatefulBuilder(
+          builder: (dialogCtx, setState) {
             setDialogState = setState;
             return AlertDialog(
               content: Column(
@@ -318,25 +251,27 @@ class _HomeTabState extends ConsumerState<HomeTab> with AutomaticKeepAliveClient
     
     // Close progress dialog
     if (dialogShown && mounted) {
-      Navigator.of(dialogContext).pop();
+      Navigator.of(this.context).pop();
     }
     
     if (tracks.isNotEmpty) {
       final settings = ref.read(settingsProvider);
       
+      if (!mounted) return;
+      
       // Optionally show confirmation dialog
       final confirmed = await showDialog<bool>(
-        context: context,
-        builder: (context) => AlertDialog(
+        context: this.context,
+        builder: (dialogCtx) => AlertDialog(
           title: const Text('Import Playlist'),
           content: Text('Found ${tracks.length} tracks in CSV. Add them to download queue?'),
           actions: [
             TextButton(
-              onPressed: () => Navigator.pop(context, false),
+              onPressed: () => Navigator.pop(dialogCtx, false),
               child: const Text('Cancel'),
             ),
             FilledButton(
-              onPressed: () => Navigator.pop(context, true),
+              onPressed: () => Navigator.pop(dialogCtx, true),
               child: const Text('Import'),
             ),
           ],
@@ -346,7 +281,7 @@ class _HomeTabState extends ConsumerState<HomeTab> with AutomaticKeepAliveClient
       if (confirmed == true) {
         ref.read(downloadQueueProvider.notifier).addMultipleToQueue(tracks, settings.defaultService);
         if (mounted) {
-           ScaffoldMessenger.of(context).showSnackBar(
+           ScaffoldMessenger.of(this.context).showSnackBar(
             SnackBar(
               content: Text('Added ${tracks.length} tracks to queue'),
               action: SnackBarAction(
@@ -385,6 +320,10 @@ class _HomeTabState extends ConsumerState<HomeTab> with AutomaticKeepAliveClient
     final error = ref.watch(trackProvider.select((s) => s.error));
     final hasSearchedBefore = ref.watch(settingsProvider.select((s) => s.hasSearchedBefore));
     
+    // Watch extension state to update search hint when extensions load/change
+    ref.watch(extensionProvider.select((s) => s.isInitialized));
+    ref.watch(extensionProvider.select((s) => s.extensions));
+    
     final colorScheme = Theme.of(context).colorScheme;
     final hasResults = _isTyping || tracks.isNotEmpty || (searchArtists != null && searchArtists.isNotEmpty) || isLoading;
     final screenHeight = MediaQuery.of(context).size.height;
@@ -836,6 +775,32 @@ class _HomeTabState extends ConsumerState<HomeTab> with AutomaticKeepAliveClient
     ));
   }
 
+  /// Get search hint based on selected provider
+  String _getSearchHint() {
+    final settings = ref.read(settingsProvider);
+    final searchProvider = settings.searchProvider;
+    final extState = ref.read(extensionProvider);
+    
+    // If extension system not initialized yet, show default hint
+    if (!extState.isInitialized) {
+      return 'Paste Spotify URL or search...';
+    }
+    
+    if (searchProvider != null && searchProvider.isNotEmpty) {
+      final ext = extState.extensions.where((e) => e.id == searchProvider).firstOrNull;
+      // Only show extension placeholder if extension exists AND is enabled
+      if (ext != null && ext.enabled) {
+        if (ext.searchBehavior?.placeholder != null) {
+          return ext.searchBehavior!.placeholder!;
+        }
+        return 'Search with ${ext.displayName}...';
+      }
+      // Extension not found or disabled - clear the search provider setting
+      // and return default hint
+    }
+    return 'Paste Spotify URL or search...';
+  }
+
   Widget _buildSearchBar(ColorScheme colorScheme) {
     final hasText = _urlController.text.isNotEmpty;
     
@@ -844,7 +809,7 @@ class _HomeTabState extends ConsumerState<HomeTab> with AutomaticKeepAliveClient
       focusNode: _searchFocusNode,
       autofocus: false,
       decoration: InputDecoration(
-        hintText: 'Paste Spotify URL or search...',
+        hintText: _getSearchHint(),
         filled: true,
         fillColor: colorScheme.surfaceContainerHighest,
         border: OutlineInputBorder(
@@ -910,147 +875,6 @@ class _HomeTabState extends ConsumerState<HomeTab> with AutomaticKeepAliveClient
 
 }
 
-class _QualityPickerOption extends StatelessWidget {
-  final String title;
-  final String subtitle;
-  final IconData icon;
-  final VoidCallback onTap;
-  const _QualityPickerOption({required this.title, required this.subtitle, required this.icon, required this.onTap});
-
-  @override
-  Widget build(BuildContext context) {
-    final colorScheme = Theme.of(context).colorScheme;
-    return ListTile(
-      contentPadding: const EdgeInsets.symmetric(horizontal: 24, vertical: 4),
-      leading: Container(padding: const EdgeInsets.all(10), decoration: BoxDecoration(color: colorScheme.primaryContainer, borderRadius: BorderRadius.circular(12)), child: Icon(icon, color: colorScheme.onPrimaryContainer, size: 20)),
-      title: Text(title, style: const TextStyle(fontWeight: FontWeight.w500)),
-      subtitle: Text(subtitle, style: TextStyle(color: colorScheme.onSurfaceVariant)),
-      onTap: onTap,
-    );
-  }
-}
-
-class _ServiceChip extends StatelessWidget {
-  final String label;
-  final bool isSelected;
-  final VoidCallback onTap;
-  const _ServiceChip({required this.label, required this.isSelected, required this.onTap});
-
-  @override
-  Widget build(BuildContext context) {
-    final colorScheme = Theme.of(context).colorScheme;
-    return Expanded(
-      child: GestureDetector(
-        onTap: onTap,
-        child: AnimatedContainer(
-          duration: const Duration(milliseconds: 200),
-          padding: const EdgeInsets.symmetric(vertical: 10),
-          decoration: BoxDecoration(
-            color: isSelected ? colorScheme.primaryContainer : colorScheme.surfaceContainerHighest,
-            borderRadius: BorderRadius.circular(12),
-            border: isSelected ? null : Border.all(color: colorScheme.outlineVariant.withValues(alpha: 0.5)),
-          ),
-          child: Text(
-            label,
-            textAlign: TextAlign.center,
-            style: TextStyle(
-              fontWeight: isSelected ? FontWeight.w600 : FontWeight.normal,
-              color: isSelected ? colorScheme.onPrimaryContainer : colorScheme.onSurfaceVariant,
-            ),
-          ),
-        ),
-      ),
-    );
-  }
-}
-
-class _TrackInfoHeader extends StatefulWidget {
-  final String trackName;
-  final String? artistName;
-  final String? coverUrl;
-  const _TrackInfoHeader({required this.trackName, this.artistName, this.coverUrl});
-
-  @override
-  State<_TrackInfoHeader> createState() => _TrackInfoHeaderState();
-}
-
-class _TrackInfoHeaderState extends State<_TrackInfoHeader> {
-  bool _expanded = false;
-  bool _isOverflowing = false;
-
-  @override
-  Widget build(BuildContext context) {
-    final colorScheme = Theme.of(context).colorScheme;
-    return Material(
-      color: Colors.transparent,
-      child: InkWell(
-        onTap: _isOverflowing ? () => setState(() => _expanded = !_expanded) : null,
-        borderRadius: const BorderRadius.only(topLeft: Radius.circular(28), topRight: Radius.circular(28)),
-        child: Column(
-          children: [
-            const SizedBox(height: 8),
-            Container(width: 40, height: 4, decoration: BoxDecoration(color: colorScheme.onSurfaceVariant.withValues(alpha: 0.4), borderRadius: BorderRadius.circular(2))),
-            Padding(
-              padding: const EdgeInsets.fromLTRB(16, 12, 16, 12),
-              child: Row(
-                children: [
-                  ClipRRect(
-                    borderRadius: BorderRadius.circular(8),
-                    child: widget.coverUrl != null
-                        ? Image.network(widget.coverUrl!, width: 56, height: 56, fit: BoxFit.cover,
-                            errorBuilder: (_, e, s) => Container(width: 56, height: 56, color: colorScheme.surfaceContainerHighest, child: Icon(Icons.music_note, color: colorScheme.onSurfaceVariant)))
-                        : Container(width: 56, height: 56, color: colorScheme.surfaceContainerHighest, child: Icon(Icons.music_note, color: colorScheme.onSurfaceVariant)),
-                  ),
-                  const SizedBox(width: 12),
-                  Expanded(
-                    child: LayoutBuilder(
-                      builder: (context, constraints) {
-                        final titleStyle = Theme.of(context).textTheme.titleMedium?.copyWith(fontWeight: FontWeight.w600);
-                        final titleSpan = TextSpan(text: widget.trackName, style: titleStyle);
-                        final titlePainter = TextPainter(text: titleSpan, maxLines: 1, textDirection: TextDirection.ltr)..layout(maxWidth: constraints.maxWidth);
-                        final titleOverflows = titlePainter.didExceedMaxLines;
-                        
-                        WidgetsBinding.instance.addPostFrameCallback((_) {
-                          if (mounted && _isOverflowing != titleOverflows) {
-                            setState(() => _isOverflowing = titleOverflows);
-                          }
-                        });
-                        
-                        return Column(
-                          crossAxisAlignment: CrossAxisAlignment.start,
-                          children: [
-                            Text(
-                              widget.trackName,
-                              style: titleStyle,
-                              maxLines: _expanded ? 10 : 1,
-                              overflow: _expanded ? TextOverflow.visible : TextOverflow.ellipsis,
-                            ),
-                            if (widget.artistName != null) ...[
-                              const SizedBox(height: 2),
-                              Text(
-                                widget.artistName!,
-                                style: Theme.of(context).textTheme.bodyMedium?.copyWith(color: colorScheme.onSurfaceVariant),
-                                maxLines: _expanded ? 3 : 1,
-                                overflow: _expanded ? TextOverflow.visible : TextOverflow.ellipsis,
-                              ),
-                            ],
-                          ],
-                        );
-                      },
-                    ),
-                  ),
-                  if (_isOverflowing || _expanded)
-                    Icon(_expanded ? Icons.expand_less : Icons.expand_more, color: colorScheme.onSurfaceVariant, size: 20),
-                ],
-              ),
-            ),
-          ],
-        ),
-      ),
-    );
-  }
-}
-
 /// Separate Consumer widget for each track item - only rebuilds when this specific track's status changes
 class _TrackItemWithStatus extends ConsumerWidget {
   final Track track;
@@ -1080,6 +904,28 @@ class _TrackItemWithStatus extends ConsumerWidget {
       return state.isDownloaded(track.id);
     }));
     
+    // Get thumbnail size from extension if track is from extension
+    double thumbWidth = 56;
+    double thumbHeight = 56;
+    
+    // Get extension ID from track.source or from TrackState.searchExtensionId
+    final trackState = ref.watch(trackProvider);
+    final extensionId = track.source ?? trackState.searchExtensionId;
+    
+    if (extensionId != null && extensionId.isNotEmpty) {
+      final extState = ref.watch(extensionProvider);
+      final extension = extState.extensions.where((e) => e.id == extensionId).firstOrNull;
+      if (extension?.searchBehavior != null) {
+        final size = extension!.searchBehavior!.getThumbnailSize(defaultSize: 56);
+        thumbWidth = size.$1;
+        thumbHeight = size.$2;
+        // Debug: log only when using custom size
+        if (thumbWidth != 56 || thumbHeight != 56) {
+          debugPrint('[Thumbnail] ${track.name}: using ${thumbWidth.toInt()}x${thumbHeight.toInt()} from ${extension.id}');
+        }
+      }
+    }
+    
     final isQueued = queueItem != null;
     final isDownloading = queueItem?.status == DownloadStatus.downloading;
     final isFinalizing = queueItem?.status == DownloadStatus.finalizing;
@@ -1100,21 +946,21 @@ class _TrackItemWithStatus extends ConsumerWidget {
             padding: const EdgeInsets.symmetric(horizontal: 12, vertical: 10),
             child: Row(
               children: [
-                // Album art
+                // Album art with dynamic size based on extension config
                 ClipRRect(
                   borderRadius: BorderRadius.circular(10),
                   child: track.coverUrl != null
                       ? CachedNetworkImage(
                           imageUrl: track.coverUrl!,
-                          width: 56,
-                          height: 56,
+                          width: thumbWidth,
+                          height: thumbHeight,
                           fit: BoxFit.cover,
-                          memCacheWidth: 112,
-                          memCacheHeight: 112,
+                          memCacheWidth: (thumbWidth * 2).toInt(),
+                          memCacheHeight: (thumbHeight * 2).toInt(),
                         )
                       : Container(
-                          width: 56,
-                          height: 56,
+                          width: thumbWidth,
+                          height: thumbHeight,
                           color: colorScheme.surfaceContainerHighest,
                           child: Icon(Icons.music_note, color: colorScheme.onSurfaceVariant),
                         ),
@@ -1151,7 +997,7 @@ class _TrackItemWithStatus extends ConsumerWidget {
           Divider(
             height: 1,
             thickness: 1,
-            indent: 80,
+            indent: thumbWidth + 24, // Adjust divider indent based on thumbnail width
             endIndent: 12,
             color: colorScheme.outlineVariant.withValues(alpha: 0.3),
           ),

lib/screens/main_shell.dart

@@ -6,6 +6,7 @@ import 'package:spotiflac_android/providers/download_queue_provider.dart';
 import 'package:spotiflac_android/providers/settings_provider.dart';
 import 'package:spotiflac_android/providers/track_provider.dart';
 import 'package:spotiflac_android/screens/home_tab.dart';
+import 'package:spotiflac_android/screens/store_tab.dart';
 import 'package:spotiflac_android/screens/queue_tab.dart';
 import 'package:spotiflac_android/screens/settings/settings_tab.dart';
 import 'package:spotiflac_android/services/share_intent_service.dart';
@@ -172,6 +173,7 @@ class _MainShellState extends ConsumerState<MainShell> {
   Widget build(BuildContext context) {
     final queueState = ref.watch(downloadQueueProvider.select((s) => s.queuedCount));
     final trackState = ref.watch(trackProvider);
+    final showStore = ref.watch(settingsProvider.select((s) => s.showExtensionStore));
     
     // Check if keyboard is visible (bottom inset > 0 means keyboard is showing)
     final isKeyboardVisible = MediaQuery.of(context).viewInsets.bottom > 0;
@@ -185,6 +187,57 @@ class _MainShellState extends ConsumerState<MainShell> {
                    !trackState.isLoading &&
                    !isKeyboardVisible;
 
+    // Build tabs and destinations based on settings
+    final tabs = <Widget>[
+      const HomeTab(),
+      const QueueTab(),
+      if (showStore) const StoreTab(),
+      const SettingsTab(),
+    ];
+
+    final destinations = <NavigationDestination>[
+      const NavigationDestination(
+        icon: Icon(Icons.home_outlined),
+        selectedIcon: Icon(Icons.home),
+        label: 'Home',
+      ),
+      NavigationDestination(
+        icon: Badge(
+          isLabelVisible: queueState > 0,
+          label: Text('$queueState'),
+          child: const Icon(Icons.history_outlined),
+        ),
+        selectedIcon: Badge(
+          isLabelVisible: queueState > 0,
+          label: Text('$queueState'),
+          child: const Icon(Icons.history),
+        ),
+        label: 'History',
+      ),
+      if (showStore)
+        const NavigationDestination(
+          icon: Icon(Icons.store_outlined),
+          selectedIcon: Icon(Icons.store),
+          label: 'Store',
+        ),
+      const NavigationDestination(
+        icon: Icon(Icons.settings_outlined),
+        selectedIcon: Icon(Icons.settings),
+        label: 'Settings',
+      ),
+    ];
+
+    // Clamp current index if tabs changed
+    final maxIndex = tabs.length - 1;
+    if (_currentIndex > maxIndex) {
+      WidgetsBinding.instance.addPostFrameCallback((_) {
+        if (mounted) {
+          setState(() => _currentIndex = maxIndex);
+          _pageController.jumpToPage(maxIndex);
+        }
+      });
+    }
+
     return PopScope(
       canPop: canPop,
       onPopInvokedWithResult: (didPop, result) async {
@@ -202,44 +255,16 @@ class _MainShellState extends ConsumerState<MainShell> {
           controller: _pageController,
           onPageChanged: _onPageChanged,
           physics: const BouncingScrollPhysics(),
-          children: const [
-            HomeTab(),
-            QueueTab(),
-            SettingsTab(),
-          ],
+          children: tabs,
         ),
         bottomNavigationBar: NavigationBar(
-          selectedIndex: _currentIndex,
+          selectedIndex: _currentIndex.clamp(0, maxIndex),
           onDestinationSelected: _onNavTap,
           animationDuration: const Duration(milliseconds: 200),
           backgroundColor: Theme.of(context).brightness == Brightness.dark
               ? Color.alphaBlend(Colors.white.withValues(alpha: 0.05), Theme.of(context).colorScheme.surface)
               : Color.alphaBlend(Colors.black.withValues(alpha: 0.03), Theme.of(context).colorScheme.surface),
-          destinations: [
-            const NavigationDestination(
-              icon: Icon(Icons.home_outlined),
-              selectedIcon: Icon(Icons.home),
-              label: 'Home',
-            ),
-            NavigationDestination(
-              icon: Badge(
-                isLabelVisible: queueState > 0,
-                label: Text('$queueState'),
-                child: const Icon(Icons.history_outlined),
-              ),
-              selectedIcon: Badge(
-                isLabelVisible: queueState > 0,
-                label: Text('$queueState'),
-                child: const Icon(Icons.history),
-              ),
-              label: 'History',
-            ),
-            const NavigationDestination(
-              icon: Icon(Icons.settings_outlined),
-              selectedIcon: Icon(Icons.settings),
-              label: 'Settings',
-            ),
-          ],
+          destinations: destinations,
         ),
       ),
     );

lib/screens/playlist_screen.dart

@@ -6,6 +6,7 @@ import 'package:spotiflac_android/models/track.dart';
 import 'package:spotiflac_android/models/download_item.dart';
 import 'package:spotiflac_android/providers/download_queue_provider.dart';
 import 'package:spotiflac_android/providers/settings_provider.dart';
+import 'package:spotiflac_android/widgets/download_service_picker.dart';
 
 /// Playlist detail screen with Material Expressive 3 design
 class PlaylistScreen extends ConsumerWidget {
@@ -168,10 +169,16 @@ class PlaylistScreen extends ConsumerWidget {
   void _downloadTrack(BuildContext context, WidgetRef ref, Track track) {
     final settings = ref.read(settingsProvider);
     if (settings.askQualityBeforeDownload) {
-      _showQualityPicker(context, ref, (quality, service) {
-        ref.read(downloadQueueProvider.notifier).addToQueue(track, service, qualityOverride: quality);
-        ScaffoldMessenger.of(context).showSnackBar(SnackBar(content: Text('Added "${track.name}" to queue')));
-      }, trackName: track.name, artistName: track.artistName, coverUrl: track.coverUrl);
+      DownloadServicePicker.show(
+        context,
+        trackName: track.name,
+        artistName: track.artistName,
+        coverUrl: track.coverUrl,
+        onSelect: (quality, service) {
+          ref.read(downloadQueueProvider.notifier).addToQueue(track, service, qualityOverride: quality);
+          ScaffoldMessenger.of(context).showSnackBar(SnackBar(content: Text('Added "${track.name}" to queue')));
+        },
+      );
     } else {
       ref.read(downloadQueueProvider.notifier).addToQueue(track, settings.defaultService);
       ScaffoldMessenger.of(context).showSnackBar(SnackBar(content: Text('Added "${track.name}" to queue')));
@@ -182,222 +189,20 @@ class PlaylistScreen extends ConsumerWidget {
     if (tracks.isEmpty) return;
     final settings = ref.read(settingsProvider);
     if (settings.askQualityBeforeDownload) {
-      _showQualityPicker(context, ref, (quality, service) {
-        ref.read(downloadQueueProvider.notifier).addMultipleToQueue(tracks, service, qualityOverride: quality);
-        ScaffoldMessenger.of(context).showSnackBar(SnackBar(content: Text('Added ${tracks.length} tracks to queue')));
-      }, trackName: '${tracks.length} tracks', artistName: playlistName);
+      DownloadServicePicker.show(
+        context,
+        trackName: '${tracks.length} tracks',
+        artistName: playlistName,
+        onSelect: (quality, service) {
+          ref.read(downloadQueueProvider.notifier).addMultipleToQueue(tracks, service, qualityOverride: quality);
+          ScaffoldMessenger.of(context).showSnackBar(SnackBar(content: Text('Added ${tracks.length} tracks to queue')));
+        },
+      );
     } else {
       ref.read(downloadQueueProvider.notifier).addMultipleToQueue(tracks, settings.defaultService);
       ScaffoldMessenger.of(context).showSnackBar(SnackBar(content: Text('Added ${tracks.length} tracks to queue')));
     }
   }
-
-  void _showQualityPicker(BuildContext context, WidgetRef ref, void Function(String quality, String service) onSelect, {String? trackName, String? artistName, String? coverUrl}) {
-    final colorScheme = Theme.of(context).colorScheme;
-    final settings = ref.read(settingsProvider);
-    String selectedService = settings.defaultService;
-    
-    showModalBottomSheet(
-      context: context,
-      backgroundColor: colorScheme.surfaceContainerHigh,
-      shape: const RoundedRectangleBorder(borderRadius: BorderRadius.vertical(top: Radius.circular(28))),
-      isScrollControlled: true,
-      builder: (context) => StatefulBuilder(
-        builder: (context, setModalState) => SafeArea(
-          child: SingleChildScrollView(
-            child: Column(
-              mainAxisSize: MainAxisSize.min,
-              crossAxisAlignment: CrossAxisAlignment.start,
-              children: [
-                if (trackName != null) ...[
-                  _TrackInfoHeader(trackName: trackName, artistName: artistName, coverUrl: coverUrl),
-                  Divider(height: 1, color: colorScheme.outlineVariant.withValues(alpha: 0.5)),
-                ] else ...[
-                  const SizedBox(height: 8),
-                  Center(child: Container(width: 40, height: 4, decoration: BoxDecoration(color: colorScheme.onSurfaceVariant.withValues(alpha: 0.4), borderRadius: BorderRadius.circular(2)))),
-                ],
-                // Service selector
-                Padding(
-                  padding: const EdgeInsets.fromLTRB(24, 16, 24, 8),
-                  child: Text('Download From', style: Theme.of(context).textTheme.titleMedium?.copyWith(fontWeight: FontWeight.bold)),
-                ),
-                Padding(
-                  padding: const EdgeInsets.symmetric(horizontal: 20),
-                  child: Row(
-                    children: [
-                      _ServiceChip(label: 'Tidal', isSelected: selectedService == 'tidal', onTap: () => setModalState(() => selectedService = 'tidal')),
-                      const SizedBox(width: 8),
-                      _ServiceChip(label: 'Qobuz', isSelected: selectedService == 'qobuz', onTap: () => setModalState(() => selectedService = 'qobuz')),
-                      const SizedBox(width: 8),
-                      _ServiceChip(label: 'Amazon', isSelected: selectedService == 'amazon', onTap: () => setModalState(() => selectedService = 'amazon')),
-                    ],
-                  ),
-                ),
-                Padding(padding: const EdgeInsets.fromLTRB(24, 16, 24, 8), child: Text('Select Quality', style: Theme.of(context).textTheme.titleMedium?.copyWith(fontWeight: FontWeight.bold))),
-                // Disclaimer
-                Padding(
-                  padding: const EdgeInsets.fromLTRB(24, 0, 24, 12),
-                  child: Text(
-                    'Actual quality depends on track availability. Hi-Res may not be available for all tracks.',
-                    style: Theme.of(context).textTheme.bodySmall?.copyWith(
-                      color: colorScheme.onSurfaceVariant,
-                      fontStyle: FontStyle.italic,
-                    ),
-                  ),
-                ),
-                _QualityOption(title: 'FLAC Lossless', subtitle: '16-bit / 44.1kHz', icon: Icons.music_note, onTap: () { Navigator.pop(context); onSelect('LOSSLESS', selectedService); }),
-                _QualityOption(title: 'Hi-Res FLAC', subtitle: '24-bit / up to 96kHz', icon: Icons.high_quality, onTap: () { Navigator.pop(context); onSelect('HI_RES', selectedService); }),
-                _QualityOption(title: 'Hi-Res FLAC Max', subtitle: '24-bit / up to 192kHz', icon: Icons.four_k, onTap: () { Navigator.pop(context); onSelect('HI_RES_LOSSLESS', selectedService); }),
-                const SizedBox(height: 16),
-              ],
-            ),
-          ),
-        ),
-      ),
-    );
-  }
-}
-
-class _QualityOption extends StatelessWidget {
-  final String title;
-  final String subtitle;
-  final IconData icon;
-  final VoidCallback onTap;
-
-  const _QualityOption({required this.title, required this.subtitle, required this.icon, required this.onTap});
-
-  @override
-  Widget build(BuildContext context) {
-    final colorScheme = Theme.of(context).colorScheme;
-    return ListTile(
-      contentPadding: const EdgeInsets.symmetric(horizontal: 24, vertical: 4),
-      leading: Container(padding: const EdgeInsets.all(10), decoration: BoxDecoration(color: colorScheme.primaryContainer, borderRadius: BorderRadius.circular(12)), child: Icon(icon, color: colorScheme.onPrimaryContainer, size: 20)),
-      title: Text(title, style: const TextStyle(fontWeight: FontWeight.w500)),
-      subtitle: Text(subtitle, style: TextStyle(color: colorScheme.onSurfaceVariant)),
-      onTap: onTap,
-    );
-  }
-}
-
-class _ServiceChip extends StatelessWidget {
-  final String label;
-  final bool isSelected;
-  final VoidCallback onTap;
-  const _ServiceChip({required this.label, required this.isSelected, required this.onTap});
-
-  @override
-  Widget build(BuildContext context) {
-    final colorScheme = Theme.of(context).colorScheme;
-    return Expanded(
-      child: GestureDetector(
-        onTap: onTap,
-        child: AnimatedContainer(
-          duration: const Duration(milliseconds: 200),
-          padding: const EdgeInsets.symmetric(vertical: 10),
-          decoration: BoxDecoration(
-            color: isSelected ? colorScheme.primaryContainer : colorScheme.surfaceContainerHighest,
-            borderRadius: BorderRadius.circular(12),
-            border: isSelected ? null : Border.all(color: colorScheme.outlineVariant.withValues(alpha: 0.5)),
-          ),
-          child: Text(
-            label,
-            textAlign: TextAlign.center,
-            style: TextStyle(
-              fontWeight: isSelected ? FontWeight.w600 : FontWeight.normal,
-              color: isSelected ? colorScheme.onPrimaryContainer : colorScheme.onSurfaceVariant,
-            ),
-          ),
-        ),
-      ),
-    );
-  }
-}
-
-class _TrackInfoHeader extends StatefulWidget {
-  final String trackName;
-  final String? artistName;
-  final String? coverUrl;
-  const _TrackInfoHeader({required this.trackName, this.artistName, this.coverUrl});
-
-  @override
-  State<_TrackInfoHeader> createState() => _TrackInfoHeaderState();
-}
-
-class _TrackInfoHeaderState extends State<_TrackInfoHeader> {
-  bool _expanded = false;
-  bool _isOverflowing = false;
-
-  @override
-  Widget build(BuildContext context) {
-    final colorScheme = Theme.of(context).colorScheme;
-    return Material(
-      color: Colors.transparent,
-      child: InkWell(
-        onTap: _isOverflowing ? () => setState(() => _expanded = !_expanded) : null,
-        borderRadius: const BorderRadius.only(topLeft: Radius.circular(28), topRight: Radius.circular(28)),
-        child: Column(
-          children: [
-            const SizedBox(height: 8),
-            Container(width: 40, height: 4, decoration: BoxDecoration(color: colorScheme.onSurfaceVariant.withValues(alpha: 0.4), borderRadius: BorderRadius.circular(2))),
-            Padding(
-              padding: const EdgeInsets.fromLTRB(16, 12, 16, 12),
-              child: Row(
-                children: [
-                  ClipRRect(
-                    borderRadius: BorderRadius.circular(8),
-                    child: widget.coverUrl != null
-                        ? Image.network(widget.coverUrl!, width: 56, height: 56, fit: BoxFit.cover,
-                            errorBuilder: (_, e, s) => Container(width: 56, height: 56, color: colorScheme.surfaceContainerHighest, child: Icon(Icons.music_note, color: colorScheme.onSurfaceVariant)))
-                        : Container(width: 56, height: 56, color: colorScheme.surfaceContainerHighest, child: Icon(Icons.music_note, color: colorScheme.onSurfaceVariant)),
-                  ),
-                  const SizedBox(width: 12),
-                  Expanded(
-                    child: LayoutBuilder(
-                      builder: (context, constraints) {
-                        final titleStyle = Theme.of(context).textTheme.titleMedium?.copyWith(fontWeight: FontWeight.w600);
-                        final titleSpan = TextSpan(text: widget.trackName, style: titleStyle);
-                        final titlePainter = TextPainter(text: titleSpan, maxLines: 1, textDirection: TextDirection.ltr)..layout(maxWidth: constraints.maxWidth);
-                        final titleOverflows = titlePainter.didExceedMaxLines;
-                        
-                        WidgetsBinding.instance.addPostFrameCallback((_) {
-                          if (mounted && _isOverflowing != titleOverflows) {
-                            setState(() => _isOverflowing = titleOverflows);
-                          }
-                        });
-                        
-                        return Column(
-                          crossAxisAlignment: CrossAxisAlignment.start,
-                          children: [
-                            Text(
-                              widget.trackName,
-                              style: titleStyle,
-                              maxLines: _expanded ? 10 : 1,
-                              overflow: _expanded ? TextOverflow.visible : TextOverflow.ellipsis,
-                            ),
-                            if (widget.artistName != null) ...[
-                              const SizedBox(height: 2),
-                              Text(
-                                widget.artistName!,
-                                style: Theme.of(context).textTheme.bodyMedium?.copyWith(color: colorScheme.onSurfaceVariant),
-                                maxLines: _expanded ? 3 : 1,
-                                overflow: _expanded ? TextOverflow.visible : TextOverflow.ellipsis,
-                              ),
-                            ],
-                          ],
-                        );
-                      },
-                    ),
-                  ),
-                  if (_isOverflowing || _expanded)
-                    Icon(_expanded ? Icons.expand_less : Icons.expand_more, color: colorScheme.onSurfaceVariant, size: 20),
-                ],
-              ),
-            ),
-          ],
-        ),
-      ),
-    );
-  }
 }
 
 /// Separate Consumer widget for each track - only rebuilds when this specific track's status changes

lib/screens/settings/download_settings_page.dart

@@ -4,16 +4,23 @@ import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:file_picker/file_picker.dart';
 import 'package:path_provider/path_provider.dart';
 import 'package:spotiflac_android/providers/settings_provider.dart';
+import 'package:spotiflac_android/providers/extension_provider.dart';
 import 'package:spotiflac_android/widgets/settings_group.dart';
 
 class DownloadSettingsPage extends ConsumerWidget {
   const DownloadSettingsPage({super.key});
+  
+  // Built-in services that support quality options
+  static const _builtInServices = ['tidal', 'qobuz', 'amazon'];
 
   @override
   Widget build(BuildContext context, WidgetRef ref) {
     final settings = ref.watch(settingsProvider);
     final colorScheme = Theme.of(context).colorScheme;
     final topPadding = MediaQuery.of(context).padding.top;
+    
+    // Check if current service is built-in (supports quality options)
+    final isBuiltInService = _builtInServices.contains(settings.defaultService);
 
     return PopScope(
       canPop: true,
@@ -87,13 +94,17 @@ class DownloadSettingsPage extends ConsumerWidget {
                   SettingsSwitchItem(
                     icon: Icons.tune,
                     title: 'Ask Before Download',
-                    subtitle: 'Choose quality for each download',
+                    subtitle: isBuiltInService 
+                        ? 'Choose quality for each download'
+                        : 'Select a built-in service to enable',
                     value: settings.askQualityBeforeDownload,
+                    // Not selected visually if extension is active
+                    enabled: isBuiltInService,
                     onChanged: (value) => ref
                         .read(settingsProvider.notifier)
                         .setAskQualityBeforeDownload(value),
                   ),
-                  if (!settings.askQualityBeforeDownload) ...[
+                  if (!settings.askQualityBeforeDownload && isBuiltInService) ...[
                     _QualityOption(
                       title: 'FLAC Lossless',
                       subtitle: '16-bit / 44.1kHz',
@@ -120,6 +131,29 @@ class DownloadSettingsPage extends ConsumerWidget {
                       showDivider: false,
                     ),
                   ],
+                  if (!isBuiltInService) ...[
+                    Padding(
+                      padding: const EdgeInsets.fromLTRB(16, 8, 16, 16),
+                      child: Row(
+                        children: [
+                          Icon(
+                            Icons.info_outline,
+                            size: 16,
+                            color: colorScheme.onSurfaceVariant,
+                          ),
+                          const SizedBox(width: 8),
+                          Expanded(
+                            child: Text(
+                              'Select Tidal, Qobuz, or Amazon above to configure quality',
+                              style: Theme.of(context).textTheme.bodySmall?.copyWith(
+                                color: colorScheme.onSurfaceVariant,
+                              ),
+                            ),
+                          ),
+                        ],
+                      ),
+                    ),
+                  ],
                 ],
               ),
             ),
@@ -151,19 +185,31 @@ class DownloadSettingsPage extends ConsumerWidget {
                         : settings.downloadDirectory,
                     onTap: () => _pickDirectory(context, ref),
                   ),
-                  SettingsItem(
-                    icon: Icons.create_new_folder_outlined,
-                    title: 'Folder Organization',
-                    subtitle: _getFolderOrganizationLabel(
-                      settings.folderOrganization,
-                    ),
-                    onTap: () => _showFolderOrganizationPicker(
-                      context,
-                      ref,
-                      settings.folderOrganization,
-                    ),
-                    showDivider: false,
+                  SettingsSwitchItem(
+                    icon: Icons.library_music_outlined,
+                    title: 'Separate Singles Folder',
+                    subtitle: settings.separateSingles
+                        ? 'Albums/ and Singles/ folders'
+                        : 'All files in same structure',
+                    value: settings.separateSingles,
+                    onChanged: (value) => ref
+                        .read(settingsProvider.notifier)
+                        .setSeparateSingles(value),
                   ),
+                  if (!settings.separateSingles)
+                    SettingsItem(
+                      icon: Icons.create_new_folder_outlined,
+                      title: 'Folder Organization',
+                      subtitle: _getFolderOrganizationLabel(
+                        settings.folderOrganization,
+                      ),
+                      onTap: () => _showFolderOrganizationPicker(
+                        context,
+                        ref,
+                        settings.folderOrganization,
+                      ),
+                      showDivider: false,
+                    ),
                 ],
               ),
             ),
@@ -555,7 +601,7 @@ class DownloadSettingsPage extends ConsumerWidget {
   }
 }
 
-class _ServiceSelector extends StatelessWidget {
+class _ServiceSelector extends ConsumerWidget {
   final String currentService;
   final ValueChanged<String> onChanged;
   const _ServiceSelector({
@@ -564,31 +610,75 @@ class _ServiceSelector extends StatelessWidget {
   });
 
   @override
-  Widget build(BuildContext context) {
+  Widget build(BuildContext context, WidgetRef ref) {
+    final extState = ref.watch(extensionProvider);
+    
+    // Get enabled extension download providers
+    final extensionProviders = extState.extensions
+        .where((e) => e.enabled && e.hasDownloadProvider)
+        .toList();
+    
+    // Check if current service is an extension that's now disabled
+    final isExtensionService = !['tidal', 'qobuz', 'amazon'].contains(currentService);
+    final isCurrentExtensionEnabled = isExtensionService 
+        ? extensionProviders.any((e) => e.id == currentService)
+        : true;
+    
+    // If current extension is disabled, show it as not selected
+    final effectiveService = isCurrentExtensionEnabled ? currentService : '';
+    
     return Padding(
       padding: const EdgeInsets.all(12),
-      child: Row(
+      child: Column(
         children: [
-          _ServiceChip(
-            icon: Icons.music_note,
-            label: 'Tidal',
-            isSelected: currentService == 'tidal',
-            onTap: () => onChanged('tidal'),
-          ),
-          const SizedBox(width: 8),
-          _ServiceChip(
-            icon: Icons.album,
-            label: 'Qobuz',
-            isSelected: currentService == 'qobuz',
-            onTap: () => onChanged('qobuz'),
-          ),
-          const SizedBox(width: 8),
-          _ServiceChip(
-            icon: Icons.shopping_bag,
-            label: 'Amazon',
-            isSelected: currentService == 'amazon',
-            onTap: () => onChanged('amazon'),
+          Row(
+            children: [
+              _ServiceChip(
+                icon: Icons.music_note,
+                label: 'Tidal',
+                isSelected: effectiveService == 'tidal',
+                onTap: () => onChanged('tidal'),
+              ),
+              const SizedBox(width: 8),
+              _ServiceChip(
+                icon: Icons.album,
+                label: 'Qobuz',
+                isSelected: effectiveService == 'qobuz',
+                onTap: () => onChanged('qobuz'),
+              ),
+              const SizedBox(width: 8),
+              _ServiceChip(
+                icon: Icons.shopping_bag,
+                label: 'Amazon',
+                isSelected: effectiveService == 'amazon',
+                onTap: () => onChanged('amazon'),
+              ),
+            ],
           ),
+          // Show extension download providers if any
+          if (extensionProviders.isNotEmpty) ...[
+            const SizedBox(height: 8),
+            Row(
+              children: [
+                for (int i = 0; i < extensionProviders.length; i++) ...[
+                  if (i > 0) const SizedBox(width: 8),
+                  Expanded(
+                    child: _ServiceChip(
+                      icon: Icons.extension,
+                      label: extensionProviders[i].displayName,
+                      isSelected: effectiveService == extensionProviders[i].id,
+                      onTap: () => onChanged(extensionProviders[i].id),
+                    ),
+                  ),
+                ],
+                // Fill remaining space if less than 3 extensions
+                for (int i = extensionProviders.length; i < 3; i++) ...[
+                  const SizedBox(width: 8),
+                  const Expanded(child: SizedBox()),
+                ],
+              ],
+            ),
+          ],
         ],
       ),
     );

lib/screens/settings/extension_detail_page.dart

@@ -0,0 +1,967 @@
+import 'dart:io';
+
+import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:spotiflac_android/providers/extension_provider.dart';
+import 'package:spotiflac_android/providers/store_provider.dart';
+import 'package:spotiflac_android/widgets/settings_group.dart';
+
+class ExtensionDetailPage extends ConsumerStatefulWidget {
+  final String extensionId;
+
+  const ExtensionDetailPage({super.key, required this.extensionId});
+
+  @override
+  ConsumerState<ExtensionDetailPage> createState() => _ExtensionDetailPageState();
+}
+
+class _ExtensionDetailPageState extends ConsumerState<ExtensionDetailPage> {
+  Map<String, dynamic> _settings = {};
+  bool _isLoadingSettings = true;
+
+  @override
+  void initState() {
+    super.initState();
+    _loadSettings();
+  }
+
+  Future<void> _loadSettings() async {
+    final settings = await ref
+        .read(extensionProvider.notifier)
+        .getExtensionSettings(widget.extensionId);
+    setState(() {
+      _settings = settings;
+      _isLoadingSettings = false;
+    });
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    final extState = ref.watch(extensionProvider);
+    final extension = extState.extensions.firstWhere(
+      (e) => e.id == widget.extensionId,
+      orElse: () => const Extension(
+        id: '',
+        name: '',
+        displayName: 'Unknown',
+        version: '0.0.0',
+        author: 'Unknown',
+        description: '',
+        enabled: false,
+        status: 'error',
+      ),
+    );
+
+    final colorScheme = Theme.of(context).colorScheme;
+    final topPadding = MediaQuery.of(context).padding.top;
+    final hasError = extension.status == 'error';
+
+    return Scaffold(
+      body: CustomScrollView(
+        slivers: [
+          // App Bar
+          SliverAppBar(
+            expandedHeight: 120 + topPadding,
+            collapsedHeight: kToolbarHeight,
+            floating: false,
+            pinned: true,
+            backgroundColor: colorScheme.surface,
+            surfaceTintColor: Colors.transparent,
+            leading: IconButton(
+              icon: const Icon(Icons.arrow_back),
+              onPressed: () => Navigator.pop(context),
+            ),
+            flexibleSpace: LayoutBuilder(
+              builder: (context, constraints) {
+                final maxHeight = 120 + topPadding;
+                final minHeight = kToolbarHeight + topPadding;
+                final expandRatio = ((constraints.maxHeight - minHeight) /
+                        (maxHeight - minHeight))
+                    .clamp(0.0, 1.0);
+                final leftPadding = 56 - (32 * expandRatio);
+                return FlexibleSpaceBar(
+                  expandedTitleScale: 1.0,
+                  titlePadding: EdgeInsets.only(left: leftPadding, bottom: 16),
+                  title: Text(
+                    extension.displayName,
+                    style: TextStyle(
+                      fontSize: 20 + (8 * expandRatio),
+                      fontWeight: FontWeight.bold,
+                      color: colorScheme.onSurface,
+                    ),
+                  ),
+                );
+              },
+            ),
+          ),
+
+          // Extension Info Card
+          SliverToBoxAdapter(
+            child: Padding(
+              padding: const EdgeInsets.all(16),
+              child: Container(
+                padding: const EdgeInsets.all(20),
+                decoration: BoxDecoration(
+                  color: colorScheme.surfaceContainerHighest.withValues(alpha: 0.3),
+                  borderRadius: BorderRadius.circular(20),
+                ),
+                child: Column(
+                  crossAxisAlignment: CrossAxisAlignment.start,
+                  children: [
+                    Row(
+                      children: [
+                        Container(
+                          width: 56,
+                          height: 56,
+                          decoration: BoxDecoration(
+                            color: hasError
+                                ? colorScheme.errorContainer
+                                : colorScheme.primaryContainer,
+                            borderRadius: BorderRadius.circular(16),
+                          ),
+                          child: extension.iconPath != null && extension.iconPath!.isNotEmpty
+                              ? ClipRRect(
+                                  borderRadius: BorderRadius.circular(16),
+                                  child: Image.file(
+                                    File(extension.iconPath!),
+                                    width: 56,
+                                    height: 56,
+                                    fit: BoxFit.cover,
+                                    errorBuilder: (context, error, stackTrace) => Icon(
+                                      hasError ? Icons.error_outline : Icons.extension,
+                                      size: 28,
+                                      color: hasError
+                                          ? colorScheme.error
+                                          : colorScheme.onPrimaryContainer,
+                                    ),
+                                  ),
+                                )
+                              : Icon(
+                                  hasError ? Icons.error_outline : Icons.extension,
+                                  size: 28,
+                                  color: hasError
+                                      ? colorScheme.error
+                                      : colorScheme.onPrimaryContainer,
+                                ),
+                        ),
+                        const SizedBox(width: 16),
+                        Expanded(
+                          child: Column(
+                            crossAxisAlignment: CrossAxisAlignment.start,
+                            children: [
+                              Text(
+                                extension.displayName,
+                                style: Theme.of(context).textTheme.titleLarge?.copyWith(
+                                  fontWeight: FontWeight.bold,
+                                ),
+                              ),
+                              Text(
+                                'v${extension.version}',
+                                style: Theme.of(context).textTheme.bodyMedium?.copyWith(
+                                  color: colorScheme.onSurfaceVariant,
+                                ),
+                              ),
+                            ],
+                          ),
+                        ),
+                        Switch(
+                          value: extension.enabled,
+                          onChanged: hasError
+                              ? null
+                              : (enabled) => ref
+                                  .read(extensionProvider.notifier)
+                                  .setExtensionEnabled(widget.extensionId, enabled),
+                        ),
+                      ],
+                    ),
+                    if (extension.description.isNotEmpty) ...[
+                      const SizedBox(height: 16),
+                      Text(
+                        extension.description,
+                        style: Theme.of(context).textTheme.bodyMedium?.copyWith(
+                          color: colorScheme.onSurfaceVariant,
+                        ),
+                      ),
+                    ],
+                    const SizedBox(height: 16),
+                    _InfoRow(label: 'Author', value: extension.author),
+                    _InfoRow(label: 'ID', value: extension.id),
+                    if (hasError && extension.errorMessage != null)
+                      _InfoRow(
+                        label: 'Error',
+                        value: extension.errorMessage!,
+                        isError: true,
+                      ),
+                  ],
+                ),
+              ),
+            ),
+          ),
+
+          // Capabilities
+          const SliverToBoxAdapter(
+            child: SettingsSectionHeader(title: 'Capabilities'),
+          ),
+          SliverToBoxAdapter(
+            child: SettingsGroup(
+              children: [
+                _CapabilityItem(
+                  icon: Icons.search,
+                  title: 'Metadata Provider',
+                  enabled: extension.hasMetadataProvider,
+                ),
+                _CapabilityItem(
+                  icon: Icons.download,
+                  title: 'Download Provider',
+                  enabled: extension.hasDownloadProvider,
+                ),
+                _CapabilityItem(
+                  icon: Icons.manage_search,
+                  title: 'Custom Search',
+                  enabled: extension.hasCustomSearch,
+                  subtitle: extension.searchBehavior?.placeholder,
+                ),
+                _CapabilityItem(
+                  icon: Icons.compare_arrows,
+                  title: 'Custom Track Matching',
+                  enabled: extension.hasCustomMatching,
+                  subtitle: extension.trackMatching?.strategy != null 
+                      ? 'Strategy: ${extension.trackMatching!.strategy}'
+                      : null,
+                ),
+                _CapabilityItem(
+                  icon: Icons.auto_fix_high,
+                  title: 'Post-Processing',
+                  enabled: extension.hasPostProcessing,
+                  subtitle: extension.postProcessing?.hooks.isNotEmpty == true
+                      ? '${extension.postProcessing!.hooks.length} hook(s) available'
+                      : null,
+                  showDivider: false,
+                ),
+              ],
+            ),
+          ),
+
+          // Search Provider Section (if extension has custom search)
+          if (extension.hasCustomSearch) ...[
+            const SliverToBoxAdapter(
+              child: SettingsSectionHeader(title: 'Search Provider'),
+            ),
+            SliverToBoxAdapter(
+              child: SettingsGroup(
+                children: [
+                  _SearchProviderInfo(
+                    extension: extension,
+                  ),
+                ],
+              ),
+            ),
+          ],
+
+          // Post-Processing Hooks (if available)
+          if (extension.hasPostProcessing && extension.postProcessing!.hooks.isNotEmpty) ...[
+            const SliverToBoxAdapter(
+              child: SettingsSectionHeader(title: 'Post-Processing Hooks'),
+            ),
+            SliverToBoxAdapter(
+              child: SettingsGroup(
+                children: extension.postProcessing!.hooks.asMap().entries.map((entry) {
+                  final index = entry.key;
+                  final hook = entry.value;
+                  return _PostProcessingHookItem(
+                    hook: hook,
+                    showDivider: index < extension.postProcessing!.hooks.length - 1,
+                  );
+                }).toList(),
+              ),
+            ),
+          ],
+
+          // Permissions
+          if (extension.permissions.isNotEmpty) ...[
+            const SliverToBoxAdapter(
+              child: SettingsSectionHeader(title: 'Permissions'),
+            ),
+            SliverToBoxAdapter(
+              child: SettingsGroup(
+                children: extension.permissions.asMap().entries.map((entry) {
+                  final index = entry.key;
+                  final permission = entry.value;
+                  return _PermissionItem(
+                    permission: permission,
+                    showDivider: index < extension.permissions.length - 1,
+                  );
+                }).toList(),
+              ),
+            ),
+          ],
+
+          // Settings
+          if (extension.settings.isNotEmpty) ...[
+            const SliverToBoxAdapter(
+              child: SettingsSectionHeader(title: 'Settings'),
+            ),
+            if (_isLoadingSettings)
+              const SliverToBoxAdapter(
+                child: Padding(
+                  padding: EdgeInsets.all(32),
+                  child: Center(child: CircularProgressIndicator()),
+                ),
+              )
+            else
+              SliverToBoxAdapter(
+                child: SettingsGroup(
+                  children: extension.settings.asMap().entries.map((entry) {
+                    final index = entry.key;
+                    final setting = entry.value;
+                    return _SettingItem(
+                      setting: setting,
+                      value: _settings[setting.key] ?? setting.defaultValue,
+                      showDivider: index < extension.settings.length - 1,
+                      onChanged: (value) => _updateSetting(setting.key, value),
+                    );
+                  }).toList(),
+                ),
+              ),
+          ],
+
+          // Remove button
+          SliverToBoxAdapter(
+            child: Padding(
+              padding: const EdgeInsets.all(16),
+              child: OutlinedButton.icon(
+                onPressed: () => _confirmRemove(context),
+                icon: const Icon(Icons.delete_outline),
+                label: const Text('Remove Extension'),
+                style: OutlinedButton.styleFrom(
+                  foregroundColor: colorScheme.error,
+                  side: BorderSide(color: colorScheme.error),
+                  padding: const EdgeInsets.symmetric(vertical: 16),
+                  shape: RoundedRectangleBorder(
+                    borderRadius: BorderRadius.circular(16),
+                  ),
+                ),
+              ),
+            ),
+          ),
+
+          const SliverToBoxAdapter(child: SizedBox(height: 32)),
+        ],
+      ),
+    );
+  }
+
+  Future<void> _updateSetting(String key, dynamic value) async {
+    setState(() {
+      _settings[key] = value;
+    });
+    await ref
+        .read(extensionProvider.notifier)
+        .setExtensionSettings(widget.extensionId, _settings);
+  }
+
+  Future<void> _confirmRemove(BuildContext context) async {
+    final colorScheme = Theme.of(context).colorScheme;
+    final confirmed = await showDialog<bool>(
+      context: context,
+      builder: (context) => AlertDialog(
+        title: const Text('Remove Extension'),
+        content: const Text(
+          'Are you sure you want to remove this extension? '
+          'This action cannot be undone.',
+        ),
+        actions: [
+          TextButton(
+            onPressed: () => Navigator.pop(context, false),
+            child: const Text('Cancel'),
+          ),
+          FilledButton(
+            onPressed: () => Navigator.pop(context, true),
+            style: FilledButton.styleFrom(
+              backgroundColor: colorScheme.error,
+            ),
+            child: const Text('Remove'),
+          ),
+        ],
+      ),
+    );
+
+    if (confirmed == true && mounted) {
+      final success = await ref
+          .read(extensionProvider.notifier)
+          .removeExtension(widget.extensionId);
+      if (success && mounted) {
+        // Refresh store to update isInstalled status
+        ref.read(storeProvider.notifier).refresh();
+        Navigator.pop(this.context);
+      }
+    }
+  }
+}
+
+class _InfoRow extends StatelessWidget {
+  final String label;
+  final String value;
+  final bool isError;
+
+  const _InfoRow({
+    required this.label,
+    required this.value,
+    this.isError = false,
+  });
+
+  @override
+  Widget build(BuildContext context) {
+    final colorScheme = Theme.of(context).colorScheme;
+    return Padding(
+      padding: const EdgeInsets.only(top: 8),
+      child: Row(
+        crossAxisAlignment: CrossAxisAlignment.start,
+        children: [
+          SizedBox(
+            width: 60,
+            child: Text(
+              label,
+              style: Theme.of(context).textTheme.bodySmall?.copyWith(
+                color: colorScheme.onSurfaceVariant,
+              ),
+            ),
+          ),
+          Expanded(
+            child: Text(
+              value,
+              style: Theme.of(context).textTheme.bodySmall?.copyWith(
+                color: isError ? colorScheme.error : colorScheme.onSurface,
+              ),
+            ),
+          ),
+        ],
+      ),
+    );
+  }
+}
+
+class _CapabilityItem extends StatelessWidget {
+  final IconData icon;
+  final String title;
+  final bool enabled;
+  final bool showDivider;
+  final String? subtitle;
+
+  const _CapabilityItem({
+    required this.icon,
+    required this.title,
+    required this.enabled,
+    this.showDivider = true,
+    this.subtitle,
+  });
+
+  @override
+  Widget build(BuildContext context) {
+    final colorScheme = Theme.of(context).colorScheme;
+    return Column(
+      mainAxisSize: MainAxisSize.min,
+      children: [
+        Padding(
+          padding: const EdgeInsets.symmetric(horizontal: 16, vertical: 12),
+          child: Row(
+            children: [
+              Icon(
+                icon,
+                color: enabled ? colorScheme.primary : colorScheme.outline,
+              ),
+              const SizedBox(width: 16),
+              Expanded(
+                child: Column(
+                  crossAxisAlignment: CrossAxisAlignment.start,
+                  children: [
+                    Text(
+                      title,
+                      style: Theme.of(context).textTheme.bodyLarge,
+                    ),
+                    if (subtitle != null && enabled) ...[
+                      const SizedBox(height: 2),
+                      Text(
+                        subtitle!,
+                        style: Theme.of(context).textTheme.bodySmall?.copyWith(
+                          color: colorScheme.onSurfaceVariant,
+                        ),
+                      ),
+                    ],
+                  ],
+                ),
+              ),
+              Icon(
+                enabled ? Icons.check_circle : Icons.cancel_outlined,
+                color: enabled ? colorScheme.primary : colorScheme.outline,
+              ),
+            ],
+          ),
+        ),
+        if (showDivider)
+          Divider(
+            height: 1,
+            thickness: 1,
+            indent: 56,
+            endIndent: 16,
+            color: colorScheme.outlineVariant.withValues(alpha: 0.3),
+          ),
+      ],
+    );
+  }
+}
+
+class _PermissionItem extends StatelessWidget {
+  final String permission;
+  final bool showDivider;
+
+  const _PermissionItem({
+    required this.permission,
+    this.showDivider = true,
+  });
+
+  @override
+  Widget build(BuildContext context) {
+    final colorScheme = Theme.of(context).colorScheme;
+    
+    // Parse permission to get icon and description
+    IconData icon = Icons.security;
+    String description = permission;
+    
+    if (permission.startsWith('network:')) {
+      icon = Icons.language;
+      description = 'Network access to: ${permission.substring(8)}';
+    } else if (permission.startsWith('storage:')) {
+      icon = Icons.folder;
+      description = 'Storage access: ${permission.substring(8)}';
+    }
+
+    return Column(
+      mainAxisSize: MainAxisSize.min,
+      children: [
+        Padding(
+          padding: const EdgeInsets.symmetric(horizontal: 16, vertical: 12),
+          child: Row(
+            children: [
+              Icon(icon, color: colorScheme.onSurfaceVariant),
+              const SizedBox(width: 16),
+              Expanded(
+                child: Text(
+                  description,
+                  style: Theme.of(context).textTheme.bodyMedium,
+                ),
+              ),
+            ],
+          ),
+        ),
+        if (showDivider)
+          Divider(
+            height: 1,
+            thickness: 1,
+            indent: 56,
+            endIndent: 16,
+            color: colorScheme.outlineVariant.withValues(alpha: 0.3),
+          ),
+      ],
+    );
+  }
+}
+
+class _SettingItem extends StatelessWidget {
+  final ExtensionSetting setting;
+  final dynamic value;
+  final bool showDivider;
+  final ValueChanged<dynamic> onChanged;
+
+  const _SettingItem({
+    required this.setting,
+    required this.value,
+    required this.onChanged,
+    this.showDivider = true,
+  });
+
+  @override
+  Widget build(BuildContext context) {
+    final colorScheme = Theme.of(context).colorScheme;
+
+    Widget trailing;
+    switch (setting.type) {
+      case 'boolean':
+        trailing = Switch(
+          value: value as bool? ?? false,
+          onChanged: onChanged,
+        );
+        break;
+      case 'select':
+        trailing = DropdownButton<String>(
+          value: value as String?,
+          items: setting.options?.map((opt) {
+            return DropdownMenuItem(value: opt, child: Text(opt));
+          }).toList(),
+          onChanged: onChanged,
+          underline: const SizedBox(),
+        );
+        break;
+      default:
+        trailing = Icon(
+          Icons.chevron_right,
+          color: colorScheme.onSurfaceVariant,
+        );
+    }
+
+    return Column(
+      mainAxisSize: MainAxisSize.min,
+      children: [
+        InkWell(
+          onTap: setting.type == 'string' || setting.type == 'number'
+              ? () => _showEditDialog(context)
+              : null,
+          child: Padding(
+            padding: const EdgeInsets.symmetric(horizontal: 16, vertical: 12),
+            child: Row(
+              children: [
+                Expanded(
+                  child: Column(
+                    crossAxisAlignment: CrossAxisAlignment.start,
+                    children: [
+                      Text(
+                        setting.label,
+                        style: Theme.of(context).textTheme.bodyLarge,
+                      ),
+                      if (setting.description != null) ...[
+                        const SizedBox(height: 2),
+                        Text(
+                          setting.description!,
+                          style: Theme.of(context).textTheme.bodySmall?.copyWith(
+                            color: colorScheme.onSurfaceVariant,
+                          ),
+                        ),
+                      ],
+                      if (setting.type == 'string' || setting.type == 'number') ...[
+                        const SizedBox(height: 4),
+                        Text(
+                          value?.toString() ?? 'Not set',
+                          style: Theme.of(context).textTheme.bodySmall?.copyWith(
+                            color: colorScheme.primary,
+                          ),
+                        ),
+                      ],
+                    ],
+                  ),
+                ),
+                trailing,
+              ],
+            ),
+          ),
+        ),
+        if (showDivider)
+          Divider(
+            height: 1,
+            thickness: 1,
+            indent: 16,
+            endIndent: 16,
+            color: colorScheme.outlineVariant.withValues(alpha: 0.3),
+          ),
+      ],
+    );
+  }
+
+  void _showEditDialog(BuildContext context) {
+    final controller = TextEditingController(text: value?.toString() ?? '');
+    final colorScheme = Theme.of(context).colorScheme;
+
+    showDialog(
+      context: context,
+      builder: (context) => AlertDialog(
+        title: Text(setting.label),
+        content: TextField(
+          controller: controller,
+          keyboardType: setting.type == 'number'
+              ? TextInputType.number
+              : TextInputType.text,
+          decoration: InputDecoration(
+            hintText: setting.description ?? 'Enter value',
+            filled: true,
+            fillColor: colorScheme.surfaceContainerHighest.withValues(alpha: 0.3),
+            border: OutlineInputBorder(
+              borderRadius: BorderRadius.circular(12),
+              borderSide: BorderSide.none,
+            ),
+          ),
+        ),
+        actions: [
+          TextButton(
+            onPressed: () => Navigator.pop(context),
+            child: const Text('Cancel'),
+          ),
+          FilledButton(
+            onPressed: () {
+              final newValue = setting.type == 'number'
+                  ? num.tryParse(controller.text)
+                  : controller.text;
+              onChanged(newValue);
+              Navigator.pop(context);
+            },
+            child: const Text('Save'),
+          ),
+        ],
+      ),
+    );
+  }
+}
+
+class _PostProcessingHookItem extends StatelessWidget {
+  final PostProcessingHook hook;
+  final bool showDivider;
+
+  const _PostProcessingHookItem({
+    required this.hook,
+    this.showDivider = true,
+  });
+
+  @override
+  Widget build(BuildContext context) {
+    final colorScheme = Theme.of(context).colorScheme;
+    
+    return Column(
+      mainAxisSize: MainAxisSize.min,
+      children: [
+        Padding(
+          padding: const EdgeInsets.symmetric(horizontal: 16, vertical: 12),
+          child: Row(
+            children: [
+              Container(
+                width: 40,
+                height: 40,
+                decoration: BoxDecoration(
+                  color: colorScheme.tertiaryContainer,
+                  borderRadius: BorderRadius.circular(10),
+                ),
+                child: Icon(
+                  Icons.auto_fix_high,
+                  color: colorScheme.onTertiaryContainer,
+                  size: 20,
+                ),
+              ),
+              const SizedBox(width: 16),
+              Expanded(
+                child: Column(
+                  crossAxisAlignment: CrossAxisAlignment.start,
+                  children: [
+                    Text(
+                      hook.name,
+                      style: Theme.of(context).textTheme.bodyLarge?.copyWith(
+                        fontWeight: FontWeight.w500,
+                      ),
+                    ),
+                    if (hook.description != null) ...[
+                      const SizedBox(height: 2),
+                      Text(
+                        hook.description!,
+                        style: Theme.of(context).textTheme.bodySmall?.copyWith(
+                          color: colorScheme.onSurfaceVariant,
+                        ),
+                      ),
+                    ],
+                    if (hook.supportedFormats.isNotEmpty) ...[
+                      const SizedBox(height: 4),
+                      Wrap(
+                        spacing: 4,
+                        children: hook.supportedFormats.map((format) {
+                          return Container(
+                            padding: const EdgeInsets.symmetric(horizontal: 6, vertical: 2),
+                            decoration: BoxDecoration(
+                              color: colorScheme.surfaceContainerHighest,
+                              borderRadius: BorderRadius.circular(4),
+                            ),
+                            child: Text(
+                              format.toUpperCase(),
+                              style: Theme.of(context).textTheme.labelSmall?.copyWith(
+                                color: colorScheme.onSurfaceVariant,
+                              ),
+                            ),
+                          );
+                        }).toList(),
+                      ),
+                    ],
+                  ],
+                ),
+              ),
+              if (hook.defaultEnabled)
+                Container(
+                  padding: const EdgeInsets.symmetric(horizontal: 8, vertical: 4),
+                  decoration: BoxDecoration(
+                    color: colorScheme.primaryContainer,
+                    borderRadius: BorderRadius.circular(8),
+                  ),
+                  child: Text(
+                    'Auto',
+                    style: Theme.of(context).textTheme.labelSmall?.copyWith(
+                      color: colorScheme.onPrimaryContainer,
+                    ),
+                  ),
+                ),
+            ],
+          ),
+        ),
+        if (showDivider)
+          Divider(
+            height: 1,
+            thickness: 1,
+            indent: 72,
+            endIndent: 16,
+            color: colorScheme.outlineVariant.withValues(alpha: 0.3),
+          ),
+      ],
+    );
+  }
+}
+
+class _SearchProviderInfo extends StatelessWidget {
+  final Extension extension;
+
+  const _SearchProviderInfo({
+    required this.extension,
+  });
+
+  @override
+  Widget build(BuildContext context) {
+    final colorScheme = Theme.of(context).colorScheme;
+    final searchBehavior = extension.searchBehavior;
+    
+    return Padding(
+      padding: const EdgeInsets.all(16),
+      child: Column(
+        crossAxisAlignment: CrossAxisAlignment.start,
+        children: [
+          Row(
+            children: [
+              Container(
+                width: 48,
+                height: 48,
+                decoration: BoxDecoration(
+                  color: colorScheme.secondaryContainer,
+                  borderRadius: BorderRadius.circular(12),
+                ),
+                child: Icon(
+                  Icons.manage_search,
+                  color: colorScheme.onSecondaryContainer,
+                  size: 24,
+                ),
+              ),
+              const SizedBox(width: 16),
+              Expanded(
+                child: Column(
+                  crossAxisAlignment: CrossAxisAlignment.start,
+                  children: [
+                    Text(
+                      'Custom Search Available',
+                      style: Theme.of(context).textTheme.titleMedium?.copyWith(
+                        fontWeight: FontWeight.w600,
+                      ),
+                    ),
+                    const SizedBox(height: 2),
+                    Text(
+                      'This extension provides its own search functionality',
+                      style: Theme.of(context).textTheme.bodySmall?.copyWith(
+                        color: colorScheme.onSurfaceVariant,
+                      ),
+                    ),
+                  ],
+                ),
+              ),
+            ],
+          ),
+          const SizedBox(height: 16),
+          // Search placeholder info
+          if (searchBehavior?.placeholder != null) ...[
+            _InfoTile(
+              icon: Icons.text_fields,
+              label: 'Search Hint',
+              value: searchBehavior!.placeholder!,
+            ),
+            const SizedBox(height: 8),
+          ],
+          // Primary search info
+          _InfoTile(
+            icon: searchBehavior?.primary == true ? Icons.star : Icons.star_border,
+            label: 'Priority',
+            value: searchBehavior?.primary == true 
+                ? 'Primary search provider' 
+                : 'Secondary search provider',
+          ),
+          const SizedBox(height: 16),
+          // Usage instructions
+          Container(
+            padding: const EdgeInsets.all(12),
+            decoration: BoxDecoration(
+              color: colorScheme.surfaceContainerHighest.withValues(alpha: 0.5),
+              borderRadius: BorderRadius.circular(12),
+            ),
+            child: Row(
+              children: [
+                Icon(
+                  Icons.info_outline,
+                  size: 20,
+                  color: colorScheme.primary,
+                ),
+                const SizedBox(width: 12),
+                Expanded(
+                  child: Text(
+                    'To use this search provider, tap the search bar on the Home tab and select "${extension.displayName}" from the provider chips.',
+                    style: Theme.of(context).textTheme.bodySmall?.copyWith(
+                      color: colorScheme.onSurfaceVariant,
+                    ),
+                  ),
+                ),
+              ],
+            ),
+          ),
+        ],
+      ),
+    );
+  }
+}
+
+class _InfoTile extends StatelessWidget {
+  final IconData icon;
+  final String label;
+  final String value;
+
+  const _InfoTile({
+    required this.icon,
+    required this.label,
+    required this.value,
+  });
+
+  @override
+  Widget build(BuildContext context) {
+    final colorScheme = Theme.of(context).colorScheme;
+    
+    return Row(
+      children: [
+        Icon(
+          icon,
+          size: 18,
+          color: colorScheme.onSurfaceVariant,
+        ),
+        const SizedBox(width: 8),
+        Text(
+          '$label: ',
+          style: Theme.of(context).textTheme.bodySmall?.copyWith(
+            color: colorScheme.onSurfaceVariant,
+          ),
+        ),
+        Expanded(
+          child: Text(
+            value,
+            style: Theme.of(context).textTheme.bodySmall?.copyWith(
+              color: colorScheme.onSurface,
+              fontWeight: FontWeight.w500,
+            ),
+          ),
+        ),
+      ],
+    );
+  }
+}

lib/screens/settings/extensions_page.dart

@@ -0,0 +1,721 @@
+import 'dart:io';
+import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:file_picker/file_picker.dart';
+import 'package:path_provider/path_provider.dart';
+import 'package:spotiflac_android/providers/extension_provider.dart';
+import 'package:spotiflac_android/providers/settings_provider.dart';
+import 'package:spotiflac_android/screens/settings/extension_detail_page.dart';
+import 'package:spotiflac_android/screens/settings/provider_priority_page.dart';
+import 'package:spotiflac_android/screens/settings/metadata_provider_priority_page.dart';
+import 'package:spotiflac_android/widgets/settings_group.dart';
+
+class ExtensionsPage extends ConsumerStatefulWidget {
+  const ExtensionsPage({super.key});
+
+  @override
+  ConsumerState<ExtensionsPage> createState() => _ExtensionsPageState();
+}
+
+class _ExtensionsPageState extends ConsumerState<ExtensionsPage> {
+  @override
+  void initState() {
+    super.initState();
+    _initializeExtensions();
+  }
+
+  Future<void> _initializeExtensions() async {
+    final extState = ref.read(extensionProvider);
+    if (!extState.isInitialized) {
+      final appDir = await getApplicationDocumentsDirectory();
+      final extensionsDir = '${appDir.path}/extensions';
+      final dataDir = '${appDir.path}/extension_data';
+      
+      // Create directories if they don't exist
+      await Directory(extensionsDir).create(recursive: true);
+      await Directory(dataDir).create(recursive: true);
+      
+      await ref.read(extensionProvider.notifier).initialize(extensionsDir, dataDir);
+    }
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    final extState = ref.watch(extensionProvider);
+    final colorScheme = Theme.of(context).colorScheme;
+    final topPadding = MediaQuery.of(context).padding.top;
+
+    return Scaffold(
+      body: CustomScrollView(
+        slivers: [
+          // App Bar
+          SliverAppBar(
+            expandedHeight: 120 + topPadding,
+            collapsedHeight: kToolbarHeight,
+            floating: false,
+            pinned: true,
+            backgroundColor: colorScheme.surface,
+            surfaceTintColor: Colors.transparent,
+            leading: IconButton(
+              icon: const Icon(Icons.arrow_back),
+              onPressed: () => Navigator.pop(context),
+            ),
+            flexibleSpace: LayoutBuilder(
+              builder: (context, constraints) {
+                final maxHeight = 120 + topPadding;
+                final minHeight = kToolbarHeight + topPadding;
+                final expandRatio = ((constraints.maxHeight - minHeight) /
+                        (maxHeight - minHeight))
+                    .clamp(0.0, 1.0);
+                final leftPadding = 56 - (32 * expandRatio);
+                return FlexibleSpaceBar(
+                  expandedTitleScale: 1.0,
+                  titlePadding: EdgeInsets.only(left: leftPadding, bottom: 16),
+                  title: Text(
+                    'Extensions',
+                    style: TextStyle(
+                      fontSize: 20 + (8 * expandRatio),
+                      fontWeight: FontWeight.bold,
+                      color: colorScheme.onSurface,
+                    ),
+                  ),
+                );
+              },
+            ),
+          ),
+
+          // Loading indicator
+          if (extState.isLoading)
+            const SliverToBoxAdapter(
+              child: Padding(
+                padding: EdgeInsets.all(32),
+                child: Center(child: CircularProgressIndicator()),
+              ),
+            ),
+
+          // Error message
+          if (extState.error != null)
+            SliverToBoxAdapter(
+              child: Padding(
+                padding: const EdgeInsets.all(16),
+                child: Container(
+                  padding: const EdgeInsets.all(12),
+                  decoration: BoxDecoration(
+                    color: colorScheme.errorContainer,
+                    borderRadius: BorderRadius.circular(12),
+                  ),
+                  child: Row(
+                    children: [
+                      Icon(Icons.error_outline, color: colorScheme.error),
+                      const SizedBox(width: 12),
+                      Expanded(
+                        child: Text(
+                          extState.error!,
+                          style: TextStyle(color: colorScheme.onErrorContainer),
+                        ),
+                      ),
+                    ],
+                  ),
+                ),
+              ),
+            ),
+
+          // Provider Priority
+          const SliverToBoxAdapter(
+            child: SettingsSectionHeader(title: 'Provider Priority'),
+          ),
+          SliverToBoxAdapter(
+            child: SettingsGroup(
+              children: [
+                _DownloadPriorityItem(),
+                _MetadataPriorityItem(),
+                _SearchProviderSelector(),
+              ],
+            ),
+          ),
+
+          // Installed Extensions
+          const SliverToBoxAdapter(
+            child: SettingsSectionHeader(title: 'Installed Extensions'),
+          ),
+
+          if (extState.extensions.isEmpty && !extState.isLoading)
+            SliverToBoxAdapter(
+              child: Padding(
+                padding: const EdgeInsets.symmetric(horizontal: 16),
+                child: Container(
+                  padding: const EdgeInsets.all(24),
+                  decoration: BoxDecoration(
+                    color: colorScheme.surfaceContainerHighest.withValues(alpha: 0.3),
+                    borderRadius: BorderRadius.circular(16),
+                  ),
+                  child: Column(
+                    children: [
+                      Icon(
+                        Icons.extension_outlined,
+                        size: 48,
+                        color: colorScheme.onSurfaceVariant,
+                      ),
+                      const SizedBox(height: 12),
+                      Text(
+                        'No extensions installed',
+                        style: Theme.of(context).textTheme.titleMedium?.copyWith(
+                          color: colorScheme.onSurfaceVariant,
+                        ),
+                      ),
+                      const SizedBox(height: 4),
+                      Text(
+                        'Install .spotiflac-ext files to add new providers',
+                        style: Theme.of(context).textTheme.bodySmall?.copyWith(
+                          color: colorScheme.onSurfaceVariant,
+                        ),
+                        textAlign: TextAlign.center,
+                      ),
+                    ],
+                  ),
+                ),
+              ),
+            ),
+
+          if (extState.extensions.isNotEmpty)
+            SliverToBoxAdapter(
+              child: SettingsGroup(
+                children: extState.extensions.asMap().entries.map((entry) {
+                  final index = entry.key;
+                  final ext = entry.value;
+                  return _ExtensionItem(
+                    extension: ext,
+                    showDivider: index < extState.extensions.length - 1,
+                    onTap: () => Navigator.push(
+                      context,
+                      MaterialPageRoute(
+                        builder: (_) => ExtensionDetailPage(extensionId: ext.id),
+                      ),
+                    ),
+                    onToggle: (enabled) => ref
+                        .read(extensionProvider.notifier)
+                        .setExtensionEnabled(ext.id, enabled),
+                  );
+                }).toList(),
+              ),
+            ),
+
+          // Install button
+          SliverToBoxAdapter(
+            child: Padding(
+              padding: const EdgeInsets.all(16),
+              child: FilledButton.icon(
+                onPressed: _installExtension,
+                icon: const Icon(Icons.add),
+                label: const Text('Install Extension'),
+                style: FilledButton.styleFrom(
+                  padding: const EdgeInsets.symmetric(vertical: 16),
+                  shape: RoundedRectangleBorder(
+                    borderRadius: BorderRadius.circular(16),
+                  ),
+                ),
+              ),
+            ),
+          ),
+
+          // Info section
+          SliverToBoxAdapter(
+            child: Padding(
+              padding: const EdgeInsets.fromLTRB(16, 8, 16, 32),
+              child: Container(
+                padding: const EdgeInsets.all(12),
+                decoration: BoxDecoration(
+                  color: colorScheme.tertiaryContainer.withValues(alpha: 0.3),
+                  borderRadius: BorderRadius.circular(12),
+                ),
+                child: Row(
+                  children: [
+                    Icon(Icons.info_outline, size: 20, color: colorScheme.tertiary),
+                    const SizedBox(width: 12),
+                    Expanded(
+                      child: Text(
+                        'Extensions can add new metadata and download providers. '
+                        'Only install extensions from trusted sources.',
+                        style: Theme.of(context).textTheme.bodySmall?.copyWith(
+                          color: colorScheme.onTertiaryContainer,
+                        ),
+                      ),
+                    ),
+                  ],
+                ),
+              ),
+            ),
+          ),
+        ],
+      ),
+    );
+  }
+
+  Future<void> _installExtension() async {
+    final result = await FilePicker.platform.pickFiles(
+      type: FileType.any,
+      allowMultiple: false,
+    );
+
+    if (result != null && result.files.isNotEmpty) {
+      final file = result.files.first;
+      if (file.path != null) {
+        if (!file.path!.endsWith('.spotiflac-ext')) {
+          if (mounted) {
+            ScaffoldMessenger.of(context).showSnackBar(
+              const SnackBar(
+                content: Text('Please select a .spotiflac-ext file'),
+              ),
+            );
+          }
+          return;
+        }
+
+        final success = await ref
+            .read(extensionProvider.notifier)
+            .installExtension(file.path!);
+
+        if (mounted) {
+          final extState = ref.read(extensionProvider);
+          String message;
+          if (success) {
+            message = 'Extension installed successfully';
+          } else {
+            // Parse friendly error message
+            message = _getFriendlyErrorMessage(extState.error);
+          }
+          
+          // Clear the error from state to avoid showing it twice (in error container)
+          ref.read(extensionProvider.notifier).clearError();
+          
+          ScaffoldMessenger.of(context).showSnackBar(
+            SnackBar(content: Text(message)),
+          );
+        }
+      }
+    }
+  }
+
+  /// Parse error message to be more user-friendly
+  String _getFriendlyErrorMessage(String? error) {
+    if (error == null) return 'Failed to install extension';
+    
+    String message = error;
+    
+    // Remove PlatformException wrapper if present
+    // Format: PlatformException(ERROR, actual message, null, null)
+    if (message.contains('PlatformException')) {
+      // Try to extract the actual error message
+      final match = RegExp(r'PlatformException\([^,]+,\s*([^,]+(?:,[^,]+)?),').firstMatch(message);
+      if (match != null) {
+        message = match.group(1)?.trim() ?? message;
+      } else {
+        // Fallback: try simpler extraction
+        final simpleMatch = RegExp(r'PlatformException\([^,]+,\s*(.+?),\s*null').firstMatch(message);
+        if (simpleMatch != null) {
+          message = simpleMatch.group(1)?.trim() ?? message;
+        }
+      }
+    }
+    
+    // Clean up any remaining artifacts
+    message = message.replaceAll(RegExp(r',\s*null\s*,\s*null\)?$'), '');
+    message = message.replaceAll(RegExp(r'^\s*,\s*'), '');
+    
+    return message;
+  }
+}
+
+class _ExtensionItem extends StatelessWidget {
+  final Extension extension;
+  final bool showDivider;
+  final VoidCallback onTap;
+  final ValueChanged<bool> onToggle;
+
+  const _ExtensionItem({
+    required this.extension,
+    required this.showDivider,
+    required this.onTap,
+    required this.onToggle,
+  });
+
+  @override
+  Widget build(BuildContext context) {
+    final colorScheme = Theme.of(context).colorScheme;
+    final hasError = extension.status == 'error';
+
+    return Column(
+      mainAxisSize: MainAxisSize.min,
+      children: [
+        InkWell(
+          onTap: onTap,
+          child: Padding(
+            padding: const EdgeInsets.symmetric(horizontal: 16, vertical: 12),
+            child: Row(
+              children: [
+                // Extension icon
+                Container(
+                  width: 44,
+                  height: 44,
+                  decoration: BoxDecoration(
+                    color: hasError
+                        ? colorScheme.errorContainer
+                        : colorScheme.primaryContainer,
+                    borderRadius: BorderRadius.circular(12),
+                  ),
+                  child: extension.iconPath != null && extension.iconPath!.isNotEmpty
+                      ? ClipRRect(
+                          borderRadius: BorderRadius.circular(12),
+                          child: Image.file(
+                            File(extension.iconPath!),
+                            width: 44,
+                            height: 44,
+                            fit: BoxFit.cover,
+                            errorBuilder: (context, error, stackTrace) => Icon(
+                              hasError ? Icons.error_outline : Icons.extension,
+                              color: hasError
+                                  ? colorScheme.error
+                                  : colorScheme.onPrimaryContainer,
+                            ),
+                          ),
+                        )
+                      : Icon(
+                          hasError ? Icons.error_outline : Icons.extension,
+                          color: hasError
+                              ? colorScheme.error
+                              : colorScheme.onPrimaryContainer,
+                        ),
+                ),
+                const SizedBox(width: 16),
+                // Extension info
+                Expanded(
+                  child: Column(
+                    crossAxisAlignment: CrossAxisAlignment.start,
+                    children: [
+                      Text(
+                        extension.displayName,
+                        style: Theme.of(context).textTheme.bodyLarge?.copyWith(
+                          fontWeight: FontWeight.w500,
+                        ),
+                      ),
+                      const SizedBox(height: 2),
+                      Text(
+                        hasError
+                            ? extension.errorMessage ?? 'Error loading extension'
+                            : 'v${extension.version} by ${extension.author}',
+                        style: Theme.of(context).textTheme.bodySmall?.copyWith(
+                          color: hasError
+                              ? colorScheme.error
+                              : colorScheme.onSurfaceVariant,
+                        ),
+                      ),
+                    ],
+                  ),
+                ),
+                // Toggle switch
+                Switch(
+                  value: extension.enabled,
+                  onChanged: hasError ? null : onToggle,
+                ),
+              ],
+            ),
+          ),
+        ),
+        if (showDivider)
+          Divider(
+            height: 1,
+            thickness: 1,
+            indent: 76,
+            endIndent: 16,
+            color: colorScheme.outlineVariant.withValues(alpha: 0.3),
+          ),
+      ],
+    );
+  }
+}
+
+class _DownloadPriorityItem extends ConsumerWidget {
+  const _DownloadPriorityItem();
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final extState = ref.watch(extensionProvider);
+    final colorScheme = Theme.of(context).colorScheme;
+    
+    // Check if any extension has download provider
+    final hasDownloadExtensions = extState.extensions
+        .any((e) => e.enabled && e.hasDownloadProvider);
+    
+    return InkWell(
+      onTap: hasDownloadExtensions 
+          ? () => Navigator.push(
+              context,
+              MaterialPageRoute(
+                builder: (_) => const ProviderPriorityPage(),
+              ),
+            )
+          : null,
+      child: Padding(
+        padding: const EdgeInsets.symmetric(horizontal: 16, vertical: 12),
+        child: Row(
+          children: [
+            Icon(
+              Icons.download,
+              color: hasDownloadExtensions 
+                  ? colorScheme.onSurfaceVariant 
+                  : colorScheme.outline,
+            ),
+            const SizedBox(width: 16),
+            Expanded(
+              child: Column(
+                crossAxisAlignment: CrossAxisAlignment.start,
+                children: [
+                  Text(
+                    'Download Priority',
+                    style: Theme.of(context).textTheme.bodyLarge?.copyWith(
+                      color: hasDownloadExtensions 
+                          ? null 
+                          : colorScheme.outline,
+                    ),
+                  ),
+                  const SizedBox(height: 2),
+                  Text(
+                    hasDownloadExtensions 
+                        ? 'Set download service order'
+                        : 'No extensions with download provider',
+                    style: Theme.of(context).textTheme.bodySmall?.copyWith(
+                      color: colorScheme.onSurfaceVariant,
+                    ),
+                  ),
+                ],
+              ),
+            ),
+            Icon(
+              Icons.chevron_right,
+              color: hasDownloadExtensions 
+                  ? colorScheme.onSurfaceVariant 
+                  : colorScheme.outline,
+            ),
+          ],
+        ),
+      ),
+    );
+  }
+}
+
+class _MetadataPriorityItem extends ConsumerWidget {
+  const _MetadataPriorityItem();
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final extState = ref.watch(extensionProvider);
+    final colorScheme = Theme.of(context).colorScheme;
+    
+    // Check if any extension has metadata provider
+    final hasMetadataExtensions = extState.extensions
+        .any((e) => e.enabled && e.hasMetadataProvider);
+    
+    return InkWell(
+      onTap: hasMetadataExtensions 
+          ? () => Navigator.push(
+              context,
+              MaterialPageRoute(
+                builder: (_) => const MetadataProviderPriorityPage(),
+              ),
+            )
+          : null,
+      child: Padding(
+        padding: const EdgeInsets.symmetric(horizontal: 16, vertical: 12),
+        child: Row(
+          children: [
+            Icon(
+              Icons.search,
+              color: hasMetadataExtensions 
+                  ? colorScheme.onSurfaceVariant 
+                  : colorScheme.outline,
+            ),
+            const SizedBox(width: 16),
+            Expanded(
+              child: Column(
+                crossAxisAlignment: CrossAxisAlignment.start,
+                children: [
+                  Text(
+                    'Metadata Priority',
+                    style: Theme.of(context).textTheme.bodyLarge?.copyWith(
+                      color: hasMetadataExtensions 
+                          ? null 
+                          : colorScheme.outline,
+                    ),
+                  ),
+                  const SizedBox(height: 2),
+                  Text(
+                    hasMetadataExtensions 
+                        ? 'Set search & metadata source order'
+                        : 'No extensions with metadata provider',
+                    style: Theme.of(context).textTheme.bodySmall?.copyWith(
+                      color: colorScheme.onSurfaceVariant,
+                    ),
+                  ),
+                ],
+              ),
+            ),
+            Icon(
+              Icons.chevron_right,
+              color: hasMetadataExtensions 
+                  ? colorScheme.onSurfaceVariant 
+                  : colorScheme.outline,
+            ),
+          ],
+        ),
+      ),
+    );
+  }
+}
+
+class _SearchProviderSelector extends ConsumerWidget {
+  const _SearchProviderSelector();
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final settings = ref.watch(settingsProvider);
+    final extState = ref.watch(extensionProvider);
+    final colorScheme = Theme.of(context).colorScheme;
+    
+    // Get extensions with custom search
+    final searchProviders = extState.extensions
+        .where((e) => e.enabled && e.hasCustomSearch)
+        .toList();
+    
+    // Get current provider name
+    String currentProviderName = 'Default (Deezer/Spotify)';
+    if (settings.searchProvider != null && settings.searchProvider!.isNotEmpty) {
+      final ext = searchProviders.where((e) => e.id == settings.searchProvider).firstOrNull;
+      currentProviderName = ext?.displayName ?? settings.searchProvider!;
+    }
+    
+    return Column(
+      mainAxisSize: MainAxisSize.min,
+      children: [
+        InkWell(
+          onTap: searchProviders.isEmpty 
+              ? null 
+              : () => _showSearchProviderPicker(context, ref, settings, searchProviders),
+          child: Padding(
+            padding: const EdgeInsets.symmetric(horizontal: 16, vertical: 12),
+            child: Row(
+              children: [
+                Icon(
+                  Icons.manage_search,
+                  color: searchProviders.isEmpty 
+                      ? colorScheme.outline 
+                      : colorScheme.onSurfaceVariant,
+                ),
+                const SizedBox(width: 16),
+                Expanded(
+                  child: Column(
+                    crossAxisAlignment: CrossAxisAlignment.start,
+                    children: [
+                      Text(
+                        'Search Provider',
+                        style: Theme.of(context).textTheme.bodyLarge?.copyWith(
+                          color: searchProviders.isEmpty 
+                              ? colorScheme.outline 
+                              : null,
+                        ),
+                      ),
+                      const SizedBox(height: 2),
+                      Text(
+                        searchProviders.isEmpty 
+                            ? 'No extensions with custom search'
+                            : currentProviderName,
+                        style: Theme.of(context).textTheme.bodySmall?.copyWith(
+                          color: colorScheme.onSurfaceVariant,
+                        ),
+                      ),
+                    ],
+                  ),
+                ),
+                Icon(
+                  Icons.chevron_right,
+                  color: searchProviders.isEmpty 
+                      ? colorScheme.outline 
+                      : colorScheme.onSurfaceVariant,
+                ),
+              ],
+            ),
+          ),
+        ),
+      ],
+    );
+  }
+
+  void _showSearchProviderPicker(
+    BuildContext context,
+    WidgetRef ref,
+    dynamic settings,
+    List<Extension> searchProviders,
+  ) {
+    final colorScheme = Theme.of(context).colorScheme;
+    
+    showModalBottomSheet(
+      context: context,
+      backgroundColor: colorScheme.surfaceContainerHigh,
+      shape: const RoundedRectangleBorder(
+        borderRadius: BorderRadius.vertical(top: Radius.circular(28)),
+      ),
+      builder: (ctx) => SafeArea(
+        child: Column(
+          mainAxisSize: MainAxisSize.min,
+          crossAxisAlignment: CrossAxisAlignment.start,
+          children: [
+            Padding(
+              padding: const EdgeInsets.fromLTRB(24, 24, 24, 8),
+              child: Text(
+                'Search Provider',
+                style: Theme.of(context).textTheme.titleLarge?.copyWith(
+                  fontWeight: FontWeight.bold,
+                ),
+              ),
+            ),
+            Padding(
+              padding: const EdgeInsets.fromLTRB(24, 0, 24, 16),
+              child: Text(
+                'Choose which service to use for searching tracks',
+                style: Theme.of(context).textTheme.bodyMedium?.copyWith(
+                  color: colorScheme.onSurfaceVariant,
+                ),
+              ),
+            ),
+            // Default option
+            ListTile(
+              leading: Icon(Icons.music_note, color: colorScheme.primary),
+              title: const Text('Default (Deezer/Spotify)'),
+              subtitle: const Text('Use built-in search'),
+              trailing: (settings.searchProvider == null || settings.searchProvider!.isEmpty)
+                  ? Icon(Icons.check_circle, color: colorScheme.primary)
+                  : Icon(Icons.circle_outlined, color: colorScheme.outline),
+              onTap: () {
+                ref.read(settingsProvider.notifier).setSearchProvider(null);
+                Navigator.pop(ctx);
+              },
+            ),
+            // Extension options
+            ...searchProviders.map((ext) => ListTile(
+              leading: Icon(Icons.extension, color: colorScheme.secondary),
+              title: Text(ext.displayName),
+              subtitle: Text(ext.searchBehavior?.placeholder ?? 'Custom search'),
+              trailing: settings.searchProvider == ext.id
+                  ? Icon(Icons.check_circle, color: colorScheme.primary)
+                  : Icon(Icons.circle_outlined, color: colorScheme.outline),
+              onTap: () {
+                ref.read(settingsProvider.notifier).setSearchProvider(ext.id);
+                Navigator.pop(ctx);
+              },
+            )),
+            const SizedBox(height: 16),
+          ],
+        ),
+      ),
+    );
+  }
+}

lib/screens/settings/metadata_provider_priority_page.dart

@@ -0,0 +1,366 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:spotiflac_android/providers/extension_provider.dart';
+
+class MetadataProviderPriorityPage extends ConsumerStatefulWidget {
+  const MetadataProviderPriorityPage({super.key});
+
+  @override
+  ConsumerState<MetadataProviderPriorityPage> createState() => _MetadataProviderPriorityPageState();
+}
+
+class _MetadataProviderPriorityPageState extends ConsumerState<MetadataProviderPriorityPage> {
+  late List<String> _providers;
+  bool _hasChanges = false;
+
+  @override
+  void initState() {
+    super.initState();
+    _loadProviders();
+  }
+
+  void _loadProviders() {
+    final extState = ref.read(extensionProvider);
+    final allProviders = ref.read(extensionProvider.notifier).getAllMetadataProviders();
+    
+    // Use saved priority if available, otherwise use default order
+    if (extState.metadataProviderPriority.isNotEmpty) {
+      _providers = List.from(extState.metadataProviderPriority);
+      // Add any new providers not in saved priority
+      for (final provider in allProviders) {
+        if (!_providers.contains(provider)) {
+          _providers.add(provider);
+        }
+      }
+      // Remove providers that no longer exist
+      _providers.removeWhere((p) => !allProviders.contains(p));
+    } else {
+      _providers = allProviders;
+    }
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    final colorScheme = Theme.of(context).colorScheme;
+    final topPadding = MediaQuery.of(context).padding.top;
+
+    return PopScope(
+      canPop: !_hasChanges,
+      onPopInvokedWithResult: (didPop, result) async {
+        if (didPop) return;
+        final shouldPop = await _confirmDiscard(context);
+        if (shouldPop && context.mounted) {
+          Navigator.pop(context);
+        }
+      },
+      child: Scaffold(
+        body: CustomScrollView(
+          slivers: [
+            // App Bar
+            SliverAppBar(
+              expandedHeight: 120 + topPadding,
+              collapsedHeight: kToolbarHeight,
+              floating: false,
+              pinned: true,
+              backgroundColor: colorScheme.surface,
+              surfaceTintColor: Colors.transparent,
+              leading: IconButton(
+                icon: const Icon(Icons.arrow_back),
+                onPressed: () async {
+                  if (_hasChanges) {
+                    final shouldPop = await _confirmDiscard(context);
+                    if (shouldPop && context.mounted) {
+                      Navigator.pop(context);
+                    }
+                  } else {
+                    Navigator.pop(context);
+                  }
+                },
+              ),
+              actions: [
+                if (_hasChanges)
+                  TextButton(
+                    onPressed: _saveChanges,
+                    child: const Text('Save'),
+                  ),
+              ],
+              flexibleSpace: LayoutBuilder(
+                builder: (context, constraints) {
+                  final maxHeight = 120 + topPadding;
+                  final minHeight = kToolbarHeight + topPadding;
+                  final expandRatio = ((constraints.maxHeight - minHeight) /
+                          (maxHeight - minHeight))
+                      .clamp(0.0, 1.0);
+                  final leftPadding = 56 - (32 * expandRatio);
+                  return FlexibleSpaceBar(
+                    expandedTitleScale: 1.0,
+                    titlePadding: EdgeInsets.only(left: leftPadding, bottom: 16),
+                    title: Text(
+                      'Metadata Priority',
+                      style: TextStyle(
+                        fontSize: 20 + (8 * expandRatio),
+                        fontWeight: FontWeight.bold,
+                        color: colorScheme.onSurface,
+                      ),
+                    ),
+                  );
+                },
+              ),
+            ),
+
+            // Description
+            SliverToBoxAdapter(
+              child: Padding(
+                padding: const EdgeInsets.all(16),
+                child: Text(
+                  'Drag to reorder metadata providers. The app will try providers '
+                  'from top to bottom when searching for tracks and fetching metadata.',
+                  style: Theme.of(context).textTheme.bodyMedium?.copyWith(
+                    color: colorScheme.onSurfaceVariant,
+                  ),
+                ),
+              ),
+            ),
+
+            // Provider list
+            SliverPadding(
+              padding: const EdgeInsets.symmetric(horizontal: 16),
+              sliver: SliverReorderableList(
+                itemCount: _providers.length,
+                itemBuilder: (context, index) {
+                  final provider = _providers[index];
+                  return _MetadataProviderItem(
+                    key: ValueKey(provider),
+                    provider: provider,
+                    index: index,
+                    isFirst: index == 0,
+                    isLast: index == _providers.length - 1,
+                  );
+                },
+                onReorder: (oldIndex, newIndex) {
+                  setState(() {
+                    if (newIndex > oldIndex) {
+                      newIndex -= 1;
+                    }
+                    final item = _providers.removeAt(oldIndex);
+                    _providers.insert(newIndex, item);
+                    _hasChanges = true;
+                  });
+                },
+              ),
+            ),
+
+            // Info section
+            SliverToBoxAdapter(
+              child: Padding(
+                padding: const EdgeInsets.all(16),
+                child: Container(
+                  padding: const EdgeInsets.all(12),
+                  decoration: BoxDecoration(
+                    color: colorScheme.tertiaryContainer.withValues(alpha: 0.3),
+                    borderRadius: BorderRadius.circular(12),
+                  ),
+                  child: Row(
+                    children: [
+                      Icon(Icons.info_outline, size: 20, color: colorScheme.tertiary),
+                      const SizedBox(width: 12),
+                      Expanded(
+                        child: Text(
+                          'Deezer has no rate limits and is recommended as primary. '
+                          'Spotify may rate limit after many requests.',
+                          style: Theme.of(context).textTheme.bodySmall?.copyWith(
+                            color: colorScheme.onTertiaryContainer,
+                          ),
+                        ),
+                      ),
+                    ],
+                  ),
+                ),
+              ),
+            ),
+
+            const SliverToBoxAdapter(child: SizedBox(height: 32)),
+          ],
+        ),
+      ),
+    );
+  }
+
+  Future<bool> _confirmDiscard(BuildContext context) async {
+    final result = await showDialog<bool>(
+      context: context,
+      builder: (context) => AlertDialog(
+        title: const Text('Discard Changes?'),
+        content: const Text('You have unsaved changes. Do you want to discard them?'),
+        actions: [
+          TextButton(
+            onPressed: () => Navigator.pop(context, false),
+            child: const Text('Cancel'),
+          ),
+          FilledButton(
+            onPressed: () => Navigator.pop(context, true),
+            child: const Text('Discard'),
+          ),
+        ],
+      ),
+    );
+    return result ?? false;
+  }
+
+  Future<void> _saveChanges() async {
+    await ref.read(extensionProvider.notifier).setMetadataProviderPriority(_providers);
+    setState(() {
+      _hasChanges = false;
+    });
+    if (mounted) {
+      ScaffoldMessenger.of(context).showSnackBar(
+        const SnackBar(content: Text('Metadata provider priority saved')),
+      );
+    }
+  }
+}
+
+class _MetadataProviderItem extends StatelessWidget {
+  final String provider;
+  final int index;
+  final bool isFirst;
+  final bool isLast;
+
+  const _MetadataProviderItem({
+    super.key,
+    required this.provider,
+    required this.index,
+    required this.isFirst,
+    required this.isLast,
+  });
+
+  @override
+  Widget build(BuildContext context) {
+    final colorScheme = Theme.of(context).colorScheme;
+    final isDark = Theme.of(context).brightness == Brightness.dark;
+
+    final backgroundColor = isDark
+        ? Color.alphaBlend(
+            Colors.white.withValues(alpha: 0.05),
+            colorScheme.surface,
+          )
+        : colorScheme.surfaceContainerHigh;
+
+    final info = _getProviderInfo(provider);
+
+    return Padding(
+      padding: const EdgeInsets.only(bottom: 8),
+      child: Material(
+        color: backgroundColor,
+        borderRadius: BorderRadius.circular(16),
+        child: ReorderableDragStartListener(
+          index: index,
+          child: Padding(
+            padding: const EdgeInsets.symmetric(horizontal: 16, vertical: 12),
+            child: Row(
+              children: [
+                // Priority number
+                Container(
+                  width: 28,
+                  height: 28,
+                  decoration: BoxDecoration(
+                    color: isFirst
+                        ? colorScheme.primaryContainer
+                        : colorScheme.surfaceContainerHighest,
+                    shape: BoxShape.circle,
+                  ),
+                  child: Center(
+                    child: Text(
+                      '${index + 1}',
+                      style: TextStyle(
+                        fontWeight: FontWeight.bold,
+                        color: isFirst
+                            ? colorScheme.onPrimaryContainer
+                            : colorScheme.onSurfaceVariant,
+                      ),
+                    ),
+                  ),
+                ),
+                const SizedBox(width: 16),
+                // Provider icon
+                Icon(
+                  info.icon,
+                  color: info.isBuiltIn
+                      ? colorScheme.primary
+                      : colorScheme.secondary,
+                ),
+                const SizedBox(width: 12),
+                // Provider name
+                Expanded(
+                  child: Column(
+                    crossAxisAlignment: CrossAxisAlignment.start,
+                    children: [
+                      Text(
+                        info.name,
+                        style: Theme.of(context).textTheme.bodyLarge?.copyWith(
+                          fontWeight: FontWeight.w500,
+                        ),
+                      ),
+                      Text(
+                        info.description,
+                        style: Theme.of(context).textTheme.bodySmall?.copyWith(
+                          color: colorScheme.onSurfaceVariant,
+                        ),
+                      ),
+                    ],
+                  ),
+                ),
+                // Drag handle
+                Icon(
+                  Icons.drag_handle,
+                  color: colorScheme.onSurfaceVariant,
+                ),
+              ],
+            ),
+          ),
+        ),
+      ),
+    );
+  }
+
+  _MetadataProviderInfo _getProviderInfo(String provider) {
+    switch (provider) {
+      case 'deezer':
+        return _MetadataProviderInfo(
+          name: 'Deezer',
+          icon: Icons.album,
+          description: 'No rate limits',
+          isBuiltIn: true,
+        );
+      case 'spotify':
+        return _MetadataProviderInfo(
+          name: 'Spotify',
+          icon: Icons.music_note,
+          description: 'May rate limit',
+          isBuiltIn: true,
+        );
+      default:
+        // Extension provider
+        return _MetadataProviderInfo(
+          name: provider,
+          icon: Icons.extension,
+          description: 'Extension',
+          isBuiltIn: false,
+        );
+    }
+  }
+}
+
+class _MetadataProviderInfo {
+  final String name;
+  final IconData icon;
+  final String description;
+  final bool isBuiltIn;
+
+  _MetadataProviderInfo({
+    required this.name,
+    required this.icon,
+    required this.description,
+    required this.isBuiltIn,
+  });
+}

lib/screens/settings/options_settings_page.dart

@@ -3,6 +3,7 @@ import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:spotiflac_android/models/settings.dart';
 import 'package:spotiflac_android/providers/download_queue_provider.dart';
 import 'package:spotiflac_android/providers/settings_provider.dart';
+import 'package:spotiflac_android/providers/extension_provider.dart';
 import 'package:spotiflac_android/widgets/settings_group.dart';
 
 class OptionsSettingsPage extends ConsumerWidget {
@@ -11,6 +12,8 @@ class OptionsSettingsPage extends ConsumerWidget {
   @override
   Widget build(BuildContext context, WidgetRef ref) {
     final settings = ref.watch(settingsProvider);
+    final extensionState = ref.watch(extensionProvider);
+    final hasExtensions = extensionState.extensions.isNotEmpty;
     final colorScheme = Theme.of(context).colorScheme;
     final topPadding = MediaQuery.of(context).padding.top;
 
@@ -73,38 +76,50 @@ class OptionsSettingsPage extends ConsumerWidget {
                         .setMetadataSource(v),
                   ),
                   if (settings.metadataSource == 'spotify') ...[
-                    SettingsSwitchItem(
-                      icon: Icons.toggle_on,
-                      title: 'Use Custom Credentials',
-                      subtitle: settings.useCustomSpotifyCredentials
-                          ? 'Using your credentials'
-                          : 'Using default credentials',
-                      value: settings.useCustomSpotifyCredentials,
-                      onChanged: (v) {
-                        ref
-                            .read(settingsProvider.notifier)
-                            .setUseCustomSpotifyCredentials(v);
-                        if (v && settings.spotifyClientId.isEmpty) {
-                          _showSpotifyCredentialsDialog(context, ref, settings);
-                        }
-                      },
-                      showDivider: true,
-                    ),
+                    // Info card about Spotify credentials requirement
+                    if (settings.spotifyClientId.isEmpty)
+                      Padding(
+                        padding: const EdgeInsets.fromLTRB(16, 8, 16, 8),
+                        child: Card(
+                          color: Theme.of(context).colorScheme.errorContainer,
+                          child: Padding(
+                            padding: const EdgeInsets.all(12),
+                            child: Row(
+                              children: [
+                                Icon(
+                                  Icons.warning_amber_rounded,
+                                  color: Theme.of(context).colorScheme.onErrorContainer,
+                                ),
+                                const SizedBox(width: 12),
+                                Expanded(
+                                  child: Text(
+                                    'Spotify requires your own API credentials. Get them free from developer.spotify.com',
+                                    style: TextStyle(
+                                      color: Theme.of(context).colorScheme.onErrorContainer,
+                                      fontSize: 12,
+                                    ),
+                                  ),
+                                ),
+                              ],
+                            ),
+                          ),
+                        ),
+                      ),
                     SettingsItem(
                       icon: Icons.key,
-                      title: 'Set Credentials',
+                      title: 'Spotify Credentials',
                       subtitle: settings.spotifyClientId.isNotEmpty
                           ? 'Client ID: ${settings.spotifyClientId.length > 8 ? '${settings.spotifyClientId.substring(0, 8)}...' : settings.spotifyClientId}'
-                          : 'Not configured',
+                          : 'Required - tap to configure',
                       onTap: () =>
                           _showSpotifyCredentialsDialog(context, ref, settings),
                       trailing: Icon(
                         settings.spotifyClientId.isNotEmpty
-                            ? Icons.edit
-                            : Icons.add,
+                            ? Icons.check_circle
+                            : Icons.error_outline,
                         color: settings.spotifyClientId.isNotEmpty
-                            ? Theme.of(context).colorScheme.onSurfaceVariant
-                            : Theme.of(context).colorScheme.primary,
+                            ? Theme.of(context).colorScheme.primary
+                            : Theme.of(context).colorScheme.error,
                         size: 20,
                       ),
                       showDivider: false,
@@ -129,6 +144,18 @@ class OptionsSettingsPage extends ConsumerWidget {
                     onChanged: (v) =>
                         ref.read(settingsProvider.notifier).setAutoFallback(v),
                   ),
+                  if (hasExtensions)
+                    SettingsSwitchItem(
+                      icon: Icons.extension,
+                      title: 'Use Extension Providers',
+                      subtitle: settings.useExtensionProviders
+                          ? 'Extensions will be tried first'
+                          : 'Using built-in providers only',
+                      value: settings.useExtensionProviders,
+                      onChanged: (v) => ref
+                          .read(settingsProvider.notifier)
+                          .setUseExtensionProviders(v),
+                    ),
                   SettingsSwitchItem(
                     icon: Icons.lyrics,
                     title: 'Embed Lyrics',
@@ -175,6 +202,15 @@ class OptionsSettingsPage extends ConsumerWidget {
             SliverToBoxAdapter(
               child: SettingsGroup(
                 children: [
+                  SettingsSwitchItem(
+                    icon: Icons.store,
+                    title: 'Extension Store',
+                    subtitle: 'Show Store tab in navigation',
+                    value: settings.showExtensionStore,
+                    onChanged: (v) => ref
+                        .read(settingsProvider.notifier)
+                        .setShowExtensionStore(v),
+                  ),
                   SettingsSwitchItem(
                     icon: Icons.system_update,
                     title: 'Check for Updates',
@@ -345,11 +381,15 @@ class OptionsSettingsPage extends ConsumerWidget {
                       ),
                       border: OutlineInputBorder(
                         borderRadius: BorderRadius.circular(16),
-                        borderSide: BorderSide.none,
+                        borderSide: BorderSide(
+                          color: colorScheme.outlineVariant,
+                        ),
                       ),
                       enabledBorder: OutlineInputBorder(
                         borderRadius: BorderRadius.circular(16),
-                        borderSide: BorderSide.none,
+                        borderSide: BorderSide(
+                          color: colorScheme.outlineVariant,
+                        ),
                       ),
                       focusedBorder: OutlineInputBorder(
                         borderRadius: BorderRadius.circular(16),
@@ -380,11 +420,15 @@ class OptionsSettingsPage extends ConsumerWidget {
                       ),
                       border: OutlineInputBorder(
                         borderRadius: BorderRadius.circular(16),
-                        borderSide: BorderSide.none,
+                        borderSide: BorderSide(
+                          color: colorScheme.outlineVariant,
+                        ),
                       ),
                       enabledBorder: OutlineInputBorder(
                         borderRadius: BorderRadius.circular(16),
-                        borderSide: BorderSide.none,
+                        borderSide: BorderSide(
+                          color: colorScheme.outlineVariant,
+                        ),
                       ),
                       focusedBorder: OutlineInputBorder(
                         borderRadius: BorderRadius.circular(16),
@@ -745,7 +789,7 @@ class _ChannelChip extends StatelessWidget {
   }
 }
 
-class _MetadataSourceSelector extends StatelessWidget {
+class _MetadataSourceSelector extends ConsumerWidget {
   final String currentSource;
   final ValueChanged<String> onChanged;
   const _MetadataSourceSelector({
@@ -754,8 +798,25 @@ class _MetadataSourceSelector extends StatelessWidget {
   });
 
   @override
-  Widget build(BuildContext context) {
+  Widget build(BuildContext context, WidgetRef ref) {
     final colorScheme = Theme.of(context).colorScheme;
+    final settings = ref.watch(settingsProvider);
+    final extState = ref.watch(extensionProvider);
+    
+    // Check if extension search provider is active AND enabled
+    Extension? activeExtension;
+    if (settings.searchProvider != null && settings.searchProvider!.isNotEmpty) {
+      activeExtension = extState.extensions
+          .where((e) => e.id == settings.searchProvider && e.enabled)
+          .firstOrNull;
+    }
+    final hasExtensionSearch = activeExtension != null;
+    
+    String? extensionName;
+    if (hasExtensionSearch) {
+      extensionName = activeExtension.displayName;
+    }
+    
     return Padding(
       padding: const EdgeInsets.all(16),
       child: Column(
@@ -769,9 +830,13 @@ class _MetadataSourceSelector extends StatelessWidget {
           ),
           const SizedBox(height: 4),
           Text(
-            'Service used when searching by track name.',
+            hasExtensionSearch
+                ? 'Using extension: $extensionName'
+                : 'Service used when searching by track name.',
             style: Theme.of(context).textTheme.bodyMedium?.copyWith(
-              color: colorScheme.onSurfaceVariant,
+              color: hasExtensionSearch 
+                  ? colorScheme.primary 
+                  : colorScheme.onSurfaceVariant,
             ),
           ),
           const SizedBox(height: 16),
@@ -780,18 +845,57 @@ class _MetadataSourceSelector extends StatelessWidget {
               _SourceChip(
                 icon: Icons.graphic_eq,
                 label: 'Deezer',
-                isSelected: currentSource == 'deezer',
-                onTap: () => onChanged('deezer'),
+                badge: 'Free',
+                badgeColor: colorScheme.tertiary,
+                // Not selected if extension is active
+                isSelected: currentSource == 'deezer' && !hasExtensionSearch,
+                onTap: () {
+                  // If extension was active, reset it to default
+                  if (hasExtensionSearch) {
+                    ref.read(settingsProvider.notifier).setSearchProvider(null);
+                  }
+                  onChanged('deezer');
+                },
               ),
               const SizedBox(width: 12),
               _SourceChip(
                 icon: Icons.music_note,
                 label: 'Spotify',
-                isSelected: currentSource == 'spotify',
-                onTap: () => onChanged('spotify'),
+                badge: 'API Key',
+                badgeColor: colorScheme.secondary,
+                // Not selected if extension is active
+                isSelected: currentSource == 'spotify' && !hasExtensionSearch,
+                onTap: () {
+                  // If extension was active, reset it to default
+                  if (hasExtensionSearch) {
+                    ref.read(settingsProvider.notifier).setSearchProvider(null);
+                  }
+                  onChanged('spotify');
+                },
               ),
             ],
           ),
+          if (hasExtensionSearch) ...[
+            const SizedBox(height: 12),
+            Row(
+              children: [
+                Icon(
+                  Icons.info_outline,
+                  size: 16,
+                  color: colorScheme.onSurfaceVariant,
+                ),
+                const SizedBox(width: 8),
+                Expanded(
+                  child: Text(
+                    'Tap Deezer or Spotify to switch back from extension',
+                    style: Theme.of(context).textTheme.bodySmall?.copyWith(
+                      color: colorScheme.onSurfaceVariant,
+                    ),
+                  ),
+                ),
+              ],
+            ),
+          ],
         ],
       ),
     );
@@ -802,13 +906,17 @@ class _SourceChip extends StatelessWidget {
   final IconData icon;
   final String label;
   final bool isSelected;
-  final VoidCallback onTap;
+  final VoidCallback? onTap;
+  final String? badge;
+  final Color? badgeColor;
 
   const _SourceChip({
     required this.icon,
     required this.label,
     required this.isSelected,
-    required this.onTap,
+    this.onTap,
+    this.badge,
+    this.badgeColor,
   });
 
   @override
@@ -854,6 +962,24 @@ class _SourceChip extends StatelessWidget {
                         : colorScheme.onSurfaceVariant,
                   ),
                 ),
+                if (badge != null) ...[
+                  const SizedBox(height: 4),
+                  Container(
+                    padding: const EdgeInsets.symmetric(horizontal: 6, vertical: 2),
+                    decoration: BoxDecoration(
+                      color: (badgeColor ?? colorScheme.tertiary).withValues(alpha: 0.2),
+                      borderRadius: BorderRadius.circular(4),
+                    ),
+                    child: Text(
+                      badge!,
+                      style: TextStyle(
+                        fontSize: 9,
+                        fontWeight: FontWeight.w500,
+                        color: badgeColor ?? colorScheme.tertiary,
+                      ),
+                    ),
+                  ),
+                ],
               ],
             ),
           ),

lib/screens/settings/provider_priority_page.dart

@@ -0,0 +1,369 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:spotiflac_android/providers/extension_provider.dart';
+
+class ProviderPriorityPage extends ConsumerStatefulWidget {
+  const ProviderPriorityPage({super.key});
+
+  @override
+  ConsumerState<ProviderPriorityPage> createState() => _ProviderPriorityPageState();
+}
+
+class _ProviderPriorityPageState extends ConsumerState<ProviderPriorityPage> {
+  late List<String> _providers;
+  bool _hasChanges = false;
+
+  @override
+  void initState() {
+    super.initState();
+    _loadProviders();
+  }
+
+  void _loadProviders() {
+    final extState = ref.read(extensionProvider);
+    final allProviders = ref.read(extensionProvider.notifier).getAllDownloadProviders();
+    
+    // Use saved priority if available, otherwise use default order
+    if (extState.providerPriority.isNotEmpty) {
+      // Start with saved priority
+      _providers = List.from(extState.providerPriority);
+      // Add any new providers not in saved priority
+      for (final provider in allProviders) {
+        if (!_providers.contains(provider)) {
+          _providers.add(provider);
+        }
+      }
+      // Remove providers that no longer exist
+      _providers.removeWhere((p) => !allProviders.contains(p));
+    } else {
+      _providers = allProviders;
+    }
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    final colorScheme = Theme.of(context).colorScheme;
+    final topPadding = MediaQuery.of(context).padding.top;
+
+    return PopScope(
+      canPop: !_hasChanges,
+      onPopInvokedWithResult: (didPop, result) async {
+        if (didPop) return;
+        final shouldPop = await _confirmDiscard(context);
+        if (shouldPop && context.mounted) {
+          Navigator.pop(context);
+        }
+      },
+      child: Scaffold(
+        body: CustomScrollView(
+          slivers: [
+            // App Bar
+            SliverAppBar(
+              expandedHeight: 120 + topPadding,
+              collapsedHeight: kToolbarHeight,
+              floating: false,
+              pinned: true,
+              backgroundColor: colorScheme.surface,
+              surfaceTintColor: Colors.transparent,
+              leading: IconButton(
+                icon: const Icon(Icons.arrow_back),
+                onPressed: () async {
+                  if (_hasChanges) {
+                    final shouldPop = await _confirmDiscard(context);
+                    if (shouldPop && context.mounted) {
+                      Navigator.pop(context);
+                    }
+                  } else {
+                    Navigator.pop(context);
+                  }
+                },
+              ),
+              actions: [
+                if (_hasChanges)
+                  TextButton(
+                    onPressed: _saveChanges,
+                    child: const Text('Save'),
+                  ),
+              ],
+              flexibleSpace: LayoutBuilder(
+                builder: (context, constraints) {
+                  final maxHeight = 120 + topPadding;
+                  final minHeight = kToolbarHeight + topPadding;
+                  final expandRatio = ((constraints.maxHeight - minHeight) /
+                          (maxHeight - minHeight))
+                      .clamp(0.0, 1.0);
+                  final leftPadding = 56 - (32 * expandRatio);
+                  return FlexibleSpaceBar(
+                    expandedTitleScale: 1.0,
+                    titlePadding: EdgeInsets.only(left: leftPadding, bottom: 16),
+                    title: Text(
+                      'Provider Priority',
+                      style: TextStyle(
+                        fontSize: 20 + (8 * expandRatio),
+                        fontWeight: FontWeight.bold,
+                        color: colorScheme.onSurface,
+                      ),
+                    ),
+                  );
+                },
+              ),
+            ),
+
+            // Description
+            SliverToBoxAdapter(
+              child: Padding(
+                padding: const EdgeInsets.all(16),
+                child: Text(
+                  'Drag to reorder download providers. The app will try providers '
+                  'from top to bottom when downloading tracks.',
+                  style: Theme.of(context).textTheme.bodyMedium?.copyWith(
+                    color: colorScheme.onSurfaceVariant,
+                  ),
+                ),
+              ),
+            ),
+
+            // Provider list
+            SliverPadding(
+              padding: const EdgeInsets.symmetric(horizontal: 16),
+              sliver: SliverReorderableList(
+                itemCount: _providers.length,
+                itemBuilder: (context, index) {
+                  final provider = _providers[index];
+                  return _ProviderItem(
+                    key: ValueKey(provider),
+                    provider: provider,
+                    index: index,
+                    isFirst: index == 0,
+                    isLast: index == _providers.length - 1,
+                  );
+                },
+                onReorder: (oldIndex, newIndex) {
+                  setState(() {
+                    if (newIndex > oldIndex) {
+                      newIndex -= 1;
+                    }
+                    final item = _providers.removeAt(oldIndex);
+                    _providers.insert(newIndex, item);
+                    _hasChanges = true;
+                  });
+                },
+              ),
+            ),
+
+            // Info section
+            SliverToBoxAdapter(
+              child: Padding(
+                padding: const EdgeInsets.all(16),
+                child: Container(
+                  padding: const EdgeInsets.all(12),
+                  decoration: BoxDecoration(
+                    color: colorScheme.tertiaryContainer.withValues(alpha: 0.3),
+                    borderRadius: BorderRadius.circular(12),
+                  ),
+                  child: Row(
+                    children: [
+                      Icon(Icons.info_outline, size: 20, color: colorScheme.tertiary),
+                      const SizedBox(width: 12),
+                      Expanded(
+                        child: Text(
+                          'If a track is not available on the first provider, '
+                          'the app will automatically try the next one.',
+                          style: Theme.of(context).textTheme.bodySmall?.copyWith(
+                            color: colorScheme.onTertiaryContainer,
+                          ),
+                        ),
+                      ),
+                    ],
+                  ),
+                ),
+              ),
+            ),
+
+            const SliverToBoxAdapter(child: SizedBox(height: 32)),
+          ],
+        ),
+      ),
+    );
+  }
+
+  Future<bool> _confirmDiscard(BuildContext context) async {
+    final result = await showDialog<bool>(
+      context: context,
+      builder: (context) => AlertDialog(
+        title: const Text('Discard Changes?'),
+        content: const Text('You have unsaved changes. Do you want to discard them?'),
+        actions: [
+          TextButton(
+            onPressed: () => Navigator.pop(context, false),
+            child: const Text('Cancel'),
+          ),
+          FilledButton(
+            onPressed: () => Navigator.pop(context, true),
+            child: const Text('Discard'),
+          ),
+        ],
+      ),
+    );
+    return result ?? false;
+  }
+
+  Future<void> _saveChanges() async {
+    await ref.read(extensionProvider.notifier).setProviderPriority(_providers);
+    setState(() {
+      _hasChanges = false;
+    });
+    if (mounted) {
+      ScaffoldMessenger.of(context).showSnackBar(
+        const SnackBar(content: Text('Provider priority saved')),
+      );
+    }
+  }
+}
+
+class _ProviderItem extends StatelessWidget {
+  final String provider;
+  final int index;
+  final bool isFirst;
+  final bool isLast;
+
+  const _ProviderItem({
+    super.key,
+    required this.provider,
+    required this.index,
+    required this.isFirst,
+    required this.isLast,
+  });
+
+  @override
+  Widget build(BuildContext context) {
+    final colorScheme = Theme.of(context).colorScheme;
+    final isDark = Theme.of(context).brightness == Brightness.dark;
+
+    final backgroundColor = isDark
+        ? Color.alphaBlend(
+            Colors.white.withValues(alpha: 0.05),
+            colorScheme.surface,
+          )
+        : colorScheme.surfaceContainerHigh;
+
+    // Get provider info
+    final info = _getProviderInfo(provider);
+
+    return Padding(
+      padding: const EdgeInsets.only(bottom: 8),
+      child: Material(
+        color: backgroundColor,
+        borderRadius: BorderRadius.circular(16),
+        child: ReorderableDragStartListener(
+          index: index,
+          child: Padding(
+            padding: const EdgeInsets.symmetric(horizontal: 16, vertical: 12),
+            child: Row(
+              children: [
+                // Priority number
+                Container(
+                  width: 28,
+                  height: 28,
+                  decoration: BoxDecoration(
+                    color: isFirst
+                        ? colorScheme.primaryContainer
+                        : colorScheme.surfaceContainerHighest,
+                    shape: BoxShape.circle,
+                  ),
+                  child: Center(
+                    child: Text(
+                      '${index + 1}',
+                      style: TextStyle(
+                        fontWeight: FontWeight.bold,
+                        color: isFirst
+                            ? colorScheme.onPrimaryContainer
+                            : colorScheme.onSurfaceVariant,
+                      ),
+                    ),
+                  ),
+                ),
+                const SizedBox(width: 16),
+                // Provider icon
+                Icon(
+                  info.icon,
+                  color: info.isBuiltIn
+                      ? colorScheme.primary
+                      : colorScheme.secondary,
+                ),
+                const SizedBox(width: 12),
+                // Provider name
+                Expanded(
+                  child: Column(
+                    crossAxisAlignment: CrossAxisAlignment.start,
+                    children: [
+                      Text(
+                        info.name,
+                        style: Theme.of(context).textTheme.bodyLarge?.copyWith(
+                          fontWeight: FontWeight.w500,
+                        ),
+                      ),
+                      Text(
+                        info.isBuiltIn ? 'Built-in' : 'Extension',
+                        style: Theme.of(context).textTheme.bodySmall?.copyWith(
+                          color: colorScheme.onSurfaceVariant,
+                        ),
+                      ),
+                    ],
+                  ),
+                ),
+                // Drag handle
+                Icon(
+                  Icons.drag_handle,
+                  color: colorScheme.onSurfaceVariant,
+                ),
+              ],
+            ),
+          ),
+        ),
+      ),
+    );
+  }
+
+  _ProviderInfo _getProviderInfo(String provider) {
+    switch (provider) {
+      case 'tidal':
+        return _ProviderInfo(
+          name: 'Tidal',
+          icon: Icons.music_note,
+          isBuiltIn: true,
+        );
+      case 'qobuz':
+        return _ProviderInfo(
+          name: 'Qobuz',
+          icon: Icons.album,
+          isBuiltIn: true,
+        );
+      case 'amazon':
+        return _ProviderInfo(
+          name: 'Amazon Music',
+          icon: Icons.shopping_bag,
+          isBuiltIn: true,
+        );
+      default:
+        // Extension provider
+        return _ProviderInfo(
+          name: provider,
+          icon: Icons.extension,
+          isBuiltIn: false,
+        );
+    }
+  }
+}
+
+class _ProviderInfo {
+  final String name;
+  final IconData icon;
+  final bool isBuiltIn;
+
+  _ProviderInfo({
+    required this.name,
+    required this.icon,
+    required this.isBuiltIn,
+  });
+}

lib/screens/settings/settings_tab.dart

@@ -3,6 +3,7 @@ import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:spotiflac_android/constants/app_info.dart';
 import 'package:spotiflac_android/screens/settings/appearance_settings_page.dart';
 import 'package:spotiflac_android/screens/settings/download_settings_page.dart';
+import 'package:spotiflac_android/screens/settings/extensions_page.dart';
 import 'package:spotiflac_android/screens/settings/options_settings_page.dart';
 import 'package:spotiflac_android/screens/settings/about_page.dart';
 import 'package:spotiflac_android/screens/settings/log_screen.dart';
@@ -31,8 +32,11 @@ class SettingsTab extends ConsumerWidget {
             builder: (context, constraints) {
               final maxHeight = 120 + topPadding;
               final minHeight = kToolbarHeight + topPadding;
-              final expandRatio = ((constraints.maxHeight - minHeight) / (maxHeight - minHeight)).clamp(0.0, 1.0);
-              
+              final expandRatio =
+                  ((constraints.maxHeight - minHeight) /
+                          (maxHeight - minHeight))
+                      .clamp(0.0, 1.0);
+
               return FlexibleSpaceBar(
                 expandedTitleScale: 1.0,
                 titlePadding: const EdgeInsets.only(left: 24, bottom: 16),
@@ -58,7 +62,8 @@ class SettingsTab extends ConsumerWidget {
                 icon: Icons.palette_outlined,
                 title: 'Appearance',
                 subtitle: 'Theme, colors, display',
-                onTap: () => _navigateTo(context, const AppearanceSettingsPage()),
+                onTap: () =>
+                    _navigateTo(context, const AppearanceSettingsPage()),
               ),
               SettingsItem(
                 icon: Icons.download_outlined,
@@ -71,6 +76,12 @@ class SettingsTab extends ConsumerWidget {
                 title: 'Options',
                 subtitle: 'Fallback, lyrics, cover art, updates',
                 onTap: () => _navigateTo(context, const OptionsSettingsPage()),
+              ),
+              SettingsItem(
+                icon: Icons.extension_outlined,
+                title: 'Extensions',
+                subtitle: 'Manage download providers',
+                onTap: () => _navigateTo(context, const ExtensionsPage()),
                 showDivider: false,
               ),
             ],
@@ -97,7 +108,7 @@ class SettingsTab extends ConsumerWidget {
             ],
           ),
         ),
-        
+
         // Fill remaining space
         const SliverFillRemaining(hasScrollBody: false, child: SizedBox()),
       ],

lib/screens/setup_screen.dart

@@ -444,11 +444,10 @@ class _SetupScreenState extends ConsumerState<SetupScreen> {
           _clientIdController.text.trim(),
           _clientSecretController.text.trim(),
         );
-        ref.read(settingsProvider.notifier).setUseCustomSpotifyCredentials(true);
-        // Set search source to Spotify when using custom credentials
+        // Set search source to Spotify when credentials are provided
         ref.read(settingsProvider.notifier).setMetadataSource('spotify');
       } else {
-        // Use Deezer as default search source
+        // Use Deezer as default search source (free, no credentials required)
         ref.read(settingsProvider.notifier).setMetadataSource('deezer');
       }
       

lib/screens/store_tab.dart

@@ -0,0 +1,567 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:path_provider/path_provider.dart';
+import 'package:spotiflac_android/providers/store_provider.dart';
+import 'package:spotiflac_android/widgets/settings_group.dart';
+
+class StoreTab extends ConsumerStatefulWidget {
+  const StoreTab({super.key});
+
+  @override
+  ConsumerState<StoreTab> createState() => _StoreTabState();
+}
+
+class _StoreTabState extends ConsumerState<StoreTab> {
+  final _searchController = TextEditingController();
+  bool _isInitialized = false;
+
+  @override
+  void initState() {
+    super.initState();
+    WidgetsBinding.instance.addPostFrameCallback((_) => _initialize());
+  }
+
+  Future<void> _initialize() async {
+    if (_isInitialized) return;
+    _isInitialized = true;
+
+    final cacheDir = await getApplicationCacheDirectory();
+    await ref.read(storeProvider.notifier).initialize(cacheDir.path);
+  }
+
+  @override
+  void dispose() {
+    _searchController.dispose();
+    super.dispose();
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    final state = ref.watch(storeProvider);
+    final colorScheme = Theme.of(context).colorScheme;
+    final topPadding = MediaQuery.of(context).padding.top;
+
+    return Scaffold(
+      body: RefreshIndicator(
+        onRefresh: () => ref.read(storeProvider.notifier).refresh(forceRefresh: true),
+        child: CustomScrollView(
+          slivers: [
+            // App Bar - consistent with other tabs
+            SliverAppBar(
+              expandedHeight: 120 + topPadding,
+              collapsedHeight: kToolbarHeight,
+              floating: false,
+              pinned: true,
+              backgroundColor: colorScheme.surface,
+              surfaceTintColor: Colors.transparent,
+              automaticallyImplyLeading: false,
+              flexibleSpace: LayoutBuilder(
+                builder: (context, constraints) {
+                  final maxHeight = 120 + topPadding;
+                  final minHeight = kToolbarHeight + topPadding;
+                  final expandRatio = ((constraints.maxHeight - minHeight) /
+                          (maxHeight - minHeight))
+                      .clamp(0.0, 1.0);
+
+                  return FlexibleSpaceBar(
+                    expandedTitleScale: 1.0,
+                    titlePadding: const EdgeInsets.only(left: 24, bottom: 16),
+                    title: Text(
+                      'Store',
+                      style: TextStyle(
+                        fontSize: 20 + (14 * expandRatio),
+                        fontWeight: FontWeight.bold,
+                        color: colorScheme.onSurface,
+                      ),
+                    ),
+                  );
+                },
+              ),
+            ),
+
+            // Search Bar
+            SliverToBoxAdapter(
+              child: Padding(
+                padding: const EdgeInsets.fromLTRB(16, 8, 16, 8),
+                child: TextField(
+                  controller: _searchController,
+                  decoration: InputDecoration(
+                    hintText: 'Search extensions...',
+                    prefixIcon: const Icon(Icons.search),
+                    suffixIcon: _searchController.text.isNotEmpty
+                        ? IconButton(
+                            icon: const Icon(Icons.clear),
+                            onPressed: () {
+                              _searchController.clear();
+                              ref.read(storeProvider.notifier).setSearchQuery('');
+                            },
+                          )
+                        : null,
+                    border: OutlineInputBorder(
+                      borderRadius: BorderRadius.circular(28),
+                      borderSide: BorderSide.none,
+                    ),
+                    filled: true,
+                    fillColor: Theme.of(context).brightness == Brightness.dark
+                        ? Color.alphaBlend(Colors.white.withValues(alpha: 0.08), colorScheme.surface)
+                        : colorScheme.surfaceContainerHighest,
+                    contentPadding: const EdgeInsets.symmetric(horizontal: 16, vertical: 12),
+                  ),
+                  onChanged: (value) {
+                    ref.read(storeProvider.notifier).setSearchQuery(value);
+                    setState(() {}); // Update suffix icon
+                  },
+                ),
+              ),
+            ),
+
+            // Category Chips
+            SliverToBoxAdapter(
+              child: SingleChildScrollView(
+                scrollDirection: Axis.horizontal,
+                padding: const EdgeInsets.symmetric(horizontal: 16, vertical: 8),
+                child: Row(
+                  children: [
+                    _CategoryChip(
+                      label: 'All',
+                      icon: Icons.apps,
+                      isSelected: state.selectedCategory == null,
+                      onTap: () => ref.read(storeProvider.notifier).setCategory(null),
+                    ),
+                    const SizedBox(width: 8),
+                    _CategoryChip(
+                      label: 'Metadata',
+                      icon: Icons.label_outline,
+                      isSelected: state.selectedCategory == StoreCategory.metadata,
+                      onTap: () => ref.read(storeProvider.notifier).setCategory(StoreCategory.metadata),
+                    ),
+                    const SizedBox(width: 8),
+                    _CategoryChip(
+                      label: 'Download',
+                      icon: Icons.download_outlined,
+                      isSelected: state.selectedCategory == StoreCategory.download,
+                      onTap: () => ref.read(storeProvider.notifier).setCategory(StoreCategory.download),
+                    ),
+                    const SizedBox(width: 8),
+                    _CategoryChip(
+                      label: 'Utility',
+                      icon: Icons.build_outlined,
+                      isSelected: state.selectedCategory == StoreCategory.utility,
+                      onTap: () => ref.read(storeProvider.notifier).setCategory(StoreCategory.utility),
+                    ),
+                    const SizedBox(width: 8),
+                    _CategoryChip(
+                      label: 'Lyrics',
+                      icon: Icons.lyrics_outlined,
+                      isSelected: state.selectedCategory == StoreCategory.lyrics,
+                      onTap: () => ref.read(storeProvider.notifier).setCategory(StoreCategory.lyrics),
+                    ),
+                    const SizedBox(width: 8),
+                    _CategoryChip(
+                      label: 'Integration',
+                      icon: Icons.link,
+                      isSelected: state.selectedCategory == StoreCategory.integration,
+                      onTap: () => ref.read(storeProvider.notifier).setCategory(StoreCategory.integration),
+                    ),
+                  ],
+                ),
+              ),
+            ),
+
+            // Content
+            if (state.isLoading && state.extensions.isEmpty)
+              const SliverFillRemaining(
+                child: Center(child: CircularProgressIndicator()),
+              )
+            else if (state.error != null && state.extensions.isEmpty)
+              SliverFillRemaining(
+                child: _buildErrorState(state.error!, colorScheme),
+              )
+            else if (state.filteredExtensions.isEmpty)
+              SliverFillRemaining(
+                child: _buildEmptyState(state, colorScheme),
+              )
+            else ...[
+              // Extensions count
+              SliverToBoxAdapter(
+                child: Padding(
+                  padding: const EdgeInsets.fromLTRB(16, 8, 16, 8),
+                  child: Text(
+                    '${state.filteredExtensions.length} ${state.filteredExtensions.length == 1 ? 'extension' : 'extensions'}',
+                    style: Theme.of(context).textTheme.bodyMedium?.copyWith(
+                      color: colorScheme.onSurfaceVariant,
+                    ),
+                  ),
+                ),
+              ),
+
+              // Extensions list in grouped card (like queue_tab)
+              SliverToBoxAdapter(
+                child: Padding(
+                  padding: const EdgeInsets.symmetric(horizontal: 16),
+                  child: SettingsGroup(
+                    children: state.filteredExtensions.asMap().entries.map((entry) {
+                      final index = entry.key;
+                      final ext = entry.value;
+                      return _ExtensionItem(
+                        extension: ext,
+                        showDivider: index < state.filteredExtensions.length - 1,
+                        isDownloading: state.downloadingId == ext.id,
+                        onInstall: () => _installExtension(ext),
+                        onUpdate: () => _updateExtension(ext),
+                      );
+                    }).toList(),
+                  ),
+                ),
+              ),
+
+              // Bottom padding
+              const SliverToBoxAdapter(child: SizedBox(height: 16)),
+            ],
+          ],
+        ),
+      ),
+    );
+  }
+
+  Widget _buildErrorState(String error, ColorScheme colorScheme) {
+    return Center(
+      child: Padding(
+        padding: const EdgeInsets.all(32),
+        child: Column(
+          mainAxisSize: MainAxisSize.min,
+          children: [
+            Icon(Icons.error_outline, size: 64, color: colorScheme.error),
+            const SizedBox(height: 16),
+            Text(
+              'Failed to load store',
+              style: Theme.of(context).textTheme.titleMedium,
+            ),
+            const SizedBox(height: 8),
+            Text(
+              error,
+              style: Theme.of(context).textTheme.bodySmall?.copyWith(
+                color: colorScheme.onSurfaceVariant,
+              ),
+              textAlign: TextAlign.center,
+            ),
+            const SizedBox(height: 24),
+            FilledButton.icon(
+              onPressed: () => ref.read(storeProvider.notifier).refresh(forceRefresh: true),
+              icon: const Icon(Icons.refresh),
+              label: const Text('Retry'),
+            ),
+          ],
+        ),
+      ),
+    );
+  }
+
+  Widget _buildEmptyState(StoreState state, ColorScheme colorScheme) {
+    final hasFilters = state.searchQuery.isNotEmpty || state.selectedCategory != null;
+
+    return Center(
+      child: Column(
+        mainAxisSize: MainAxisSize.min,
+        children: [
+          Icon(
+            hasFilters ? Icons.search_off : Icons.extension_off,
+            size: 64,
+            color: colorScheme.onSurfaceVariant,
+          ),
+          const SizedBox(height: 16),
+          Text(
+            hasFilters ? 'No extensions found' : 'No extensions available',
+            style: Theme.of(context).textTheme.titleMedium?.copyWith(
+              color: colorScheme.onSurfaceVariant,
+            ),
+          ),
+          if (hasFilters) ...[
+            const SizedBox(height: 8),
+            TextButton(
+              onPressed: () {
+                _searchController.clear();
+                ref.read(storeProvider.notifier).clearSearch();
+              },
+              child: const Text('Clear filters'),
+            ),
+          ],
+        ],
+      ),
+    );
+  }
+
+  Future<void> _installExtension(StoreExtension ext) async {
+    final tempDir = await getTemporaryDirectory();
+    final appDir = await getApplicationDocumentsDirectory();
+    final extensionsDir = '${appDir.path}/extensions';
+
+    final success = await ref.read(storeProvider.notifier).installExtension(
+      ext.id,
+      tempDir.path,
+      extensionsDir,
+    );
+
+    if (mounted) {
+      ScaffoldMessenger.of(context).showSnackBar(
+        SnackBar(
+          content: Text(success
+              ? '${ext.displayName} installed. Enable it in Settings > Extensions'
+              : 'Failed to install ${ext.displayName}'),
+          behavior: SnackBarBehavior.floating,
+        ),
+      );
+    }
+  }
+
+  Future<void> _updateExtension(StoreExtension ext) async {
+    final tempDir = await getTemporaryDirectory();
+
+    final success = await ref.read(storeProvider.notifier).updateExtension(
+      ext.id,
+      tempDir.path,
+    );
+
+    if (mounted) {
+      ScaffoldMessenger.of(context).showSnackBar(
+        SnackBar(
+          content: Text(success
+              ? '${ext.displayName} updated to v${ext.version}'
+              : 'Failed to update ${ext.displayName}'),
+          behavior: SnackBarBehavior.floating,
+        ),
+      );
+    }
+  }
+}
+
+
+class _CategoryChip extends StatelessWidget {
+  final String label;
+  final IconData icon;
+  final bool isSelected;
+  final VoidCallback onTap;
+
+  const _CategoryChip({
+    required this.label,
+    required this.icon,
+    required this.isSelected,
+    required this.onTap,
+  });
+
+  @override
+  Widget build(BuildContext context) {
+    return FilterChip(
+      label: Row(
+        mainAxisSize: MainAxisSize.min,
+        children: [
+          Icon(icon, size: 16),
+          const SizedBox(width: 6),
+          Text(label),
+        ],
+      ),
+      selected: isSelected,
+      onSelected: (_) => onTap(),
+      showCheckmark: false,
+    );
+  }
+}
+
+class _ExtensionItem extends StatelessWidget {
+  final StoreExtension extension;
+  final bool showDivider;
+  final bool isDownloading;
+  final VoidCallback onInstall;
+  final VoidCallback onUpdate;
+
+  const _ExtensionItem({
+    required this.extension,
+    required this.showDivider,
+    required this.isDownloading,
+    required this.onInstall,
+    required this.onUpdate,
+  });
+
+  IconData _getCategoryIcon(String category) {
+    switch (category) {
+      case StoreCategory.metadata:
+        return Icons.label_outline;
+      case StoreCategory.download:
+        return Icons.download_outlined;
+      case StoreCategory.utility:
+        return Icons.build_outlined;
+      case StoreCategory.lyrics:
+        return Icons.lyrics_outlined;
+      case StoreCategory.integration:
+        return Icons.link;
+      default:
+        return Icons.extension;
+    }
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    final colorScheme = Theme.of(context).colorScheme;
+
+    return Column(
+      mainAxisSize: MainAxisSize.min,
+      children: [
+        Padding(
+          padding: const EdgeInsets.symmetric(horizontal: 16, vertical: 12),
+          child: Row(
+            children: [
+              // Extension icon - custom or category-based
+              Container(
+                width: 44,
+                height: 44,
+                decoration: BoxDecoration(
+                  color: extension.isInstalled
+                      ? colorScheme.primaryContainer
+                      : colorScheme.surfaceContainerHighest,
+                  borderRadius: BorderRadius.circular(12),
+                ),
+                clipBehavior: Clip.antiAlias,
+                child: extension.iconUrl != null && extension.iconUrl!.isNotEmpty
+                    ? Image.network(
+                        extension.iconUrl!,
+                        width: 44,
+                        height: 44,
+                        fit: BoxFit.cover,
+                        errorBuilder: (context, error, stackTrace) => Icon(
+                          _getCategoryIcon(extension.category),
+                          color: extension.isInstalled
+                              ? colorScheme.onPrimaryContainer
+                              : colorScheme.onSurfaceVariant,
+                        ),
+                        loadingBuilder: (context, child, loadingProgress) {
+                          if (loadingProgress == null) return child;
+                          return Center(
+                            child: SizedBox(
+                              width: 20,
+                              height: 20,
+                              child: CircularProgressIndicator(
+                                strokeWidth: 2,
+                                value: loadingProgress.expectedTotalBytes != null
+                                    ? loadingProgress.cumulativeBytesLoaded /
+                                        loadingProgress.expectedTotalBytes!
+                                    : null,
+                              ),
+                            ),
+                          );
+                        },
+                      )
+                    : Icon(
+                        _getCategoryIcon(extension.category),
+                        color: extension.isInstalled
+                            ? colorScheme.onPrimaryContainer
+                            : colorScheme.onSurfaceVariant,
+                      ),
+              ),
+              const SizedBox(width: 16),
+              // Extension info
+              Expanded(
+                child: Column(
+                  crossAxisAlignment: CrossAxisAlignment.start,
+                  children: [
+                    Row(
+                      children: [
+                        Expanded(
+                          child: Text(
+                            extension.displayName,
+                            style: Theme.of(context).textTheme.bodyLarge?.copyWith(
+                              fontWeight: FontWeight.w500,
+                            ),
+                          ),
+                        ),
+                        // Version badge
+                        Container(
+                          padding: const EdgeInsets.symmetric(horizontal: 6, vertical: 2),
+                          decoration: BoxDecoration(
+                            color: colorScheme.surfaceContainerHighest,
+                            borderRadius: BorderRadius.circular(6),
+                          ),
+                          child: Text(
+                            'v${extension.version}',
+                            style: Theme.of(context).textTheme.labelSmall?.copyWith(
+                              color: colorScheme.onSurfaceVariant,
+                            ),
+                          ),
+                        ),
+                      ],
+                    ),
+                    const SizedBox(height: 2),
+                    Text(
+                      'by ${extension.author}',
+                      style: Theme.of(context).textTheme.bodySmall?.copyWith(
+                        color: colorScheme.onSurfaceVariant,
+                      ),
+                    ),
+                    const SizedBox(height: 4),
+                    Text(
+                      extension.description,
+                      style: Theme.of(context).textTheme.bodySmall?.copyWith(
+                        color: colorScheme.onSurfaceVariant,
+                      ),
+                      maxLines: 2,
+                      overflow: TextOverflow.ellipsis,
+                    ),
+                  ],
+                ),
+              ),
+              const SizedBox(width: 12),
+              // Action button
+              if (isDownloading)
+                const SizedBox(
+                  width: 24,
+                  height: 24,
+                  child: CircularProgressIndicator(strokeWidth: 2),
+                )
+              else if (extension.hasUpdate)
+                FilledButton.tonal(
+                  onPressed: onUpdate,
+                  style: FilledButton.styleFrom(
+                    padding: const EdgeInsets.symmetric(horizontal: 12),
+                    minimumSize: const Size(0, 36),
+                  ),
+                  child: const Text('Update'),
+                )
+              else if (extension.isInstalled)
+                OutlinedButton(
+                  onPressed: null,
+                  style: OutlinedButton.styleFrom(
+                    padding: const EdgeInsets.symmetric(horizontal: 12),
+                    minimumSize: const Size(0, 36),
+                  ),
+                  child: Row(
+                    mainAxisSize: MainAxisSize.min,
+                    children: [
+                      Icon(Icons.check, size: 16, color: colorScheme.outline),
+                      const SizedBox(width: 4),
+                      Text('Installed', style: TextStyle(color: colorScheme.outline)),
+                    ],
+                  ),
+                )
+              else
+                FilledButton(
+                  onPressed: onInstall,
+                  style: FilledButton.styleFrom(
+                    padding: const EdgeInsets.symmetric(horizontal: 12),
+                    minimumSize: const Size(0, 36),
+                  ),
+                  child: const Text('Install'),
+                ),
+            ],
+          ),
+        ),
+        if (showDivider)
+          Divider(
+            height: 1,
+            thickness: 1,
+            indent: 76,
+            endIndent: 16,
+            color: colorScheme.outlineVariant.withValues(alpha: 0.3),
+          ),
+      ],
+    );
+  }
+}

lib/services/platform_bridge.dart

@@ -331,7 +331,6 @@ class PlatformBridge {
   }
 
   /// Set custom Spotify API credentials
-  /// Pass empty strings to use default credentials
   static Future<void> setSpotifyCredentials(String clientId, String clientSecret) async {
     await _channel.invokeMethod('setSpotifyCredentials', {
       'client_id': clientId,
@@ -339,6 +338,13 @@ class PlatformBridge {
     });
   }
 
+  /// Check if Spotify credentials are configured
+  /// Returns true if credentials are available (custom or env vars)
+  static Future<bool> hasSpotifyCredentials() async {
+    final result = await _channel.invokeMethod('hasSpotifyCredentials');
+    return result as bool;
+  }
+
   /// Pre-warm track ID cache for album/playlist tracks
   /// This runs in background and returns immediately
   /// Speeds up subsequent downloads by caching ISRC → Track ID mappings
@@ -439,4 +445,418 @@ class PlatformBridge {
   static Future<void> setGoLoggingEnabled(bool enabled) async {
     await _channel.invokeMethod('setLoggingEnabled', {'enabled': enabled});
   }
+
+  // ==================== EXTENSION SYSTEM ====================
+
+  /// Initialize the extension system
+  static Future<void> initExtensionSystem(String extensionsDir, String dataDir) async {
+    _log.d('initExtensionSystem: $extensionsDir, $dataDir');
+    await _channel.invokeMethod('initExtensionSystem', {
+      'extensions_dir': extensionsDir,
+      'data_dir': dataDir,
+    });
+  }
+
+  /// Load all extensions from directory
+  static Future<Map<String, dynamic>> loadExtensionsFromDir(String dirPath) async {
+    _log.d('loadExtensionsFromDir: $dirPath');
+    final result = await _channel.invokeMethod('loadExtensionsFromDir', {
+      'dir_path': dirPath,
+    });
+    return jsonDecode(result as String) as Map<String, dynamic>;
+  }
+
+  /// Load a single extension from file
+  static Future<Map<String, dynamic>> loadExtensionFromPath(String filePath) async {
+    _log.d('loadExtensionFromPath: $filePath');
+    final result = await _channel.invokeMethod('loadExtensionFromPath', {
+      'file_path': filePath,
+    });
+    return jsonDecode(result as String) as Map<String, dynamic>;
+  }
+
+  /// Unload an extension
+  static Future<void> unloadExtension(String extensionId) async {
+    _log.d('unloadExtension: $extensionId');
+    await _channel.invokeMethod('unloadExtension', {
+      'extension_id': extensionId,
+    });
+  }
+
+  /// Remove an extension completely (unload + delete files)
+  static Future<void> removeExtension(String extensionId) async {
+    _log.d('removeExtension: $extensionId');
+    await _channel.invokeMethod('removeExtension', {
+      'extension_id': extensionId,
+    });
+  }
+
+  /// Upgrade an existing extension from a new package file
+  static Future<Map<String, dynamic>> upgradeExtension(String filePath) async {
+    _log.d('upgradeExtension: $filePath');
+    final result = await _channel.invokeMethod('upgradeExtension', {
+      'file_path': filePath,
+    });
+    return jsonDecode(result as String) as Map<String, dynamic>;
+  }
+
+  /// Check if a package file is an upgrade for an existing extension
+  static Future<Map<String, dynamic>> checkExtensionUpgrade(String filePath) async {
+    _log.d('checkExtensionUpgrade: $filePath');
+    final result = await _channel.invokeMethod('checkExtensionUpgrade', {
+      'file_path': filePath,
+    });
+    return jsonDecode(result as String) as Map<String, dynamic>;
+  }
+
+  /// Get all installed extensions
+  static Future<List<Map<String, dynamic>>> getInstalledExtensions() async {
+    final result = await _channel.invokeMethod('getInstalledExtensions');
+    final list = jsonDecode(result as String) as List<dynamic>;
+    return list.map((e) => e as Map<String, dynamic>).toList();
+  }
+
+  /// Enable or disable an extension
+  static Future<void> setExtensionEnabled(String extensionId, bool enabled) async {
+    _log.d('setExtensionEnabled: $extensionId = $enabled');
+    await _channel.invokeMethod('setExtensionEnabled', {
+      'extension_id': extensionId,
+      'enabled': enabled,
+    });
+  }
+
+  /// Set provider priority order
+  static Future<void> setProviderPriority(List<String> providerIds) async {
+    _log.d('setProviderPriority: $providerIds');
+    await _channel.invokeMethod('setProviderPriority', {
+      'priority': jsonEncode(providerIds),
+    });
+  }
+
+  /// Get provider priority order
+  static Future<List<String>> getProviderPriority() async {
+    final result = await _channel.invokeMethod('getProviderPriority');
+    final list = jsonDecode(result as String) as List<dynamic>;
+    return list.map((e) => e as String).toList();
+  }
+
+  /// Set metadata provider priority order
+  static Future<void> setMetadataProviderPriority(List<String> providerIds) async {
+    _log.d('setMetadataProviderPriority: $providerIds');
+    await _channel.invokeMethod('setMetadataProviderPriority', {
+      'priority': jsonEncode(providerIds),
+    });
+  }
+
+  /// Get metadata provider priority order
+  static Future<List<String>> getMetadataProviderPriority() async {
+    final result = await _channel.invokeMethod('getMetadataProviderPriority');
+    final list = jsonDecode(result as String) as List<dynamic>;
+    return list.map((e) => e as String).toList();
+  }
+
+  /// Get extension settings
+  static Future<Map<String, dynamic>> getExtensionSettings(String extensionId) async {
+    final result = await _channel.invokeMethod('getExtensionSettings', {
+      'extension_id': extensionId,
+    });
+    return jsonDecode(result as String) as Map<String, dynamic>;
+  }
+
+  /// Set extension settings
+  static Future<void> setExtensionSettings(String extensionId, Map<String, dynamic> settings) async {
+    _log.d('setExtensionSettings: $extensionId');
+    await _channel.invokeMethod('setExtensionSettings', {
+      'extension_id': extensionId,
+      'settings': jsonEncode(settings),
+    });
+  }
+
+  /// Search tracks using extension providers
+  static Future<List<Map<String, dynamic>>> searchTracksWithExtensions(String query, {int limit = 20}) async {
+    _log.d('searchTracksWithExtensions: "$query"');
+    final result = await _channel.invokeMethod('searchTracksWithExtensions', {
+      'query': query,
+      'limit': limit,
+    });
+    final list = jsonDecode(result as String) as List<dynamic>;
+    return list.map((e) => e as Map<String, dynamic>).toList();
+  }
+
+  /// Download with extension providers (includes fallback)
+  static Future<Map<String, dynamic>> downloadWithExtensions({
+    required String isrc,
+    required String spotifyId,
+    required String trackName,
+    required String artistName,
+    required String albumName,
+    String? albumArtist,
+    String? coverUrl,
+    required String outputDir,
+    required String filenameFormat,
+    String quality = 'LOSSLESS',
+    bool embedLyrics = true,
+    bool embedMaxQualityCover = true,
+    int trackNumber = 1,
+    int discNumber = 1,
+    int totalTracks = 1,
+    String? releaseDate,
+    String? itemId,
+    int durationMs = 0,
+    String? source, // Extension ID that provided this track (prioritize this extension)
+  }) async {
+    _log.i('downloadWithExtensions: "$trackName" by $artistName${source != null ? ' (source: $source)' : ''}');
+    final request = jsonEncode({
+      'isrc': isrc,
+      'spotify_id': spotifyId,
+      'track_name': trackName,
+      'artist_name': artistName,
+      'album_name': albumName,
+      'album_artist': albumArtist ?? artistName,
+      'cover_url': coverUrl,
+      'output_dir': outputDir,
+      'filename_format': filenameFormat,
+      'quality': quality,
+      'embed_lyrics': embedLyrics,
+      'embed_max_quality_cover': embedMaxQualityCover,
+      'track_number': trackNumber,
+      'disc_number': discNumber,
+      'total_tracks': totalTracks,
+      'release_date': releaseDate ?? '',
+      'item_id': itemId ?? '',
+      'duration_ms': durationMs,
+      'source': source ?? '', // Extension ID that provided this track
+    });
+    
+    final result = await _channel.invokeMethod('downloadWithExtensions', request);
+    return jsonDecode(result as String) as Map<String, dynamic>;
+  }
+
+  /// Cleanup all extensions (call on app close)
+  static Future<void> cleanupExtensions() async {
+    _log.d('cleanupExtensions');
+    await _channel.invokeMethod('cleanupExtensions');
+  }
+
+  // ==================== EXTENSION AUTH API ====================
+
+  /// Get pending auth request for an extension (if any)
+  static Future<Map<String, dynamic>?> getExtensionPendingAuth(String extensionId) async {
+    final result = await _channel.invokeMethod('getExtensionPendingAuth', {
+      'extension_id': extensionId,
+    });
+    if (result == null) return null;
+    return jsonDecode(result as String) as Map<String, dynamic>;
+  }
+
+  /// Set auth code for an extension (after OAuth callback)
+  static Future<void> setExtensionAuthCode(String extensionId, String authCode) async {
+    _log.d('setExtensionAuthCode: $extensionId');
+    await _channel.invokeMethod('setExtensionAuthCode', {
+      'extension_id': extensionId,
+      'auth_code': authCode,
+    });
+  }
+
+  /// Set tokens for an extension (after token exchange)
+  static Future<void> setExtensionTokens(
+    String extensionId, {
+    required String accessToken,
+    String? refreshToken,
+    int? expiresIn,
+  }) async {
+    _log.d('setExtensionTokens: $extensionId');
+    await _channel.invokeMethod('setExtensionTokens', {
+      'extension_id': extensionId,
+      'access_token': accessToken,
+      'refresh_token': refreshToken ?? '',
+      'expires_in': expiresIn ?? 0,
+    });
+  }
+
+  /// Clear pending auth request for an extension
+  static Future<void> clearExtensionPendingAuth(String extensionId) async {
+    await _channel.invokeMethod('clearExtensionPendingAuth', {
+      'extension_id': extensionId,
+    });
+  }
+
+  /// Check if extension is authenticated
+  static Future<bool> isExtensionAuthenticated(String extensionId) async {
+    final result = await _channel.invokeMethod('isExtensionAuthenticated', {
+      'extension_id': extensionId,
+    });
+    return result as bool;
+  }
+
+  /// Get all pending auth requests (for polling)
+  static Future<List<Map<String, dynamic>>> getAllPendingAuthRequests() async {
+    final result = await _channel.invokeMethod('getAllPendingAuthRequests');
+    final list = jsonDecode(result as String) as List<dynamic>;
+    return list.map((e) => e as Map<String, dynamic>).toList();
+  }
+
+  // ==================== EXTENSION FFMPEG API ====================
+
+  /// Get pending FFmpeg command for execution
+  static Future<Map<String, dynamic>?> getPendingFFmpegCommand(String commandId) async {
+    final result = await _channel.invokeMethod('getPendingFFmpegCommand', {
+      'command_id': commandId,
+    });
+    if (result == null) return null;
+    return jsonDecode(result as String) as Map<String, dynamic>;
+  }
+
+  /// Set FFmpeg command result
+  static Future<void> setFFmpegCommandResult(
+    String commandId, {
+    required bool success,
+    String output = '',
+    String error = '',
+  }) async {
+    await _channel.invokeMethod('setFFmpegCommandResult', {
+      'command_id': commandId,
+      'success': success,
+      'output': output,
+      'error': error,
+    });
+  }
+
+  /// Get all pending FFmpeg commands
+  static Future<List<Map<String, dynamic>>> getAllPendingFFmpegCommands() async {
+    final result = await _channel.invokeMethod('getAllPendingFFmpegCommands');
+    final list = jsonDecode(result as String) as List<dynamic>;
+    return list.map((e) => e as Map<String, dynamic>).toList();
+  }
+
+  // ==================== EXTENSION CUSTOM SEARCH ====================
+
+  /// Perform custom search using an extension
+  static Future<List<Map<String, dynamic>>> customSearchWithExtension(
+    String extensionId,
+    String query, {
+    Map<String, dynamic>? options,
+  }) async {
+    final result = await _channel.invokeMethod('customSearchWithExtension', {
+      'extension_id': extensionId,
+      'query': query,
+      'options': options != null ? jsonEncode(options) : '',
+    });
+    final list = jsonDecode(result as String) as List<dynamic>;
+    return list.map((e) => e as Map<String, dynamic>).toList();
+  }
+
+  /// Get all extensions that provide custom search
+  static Future<List<Map<String, dynamic>>> getSearchProviders() async {
+    final result = await _channel.invokeMethod('getSearchProviders');
+    final list = jsonDecode(result as String) as List<dynamic>;
+    return list.map((e) => e as Map<String, dynamic>).toList();
+  }
+
+  // ==================== EXTENSION URL HANDLER ====================
+
+  /// Handle a URL with any matching extension
+  /// Returns null if no extension can handle the URL
+  static Future<Map<String, dynamic>?> handleURLWithExtension(String url) async {
+    try {
+      final result = await _channel.invokeMethod('handleURLWithExtension', {
+        'url': url,
+      });
+      if (result == null || result == '') return null;
+      return jsonDecode(result as String) as Map<String, dynamic>;
+    } catch (e) {
+      // No extension found or error handling URL
+      return null;
+    }
+  }
+
+  /// Find an extension that can handle the given URL
+  /// Returns extension ID or null if none found
+  static Future<String?> findURLHandler(String url) async {
+    final result = await _channel.invokeMethod('findURLHandler', {
+      'url': url,
+    });
+    if (result == null || result == '') return null;
+    return result as String;
+  }
+
+  /// Get all extensions that handle custom URLs
+  static Future<List<Map<String, dynamic>>> getURLHandlers() async {
+    final result = await _channel.invokeMethod('getURLHandlers');
+    final list = jsonDecode(result as String) as List<dynamic>;
+    return list.map((e) => e as Map<String, dynamic>).toList();
+  }
+
+  // ==================== EXTENSION POST-PROCESSING ====================
+
+  /// Run post-processing hooks on a file
+  static Future<Map<String, dynamic>> runPostProcessing(
+    String filePath, {
+    Map<String, dynamic>? metadata,
+  }) async {
+    final result = await _channel.invokeMethod('runPostProcessing', {
+      'file_path': filePath,
+      'metadata': metadata != null ? jsonEncode(metadata) : '',
+    });
+    return jsonDecode(result as String) as Map<String, dynamic>;
+  }
+
+  /// Get all extensions that provide post-processing
+  static Future<List<Map<String, dynamic>>> getPostProcessingProviders() async {
+    final result = await _channel.invokeMethod('getPostProcessingProviders');
+    final list = jsonDecode(result as String) as List<dynamic>;
+    return list.map((e) => e as Map<String, dynamic>).toList();
+  }
+
+  // ==================== EXTENSION STORE ====================
+
+  /// Initialize extension store
+  static Future<void> initExtensionStore(String cacheDir) async {
+    _log.d('initExtensionStore: $cacheDir');
+    await _channel.invokeMethod('initExtensionStore', {'cache_dir': cacheDir});
+  }
+
+  /// Get all extensions from store with installation status
+  static Future<List<Map<String, dynamic>>> getStoreExtensions({bool forceRefresh = false}) async {
+    _log.d('getStoreExtensions (forceRefresh: $forceRefresh)');
+    final result = await _channel.invokeMethod('getStoreExtensions', {
+      'force_refresh': forceRefresh,
+    });
+    final list = jsonDecode(result as String) as List<dynamic>;
+    return list.map((e) => e as Map<String, dynamic>).toList();
+  }
+
+  /// Search extensions in store
+  static Future<List<Map<String, dynamic>>> searchStoreExtensions(String query, {String? category}) async {
+    _log.d('searchStoreExtensions: "$query" (category: $category)');
+    final result = await _channel.invokeMethod('searchStoreExtensions', {
+      'query': query,
+      'category': category ?? '',
+    });
+    final list = jsonDecode(result as String) as List<dynamic>;
+    return list.map((e) => e as Map<String, dynamic>).toList();
+  }
+
+  /// Get store categories
+  static Future<List<String>> getStoreCategories() async {
+    final result = await _channel.invokeMethod('getStoreCategories');
+    final list = jsonDecode(result as String) as List<dynamic>;
+    return list.cast<String>();
+  }
+
+  /// Download extension from store
+  static Future<String> downloadStoreExtension(String extensionId, String destDir) async {
+    _log.i('downloadStoreExtension: $extensionId to $destDir');
+    final result = await _channel.invokeMethod('downloadStoreExtension', {
+      'extension_id': extensionId,
+      'dest_dir': destDir,
+    });
+    return result as String;
+  }
+
+  /// Clear store cache
+  static Future<void> clearStoreCache() async {
+    _log.d('clearStoreCache');
+    await _channel.invokeMethod('clearStoreCache');
+  }
 }

lib/widgets/download_service_picker.dart

@@ -0,0 +1,483 @@
+import 'dart:io';
+import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:spotiflac_android/providers/extension_provider.dart';
+import 'package:spotiflac_android/providers/settings_provider.dart';
+
+/// Built-in service info with quality options
+class BuiltInService {
+  final String id;
+  final String label;
+  final List<QualityOption> qualityOptions;
+
+  const BuiltInService({
+    required this.id,
+    required this.label,
+    required this.qualityOptions,
+  });
+}
+
+/// Default quality options for built-in services (Tidal, Qobuz, Amazon)
+const _builtInServices = [
+  BuiltInService(
+    id: 'tidal',
+    label: 'Tidal',
+    qualityOptions: [
+      QualityOption(id: 'LOSSLESS', label: 'FLAC Lossless', description: '16-bit / 44.1kHz'),
+      QualityOption(id: 'HI_RES', label: 'Hi-Res FLAC', description: '24-bit / up to 96kHz'),
+      QualityOption(id: 'HI_RES_LOSSLESS', label: 'Hi-Res FLAC Max', description: '24-bit / up to 192kHz'),
+    ],
+  ),
+  BuiltInService(
+    id: 'qobuz',
+    label: 'Qobuz',
+    qualityOptions: [
+      QualityOption(id: 'LOSSLESS', label: 'FLAC Lossless', description: '16-bit / 44.1kHz'),
+      QualityOption(id: 'HI_RES', label: 'Hi-Res FLAC', description: '24-bit / up to 96kHz'),
+      QualityOption(id: 'HI_RES_LOSSLESS', label: 'Hi-Res FLAC Max', description: '24-bit / up to 192kHz'),
+    ],
+  ),
+  BuiltInService(
+    id: 'amazon',
+    label: 'Amazon',
+    qualityOptions: [
+      QualityOption(id: 'LOSSLESS', label: 'FLAC Lossless', description: '16-bit / 44.1kHz'),
+      QualityOption(id: 'HI_RES', label: 'Hi-Res FLAC', description: '24-bit / up to 96kHz'),
+      QualityOption(id: 'HI_RES_LOSSLESS', label: 'Hi-Res FLAC Max', description: '24-bit / up to 192kHz'),
+    ],
+  ),
+];
+
+/// A reusable widget for selecting download service (built-in + extensions)
+class DownloadServicePicker extends ConsumerStatefulWidget {
+  final String? trackName;
+  final String? artistName;
+  final String? coverUrl;
+  final void Function(String quality, String service) onSelect;
+
+  const DownloadServicePicker({
+    super.key,
+    this.trackName,
+    this.artistName,
+    this.coverUrl,
+    required this.onSelect,
+  });
+
+  @override
+  ConsumerState<DownloadServicePicker> createState() => _DownloadServicePickerState();
+
+  /// Show the download service picker as a modal bottom sheet
+  static void show(
+    BuildContext context, {
+    String? trackName,
+    String? artistName,
+    String? coverUrl,
+    required void Function(String quality, String service) onSelect,
+  }) {
+    final colorScheme = Theme.of(context).colorScheme;
+    
+    showModalBottomSheet(
+      context: context,
+      backgroundColor: colorScheme.surfaceContainerHigh,
+      shape: const RoundedRectangleBorder(
+        borderRadius: BorderRadius.vertical(top: Radius.circular(28)),
+      ),
+      isScrollControlled: true,
+      builder: (context) => DownloadServicePicker(
+        trackName: trackName,
+        artistName: artistName,
+        coverUrl: coverUrl,
+        onSelect: onSelect,
+      ),
+    );
+  }
+}
+
+class _DownloadServicePickerState extends ConsumerState<DownloadServicePicker> {
+  late String _selectedService;
+
+  @override
+  void initState() {
+    super.initState();
+    _selectedService = ref.read(settingsProvider).defaultService;
+  }
+
+  /// Get quality options for the selected service
+  List<QualityOption> _getQualityOptions() {
+    // Check if it's a built-in service
+    final builtIn = _builtInServices.where((s) => s.id == _selectedService).firstOrNull;
+    if (builtIn != null) {
+      return builtIn.qualityOptions;
+    }
+
+    // Check if it's an extension
+    final extensionState = ref.read(extensionProvider);
+    final ext = extensionState.extensions.where((e) => e.id == _selectedService).firstOrNull;
+    if (ext != null && ext.qualityOptions.isNotEmpty) {
+      return ext.qualityOptions;
+    }
+
+    // Default quality options if extension doesn't specify any
+    return const [
+      QualityOption(id: 'DEFAULT', label: 'Default Quality', description: 'Best available'),
+    ];
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    final colorScheme = Theme.of(context).colorScheme;
+    final extensionState = ref.watch(extensionProvider);
+    
+    // Get enabled download provider extensions
+    final downloadExtensions = extensionState.extensions
+        .where((ext) => ext.enabled && ext.hasDownloadProvider)
+        .toList();
+
+    final qualityOptions = _getQualityOptions();
+
+    return SafeArea(
+      child: SingleChildScrollView(
+        child: Column(
+          mainAxisSize: MainAxisSize.min,
+          crossAxisAlignment: CrossAxisAlignment.start,
+          children: [
+            // Track info header (if provided)
+            if (widget.trackName != null) ...[
+              _TrackInfoHeader(
+                trackName: widget.trackName!,
+                artistName: widget.artistName,
+                coverUrl: widget.coverUrl,
+              ),
+              Divider(height: 1, color: colorScheme.outlineVariant.withValues(alpha: 0.5)),
+            ] else ...[
+              const SizedBox(height: 8),
+              Center(
+                child: Container(
+                  width: 40,
+                  height: 4,
+                  decoration: BoxDecoration(
+                    color: colorScheme.onSurfaceVariant.withValues(alpha: 0.4),
+                    borderRadius: BorderRadius.circular(2),
+                  ),
+                ),
+              ),
+            ],
+
+            // Service selector section
+            Padding(
+              padding: const EdgeInsets.fromLTRB(24, 16, 24, 8),
+              child: Text(
+                'Download From',
+                style: Theme.of(context).textTheme.titleMedium?.copyWith(fontWeight: FontWeight.bold),
+              ),
+            ),
+
+            // Built-in services
+            Padding(
+              padding: const EdgeInsets.symmetric(horizontal: 20),
+              child: Wrap(
+                spacing: 8,
+                runSpacing: 8,
+                children: [
+                  // Built-in services
+                  for (final service in _builtInServices)
+                    _ServiceChip(
+                      label: service.label,
+                      isSelected: _selectedService == service.id,
+                      onTap: () => setState(() => _selectedService = service.id),
+                    ),
+                  // Extension services
+                  for (final ext in downloadExtensions)
+                    _ServiceChip(
+                      label: ext.displayName,
+                      isSelected: _selectedService == ext.id,
+                      onTap: () => setState(() => _selectedService = ext.id),
+                      iconPath: ext.iconPath,
+                    ),
+                ],
+              ),
+            ),
+
+            // Quality selector section
+            Padding(
+              padding: const EdgeInsets.fromLTRB(24, 16, 24, 8),
+              child: Text(
+                'Select Quality',
+                style: Theme.of(context).textTheme.titleMedium?.copyWith(fontWeight: FontWeight.bold),
+              ),
+            ),
+
+            // Disclaimer for built-in services
+            if (_builtInServices.any((s) => s.id == _selectedService))
+              Padding(
+                padding: const EdgeInsets.fromLTRB(24, 0, 24, 12),
+                child: Text(
+                  'Actual quality depends on track availability. Hi-Res may not be available for all tracks.',
+                  style: Theme.of(context).textTheme.bodySmall?.copyWith(
+                    color: colorScheme.onSurfaceVariant,
+                    fontStyle: FontStyle.italic,
+                  ),
+                ),
+              ),
+
+            // Quality options
+            for (final quality in qualityOptions)
+              _QualityOption(
+                title: quality.label,
+                subtitle: quality.description ?? '',
+                icon: _getQualityIcon(quality.id),
+                onTap: () {
+                  Navigator.pop(context);
+                  widget.onSelect(quality.id, _selectedService);
+                },
+              ),
+
+            const SizedBox(height: 16),
+          ],
+        ),
+      ),
+    );
+  }
+
+  IconData _getQualityIcon(String qualityId) {
+    switch (qualityId.toUpperCase()) {
+      case 'HI_RES_LOSSLESS':
+        return Icons.four_k;
+      case 'HI_RES':
+        return Icons.high_quality;
+      case 'LOSSLESS':
+        return Icons.music_note;
+      case 'MP3_320':
+      case 'MP3':
+        return Icons.audiotrack;
+      case 'OPUS':
+      case 'OPUS_128':
+        return Icons.graphic_eq;
+      default:
+        return Icons.music_note;
+    }
+  }
+}
+
+
+class _QualityOption extends StatelessWidget {
+  final String title;
+  final String subtitle;
+  final IconData icon;
+  final VoidCallback onTap;
+
+  const _QualityOption({
+    required this.title,
+    required this.subtitle,
+    required this.icon,
+    required this.onTap,
+  });
+
+  @override
+  Widget build(BuildContext context) {
+    final colorScheme = Theme.of(context).colorScheme;
+    return ListTile(
+      contentPadding: const EdgeInsets.symmetric(horizontal: 24, vertical: 4),
+      leading: Container(
+        padding: const EdgeInsets.all(10),
+        decoration: BoxDecoration(
+          color: colorScheme.primaryContainer,
+          borderRadius: BorderRadius.circular(12),
+        ),
+        child: Icon(icon, color: colorScheme.onPrimaryContainer, size: 20),
+      ),
+      title: Text(title, style: const TextStyle(fontWeight: FontWeight.w500)),
+      subtitle: subtitle.isNotEmpty
+          ? Text(subtitle, style: TextStyle(color: colorScheme.onSurfaceVariant))
+          : null,
+      onTap: onTap,
+    );
+  }
+}
+
+class _ServiceChip extends StatelessWidget {
+  final String label;
+  final bool isSelected;
+  final VoidCallback onTap;
+  final String? iconPath;
+
+  const _ServiceChip({
+    required this.label,
+    required this.isSelected,
+    required this.onTap,
+    this.iconPath,
+  });
+
+  @override
+  Widget build(BuildContext context) {
+    final colorScheme = Theme.of(context).colorScheme;
+    return GestureDetector(
+      onTap: onTap,
+      child: AnimatedContainer(
+        duration: const Duration(milliseconds: 200),
+        padding: const EdgeInsets.symmetric(horizontal: 16, vertical: 10),
+        decoration: BoxDecoration(
+          color: isSelected ? colorScheme.primaryContainer : colorScheme.surfaceContainerHighest,
+          borderRadius: BorderRadius.circular(12),
+          border: isSelected ? null : Border.all(color: colorScheme.outlineVariant.withValues(alpha: 0.5)),
+        ),
+        child: Row(
+          mainAxisSize: MainAxisSize.min,
+          children: [
+            if (iconPath != null) ...[
+              ClipRRect(
+                borderRadius: BorderRadius.circular(4),
+                child: Image.file(
+                  File(iconPath!),
+                  width: 18,
+                  height: 18,
+                  fit: BoxFit.cover,
+                  errorBuilder: (context, error, stackTrace) => Icon(
+                    Icons.extension,
+                    size: 18,
+                    color: isSelected ? colorScheme.onPrimaryContainer : colorScheme.onSurfaceVariant,
+                  ),
+                ),
+              ),
+              const SizedBox(width: 6),
+            ],
+            Text(
+              label,
+              style: TextStyle(
+                fontWeight: isSelected ? FontWeight.w600 : FontWeight.normal,
+                color: isSelected ? colorScheme.onPrimaryContainer : colorScheme.onSurfaceVariant,
+              ),
+            ),
+          ],
+        ),
+      ),
+    );
+  }
+}
+
+class _TrackInfoHeader extends StatefulWidget {
+  final String trackName;
+  final String? artistName;
+  final String? coverUrl;
+
+  const _TrackInfoHeader({
+    required this.trackName,
+    this.artistName,
+    this.coverUrl,
+  });
+
+  @override
+  State<_TrackInfoHeader> createState() => _TrackInfoHeaderState();
+}
+
+class _TrackInfoHeaderState extends State<_TrackInfoHeader> {
+  bool _expanded = false;
+  bool _isOverflowing = false;
+
+  @override
+  Widget build(BuildContext context) {
+    final colorScheme = Theme.of(context).colorScheme;
+    return Material(
+      color: Colors.transparent,
+      child: InkWell(
+        onTap: _isOverflowing ? () => setState(() => _expanded = !_expanded) : null,
+        borderRadius: const BorderRadius.only(
+          topLeft: Radius.circular(28),
+          topRight: Radius.circular(28),
+        ),
+        child: Column(
+          children: [
+            const SizedBox(height: 8),
+            Container(
+              width: 40,
+              height: 4,
+              decoration: BoxDecoration(
+                color: colorScheme.onSurfaceVariant.withValues(alpha: 0.4),
+                borderRadius: BorderRadius.circular(2),
+              ),
+            ),
+            Padding(
+              padding: const EdgeInsets.fromLTRB(16, 12, 16, 12),
+              child: Row(
+                children: [
+                  ClipRRect(
+                    borderRadius: BorderRadius.circular(8),
+                    child: widget.coverUrl != null
+                        ? Image.network(
+                            widget.coverUrl!,
+                            width: 56,
+                            height: 56,
+                            fit: BoxFit.cover,
+                            errorBuilder: (context, error, stackTrace) => Container(
+                              width: 56,
+                              height: 56,
+                              color: colorScheme.surfaceContainerHighest,
+                              child: Icon(Icons.music_note, color: colorScheme.onSurfaceVariant),
+                            ),
+                          )
+                        : Container(
+                            width: 56,
+                            height: 56,
+                            color: colorScheme.surfaceContainerHighest,
+                            child: Icon(Icons.music_note, color: colorScheme.onSurfaceVariant),
+                          ),
+                  ),
+                  const SizedBox(width: 12),
+                  Expanded(
+                    child: LayoutBuilder(
+                      builder: (context, constraints) {
+                        final titleStyle = Theme.of(context).textTheme.titleMedium?.copyWith(fontWeight: FontWeight.w600);
+                        final titleSpan = TextSpan(text: widget.trackName, style: titleStyle);
+                        final titlePainter = TextPainter(
+                          text: titleSpan,
+                          maxLines: 1,
+                          textDirection: TextDirection.ltr,
+                        )..layout(maxWidth: constraints.maxWidth);
+                        final titleOverflows = titlePainter.didExceedMaxLines;
+
+                        WidgetsBinding.instance.addPostFrameCallback((_) {
+                          if (mounted && _isOverflowing != titleOverflows) {
+                            setState(() => _isOverflowing = titleOverflows);
+                          }
+                        });
+
+                        return Column(
+                          crossAxisAlignment: CrossAxisAlignment.start,
+                          children: [
+                            Text(
+                              widget.trackName,
+                              style: titleStyle,
+                              maxLines: _expanded ? 10 : 1,
+                              overflow: _expanded ? TextOverflow.visible : TextOverflow.ellipsis,
+                            ),
+                            if (widget.artistName != null) ...[
+                              const SizedBox(height: 2),
+                              Text(
+                                widget.artistName!,
+                                style: Theme.of(context).textTheme.bodyMedium?.copyWith(
+                                  color: colorScheme.onSurfaceVariant,
+                                ),
+                                maxLines: _expanded ? 3 : 1,
+                                overflow: _expanded ? TextOverflow.visible : TextOverflow.ellipsis,
+                              ),
+                            ],
+                          ],
+                        );
+                      },
+                    ),
+                  ),
+                  if (_isOverflowing || _expanded)
+                    Icon(
+                      _expanded ? Icons.expand_less : Icons.expand_more,
+                      color: colorScheme.onSurfaceVariant,
+                      size: 20,
+                    ),
+                ],
+              ),
+            ),
+          ],
+        ),
+      ),
+    );
+  }
+}

lib/widgets/settings_group.dart

@@ -133,6 +133,7 @@ class SettingsSwitchItem extends StatelessWidget {
   final bool value;
   final ValueChanged<bool>? onChanged;
   final bool showDivider;
+  final bool enabled;
 
   const SettingsSwitchItem({
     super.key,
@@ -142,53 +143,60 @@ class SettingsSwitchItem extends StatelessWidget {
     required this.value,
     this.onChanged,
     this.showDivider = true,
+    this.enabled = true,
   });
 
   @override
   Widget build(BuildContext context) {
     final colorScheme = Theme.of(context).colorScheme;
+    final isDisabled = !enabled || onChanged == null;
     
     return Column(
       mainAxisSize: MainAxisSize.min,
       children: [
-        InkWell(
-          onTap: onChanged != null ? () => onChanged!(!value) : null,
-          splashColor: colorScheme.primary.withValues(alpha: 0.12),
-          highlightColor: colorScheme.primary.withValues(alpha: 0.08),
-          child: Padding(
-            padding: const EdgeInsets.symmetric(horizontal: 20, vertical: 12),
-            child: Row(
-              children: [
-                if (icon != null) ...[
-                  Icon(icon, color: colorScheme.onSurfaceVariant, size: 24),
-                  const SizedBox(width: 16),
-                ],
-                Expanded(
-                  child: Column(
-                    crossAxisAlignment: CrossAxisAlignment.start,
-                    children: [
-                      Text(
-                        title,
-                        style: Theme.of(context).textTheme.bodyLarge,
-                      ),
-                      if (subtitle != null) ...[
-                        const SizedBox(height: 2),
+        Opacity(
+          opacity: isDisabled ? 0.5 : 1.0,
+          child: InkWell(
+            onTap: isDisabled ? null : () => onChanged!(!value),
+            splashColor: colorScheme.primary.withValues(alpha: 0.12),
+            highlightColor: colorScheme.primary.withValues(alpha: 0.08),
+            child: Padding(
+              padding: const EdgeInsets.symmetric(horizontal: 20, vertical: 12),
+              child: Row(
+                children: [
+                  if (icon != null) ...[
+                    Icon(icon, color: isDisabled ? colorScheme.outline : colorScheme.onSurfaceVariant, size: 24),
+                    const SizedBox(width: 16),
+                  ],
+                  Expanded(
+                    child: Column(
+                      crossAxisAlignment: CrossAxisAlignment.start,
+                      children: [
                         Text(
-                          subtitle!,
-                          style: Theme.of(context).textTheme.bodyMedium?.copyWith(
-                            color: colorScheme.onSurfaceVariant,
+                          title,
+                          style: Theme.of(context).textTheme.bodyLarge?.copyWith(
+                            color: isDisabled ? colorScheme.outline : null,
                           ),
                         ),
+                        if (subtitle != null) ...[
+                          const SizedBox(height: 2),
+                          Text(
+                            subtitle!,
+                            style: Theme.of(context).textTheme.bodyMedium?.copyWith(
+                              color: isDisabled ? colorScheme.outline : colorScheme.onSurfaceVariant,
+                            ),
+                          ),
+                        ],
                       ],
-                    ],
+                    ),
                   ),
-                ),
-                const SizedBox(width: 8),
-                Switch(
-                  value: value,
-                  onChanged: onChanged,
-                ),
-              ],
+                  const SizedBox(width: 8),
+                  Switch(
+                    value: value,
+                    onChanged: isDisabled ? null : onChanged,
+                  ),
+                ],
+              ),
             ),
           ),
         ),

pubspec.yaml

@@ -1,7 +1,7 @@
 name: spotiflac_android
 description: Download Spotify tracks in FLAC from Tidal, Qobuz & Amazon Music
 publish_to: "none"
-version: 2.2.9+51
+version: 3.0.0-alpha.4+53
 
 environment:
   sdk: ^3.10.0

pubspec_ios.yaml

@@ -1,7 +1,7 @@
 name: spotiflac_android
 description: Download Spotify tracks in FLAC from Tidal, Qobuz & Amazon Music
 publish_to: "none"
-version: 2.2.9+51
+version: 3.0.0-alpha.4+53
 
 environment:
   sdk: ^3.10.0