Merge dev into main: v3.0.0 stable release

Replaced by parallel version for faster API responses

.github/workflows/release.yml

@@ -345,6 +345,8 @@ jobs:
             CHANGELOG="See CHANGELOG.md for details."
           else
             echo "Found changelog content"
+            # Remove trailing --- separator if present (CHANGELOG uses --- between versions)
+            CHANGELOG=$(echo "$CHANGELOG" | sed '/^---$/d')
           fi
 
           # Save to file for multiline support

.gitignore

@@ -53,3 +53,9 @@ ios/.symlinks/
 ios/Flutter/Flutter.framework/
 ios/Flutter/Flutter.podspec
 android/app/libs/gobackend-sources.jar
+
+# Extension folder
+extension/
+
+# Agent instructions
+AGENTS.md

CHANGELOG.md

@@ -1,5 +1,322 @@
 # Changelog
 
+## [3.0.0] - 2026-01-14
+
+### Extension System (Major Feature)
+
+SpotiFLAC 3.0 introduces a powerful extension system that allows third-party integrations for metadata, downloads, and more.
+
+#### Extension Store
+
+- Browse and install extensions directly from the app
+- New "Store" tab in bottom navigation
+- Browse by category: Metadata, Download, Utility, Lyrics, Integration
+- Search extensions by name, description, or tags
+- One-tap install, update, and uninstall
+- Offline cache for browsing without internet
+
+#### Spotify Web Extension
+
+- Available in Extension Store - install and enable in Settings > Extensions
+- Metadata provider using Spotify's internal web player API
+- Download tracks from Daily Mix, Discover Weekly, and other personalized playlists
+- Useful when official Spotify API is rate-limited or unavailable
+
+#### Extension Capabilities
+
+- **Custom Search Providers**
+- **Custom URL Handlers**
+- **Custom Thumbnail Ratios**: Square (1:1), Wide (16:9), Portrait (2:3)
+- **Post-Processing Hooks**: Extensions can process downloaded files
+- **Quality Options**: Extensions can define custom quality settings
+
+#### Extension APIs
+
+- Full HTTP support: GET, POST, PUT, DELETE, PATCH
+- Persistent cookie jar per extension
+- Browser-like polyfills: `fetch()`, `atob()`/`btoa()`, `TextEncoder`/`TextDecoder`, `URL`/`URLSearchParams`
+- Storage API for persistent data
+- File API for file operations
+- HMAC-SHA1 utility for cryptographic operations
+
+#### Security
+
+- Sandboxed JavaScript runtime (goja)
+- Permission-based access control
+- Network domain whitelisting
+- Improved credential encryption with per-installation random salt
+
+### Added
+
+- **Album Folder Structure Setting**: Option to remove artist folder from album path
+
+  - `Artist / Album` (default): `Albums/Artist Name/Album Name/`
+  - `Album Only`: `Albums/Album Name/`
+
+- **Separate Singles Folder**: Organize downloads into Albums/ and Singles/ folders
+
+  - Based on `album_type` from Spotify/Deezer metadata
+  - Toggle in Settings > Download > Separate Singles Folder
+
+- **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
+
+### UI/UX Improvements
+
+- **Swipeable History Filters**: History tab now supports swipe gestures between All, Albums, and Singles filters
+
+  - Swipe left/right to switch between filter tabs
+  - Filter chips sync with swipe position
+  - Smooth edge-to-edge transition: swipe past Singles to go to Store, swipe past All to go to Home
+  - Natural gesture feel - drag connects to parent navigation
+
+  - **Improved File Open Intent**: Play button in History now correctly opens music players only
+  - Added proper MIME type (`audio/flac`, `audio/mpeg`, etc.) when opening downloaded files
+  - Prevents system from showing unrelated apps in the "Open with" dialog
+
+### Fixed
+
+- **Fixed Tab Edge Overscroll**: Home and Settings tabs now stop at edges instead of bouncing into empty space
+
+- **Fixed Extension Duplicate Load Error**: Extension loading now silently skips already-loaded extensions instead of throwing error
+
+- **Fixed Settings Item Highlight on Swipe**: Settings items no longer highlight when swiping at page edge
+
+- **Fixed Keyboard Appearing on Tab Switch**: Keyboard now auto-dismisses when swiping between tabs
+
+- **Removed Search Source Badges**: Removed "Free" and "API Key" labels from Deezer/Spotify selector in Options
+
+- **Back Gesture Freeze on Android 13+**: Fixed app freeze when using back gesture in settings
+
+  - Added `PopScope` with `canPop: true` to all settings pages
+  - Changed navigation to use `PageRouteBuilder` with proper slide transition
+
+- **Bottom Overflow in Folder Organization Dialog**: Fixed overflow in portrait and landscape mode
+
+  - Made dialog scrollable with max height constraint
+
+- **Japanese Artist Name Order**: Fixed artist mismatch for Japanese names
+
+  - "Sawano Hiroyuki" vs "Hiroyuki Sawano" now correctly matches
+
+- **Multi-Artist Matching**: Fixed artist mismatch for collaboration tracks
+
+  - "RADWIMPS feat. Toko Miura" now matches when service only shows "Toko Miura"
+
+- **Max Resolution Cover Download**: Fixed cover not upgrading to max resolution on mobile
+
+  - Mobile now correctly upgrades 300x300 → 640x640 → max resolution (~2000x2000)
+
+- **EXISTS: Prefix in File Path**: Fixed "File not found" error in metadata screen
+
+  - Duplicate detection prefix now stripped before saving to history
+
+- **Extension Search Result Parsing**: Fixed "cannot unmarshal array" error
+
+  - Go backend now handles both array and object formats from extensions
+
+- **Store Tab Unmount Crash**: Fixed "Using ref when widget is unmounted" error
+
+- **Duplicate History Entries**: Fixed duplicate entries when re-downloading same track
+
+  - Detects existing entries by Spotify ID, Deezer ID, or ISRC
+
+- **Permission Error Message**: Fixed download showing "Song not found" when actually permission error
+
+  - Now shows proper message: "Cannot write to folder, check storage permission"
+
+- **Android 13+ Storage Permission**: Fixed storage permission not working on Android 13+
+  - Now requests both `MANAGE_EXTERNAL_STORAGE` and `READ_MEDIA_AUDIO`
+
+### Changed
+
+- **Extension Manifest**: New `file` permission required for file operations
+  ```json
+  "permissions": {
+    "network": ["api.example.com"],
+    "storage": true,
+    "file": true
+  }
+  ```
+
+### Technical
+
+- Go backend: Simplified parallel download result handling in Tidal/Qobuz
+- Go backend: Removed unused functions and fixed bit shifting warnings
+- Release workflow: Fixed duplicate `---` separator in release notes
+
+---
+
+## [3.0.0-beta.2] - 2026-01-13
+
+### Added
+
+- **Album Folder Structure Setting**: Option to remove artist folder from album path
+  - New setting in Download Settings when "Separate Singles Folder" is enabled
+  - `Artist / Album` (default): `Albums/Artist Name/Album Name/`
+  - `Album Only`: `Albums/Album Name/`
+  - Requested by user who prefers flat album organization
+
+### Fixed
+
+- **Back Gesture Freeze on OnePlus/Android 13+**: Fixed app freeze when using back gesture in settings
+
+  - Added `PopScope` with `canPop: true` to all settings pages
+  - Changed navigation to use `PageRouteBuilder` with proper slide transition
+  - Fixes predictive back gesture conflict on devices with gesture navigation
+  - Affected pages: Download, Appearance, Options, Extensions, About, Logs, Extension Detail
+
+- **Extension Search Result Parsing**: Fixed "cannot unmarshal array into Go value" error
+
+  - Go backend now handles both array and object formats from extensions
+  - Extensions returning `[{track}, {track}]` now work correctly
+  - Extensions returning `{tracks: [...], total: N}` still work as before
+
+- **Max Resolution Cover Download**: Fixed cover not upgrading to max resolution on mobile
+
+  - Added missing `spotifySize300` constant (300x300 size code)
+  - Mobile now correctly upgrades 300x300 → 640x640 → max resolution (~2000x2000)
+  - Added `_upgradeToMaxQualityCover()` helper in Flutter for M4A conversion path
+  - Go backend `cover.go` now directly replaces URL without HEAD verification
+
+- **Extension Search Provider Reset**: Fixed search provider not resetting to default when disabled
+
+  - `copyWith` in `AppSettings` couldn't set `searchProvider` to `null`
+  - Added `clearSearchProvider` boolean parameter to properly clear the value
+  - Settings menu now correctly switches back to default provider
+
+- **Extension Disabled Search Fallback**: Fixed error when extension is disabled but still called
+
+  - `_performSearch` now checks if extension is still enabled before calling custom search
+  - Automatically falls back to Deezer/Spotify search if extension was disabled
+  - Clears `searchProvider` setting if extension no longer available
+
+- **Store Tab Unmount Crash**: Fixed "Using ref when widget is unmounted" error
+
+  - Added `mounted` check after async operation in `_initialize()`
+  - Prevents crash when navigating away from Store tab during initialization
+
+- **EXISTS: Prefix in File Path**: Fixed "File not found" error in metadata screen after download
+
+  - Duplicate detection was adding `EXISTS:` prefix to file paths
+  - Prefix now stripped before saving to download history
+  - Legacy history items with prefix are handled gracefully
+
+- **History Error Badge**: Fixed error badge showing on history items even when file exists
+
+  - `queue_tab.dart` now strips `EXISTS:` prefix before checking file existence
+  - File open and delete operations also use cleaned path
+
+- **Extension Artist URL Handler**: Fixed artist pages showing "0 releases" from extensions
+
+  - Extension `fetchArtist` now returns correct format: `{ type: "artist", artist: { albums } }`
+  - Go backend `HandleURLWithExtensionJSON` now includes albums in artist response
+  - Added `AlbumType` field to `ExtAlbumMetadata` struct
+
+- **Extension Artist Name in Logs**: Fixed empty artist name in extension track logs
+
+  - Now uses `firstArtist` + `otherArtists` instead of deprecated `artists.items`
+  - Logs correctly show "Fetched track: {title} by {artist}"
+
+- **Japanese Artist Name Order**: Fixed artist mismatch for Japanese names with different order
+
+  - "Sawano Hiroyuki" vs "Hiroyuki Sawano" now correctly matches
+  - Added `sameWordsUnordered` check to both Tidal and Qobuz artist matching
+  - Handles Japanese name order (family name first) vs Western name order (given name first)
+
+- **Multi-Artist Matching**: Fixed artist mismatch for collaboration tracks
+
+  - "RADWIMPS feat. Toko Miura" now matches when Qobuz/Tidal only shows "Toko Miura"
+  - Split artists by separators (`, `, `feat.`, `ft.`, `&`, `and`, `x`)
+  - Match if ANY expected artist matches ANY found artist
+
+- **Cover Download Logging**: Improved cover download logs for debugging
+  - Shows original URL, upgrade steps, and final URL
+  - Displays estimated resolution based on file size
+  - Logs now appear in Settings > Logs via GoLog
+
+---
+
+## [3.0.0-beta.1] - 2026-01-13
+
+### Security
+
+- Improved extension sandbox security
+- Improved credential encryption with per-installation random salt
+
+### Changed
+
+- **Extension Manifest**: New `file` permission required for file operations
+  ```json
+  "permissions": {
+    "network": ["api.example.com"],
+    "storage": true,
+    "file": true
+  }
+  ```
+  Extensions that need to download files must declare `"file": true` in manifest.
+
+### Fixed
+
+- Extension packages now preserve directory structure (subdirectories supported)
+- Back gesture freeze in settings pages on Android gesture navigation
+
+---
+
+## [3.0.0-alpha.4] - 2026-01-12
+
+### 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
@@ -48,7 +365,7 @@
 
 - **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.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
@@ -90,6 +407,7 @@
 ## [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
@@ -168,16 +486,6 @@
 - **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

README.md

@@ -40,30 +40,19 @@ 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)
+## Extensions
 
-> **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
+Extensions allow the community to add new music sources and features without waiting for app updates. When a streaming service API changes or a new source becomes available, extensions can be updated independently.
 
 ### Installing Extensions
-1. Download a `.spotiflac-ext` file
-2. Go to **Settings > Extensions**
-3. Tap **Install Extension** and select the file
+1. Go to **Store** tab in the app
+2. Browse and install extensions with one tap
+3. Or download a `.spotiflac-ext` file and install manually via **Settings > Extensions**
 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:
+Want to create your own extension? Check out the [Extension Development Guide](https://zarz.moe/docs) for complete documentation.
 
 ## Other project
 
@@ -74,8 +63,6 @@ Get Spotify tracks in true FLAC from Tidal, Qobuz & Amazon Music for Windows, ma
 
 ## Disclaimer
 
-> **iOS Support**: This app is primarily tested on Android. iOS support is experimental and may have bugs — the developer is too poor to afford an iPhone for proper testing. If you encounter issues on iOS, please report them!
-
 This project is for **educational and private use only**. The developer does not condone or encourage copyright infringement.
 
 **SpotiFLAC** is a third-party tool and is not affiliated with, endorsed by, or connected to Spotify, Tidal, Qobuz, Amazon Music, or any other streaming service.

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

@@ -551,6 +551,27 @@ class MainActivity: FlutterActivity() {
                             }
                             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") ?: ""
@@ -566,6 +587,49 @@ class MainActivity: FlutterActivity() {
                             }
                             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/cover.go

@@ -9,10 +9,20 @@ import (
 
 // Spotify image size codes (same as PC version)
 const (
-	spotifySize640 = "ab67616d0000b273" // 640x640
+	spotifySize300 = "ab67616d00001e02" // 300x300 (small)
+	spotifySize640 = "ab67616d0000b273" // 640x640 (medium)
 	spotifySizeMax = "ab67616d000082c1" // Max resolution (~2000x2000)
 )
 
+// convertSmallToMedium upgrades 300x300 cover URL to 640x640
+// Same logic as PC version for consistency
+func convertSmallToMedium(imageURL string) string {
+	if strings.Contains(imageURL, spotifySize300) {
+		return strings.Replace(imageURL, spotifySize300, spotifySize640, 1)
+	}
+	return imageURL
+}
+
 // downloadCoverToMemory downloads cover art and returns as bytes (no file creation)
 // This avoids file permission issues on Android
 func downloadCoverToMemory(coverURL string, maxQuality bool) ([]byte, error) {
@@ -20,17 +30,27 @@ func downloadCoverToMemory(coverURL string, maxQuality bool) ([]byte, error) {
 		return nil, fmt.Errorf("no cover URL provided")
 	}
 
-	fmt.Printf("[Cover] Downloading cover from: %s\n", coverURL)
+	GoLog("[Cover] Original URL: %s", coverURL)
 
-	// Upgrade to max quality if requested
-	downloadURL := coverURL
+	// First upgrade small (300) to medium (640) - always do this
+	downloadURL := convertSmallToMedium(coverURL)
+	if downloadURL != coverURL {
+		GoLog("[Cover] Upgraded 300x300 → 640x640")
+	}
+
+	// Then upgrade to max quality if requested
 	if maxQuality {
-		downloadURL = upgradeToMaxQuality(coverURL)
-		if downloadURL != coverURL {
-			fmt.Printf("[Cover] Upgraded to max quality URL: %s\n", downloadURL)
+		maxURL := upgradeToMaxQuality(downloadURL)
+		if maxURL != downloadURL {
+			downloadURL = maxURL
+			GoLog("[Cover] Upgraded to max resolution (~2000x2000)")
+		} else {
+			GoLog("[Cover] Max resolution not available, using 640x640")
 		}
 	}
 
+	GoLog("[Cover] Final URL: %s", downloadURL)
+
 	client := NewHTTPClientWithTimeout(DefaultTimeout)
 
 	// Create request with User-Agent (required by Spotify CDN)
@@ -54,12 +74,25 @@ func downloadCoverToMemory(coverURL string, maxQuality bool) ([]byte, error) {
 		return nil, fmt.Errorf("failed to read cover data: %w", err)
 	}
 
-	fmt.Printf("[Cover] Downloaded %d bytes\n", len(data))
+	// Calculate approximate resolution from file size
+	// JPEG ~2000x2000 is typically 300-600KB, 640x640 is ~50-100KB
+	sizeKB := len(data) / 1024
+	var resolution string
+	if sizeKB > 200 {
+		resolution = "~2000x2000 (hi-res)"
+	} else if sizeKB > 50 {
+		resolution = "~640x640"
+	} else {
+		resolution = "~300x300"
+	}
+	GoLog("[Cover] Downloaded %d KB (%s)", sizeKB, resolution)
+
 	return data, nil
 }
 
 // upgradeToMaxQuality upgrades Spotify cover URL to maximum quality
-// Uses same logic as PC version - replaces 640x640 size code with max resolution
+// Same logic as PC version - directly replaces 640x640 size code with max resolution
+// No HEAD verification needed - Spotify CDN always serves max resolution if available
 func upgradeToMaxQuality(coverURL string) string {
 	// Spotify image URLs can be upgraded by changing the size parameter
 	// Format: https://i.scdn.co/image/ab67616d0000b273...
@@ -67,21 +100,7 @@ func upgradeToMaxQuality(coverURL string) string {
 	// ab67616d000082c1 = Max resolution (~2000x2000)
 
 	if strings.Contains(coverURL, spotifySize640) {
-		// Try max resolution first
-		maxURL := strings.Replace(coverURL, spotifySize640, spotifySizeMax, 1)
-
-		// Verify max resolution URL is available
-		client := NewHTTPClientWithTimeout(DefaultTimeout)
-		req, err := http.NewRequest("HEAD", maxURL, nil)
-		if err == nil {
-			resp, err := DoRequestWithUserAgent(client, req)
-			if err == nil {
-				resp.Body.Close()
-				if resp.StatusCode == http.StatusOK {
-					return maxURL
-				}
-			}
-		}
+		return strings.Replace(coverURL, spotifySize640, spotifySizeMax, 1)
 	}
 
 	return coverURL
@@ -93,9 +112,12 @@ func GetCoverFromSpotify(imageURL string, maxQuality bool) string {
 		return ""
 	}
 
+	// Always upgrade small to medium first
+	result := convertSmallToMedium(imageURL)
+
 	if maxQuality {
-		return upgradeToMaxQuality(imageURL)
+		result = upgradeToMaxQuality(result)
 	}
 
-	return imageURL
+	return result
 }

go_backend/exports.go

@@ -208,6 +208,11 @@ func DownloadTrack(requestJSON string) (string, error) {
 	req.AlbumArtist = strings.TrimSpace(req.AlbumArtist)
 	req.OutputDir = strings.TrimSpace(req.OutputDir)
 
+	// Add output directory to allowed download dirs for extensions
+	if req.OutputDir != "" {
+		AddAllowedDownloadDir(req.OutputDir)
+	}
+
 	var result DownloadResult
 	var err error
 
@@ -345,6 +350,11 @@ func DownloadWithFallback(requestJSON string) (string, error) {
 	req.AlbumArtist = strings.TrimSpace(req.AlbumArtist)
 	req.OutputDir = strings.TrimSpace(req.OutputDir)
 
+	// Add output directory to allowed download dirs for extensions
+	if req.OutputDir != "" {
+		AddAllowedDownloadDir(req.OutputDir)
+	}
+
 	// Build service order starting with preferred service
 	allServices := []string{"tidal", "qobuz", "amazon"}
 	preferredService := req.Service
@@ -1430,6 +1440,41 @@ func GetAllPendingFFmpegCommandsJSON() (string, error) {
 
 // ==================== EXTENSION CUSTOM SEARCH ====================
 
+// EnrichTrackWithExtensionJSON enriches track metadata using the source extension
+// This is called lazily before download starts, allowing extension to fetch real ISRC etc.
+func EnrichTrackWithExtensionJSON(extensionID, trackJSON string) (string, error) {
+	manager := GetExtensionManager()
+	ext, err := manager.GetExtension(extensionID)
+	if err != nil {
+		// Extension not found, return original track
+		return trackJSON, nil
+	}
+
+	if !ext.Manifest.IsMetadataProvider() {
+		// Not a metadata provider, return original
+		return trackJSON, nil
+	}
+
+	var track ExtTrackMetadata
+	if err := json.Unmarshal([]byte(trackJSON), &track); err != nil {
+		return trackJSON, fmt.Errorf("failed to parse track: %w", err)
+	}
+
+	provider := NewExtensionProviderWrapper(ext)
+	enrichedTrack, err := provider.EnrichTrack(&track)
+	if err != nil {
+		// Error enriching, return original
+		return trackJSON, nil
+	}
+
+	jsonBytes, err := json.Marshal(enrichedTrack)
+	if err != nil {
+		return trackJSON, nil
+	}
+
+	return string(jsonBytes), nil
+}
+
 // CustomSearchWithExtensionJSON performs custom search using an extension
 func CustomSearchWithExtensionJSON(extensionID, query string, optionsJSON string) (string, error) {
 	manager := GetExtensionManager()
@@ -1506,6 +1551,158 @@ func GetSearchProvidersJSON() (string, error) {
 	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 {
+		artistResponse := map[string]interface{}{
+			"id":        result.Artist.ID,
+			"name":      result.Artist.Name,
+			"image_url": result.Artist.ImageURL,
+		}
+
+		// Add albums if present
+		if len(result.Artist.Albums) > 0 {
+			albums := make([]map[string]interface{}, len(result.Artist.Albums))
+			for i, album := range result.Artist.Albums {
+				albumType := album.AlbumType
+				if albumType == "" {
+					albumType = "album"
+				}
+				albums[i] = map[string]interface{}{
+					"id":           album.ID,
+					"name":         album.Name,
+					"artists":      album.Artists,
+					"images":       album.CoverURL,
+					"release_date": album.ReleaseDate,
+					"total_tracks": album.TotalTracks,
+					"album_type":   albumType,
+				}
+			}
+			artistResponse["albums"] = albums
+		}
+
+		response["artist"] = artistResponse
+	}
+
+	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
@@ -1563,3 +1760,100 @@ func GetPostProcessingProvidersJSON() (string, error) {
 
 	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

@@ -191,14 +191,26 @@ func (m *ExtensionManager) LoadExtensionFromFile(filePath string) (*LoadedExtens
 		return nil, fmt.Errorf("failed to create extension directory: %w", err)
 	}
 
-	// Extract all files
+	// Extract all files (preserving directory structure)
 	for _, file := range zipReader.File {
 		if file.FileInfo().IsDir() {
 			continue
 		}
 
-		// Get relative path within the zip
-		destPath := filepath.Join(extDir, filepath.Base(file.Name))
+		// Preserve relative path within the zip (support subdirectories)
+		// Clean the path to prevent path traversal attacks
+		relPath := filepath.Clean(file.Name)
+		if strings.HasPrefix(relPath, "..") || filepath.IsAbs(relPath) {
+			GoLog("[Extension] Skipping unsafe path in archive: %s\n", file.Name)
+			continue
+		}
+		destPath := filepath.Join(extDir, relPath)
+
+		// Create parent directories if needed
+		destDir := filepath.Dir(destPath)
+		if err := os.MkdirAll(destDir, 0755); err != nil {
+			return nil, fmt.Errorf("failed to create directory %s: %w", destDir, err)
+		}
 
 		// Create destination file
 		destFile, err := os.Create(destPath)
@@ -231,7 +243,7 @@ func (m *ExtensionManager) LoadExtensionFromFile(filePath string) (*LoadedExtens
 	ext := &LoadedExtension{
 		ID:        manifest.Name,
 		Manifest:  manifest,
-		Enabled:   true,
+		Enabled:   false, // New extensions start disabled
 		DataDir:   extDataDir,
 		SourceDir: extDir,
 	}
@@ -444,9 +456,10 @@ func (m *ExtensionManager) loadExtensionFromDirectory(dirPath string) (*LoadedEx
 		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)
+	// Check if extension already loaded - skip silently (for directory loading on startup)
+	if existing, exists := m.extensions[manifest.Name]; exists {
+		GoLog("[Extension] Extension '%s' already loaded, skipping\n", manifest.DisplayName)
+		return existing, nil
 	}
 
 	// Create data directory for extension
@@ -459,7 +472,7 @@ func (m *ExtensionManager) loadExtensionFromDirectory(dirPath string) (*LoadedEx
 	ext := &LoadedExtension{
 		ID:        manifest.Name,
 		Manifest:  manifest,
-		Enabled:   true,
+		Enabled:   false, // Will be restored from settings store
 		DataDir:   extDataDir,
 		SourceDir: dirPath,
 	}
@@ -583,9 +596,10 @@ func (m *ExtensionManager) UpgradeExtension(filePath string) (*LoadedExtension,
 
 	GoLog("[Extension] Upgrading %s from v%s to v%s\n", newManifest.DisplayName, existing.Manifest.Version, newManifest.Version)
 
-	// Save data directory path (we want to preserve it)
+	// 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)
@@ -603,14 +617,26 @@ func (m *ExtensionManager) UpgradeExtension(filePath string) (*LoadedExtension,
 		return nil, fmt.Errorf("failed to create extension directory: %w", err)
 	}
 
-	// Extract all files from new package
+	// Extract all files from new package (preserving directory structure)
 	for _, file := range zipReader.File {
 		if file.FileInfo().IsDir() {
 			continue
 		}
 
-		// Get relative path within the zip
-		destPath := filepath.Join(extDir, filepath.Base(file.Name))
+		// Preserve relative path within the zip (support subdirectories)
+		// Clean the path to prevent path traversal attacks
+		relPath := filepath.Clean(file.Name)
+		if strings.HasPrefix(relPath, "..") || filepath.IsAbs(relPath) {
+			GoLog("[Extension] Skipping unsafe path in archive: %s\n", file.Name)
+			continue
+		}
+		destPath := filepath.Join(extDir, relPath)
+
+		// Create parent directories if needed
+		destDir := filepath.Dir(destPath)
+		if err := os.MkdirAll(destDir, 0755); err != nil {
+			return nil, fmt.Errorf("failed to create directory %s: %w", destDir, err)
+		}
 
 		// Create destination file
 		destFile, err := os.Create(destPath)
@@ -633,11 +659,11 @@ func (m *ExtensionManager) UpgradeExtension(filePath string) (*LoadedExtension,
 		}
 	}
 
-	// Create new loaded extension (reusing data directory)
+	// Create new loaded extension (reusing data directory, preserving enabled state)
 	ext := &LoadedExtension{
 		ID:        newManifest.Name,
 		Manifest:  newManifest,
-		Enabled:   true,
+		Enabled:   wasEnabled, // Preserve enabled state from before upgrade
 		DataDir:   extDataDir,
 		SourceDir: extDir,
 	}

go_backend/extension_manifest.go

@@ -29,6 +29,7 @@ const (
 type ExtensionPermissions struct {
 	Network []string `json:"network"` // List of allowed domains
 	Storage bool     `json:"storage"` // Whether extension can use storage API
+	File    bool     `json:"file"`    // Whether extension can use file API
 }
 
 // ExtensionSetting defines a configurable setting for an extension
@@ -74,6 +75,12 @@ type SearchBehaviorConfig struct {
 	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
@@ -113,6 +120,7 @@ type ExtensionManifest struct {
 	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
 }
@@ -270,6 +278,29 @@ 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 {

go_backend/extension_providers.go

@@ -7,6 +7,7 @@ import (
 	"path/filepath"
 	"strings"
 	"sync"
+	"time"
 
 	"github.com/dop251/goja"
 )
@@ -46,6 +47,7 @@ type ExtAlbumMetadata struct {
 	CoverURL    string             `json:"cover_url,omitempty"`
 	ReleaseDate string             `json:"release_date,omitempty"`
 	TotalTracks int                `json:"total_tracks"`
+	AlbumType   string             `json:"album_type,omitempty"`
 	Tracks      []ExtTrackMetadata `json:"tracks"`
 	ProviderID  string             `json:"provider_id"`
 }
@@ -140,8 +142,11 @@ func (p *ExtensionProviderWrapper) SearchTracks(query string, limit int) (*ExtSe
 		})()
 	`, query, limit)
 
-	result, err := p.vm.RunString(script)
+	result, err := RunWithTimeoutAndRecover(p.vm, script, DefaultJSTimeout)
 	if err != nil {
+		if IsTimeoutError(err) {
+			return nil, fmt.Errorf("searchTracks timeout: extension took too long to respond")
+		}
 		return nil, fmt.Errorf("searchTracks failed: %w", err)
 	}
 
@@ -157,8 +162,19 @@ func (p *ExtensionProviderWrapper) SearchTracks(query string, limit int) (*ExtSe
 	}
 
 	var searchResult ExtSearchResult
+
+	// Try to parse as ExtSearchResult object first
 	if err := json.Unmarshal(jsonBytes, &searchResult); err != nil {
-		return nil, fmt.Errorf("failed to parse search result: %w", err)
+		// If that fails, try parsing as array of tracks directly
+		var tracks []ExtTrackMetadata
+		if arrErr := json.Unmarshal(jsonBytes, &tracks); arrErr != nil {
+			return nil, fmt.Errorf("failed to parse search result: %w (also tried array: %v)", err, arrErr)
+		}
+		// Wrap array in ExtSearchResult
+		searchResult = ExtSearchResult{
+			Tracks: tracks,
+			Total:  len(tracks),
+		}
 	}
 
 	// Set provider ID on all tracks
@@ -188,8 +204,11 @@ func (p *ExtensionProviderWrapper) GetTrack(trackID string) (*ExtTrackMetadata,
 		})()
 	`, trackID)
 
-	result, err := p.vm.RunString(script)
+	result, err := RunWithTimeoutAndRecover(p.vm, script, DefaultJSTimeout)
 	if err != nil {
+		if IsTimeoutError(err) {
+			return nil, fmt.Errorf("getTrack timeout: extension took too long to respond")
+		}
 		return nil, fmt.Errorf("getTrack failed: %w", err)
 	}
 
@@ -231,8 +250,11 @@ func (p *ExtensionProviderWrapper) GetAlbum(albumID string) (*ExtAlbumMetadata,
 		})()
 	`, albumID)
 
-	result, err := p.vm.RunString(script)
+	result, err := RunWithTimeoutAndRecover(p.vm, script, DefaultJSTimeout)
 	if err != nil {
+		if IsTimeoutError(err) {
+			return nil, fmt.Errorf("getAlbum timeout: extension took too long to respond")
+		}
 		return nil, fmt.Errorf("getAlbum failed: %w", err)
 	}
 
@@ -277,8 +299,11 @@ func (p *ExtensionProviderWrapper) GetArtist(artistID string) (*ExtArtistMetadat
 		})()
 	`, artistID)
 
-	result, err := p.vm.RunString(script)
+	result, err := RunWithTimeoutAndRecover(p.vm, script, DefaultJSTimeout)
 	if err != nil {
+		if IsTimeoutError(err) {
+			return nil, fmt.Errorf("getArtist timeout: extension took too long to respond")
+		}
 		return nil, fmt.Errorf("getArtist failed: %w", err)
 	}
 
@@ -301,6 +326,72 @@ func (p *ExtensionProviderWrapper) GetArtist(artistID string) (*ExtArtistMetadat
 	return &artist, nil
 }
 
+// EnrichTrack enriches track metadata before download (e.g., fetch real ISRC)
+// This is called lazily when download starts, not when playlist/album is loaded
+// Extension should implement enrichTrack(track) function that returns enriched track
+func (p *ExtensionProviderWrapper) EnrichTrack(track *ExtTrackMetadata) (*ExtTrackMetadata, error) {
+	if !p.extension.Manifest.IsMetadataProvider() {
+		return track, nil // Not a metadata provider, return as-is
+	}
+
+	if !p.extension.Enabled {
+		return track, nil // Extension disabled, return as-is
+	}
+
+	// Convert track to JSON for passing to JS
+	trackJSON, err := json.Marshal(track)
+	if err != nil {
+		GoLog("[Extension] EnrichTrack: failed to marshal track: %v\n", err)
+		return track, nil // Return original on error
+	}
+
+	script := fmt.Sprintf(`
+		(function() {
+			if (typeof extension !== 'undefined' && typeof extension.enrichTrack === 'function') {
+				var track = %s;
+				return extension.enrichTrack(track);
+			}
+			return null;
+		})()
+	`, string(trackJSON))
+
+	result, err := RunWithTimeoutAndRecover(p.vm, script, DefaultJSTimeout)
+	if err != nil {
+		if IsTimeoutError(err) {
+			GoLog("[Extension] EnrichTrack timeout for %s\n", p.extension.ID)
+		} else {
+			GoLog("[Extension] EnrichTrack error for %s: %v\n", p.extension.ID, err)
+		}
+		return track, nil // Return original on error
+	}
+
+	// If extension doesn't implement enrichTrack or returns null, return original
+	if result == nil || goja.IsUndefined(result) || goja.IsNull(result) {
+		return track, nil
+	}
+
+	exported := result.Export()
+	jsonBytes, err := json.Marshal(exported)
+	if err != nil {
+		GoLog("[Extension] EnrichTrack: failed to marshal result: %v\n", err)
+		return track, nil
+	}
+
+	var enrichedTrack ExtTrackMetadata
+	if err := json.Unmarshal(jsonBytes, &enrichedTrack); err != nil {
+		GoLog("[Extension] EnrichTrack: failed to parse enriched track: %v\n", err)
+		return track, nil
+	}
+
+	// Preserve provider ID
+	enrichedTrack.ProviderID = track.ProviderID
+
+	GoLog("[Extension] EnrichTrack: enriched track from %s (ISRC: %s -> %s)\n",
+		p.extension.ID, track.ISRC, enrichedTrack.ISRC)
+
+	return &enrichedTrack, nil
+}
+
 // ==================== Download Provider Methods ====================
 
 // CheckAvailability checks if a track is available for download
@@ -322,8 +413,11 @@ func (p *ExtensionProviderWrapper) CheckAvailability(isrc, trackName, artistName
 		})()
 	`, isrc, trackName, artistName)
 
-	result, err := p.vm.RunString(script)
+	result, err := RunWithTimeoutAndRecover(p.vm, script, DefaultJSTimeout)
 	if err != nil {
+		if IsTimeoutError(err) {
+			return nil, fmt.Errorf("checkAvailability timeout: extension took too long to respond")
+		}
 		return nil, fmt.Errorf("checkAvailability failed: %w", err)
 	}
 
@@ -364,8 +458,11 @@ func (p *ExtensionProviderWrapper) GetDownloadURL(trackID, quality string) (*Ext
 		})()
 	`, trackID, quality)
 
-	result, err := p.vm.RunString(script)
+	result, err := RunWithTimeoutAndRecover(p.vm, script, DefaultJSTimeout)
 	if err != nil {
+		if IsTimeoutError(err) {
+			return nil, fmt.Errorf("getDownloadUrl timeout: extension took too long to respond")
+		}
 		return nil, fmt.Errorf("getDownloadUrl failed: %w", err)
 	}
 
@@ -387,6 +484,9 @@ func (p *ExtensionProviderWrapper) GetDownloadURL(trackID, quality string) (*Ext
 	return &urlResult, nil
 }
 
+// ExtDownloadTimeout is longer for extension download operations (5 minutes)
+const ExtDownloadTimeout = 5 * time.Minute
+
 // Download downloads a track with progress reporting
 func (p *ExtensionProviderWrapper) Download(trackID, quality, outputPath string, onProgress func(percent int)) (*ExtDownloadResult, error) {
 	if !p.extension.Manifest.IsDownloadProvider() {
@@ -424,12 +524,19 @@ func (p *ExtensionProviderWrapper) Download(trackID, quality, outputPath string,
 		})()
 	`, trackID, quality, outputPath)
 
-	result, err := p.vm.RunString(script)
+	// Use longer timeout for downloads (5 minutes)
+	result, err := RunWithTimeoutAndRecover(p.vm, script, ExtDownloadTimeout)
 	if err != nil {
+		errMsg := err.Error()
+		errType := "script_error"
+		if IsTimeoutError(err) {
+			errMsg = "download timeout: extension took too long to complete"
+			errType = "timeout"
+		}
 		return &ExtDownloadResult{
 			Success:      false,
-			ErrorMessage: err.Error(),
-			ErrorType:    "script_error",
+			ErrorMessage: errMsg,
+			ErrorType:    errType,
 		}, nil
 	}
 
@@ -595,6 +702,45 @@ func DownloadWithExtensionFallback(req DownloadRequest) (*DownloadResponse, erro
 	var lastErr error
 	var skipBuiltIn bool // If source extension has skipBuiltInFallback, don't try built-in providers
 
+	// LAZY ENRICHMENT: If track came from an extension, try to enrich metadata (e.g., get real ISRC)
+	// This is done lazily at download time, not when playlist/album is loaded
+	if req.Source != "" && !isBuiltInProvider(req.Source) {
+		ext, err := extManager.GetExtension(req.Source)
+		if err == nil && ext.Enabled && ext.Error == "" && ext.Manifest.IsMetadataProvider() {
+			GoLog("[DownloadWithExtensionFallback] Enriching track from extension '%s'...\n", req.Source)
+
+			provider := NewExtensionProviderWrapper(ext)
+			trackMeta := &ExtTrackMetadata{
+				ID:          req.SpotifyID,
+				Name:        req.TrackName,
+				Artists:     req.ArtistName,
+				AlbumName:   req.AlbumName,
+				DurationMS:  req.DurationMS,
+				ISRC:        req.ISRC,
+				ReleaseDate: req.ReleaseDate,
+				TrackNumber: req.TrackNumber,
+				DiscNumber:  req.DiscNumber,
+				ProviderID:  req.Source,
+			}
+
+			enrichedTrack, err := provider.EnrichTrack(trackMeta)
+			if err == nil && enrichedTrack != nil {
+				// Update request with enriched data
+				if enrichedTrack.ISRC != "" && enrichedTrack.ISRC != req.ISRC {
+					GoLog("[DownloadWithExtensionFallback] ISRC enriched: %s -> %s\n", req.ISRC, enrichedTrack.ISRC)
+					req.ISRC = enrichedTrack.ISRC
+				}
+				// Can also update other fields if needed
+				if enrichedTrack.Name != "" {
+					req.TrackName = enrichedTrack.Name
+				}
+				if enrichedTrack.Artists != "" {
+					req.ArtistName = enrichedTrack.Artists
+				}
+			}
+		}
+	}
+
 	// If source extension is specified, try it first before the priority list
 	if req.Source != "" && !isBuiltInProvider(req.Source) {
 		GoLog("[DownloadWithExtensionFallback] Track source is extension '%s', trying it first\n", req.Source)
@@ -947,8 +1093,11 @@ func (p *ExtensionProviderWrapper) CustomSearch(query string, options map[string
 		})()
 	`, query, string(optionsJSON))
 
-	result, err := p.vm.RunString(script)
+	result, err := RunWithTimeoutAndRecover(p.vm, script, DefaultJSTimeout)
 	if err != nil {
+		if IsTimeoutError(err) {
+			return nil, fmt.Errorf("customSearch timeout: extension took too long to respond")
+		}
 		return nil, fmt.Errorf("customSearch failed: %w", err)
 	}
 
@@ -981,6 +1130,72 @@ func (p *ExtensionProviderWrapper) CustomSearch(query string, options map[string
 	return tracks, nil
 }
 
+// ==================== Custom URL Handler ====================
+
+// ExtURLHandleResult represents the result of URL handling
+type ExtURLHandleResult struct {
+	Type     string             `json:"type"`                // "track", "album", "playlist", "artist"
+	Track    *ExtTrackMetadata  `json:"track,omitempty"`     // For single track
+	Tracks   []ExtTrackMetadata `json:"tracks,omitempty"`    // For album/playlist
+	Album    *ExtAlbumMetadata  `json:"album,omitempty"`     // Album info
+	Artist   *ExtArtistMetadata `json:"artist,omitempty"`    // Artist info
+	Name     string             `json:"name,omitempty"`      // Playlist/album name
+	CoverURL string             `json:"cover_url,omitempty"` // Cover image
+}
+
+// HandleURL processes a URL using the extension's URL handler
+func (p *ExtensionProviderWrapper) HandleURL(url string) (*ExtURLHandleResult, error) {
+	if !p.extension.Manifest.HasURLHandler() {
+		return nil, fmt.Errorf("extension '%s' does not support URL handling", p.extension.ID)
+	}
+
+	if !p.extension.Enabled {
+		return nil, fmt.Errorf("extension '%s' is disabled", p.extension.ID)
+	}
+
+	script := fmt.Sprintf(`
+		(function() {
+			if (typeof extension !== 'undefined' && typeof extension.handleUrl === 'function') {
+				return extension.handleUrl(%q);
+			}
+			return null;
+		})()
+	`, url)
+
+	result, err := RunWithTimeoutAndRecover(p.vm, script, DefaultJSTimeout)
+	if err != nil {
+		if IsTimeoutError(err) {
+			return nil, fmt.Errorf("handleUrl timeout: extension took too long to respond")
+		}
+		return nil, fmt.Errorf("handleUrl failed: %w", err)
+	}
+
+	if result == nil || goja.IsUndefined(result) || goja.IsNull(result) {
+		return nil, fmt.Errorf("handleUrl returned null - URL not recognized")
+	}
+
+	exported := result.Export()
+	jsonBytes, err := json.Marshal(exported)
+	if err != nil {
+		return nil, fmt.Errorf("failed to marshal result: %w", err)
+	}
+
+	var handleResult ExtURLHandleResult
+	if err := json.Unmarshal(jsonBytes, &handleResult); err != nil {
+		return nil, fmt.Errorf("failed to parse URL handle result: %w", err)
+	}
+
+	// Set provider ID on tracks
+	if handleResult.Track != nil {
+		handleResult.Track.ProviderID = p.extension.ID
+	}
+	for i := range handleResult.Tracks {
+		handleResult.Tracks[i].ProviderID = p.extension.ID
+	}
+
+	return &handleResult, nil
+}
+
 // ==================== Custom Track Matching ====================
 
 // MatchTrackResult represents the result of custom track matching
@@ -1013,8 +1228,11 @@ func (p *ExtensionProviderWrapper) MatchTrack(sourceTrack map[string]interface{}
 		})()
 	`, string(sourceJSON), string(candidatesJSON))
 
-	result, err := p.vm.RunString(script)
+	result, err := RunWithTimeoutAndRecover(p.vm, script, DefaultJSTimeout)
 	if err != nil {
+		if IsTimeoutError(err) {
+			return nil, fmt.Errorf("matchTrack timeout: extension took too long to respond")
+		}
 		return nil, fmt.Errorf("matchTrack failed: %w", err)
 	}
 
@@ -1048,6 +1266,9 @@ type PostProcessResult struct {
 	SampleRate int `json:"sample_rate,omitempty"`
 }
 
+// PostProcessTimeout is longer for post-processing (2 minutes)
+const PostProcessTimeout = 2 * time.Minute
+
 // PostProcess runs post-processing hooks on a downloaded file
 func (p *ExtensionProviderWrapper) PostProcess(filePath string, metadata map[string]interface{}, hookID string) (*PostProcessResult, error) {
 	if !p.extension.Manifest.HasPostProcessing() {
@@ -1069,11 +1290,15 @@ func (p *ExtensionProviderWrapper) PostProcess(filePath string, metadata map[str
 		})()
 	`, filePath, string(metadataJSON), hookID)
 
-	result, err := p.vm.RunString(script)
+	result, err := RunWithTimeoutAndRecover(p.vm, script, PostProcessTimeout)
 	if err != nil {
+		errMsg := err.Error()
+		if IsTimeoutError(err) {
+			errMsg = "postProcess timeout: extension took too long to complete"
+		}
 		return &PostProcessResult{
 			Success: false,
-			Error:   err.Error(),
+			Error:   errMsg,
 		}, nil
 	}
 
@@ -1120,6 +1345,61 @@ func (m *ExtensionManager) GetSearchProviders() []*ExtensionProviderWrapper {
 	return providers
 }
 
+// GetURLHandlers returns all extensions that handle custom URLs
+func (m *ExtensionManager) GetURLHandlers() []*ExtensionProviderWrapper {
+	m.mu.RLock()
+	defer m.mu.RUnlock()
+
+	var providers []*ExtensionProviderWrapper
+	for _, ext := range m.extensions {
+		if ext.Enabled && ext.Manifest.HasURLHandler() && ext.Error == "" {
+			providers = append(providers, NewExtensionProviderWrapper(ext))
+		}
+	}
+	return providers
+}
+
+// FindURLHandler finds an extension that can handle the given URL
+func (m *ExtensionManager) FindURLHandler(url string) *ExtensionProviderWrapper {
+	m.mu.RLock()
+	defer m.mu.RUnlock()
+
+	for _, ext := range m.extensions {
+		if ext.Enabled && ext.Manifest.MatchesURL(url) && ext.Error == "" {
+			return NewExtensionProviderWrapper(ext)
+		}
+	}
+	return nil
+}
+
+// ExtURLHandleResultWithExtID wraps ExtURLHandleResult with extension ID for gomobile compatibility
+type ExtURLHandleResultWithExtID struct {
+	Result      *ExtURLHandleResult
+	ExtensionID string
+}
+
+// HandleURLWithExtension tries to handle a URL with any matching extension
+// Returns result with extension ID, or error if no handler found
+func (m *ExtensionManager) HandleURLWithExtension(url string) (*ExtURLHandleResultWithExtID, error) {
+	handler := m.FindURLHandler(url)
+	if handler == nil {
+		return nil, fmt.Errorf("no extension found to handle URL: %s", url)
+	}
+
+	result, err := handler.HandleURL(url)
+	if err != nil {
+		return &ExtURLHandleResultWithExtID{
+			Result:      nil,
+			ExtensionID: handler.extension.ID,
+		}, err
+	}
+
+	return &ExtURLHandleResultWithExtID{
+		Result:      result,
+		ExtensionID: handler.extension.ID,
+	}, nil
+}
+
 // GetPostProcessingProviders returns all extensions that provide post-processing
 func (m *ExtensionManager) GetPostProcessingProviders() []*ExtensionProviderWrapper {
 	m.mu.RLock()

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 +1,523 @@
+// Package gobackend provides File API for extension runtime
+package gobackend
+
+import (
+	"fmt"
+	"io"
+	"net/http"
+	"os"
+	"path/filepath"
+	"strings"
+	"sync"
+
+	"github.com/dop251/goja"
+)
+
+// ==================== File API (Sandboxed) ====================
+
+// List of allowed directories for file operations (set by Go backend for download operations)
+var (
+	allowedDownloadDirs   []string
+	allowedDownloadDirsMu sync.RWMutex
+)
+
+// SetAllowedDownloadDirs sets the list of directories where extensions can write files
+// This should be called by the Go backend when setting up download paths
+func SetAllowedDownloadDirs(dirs []string) {
+	allowedDownloadDirsMu.Lock()
+	defer allowedDownloadDirsMu.Unlock()
+	allowedDownloadDirs = dirs
+	GoLog("[Extension] Allowed download directories set: %v\n", dirs)
+}
+
+// AddAllowedDownloadDir adds a directory to the allowed list
+func AddAllowedDownloadDir(dir string) {
+	allowedDownloadDirsMu.Lock()
+	defer allowedDownloadDirsMu.Unlock()
+	absDir, err := filepath.Abs(dir)
+	if err == nil {
+		allowedDownloadDirs = append(allowedDownloadDirs, absDir)
+	}
+}
+
+// isPathInAllowedDirs checks if an absolute path is within any allowed directory
+func isPathInAllowedDirs(absPath string) bool {
+	allowedDownloadDirsMu.RLock()
+	defer allowedDownloadDirsMu.RUnlock()
+
+	for _, allowedDir := range allowedDownloadDirs {
+		if strings.HasPrefix(absPath, allowedDir) {
+			return true
+		}
+	}
+	return false
+}
+
+// validatePath checks if the path is within the extension's sandbox
+// Security: Absolute paths are BLOCKED unless they're in allowed download directories
+// Extensions should use relative paths for their own data storage
+func (r *ExtensionRuntime) validatePath(path string) (string, error) {
+	// Check if extension has file permission
+	if !r.manifest.Permissions.File {
+		return "", fmt.Errorf("file access denied: extension does not have 'file' permission")
+	}
+
+	// Clean and resolve the path
+	cleanPath := filepath.Clean(path)
+
+	// SECURITY: Block absolute paths by default
+	// Only allow if path is in explicitly allowed download directories
+	if filepath.IsAbs(cleanPath) {
+		absPath, err := filepath.Abs(cleanPath)
+		if err != nil {
+			return "", fmt.Errorf("invalid path: %w", err)
+		}
+
+		// Check if path is in allowed download directories
+		if isPathInAllowedDirs(absPath) {
+			return absPath, nil
+		}
+
+		// Block all other absolute paths
+		return "", fmt.Errorf("file access denied: absolute paths are not allowed. Use relative paths within extension sandbox")
+	}
+
+	// For relative paths, join with data directory (extension's sandbox)
+	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 (prevent path traversal)
+	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 +1,505 @@
+// 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()
+
+	// Block private/local network access (SSRF protection)
+	if isPrivateIP(domain) {
+		return fmt.Errorf("network access denied: private/local network '%s' not allowed", domain)
+	}
+
+	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 +1,381 @@
+// 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")
+}
+
+// getSaltPath returns the path to the extension's encryption salt file
+func (r *ExtensionRuntime) getSaltPath() string {
+	return filepath.Join(r.dataDir, ".cred_salt")
+}
+
+// getOrCreateSalt gets existing salt or creates a new random one
+func (r *ExtensionRuntime) getOrCreateSalt() ([]byte, error) {
+	saltPath := r.getSaltPath()
+
+	// Try to read existing salt
+	salt, err := os.ReadFile(saltPath)
+	if err == nil && len(salt) == 32 {
+		return salt, nil
+	}
+
+	// Generate new random salt (32 bytes)
+	salt = make([]byte, 32)
+	if _, err := io.ReadFull(rand.Reader, salt); err != nil {
+		return nil, fmt.Errorf("failed to generate salt: %w", err)
+	}
+
+	// Save salt to file
+	if err := os.WriteFile(saltPath, salt, 0600); err != nil {
+		return nil, fmt.Errorf("failed to save salt: %w", err)
+	}
+
+	return salt, nil
+}
+
+// getEncryptionKey derives an encryption key from extension ID + random salt
+func (r *ExtensionRuntime) getEncryptionKey() ([]byte, error) {
+	// Get or create per-installation random salt
+	salt, err := r.getOrCreateSalt()
+	if err != nil {
+		return nil, err
+	}
+
+	// Combine extension ID + random salt for key derivation
+	// This makes each installation unique, preventing mass decryption attacks
+	combined := append([]byte(r.extensionID), salt...)
+	hash := sha256.Sum256(combined)
+	return hash[:], nil
+}
+
+// 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, err := r.getEncryptionKey()
+	if err != nil {
+		return nil, fmt.Errorf("failed to get encryption key: %w", err)
+	}
+	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, err := r.getEncryptionKey()
+	if err != nil {
+		return fmt.Errorf("failed to get encryption key: %w", err)
+	}
+	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_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

@@ -1,6 +1,7 @@
 package gobackend
 
 import (
+	"path/filepath"
 	"testing"
 
 	"github.com/dop251/goja"
@@ -137,6 +138,9 @@ func TestExtensionRuntime_FileSandbox(t *testing.T) {
 		ID: "test-ext",
 		Manifest: &ExtensionManifest{
 			Name: "test-ext",
+			Permissions: ExtensionPermissions{
+				File: true, // Enable file permission for test
+			},
 		},
 		DataDir: tempDir,
 	}
@@ -166,6 +170,36 @@ func TestExtensionRuntime_FileSandbox(t *testing.T) {
 	if nestedPath == "" {
 		t.Error("Expected non-empty nested path")
 	}
+
+	// Test absolute path should be blocked (security fix)
+	// Use platform-appropriate absolute path
+	var absPath string
+	if filepath.IsAbs("C:\\Windows\\System32") {
+		absPath = "C:\\Windows\\System32\\test.txt" // Windows
+	} else {
+		absPath = "/etc/passwd" // Unix
+	}
+	_, err = runtime.validatePath(absPath)
+	if err == nil {
+		t.Error("Expected absolute path to be blocked")
+	}
+
+	// Test that extension without file permission is blocked
+	extNoFile := &LoadedExtension{
+		ID: "test-ext-no-file",
+		Manifest: &ExtensionManifest{
+			Name: "test-ext-no-file",
+			Permissions: ExtensionPermissions{
+				File: false, // No file permission
+			},
+		},
+		DataDir: tempDir,
+	}
+	runtimeNoFile := NewExtensionRuntime(extNoFile)
+	_, err = runtimeNoFile.validatePath("test.txt")
+	if err == nil {
+		t.Error("Expected file access to be denied without file permission")
+	}
 }
 
 func TestExtensionRuntime_UtilityFunctions(t *testing.T) {
@@ -217,3 +251,79 @@ func TestExtensionRuntime_UtilityFunctions(t *testing.T) {
 		t.Error("Expected non-empty JSON string")
 	}
 }
+
+func TestExtensionRuntime_SSRFProtection(t *testing.T) {
+	// Create extension with limited network permissions
+	ext := &LoadedExtension{
+		ID: "test-ext",
+		Manifest: &ExtensionManifest{
+			Name: "test-ext",
+			Permissions: ExtensionPermissions{
+				Network: []string{"api.example.com"},
+			},
+		},
+		DataDir: t.TempDir(),
+	}
+
+	runtime := NewExtensionRuntime(ext)
+
+	// Test that private IPs are blocked (SSRF protection)
+	privateIPs := []string{
+		"http://localhost/admin",
+		"http://127.0.0.1/admin",
+		"http://192.168.1.1/admin",
+		"http://10.0.0.1/admin",
+		"http://172.16.0.1/admin",
+		"http://169.254.169.254/latest/meta-data/", // AWS metadata
+		"http://router.local/admin",
+	}
+
+	for _, url := range privateIPs {
+		err := runtime.validateDomain(url)
+		if err == nil {
+			t.Errorf("Expected private IP/host '%s' to be blocked", url)
+		}
+	}
+
+	// Test that allowed public domain still works
+	if err := runtime.validateDomain("https://api.example.com/path"); err != nil {
+		t.Errorf("Expected api.example.com to be allowed, got error: %v", err)
+	}
+}
+
+func TestIsPrivateIP(t *testing.T) {
+	tests := []struct {
+		host     string
+		expected bool
+	}{
+		// Private IPs should be blocked
+		{"localhost", true},
+		{"127.0.0.1", true},
+		{"127.0.0.2", true},
+		{"10.0.0.1", true},
+		{"10.255.255.255", true},
+		{"172.16.0.1", true},
+		{"172.31.255.255", true},
+		{"192.168.0.1", true},
+		{"192.168.255.255", true},
+		{"169.254.169.254", true}, // AWS metadata
+		{"router.local", true},
+		{"mydevice.local", true},
+
+		// Public IPs should be allowed
+		{"8.8.8.8", false},
+		{"1.1.1.1", false},
+		{"api.example.com", false},
+		{"google.com", false},
+		{"172.15.0.1", false},  // Just outside 172.16-31 range
+		{"172.32.0.1", false},  // Just outside 172.16-31 range
+		{"192.167.0.1", false}, // Not 192.168.x.x
+	}
+
+	for _, tt := range tests {
+		result := isPrivateIP(tt.host)
+		if result != tt.expected {
+			t.Errorf("isPrivateIP(%s) = %v, expected %v", tt.host, result, tt.expected)
+		}
+	}
+}

go_backend/extension_timeout.go

@@ -0,0 +1,118 @@
+// Package gobackend provides timeout execution for extension JS code
+package gobackend
+
+import (
+	"context"
+	"fmt"
+	"sync"
+	"time"
+
+	"github.com/dop251/goja"
+)
+
+// JSExecutionError represents an error during JS execution
+type JSExecutionError struct {
+	Message   string
+	IsTimeout bool
+}
+
+func (e *JSExecutionError) Error() string {
+	return e.Message
+}
+
+// RunWithTimeout executes JavaScript code with a timeout
+// Returns the result value and any error (including timeout)
+func RunWithTimeout(vm *goja.Runtime, script string, timeout time.Duration) (goja.Value, error) {
+	if timeout <= 0 {
+		timeout = DefaultJSTimeout
+	}
+
+	ctx, cancel := context.WithTimeout(context.Background(), timeout)
+	defer cancel()
+
+	// Channel to receive result
+	type result struct {
+		value goja.Value
+		err   error
+	}
+	resultCh := make(chan result, 1)
+
+	// Track if we've interrupted
+	var interrupted bool
+	var interruptMu sync.Mutex
+
+	// Run script in goroutine
+	go func() {
+		defer func() {
+			if r := recover(); r != nil {
+				// Check if this was our interrupt
+				interruptMu.Lock()
+				wasInterrupted := interrupted
+				interruptMu.Unlock()
+
+				if wasInterrupted {
+					resultCh <- result{nil, &JSExecutionError{
+						Message:   "execution timeout exceeded",
+						IsTimeout: true,
+					}}
+				} else {
+					resultCh <- result{nil, fmt.Errorf("panic during execution: %v", r)}
+				}
+			}
+		}()
+
+		val, err := vm.RunString(script)
+		resultCh <- result{val, err}
+	}()
+
+	// Wait for result or timeout
+	select {
+	case res := <-resultCh:
+		return res.value, res.err
+	case <-ctx.Done():
+		// Timeout - interrupt the VM
+		interruptMu.Lock()
+		interrupted = true
+		interruptMu.Unlock()
+
+		vm.Interrupt("execution timeout")
+
+		// Wait a bit for the goroutine to finish
+		select {
+		case res := <-resultCh:
+			// If we got a result after interrupt, it might be the timeout error
+			if res.err != nil {
+				return nil, res.err
+			}
+			return nil, &JSExecutionError{
+				Message:   "execution timeout exceeded",
+				IsTimeout: true,
+			}
+		case <-time.After(1 * time.Second):
+			// Force return timeout error
+			return nil, &JSExecutionError{
+				Message:   "execution timeout exceeded (force)",
+				IsTimeout: true,
+			}
+		}
+	}
+}
+
+// RunWithTimeoutAndRecover runs JS with timeout and clears interrupt state after
+// This should be used when you want to continue using the VM after a timeout
+func RunWithTimeoutAndRecover(vm *goja.Runtime, script string, timeout time.Duration) (goja.Value, error) {
+	result, err := RunWithTimeout(vm, script, timeout)
+
+	// Clear any interrupt state so VM can be reused
+	vm.ClearInterrupt()
+
+	return result, err
+}
+
+// IsTimeoutError checks if an error is a timeout error
+func IsTimeoutError(err error) bool {
+	if jsErr, ok := err.(*JSExecutionError); ok {
+		return jsErr.IsTimeout
+	}
+	return false
+}

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/metadata.go

@@ -498,7 +498,7 @@ func EmbedM4AMetadata(filePath string, metadata Metadata, coverData []byte) erro
 	}
 
 	// Find udta atom inside moov, or create one
-	moovSize := int(data[moovPos]<<24 | data[moovPos+1]<<16 | data[moovPos+2]<<8 | data[moovPos+3])
+	moovSize := int(uint32(data[moovPos])<<24 | uint32(data[moovPos+1])<<16 | uint32(data[moovPos+2])<<8 | uint32(data[moovPos+3]))
 	udtaPos := findAtom(data, "udta", moovPos+8)
 
 	// Build new metadata atoms
@@ -507,12 +507,12 @@ func EmbedM4AMetadata(filePath string, metadata Metadata, coverData []byte) erro
 	var newData []byte
 	if udtaPos >= 0 && udtaPos < moovPos+moovSize {
 		// udta exists, find meta inside it or replace
-		udtaSize := int(data[udtaPos]<<24 | data[udtaPos+1]<<16 | data[udtaPos+2]<<8 | data[udtaPos+3])
+		udtaSize := int(uint32(data[udtaPos])<<24 | uint32(data[udtaPos+1])<<16 | uint32(data[udtaPos+2])<<8 | uint32(data[udtaPos+3]))
 		metaPos := findAtom(data, "meta", udtaPos+8)
 
 		if metaPos >= 0 && metaPos < udtaPos+udtaSize {
 			// Replace existing meta atom
-			metaSize := int(data[metaPos]<<24 | data[metaPos+1]<<16 | data[metaPos+2]<<8 | data[metaPos+3])
+			metaSize := int(uint32(data[metaPos])<<24 | uint32(data[metaPos+1])<<16 | uint32(data[metaPos+2])<<8 | uint32(data[metaPos+3]))
 			newData = append(newData, data[:metaPos]...)
 			newData = append(newData, metaAtom...)
 			newData = append(newData, data[metaPos+metaSize:]...)
@@ -570,7 +570,7 @@ func EmbedM4AMetadata(filePath string, metadata Metadata, coverData []byte) erro
 // findAtom finds an atom by name starting from offset
 func findAtom(data []byte, name string, offset int) int {
 	for i := offset; i < len(data)-8; {
-		size := int(data[i]<<24 | data[i+1]<<16 | data[i+2]<<8 | data[i+3])
+		size := int(uint32(data[i])<<24 | uint32(data[i+1])<<16 | uint32(data[i+2])<<8 | uint32(data[i+3]))
 		if size < 8 {
 			break
 		}

go_backend/qobuz.go

@@ -64,24 +64,27 @@ func qobuzArtistsMatch(expectedArtist, foundArtist string) bool {
 		return true
 	}
 
-	// Check first artist (before comma or feat)
-	expectedFirst := strings.Split(normExpected, ",")[0]
-	expectedFirst = strings.Split(expectedFirst, " feat")[0]
-	expectedFirst = strings.Split(expectedFirst, " ft.")[0]
-	expectedFirst = strings.TrimSpace(expectedFirst)
+	// Split expected artists by common separators (comma, feat, ft., &, and)
+	// e.g., "RADWIMPS, Toko Miura" or "RADWIMPS feat. Toko Miura"
+	expectedArtists := qobuzSplitArtists(normExpected)
+	foundArtists := qobuzSplitArtists(normFound)
 
-	foundFirst := strings.Split(normFound, ",")[0]
-	foundFirst = strings.Split(foundFirst, " feat")[0]
-	foundFirst = strings.Split(foundFirst, " ft.")[0]
-	foundFirst = strings.TrimSpace(foundFirst)
-
-	if expectedFirst == foundFirst {
-		return true
-	}
-
-	// Check if first artist is contained in the other
-	if strings.Contains(expectedFirst, foundFirst) || strings.Contains(foundFirst, expectedFirst) {
-		return true
+	// Check if ANY expected artist matches ANY found artist
+	for _, exp := range expectedArtists {
+		for _, fnd := range foundArtists {
+			if exp == fnd {
+				return true
+			}
+			// Also check contains for partial matches
+			if strings.Contains(exp, fnd) || strings.Contains(fnd, exp) {
+				return true
+			}
+			// Check same words different order
+			if qobuzSameWordsUnordered(exp, fnd) {
+				GoLog("[Qobuz] Artist names have same words in different order: '%s' vs '%s'\n", exp, fnd)
+				return true
+			}
+		}
 	}
 
 	// If scripts are TRULY different (Latin vs CJK/Arabic/Cyrillic), assume match (transliteration)
@@ -96,6 +99,67 @@ func qobuzArtistsMatch(expectedArtist, foundArtist string) bool {
 	return false
 }
 
+// qobuzSplitArtists splits artist string by common separators
+func qobuzSplitArtists(artists string) []string {
+	// Replace common separators with a standard one
+	normalized := artists
+	normalized = strings.ReplaceAll(normalized, " feat. ", "|")
+	normalized = strings.ReplaceAll(normalized, " feat ", "|")
+	normalized = strings.ReplaceAll(normalized, " ft. ", "|")
+	normalized = strings.ReplaceAll(normalized, " ft ", "|")
+	normalized = strings.ReplaceAll(normalized, " & ", "|")
+	normalized = strings.ReplaceAll(normalized, " and ", "|")
+	normalized = strings.ReplaceAll(normalized, ", ", "|")
+	normalized = strings.ReplaceAll(normalized, " x ", "|")
+
+	parts := strings.Split(normalized, "|")
+	result := make([]string, 0, len(parts))
+	for _, p := range parts {
+		trimmed := strings.TrimSpace(p)
+		if trimmed != "" {
+			result = append(result, trimmed)
+		}
+	}
+	return result
+}
+
+// qobuzSameWordsUnordered checks if two strings have the same words regardless of order
+// Useful for Japanese names: "Sawano Hiroyuki" vs "Hiroyuki Sawano"
+func qobuzSameWordsUnordered(a, b string) bool {
+	wordsA := strings.Fields(a)
+	wordsB := strings.Fields(b)
+
+	// Must have same number of words
+	if len(wordsA) != len(wordsB) || len(wordsA) == 0 {
+		return false
+	}
+
+	// Sort and compare
+	sortedA := make([]string, len(wordsA))
+	sortedB := make([]string, len(wordsB))
+	copy(sortedA, wordsA)
+	copy(sortedB, wordsB)
+
+	// Simple bubble sort (usually just 2-3 words)
+	for i := 0; i < len(sortedA)-1; i++ {
+		for j := i + 1; j < len(sortedA); j++ {
+			if sortedA[i] > sortedA[j] {
+				sortedA[i], sortedA[j] = sortedA[j], sortedA[i]
+			}
+			if sortedB[i] > sortedB[j] {
+				sortedB[i], sortedB[j] = sortedB[j], sortedB[i]
+			}
+		}
+	}
+
+	for i := range sortedA {
+		if sortedA[i] != sortedB[i] {
+			return false
+		}
+	}
+	return true
+}
+
 // qobuzTitlesMatch checks if track titles are similar enough
 func qobuzTitlesMatch(expectedTitle, foundTitle string) bool {
 	normExpected := strings.ToLower(strings.TrimSpace(expectedTitle))
@@ -702,7 +766,7 @@ func getQobuzDownloadURLParallel(apis []string, trackID int64, quality string) (
 				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)}
+				resultChan <- qobuzAPIResult{apiURL: api, err: fmt.Errorf("%s", errorResp.Error), duration: time.Since(reqStart)}
 				return
 			}
 
@@ -725,12 +789,10 @@ func getQobuzDownloadURLParallel(apis []string, trackID int64, quality string) (
 
 	// 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
+		if result.err == nil {
 			GoLog("[Qobuz] [Parallel] ✓ Got response from %s in %v\n", result.apiURL, result.duration)
 
 			// Drain remaining results to avoid goroutine leaks
@@ -741,91 +803,19 @@ func getQobuzDownloadURLParallel(apis []string, trackID int64, quality string) (
 			}(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))
+			return result.apiURL, result.downloadURL, 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) {
-	if len(apis) == 0 {
-		return "", "", fmt.Errorf("no APIs available")
-	}
-
-	client := NewHTTPClientWithTimeout(DefaultTimeout)
-	retryConfig := DefaultRetryConfig()
-	var errors []string
-
-	for _, apiURL := range apis {
-		// All APIs now use same format: https://domain/api/stream?trackId={id}&quality={quality}
-		// The apiURL already includes the path, just append trackID and quality
-		reqURL := fmt.Sprintf("%s%d&quality=%s", apiURL, trackID, quality)
-
-		GoLog("[Qobuz] Trying: %s\n", reqURL)
-
-		req, err := http.NewRequest("GET", reqURL, nil)
-		if err != nil {
-			errors = append(errors, BuildErrorMessage(apiURL, 0, err.Error()))
-			continue
-		}
-
-		resp, err := DoRequestWithRetry(client, req, retryConfig)
-		if err != nil {
-			errors = append(errors, BuildErrorMessage(apiURL, 0, err.Error()))
-			continue
-		}
-
-		body, err := ReadResponseBody(resp)
-		resp.Body.Close()
-		if err != nil {
-			errors = append(errors, BuildErrorMessage(apiURL, resp.StatusCode, err.Error()))
-			continue
-		}
-
-		// Check if response is HTML (error page)
-		if len(body) > 0 && body[0] == '<' {
-			errors = append(errors, BuildErrorMessage(apiURL, resp.StatusCode, "received HTML instead of JSON"))
-			continue
-		}
-
-		// Check for error in JSON response
-		var errorResp struct {
-			Error string `json:"error"`
-		}
-		if json.Unmarshal(body, &errorResp) == nil && errorResp.Error != "" {
-			errors = append(errors, BuildErrorMessage(apiURL, resp.StatusCode, errorResp.Error))
-			continue
-		}
-
-		var result struct {
-			URL string `json:"url"`
-		}
-		if err := json.Unmarshal(body, &result); err != nil {
-			errors = append(errors, BuildErrorMessage(apiURL, resp.StatusCode, "invalid JSON: "+err.Error()))
-			continue
-		}
-
-		if result.URL != "" {
-			GoLog("[Qobuz] Got download URL from: %s\n", apiURL)
-			return apiURL, result.URL, nil
-		}
-
-		errors = append(errors, BuildErrorMessage(apiURL, resp.StatusCode, "no download URL in response"))
-	}
-
-	return "", "", fmt.Errorf("all %d Qobuz APIs failed. Errors: %v", len(apis), errors)
-}
-
 // 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) {

go_backend/tidal.go

@@ -738,13 +738,11 @@ func getDownloadURLParallel(apis []string, trackID int64, quality string) (strin
 
 	// Collect results - return first success
 	var errors []string
-	var firstSuccess *tidalAPIResult
 
 	for i := 0; i < len(apis); i++ {
 		result := <-resultChan
-		if result.err == nil && firstSuccess == nil {
+		if result.err == 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)
 
@@ -756,109 +754,19 @@ func getDownloadURLParallel(apis []string, trackID int64, quality string) (strin
 			}(len(apis) - i - 1)
 
 			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))
+			return result.apiURL, result.info, 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] All %d APIs failed in %v\n", len(apis), time.Since(startTime))
 	return "", TidalDownloadInfo{}, fmt.Errorf("all %d Tidal APIs failed. Errors: %v", len(apis), errors)
 }
 
-// getDownloadURLSequential requests download URL from APIs sequentially (fallback)
-// Returns the first successful result (supports both v1 and v2 API formats)
-func getDownloadURLSequential(apis []string, trackID int64, quality string) (string, TidalDownloadInfo, error) {
-	if len(apis) == 0 {
-		return "", TidalDownloadInfo{}, fmt.Errorf("no APIs available")
-	}
-
-	client := NewHTTPClientWithTimeout(DefaultTimeout)
-	retryConfig := DefaultRetryConfig()
-	var errors []string
-
-	for _, apiURL := range apis {
-		reqURL := fmt.Sprintf("%s/track/?id=%d&quality=%s", apiURL, trackID, quality)
-		GoLog("[Tidal] Trying API: %s\n", reqURL)
-
-		req, err := http.NewRequest("GET", reqURL, nil)
-		if err != nil {
-			errors = append(errors, BuildErrorMessage(apiURL, 0, err.Error()))
-			continue
-		}
-
-		resp, err := DoRequestWithRetry(client, req, retryConfig)
-		if err != nil {
-			GoLog("[Tidal] API error: %v\n", err)
-			errors = append(errors, BuildErrorMessage(apiURL, 0, err.Error()))
-			continue
-		}
-
-		body, err := ReadResponseBody(resp)
-		resp.Body.Close()
-		if err != nil {
-			GoLog("[Tidal] Read body error: %v\n", err)
-			errors = append(errors, BuildErrorMessage(apiURL, resp.StatusCode, err.Error()))
-			continue
-		}
-
-		// Log response preview
-		bodyPreview := string(body)
-		if len(bodyPreview) > 300 {
-			bodyPreview = bodyPreview[:300] + "..."
-		}
-		GoLog("[Tidal] API response (HTTP %d): %s\n", resp.StatusCode, bodyPreview)
-
-		// Try v2 format first (object with manifest)
-		var v2Response TidalAPIResponseV2
-		if err := json.Unmarshal(body, &v2Response); err == nil && v2Response.Data.Manifest != "" {
-			GoLog("[Tidal] Got v2 response from %s - Quality: %d-bit/%dHz, AssetPresentation: %s\n",
-				apiURL, v2Response.Data.BitDepth, v2Response.Data.SampleRate, v2Response.Data.AssetPresentation)
-
-			// IMPORTANT: Reject PREVIEW responses - we need FULL tracks
-			if v2Response.Data.AssetPresentation == "PREVIEW" {
-				GoLog("[Tidal] ✗ Rejecting PREVIEW response from %s, trying next API...\n", apiURL)
-				errors = append(errors, BuildErrorMessage(apiURL, resp.StatusCode, "returned PREVIEW instead of FULL"))
-				continue
-			}
-
-			GoLog("[Tidal] ✓ Got FULL track from %s\n", apiURL)
-			info := TidalDownloadInfo{
-				URL:        "MANIFEST:" + v2Response.Data.Manifest,
-				BitDepth:   v2Response.Data.BitDepth,
-				SampleRate: v2Response.Data.SampleRate,
-			}
-			return apiURL, info, nil
-		}
-
-		// Fallback to v1 format (array with OriginalTrackUrl)
-		var v1Responses []struct {
-			OriginalTrackURL string `json:"OriginalTrackUrl"`
-		}
-		if err := json.Unmarshal(body, &v1Responses); err == nil {
-			for _, item := range v1Responses {
-				if item.OriginalTrackURL != "" {
-					// v1 format doesn't have quality info, assume 16-bit/44.1kHz
-					info := TidalDownloadInfo{
-						URL:        item.OriginalTrackURL,
-						BitDepth:   16,
-						SampleRate: 44100,
-					}
-					return apiURL, info, nil
-				}
-			}
-		}
-
-		errors = append(errors, BuildErrorMessage(apiURL, resp.StatusCode, "no download URL or manifest in response"))
-	}
-
-	return "", TidalDownloadInfo{}, fmt.Errorf("all %d Tidal APIs failed. Errors: %v", len(apis), errors)
-}
-
 // 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) {
@@ -1253,24 +1161,27 @@ func artistsMatch(spotifyArtist, tidalArtist string) bool {
 		return true
 	}
 
-	// Check first artist (before comma or feat)
-	spotifyFirst := strings.Split(normSpotify, ",")[0]
-	spotifyFirst = strings.Split(spotifyFirst, " feat")[0]
-	spotifyFirst = strings.Split(spotifyFirst, " ft.")[0]
-	spotifyFirst = strings.TrimSpace(spotifyFirst)
+	// Split artists by common separators (comma, feat, ft., &, and)
+	// e.g., "RADWIMPS, Toko Miura" or "RADWIMPS feat. Toko Miura"
+	spotifyArtists := splitArtists(normSpotify)
+	tidalArtists := splitArtists(normTidal)
 
-	tidalFirst := strings.Split(normTidal, ",")[0]
-	tidalFirst = strings.Split(tidalFirst, " feat")[0]
-	tidalFirst = strings.Split(tidalFirst, " ft.")[0]
-	tidalFirst = strings.TrimSpace(tidalFirst)
-
-	if spotifyFirst == tidalFirst {
-		return true
-	}
-
-	// Check if first artist is contained in the other
-	if strings.Contains(spotifyFirst, tidalFirst) || strings.Contains(tidalFirst, spotifyFirst) {
-		return true
+	// Check if ANY expected artist matches ANY found artist
+	for _, exp := range spotifyArtists {
+		for _, fnd := range tidalArtists {
+			if exp == fnd {
+				return true
+			}
+			// Also check contains for partial matches
+			if strings.Contains(exp, fnd) || strings.Contains(fnd, exp) {
+				return true
+			}
+			// Check same words different order
+			if sameWordsUnordered(exp, fnd) {
+				GoLog("[Tidal] Artist names have same words in different order: '%s' vs '%s'\n", exp, fnd)
+				return true
+			}
+		}
 	}
 
 	// If scripts are TRULY different (Latin vs CJK/Arabic/Cyrillic), assume match (transliteration)
@@ -1286,6 +1197,67 @@ func artistsMatch(spotifyArtist, tidalArtist string) bool {
 	return false
 }
 
+// splitArtists splits artist string by common separators
+func splitArtists(artists string) []string {
+	// Replace common separators with a standard one
+	normalized := artists
+	normalized = strings.ReplaceAll(normalized, " feat. ", "|")
+	normalized = strings.ReplaceAll(normalized, " feat ", "|")
+	normalized = strings.ReplaceAll(normalized, " ft. ", "|")
+	normalized = strings.ReplaceAll(normalized, " ft ", "|")
+	normalized = strings.ReplaceAll(normalized, " & ", "|")
+	normalized = strings.ReplaceAll(normalized, " and ", "|")
+	normalized = strings.ReplaceAll(normalized, ", ", "|")
+	normalized = strings.ReplaceAll(normalized, " x ", "|")
+
+	parts := strings.Split(normalized, "|")
+	result := make([]string, 0, len(parts))
+	for _, p := range parts {
+		trimmed := strings.TrimSpace(p)
+		if trimmed != "" {
+			result = append(result, trimmed)
+		}
+	}
+	return result
+}
+
+// sameWordsUnordered checks if two strings have the same words regardless of order
+// Useful for Japanese names: "Sawano Hiroyuki" vs "Hiroyuki Sawano"
+func sameWordsUnordered(a, b string) bool {
+	wordsA := strings.Fields(a)
+	wordsB := strings.Fields(b)
+
+	// Must have same number of words
+	if len(wordsA) != len(wordsB) || len(wordsA) == 0 {
+		return false
+	}
+
+	// Sort and compare
+	sortedA := make([]string, len(wordsA))
+	sortedB := make([]string, len(wordsB))
+	copy(sortedA, wordsA)
+	copy(sortedB, wordsB)
+
+	// Simple bubble sort (usually just 2-3 words)
+	for i := 0; i < len(sortedA)-1; i++ {
+		for j := i + 1; j < len(sortedA); j++ {
+			if sortedA[i] > sortedA[j] {
+				sortedA[i], sortedA[j] = sortedA[j], sortedA[i]
+			}
+			if sortedB[i] > sortedB[j] {
+				sortedB[i], sortedB[j] = sortedB[j], sortedB[i]
+			}
+		}
+	}
+
+	for i := range sortedA {
+		if sortedA[i] != sortedB[i] {
+			return false
+		}
+	}
+	return true
+}
+
 // titlesMatch checks if track titles are similar enough
 func titlesMatch(expectedTitle, foundTitle string) bool {
 	normExpected := strings.ToLower(strings.TrimSpace(expectedTitle))
@@ -1520,7 +1492,7 @@ func downloadFromTidal(req DownloadRequest) (TidalDownloadResult, error) {
 		}
 	}
 
-	// Strategy 2: Try SongLink only if ISRC search failed (slower but more accurate)
+	// Strategy 2: Try SongLink if we have Spotify ID
 	if track == nil && req.SpotifyID != "" {
 		GoLog("[Tidal] ISRC search failed, trying SongLink...\n")
 		var tidalURL string

ios/Runner/AppDelegate.swift

@@ -484,6 +484,25 @@ import Gobackend  // Import Go framework
             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]
@@ -498,6 +517,47 @@ import Gobackend  // Import Go framework
             if let error = error { throw error }
             return response
             
+        // Extension Store
+        case "initExtensionStore":
+            let args = call.arguments as! [String: Any]
+            let cacheDir = args["cache_dir"] as! String
+            GobackendInitExtensionStoreJSON(cacheDir, &error)
+            if let error = error { throw error }
+            return nil
+            
+        case "getStoreExtensions":
+            let args = call.arguments as! [String: Any]
+            let forceRefresh = args["force_refresh"] as? Bool ?? false
+            let response = GobackendGetStoreExtensionsJSON(forceRefresh, &error)
+            if let error = error { throw error }
+            return response
+            
+        case "searchStoreExtensions":
+            let args = call.arguments as! [String: Any]
+            let query = args["query"] as? String ?? ""
+            let category = args["category"] as? String ?? ""
+            let response = GobackendSearchStoreExtensionsJSON(query, category, &error)
+            if let error = error { throw error }
+            return response
+            
+        case "getStoreCategories":
+            let response = GobackendGetStoreCategoriesJSON(&error)
+            if let error = error { throw error }
+            return response
+            
+        case "downloadStoreExtension":
+            let args = call.arguments as! [String: Any]
+            let extensionId = args["extension_id"] as! String
+            let destDir = args["dest_dir"] as! String
+            let response = GobackendDownloadStoreExtensionJSON(extensionId, destDir, &error)
+            if let error = error { throw error }
+            return response
+            
+        case "clearStoreCache":
+            GobackendClearStoreCacheJSON(&error)
+            if let error = error { throw error }
+            return nil
+            
         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 = '3.0.0-alpha.3';
-  static const String buildNumber = '52';
+  static const String version = '3.0.0';
+  static const String buildNumber = '57';
   static const String fullVersion = '$version+$buildNumber';
   
   

lib/models/settings.dart

@@ -28,6 +28,8 @@ class AppSettings {
   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 String albumFolderStructure; // artist_album or album_only
+  final bool showExtensionStore; // Show Extension Store tab in navigation
 
   const AppSettings({
     this.defaultService = 'tidal',
@@ -54,6 +56,8 @@ class AppSettings {
     this.useExtensionProviders = true, // Default: use extensions when available
     this.searchProvider, // Default: null (use Deezer/Spotify)
     this.separateSingles = false, // Default: disabled
+    this.albumFolderStructure = 'artist_album', // Default: Albums/Artist/Album
+    this.showExtensionStore = true, // Default: show store
   });
 
   AppSettings copyWith({
@@ -80,7 +84,10 @@ class AppSettings {
     bool? enableLogging,
     bool? useExtensionProviders,
     String? searchProvider,
+    bool clearSearchProvider = false, // Set to true to clear searchProvider to null
     bool? separateSingles,
+    String? albumFolderStructure,
+    bool? showExtensionStore,
   }) {
     return AppSettings(
       defaultService: defaultService ?? this.defaultService,
@@ -105,8 +112,10 @@ class AppSettings {
       metadataSource: metadataSource ?? this.metadataSource,
       enableLogging: enableLogging ?? this.enableLogging,
       useExtensionProviders: useExtensionProviders ?? this.useExtensionProviders,
-      searchProvider: searchProvider ?? this.searchProvider,
+      searchProvider: clearSearchProvider ? null : (searchProvider ?? this.searchProvider),
       separateSingles: separateSingles ?? this.separateSingles,
+      albumFolderStructure: albumFolderStructure ?? this.albumFolderStructure,
+      showExtensionStore: showExtensionStore ?? this.showExtensionStore,
     );
   }
 

lib/models/settings.g.dart

@@ -32,6 +32,8 @@ AppSettings _$AppSettingsFromJson(Map<String, dynamic> json) => AppSettings(
   useExtensionProviders: json['useExtensionProviders'] as bool? ?? true,
   searchProvider: json['searchProvider'] as String?,
   separateSingles: json['separateSingles'] as bool? ?? false,
+  albumFolderStructure: json['albumFolderStructure'] as String? ?? 'artist_album',
+  showExtensionStore: json['showExtensionStore'] as bool? ?? true,
 );
 
 Map<String, dynamic> _$AppSettingsToJson(AppSettings instance) =>
@@ -60,4 +62,6 @@ Map<String, dynamic> _$AppSettingsToJson(AppSettings instance) =>
       'useExtensionProviders': instance.useExtensionProviders,
       'searchProvider': instance.searchProvider,
       'separateSingles': instance.separateSingles,
+      'albumFolderStructure': instance.albumFolderStructure,
+      'showExtensionStore': instance.showExtensionStore,
     };

lib/providers/download_queue_provider.dart

@@ -669,7 +669,7 @@ class DownloadQueueNotifier extends Notifier<DownloadQueueState> {
   }
 
   /// Build output directory based on folder organization setting and separateSingles
-  Future<String> _buildOutputDir(Track track, String folderOrganization, {bool separateSingles = false}) async {
+  Future<String> _buildOutputDir(Track track, String folderOrganization, {bool separateSingles = false, String albumFolderStructure = 'artist_album'}) async {
     String baseDir = state.outputDir;
 
     // If separateSingles is enabled, use Albums/Singles structure
@@ -686,10 +686,19 @@ class DownloadQueueNotifier extends Notifier<DownloadQueueState> {
         }
         return singlesPath;
       } else {
-        // Albums go to Albums/Artist/Album structure
-        final artistName = _sanitizeFolderName(track.albumArtist ?? track.artistName);
+        // Albums folder structure based on setting
         final albumName = _sanitizeFolderName(track.albumName);
-        final albumPath = '$baseDir${Platform.pathSeparator}Albums${Platform.pathSeparator}$artistName${Platform.pathSeparator}$albumName';
+        String albumPath;
+        
+        if (albumFolderStructure == 'album_only') {
+          // Albums/Album structure (no artist folder)
+          albumPath = '$baseDir${Platform.pathSeparator}Albums${Platform.pathSeparator}$albumName';
+        } else {
+          // Albums/Artist/Album structure (default)
+          final artistName = _sanitizeFolderName(track.albumArtist ?? track.artistName);
+          albumPath = '$baseDir${Platform.pathSeparator}Albums${Platform.pathSeparator}$artistName${Platform.pathSeparator}$albumName';
+        }
+        
         final dir = Directory(albumPath);
         if (!await dir.exists()) {
           await dir.create(recursive: true);
@@ -1001,13 +1010,42 @@ class DownloadQueueNotifier extends Notifier<DownloadQueueState> {
     }
   }
 
+  /// Upgrade Spotify cover URL to max quality (~2000x2000)
+  /// Same logic as Go backend cover.go
+  String _upgradeToMaxQualityCover(String coverUrl) {
+    const spotifySize300 = 'ab67616d00001e02'; // 300x300 (small)
+    const spotifySize640 = 'ab67616d0000b273'; // 640x640 (medium)
+    const spotifySizeMax = 'ab67616d000082c1'; // Max resolution (~2000x2000)
+    
+    // First upgrade small (300) to medium (640)
+    var result = coverUrl;
+    if (result.contains(spotifySize300)) {
+      result = result.replaceFirst(spotifySize300, spotifySize640);
+    }
+    
+    // Then upgrade medium (640) to max
+    if (result.contains(spotifySize640)) {
+      result = result.replaceFirst(spotifySize640, spotifySizeMax);
+    }
+    
+    return result;
+  }
+
   /// Embed metadata and cover to a FLAC file after M4A conversion
   Future<void> _embedMetadataAndCover(String flacPath, Track track) async {
+    final settings = ref.read(settingsProvider);
+    
     // Download cover first
     String? coverPath;
-    final coverUrl = track.coverUrl;
+    var coverUrl = track.coverUrl;
     if (coverUrl != null && coverUrl.isNotEmpty) {
       try {
+        // Upgrade cover URL to max quality if setting is enabled
+        if (settings.maxQualityCover) {
+          coverUrl = _upgradeToMaxQualityCover(coverUrl);
+          _log.d('Cover URL upgraded to max quality: $coverUrl');
+        }
+        
         final tempDir = await getTemporaryDirectory();
         final uniqueId =
             '${DateTime.now().millisecondsSinceEpoch}_${Random().nextInt(10000)}';
@@ -1446,6 +1484,7 @@ class DownloadQueueNotifier extends Notifier<DownloadQueueState> {
         trackToDownload,
         settings.folderOrganization,
         separateSingles: settings.separateSingles,
+        albumFolderStructure: settings.albumFolderStructure,
       );
 
       // Use quality override if set, otherwise use default from settings
@@ -1557,6 +1596,12 @@ class DownloadQueueNotifier extends Notifier<DownloadQueueState> {
 
       if (result['success'] == true) {
         var filePath = result['file_path'] as String?;
+        
+        // Strip EXISTS: prefix from duplicate detection
+        if (filePath != null && filePath.startsWith('EXISTS:')) {
+          filePath = filePath.substring(7); // Remove "EXISTS:" prefix
+        }
+        
         _log.i('Download success, file: $filePath');
 
         // Get actual quality from response (if available)

lib/providers/extension_provider.dart

@@ -24,6 +24,7 @@ class Extension {
   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
 
@@ -45,6 +46,7 @@ class Extension {
     this.hasDownloadProvider = false,
     this.skipMetadataEnrichment = false,
     this.searchBehavior,
+    this.urlHandler,
     this.trackMatching,
     this.postProcessing,
   });
@@ -74,6 +76,9 @@ class Extension {
       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,
@@ -101,6 +106,7 @@ class Extension {
     bool? hasDownloadProvider,
     bool? skipMetadataEnrichment,
     SearchBehavior? searchBehavior,
+    URLHandler? urlHandler,
     TrackMatching? trackMatching,
     PostProcessing? postProcessing,
   }) {
@@ -122,12 +128,14 @@ class Extension {
       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;
 }
@@ -226,6 +234,36 @@ class PostProcessing {
   }
 }
 
+/// 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;

lib/providers/settings_provider.dart

@@ -196,7 +196,11 @@ class SettingsNotifier extends Notifier<AppSettings> {
   }
 
   void setSearchProvider(String? provider) {
-    state = state.copyWith(searchProvider: provider);
+    if (provider == null || provider.isEmpty) {
+      state = state.copyWith(clearSearchProvider: true);
+    } else {
+      state = state.copyWith(searchProvider: provider);
+    }
     _saveSettings();
   }
 
@@ -216,6 +220,16 @@ class SettingsNotifier extends Notifier<AppSettings> {
     state = state.copyWith(separateSingles: enabled);
     _saveSettings();
   }
+
+  void setAlbumFolderStructure(String structure) {
+    state = state.copyWith(albumFolderStructure: structure);
+    _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

@@ -131,6 +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
       

lib/screens/home_tab.dart

@@ -81,6 +81,7 @@ class _HomeTabState extends ConsumerState<HomeTab> with AutomaticKeepAliveClient
 
   Future<void> _performSearch(String query) async {
     final settings = ref.read(settingsProvider);
+    final extState = ref.read(extensionProvider);
     final searchProvider = settings.searchProvider;
     
     // Skip if same query already searched with same provider
@@ -88,11 +89,20 @@ class _HomeTabState extends ConsumerState<HomeTab> with AutomaticKeepAliveClient
     if (_lastSearchQuery == searchKey) return;
     _lastSearchQuery = searchKey;
     
-    if (searchProvider != null && searchProvider.isNotEmpty) {
+    // Check if extension search provider is set AND still enabled
+    final isExtensionEnabled = searchProvider != null && 
+        searchProvider.isNotEmpty &&
+        extState.extensions.any((e) => e.id == searchProvider && e.enabled);
+    
+    if (isExtensionEnabled) {
       // Use custom search from extension
       await ref.read(trackProvider.notifier).customSearch(searchProvider, query);
     } else {
       // Use default search (Deezer/Spotify)
+      // Also clear searchProvider if it was set but extension is disabled
+      if (searchProvider != null && searchProvider.isNotEmpty && !isExtensionEnabled) {
+        ref.read(settingsProvider.notifier).setSearchProvider(null);
+      }
       await ref.read(trackProvider.notifier).search(query, metadataSource: settings.metadataSource);
     }
     ref.read(settingsProvider.notifier).setHasSearchedBefore();

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';
@@ -121,6 +122,8 @@ class _MainShellState extends ConsumerState<MainShell> {
   void _onPageChanged(int index) {
     if (_currentIndex != index) {
       setState(() => _currentIndex = index);
+      // Unfocus any text field when switching tabs to prevent keyboard from appearing
+      FocusScope.of(context).unfocus();
     }
   }
 
@@ -172,6 +175,7 @@ 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 +189,61 @@ class _MainShellState extends ConsumerState<MainShell> {
                    !trackState.isLoading &&
                    !isKeyboardVisible;
 
+    // Build tabs and destinations based on settings
+    final tabs = <Widget>[
+      const HomeTab(),
+      QueueTab(
+        parentPageController: _pageController,
+        parentPageIndex: 1,
+        nextPageIndex: showStore ? 2 : 3,
+      ),
+      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 {
@@ -201,45 +260,17 @@ class _MainShellState extends ConsumerState<MainShell> {
         body: PageView(
           controller: _pageController,
           onPageChanged: _onPageChanged,
-          physics: const BouncingScrollPhysics(),
-          children: const [
-            HomeTab(),
-            QueueTab(),
-            SettingsTab(),
-          ],
+          physics: const ClampingScrollPhysics(),
+          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/settings/about_page.dart

@@ -13,45 +13,45 @@ class AboutPage extends StatelessWidget {
     final topPadding = MediaQuery.of(context).padding.top;
 
     return PopScope(
-      canPop: true,
+      canPop: true, // Always allow back gesture
       child: Scaffold(
         body: CustomScrollView(
           slivers: [
             // Collapsing App Bar with back button
             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);
-                  // When collapsed (expandRatio=0): left=56 to avoid back button
-                  // When expanded (expandRatio=1): left=24 for normal padding
-                  final leftPadding = 56 - (32 * expandRatio); // 56 -> 24
-                  return FlexibleSpaceBar(
-                    expandedTitleScale: 1.0,
-                    titlePadding: EdgeInsets.only(left: leftPadding, bottom: 16),
-                    title: Text(
-                      'About',
-                      style: TextStyle(
-                        fontSize: 20 + (8 * expandRatio), // 20 -> 28
-                        fontWeight: FontWeight.bold,
-                        color: colorScheme.onSurface,
-                      ),
-                    ),
-                  );
-                },
-              ),
+            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);
+                // When collapsed (expandRatio=0): left=56 to avoid back button
+                // When expanded (expandRatio=1): left=24 for normal padding
+                final leftPadding = 56 - (32 * expandRatio); // 56 -> 24
+                return FlexibleSpaceBar(
+                  expandedTitleScale: 1.0,
+                  titlePadding: EdgeInsets.only(left: leftPadding, bottom: 16),
+                  title: Text(
+                    'About',
+                    style: TextStyle(
+                      fontSize: 20 + (8 * expandRatio), // 20 -> 28
+                      fontWeight: FontWeight.bold,
+                      color: colorScheme.onSurface,
+                    ),
+                  ),
+                );
+              },
+            ),
+          ),
 
           // App header card with logo and description
           SliverToBoxAdapter(
@@ -220,7 +220,7 @@ class AboutPage extends StatelessWidget {
           const SliverToBoxAdapter(child: SizedBox(height: 16)),
         ],
       ),
-      ),
+    ),
     );
   }
 

lib/screens/settings/appearance_settings_page.dart

@@ -15,27 +15,27 @@ class AppearanceSettingsPage extends ConsumerWidget {
     final topPadding = MediaQuery.of(context).padding.top;
 
     return PopScope(
-      canPop: true,
+      canPop: true, // Always allow back gesture
       child: Scaffold(
         body: CustomScrollView(
           slivers: [
             // Collapsing App Bar with back button
             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: _AppBarTitle(
-                title: 'Appearance',
-                topPadding: topPadding,
-              ),
+            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: _AppBarTitle(
+              title: 'Appearance',
+              topPadding: topPadding,
+            ),
+          ),
 
             // Preview Section
             SliverToBoxAdapter(

lib/screens/settings/download_settings_page.dart

@@ -23,49 +23,49 @@ class DownloadSettingsPage extends ConsumerWidget {
     final isBuiltInService = _builtInServices.contains(settings.defaultService);
 
     return PopScope(
-      canPop: true,
+      canPop: true, // Always allow back gesture
       child: Scaffold(
         body: CustomScrollView(
           slivers: [
             // Collapsing App Bar with back button
             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); // 56 -> 24
-                  return FlexibleSpaceBar(
-                    expandedTitleScale: 1.0,
-                    titlePadding: EdgeInsets.only(
-                      left: leftPadding,
-                      bottom: 16,
-                    ),
-                    title: Text(
-                      'Download',
-                      style: TextStyle(
-                        fontSize: 20 + (8 * expandRatio), // 20 -> 28
-                        fontWeight: FontWeight.bold,
-                        color: colorScheme.onSurface,
-                      ),
-                    ),
-                  );
-                },
-              ),
+            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); // 56 -> 24
+                return FlexibleSpaceBar(
+                  expandedTitleScale: 1.0,
+                  titlePadding: EdgeInsets.only(
+                    left: leftPadding,
+                    bottom: 16,
+                  ),
+                  title: Text(
+                    'Download',
+                    style: TextStyle(
+                      fontSize: 20 + (8 * expandRatio), // 20 -> 28
+                      fontWeight: FontWeight.bold,
+                      color: colorScheme.onSurface,
+                    ),
+                  ),
+                );
+              },
+            ),
+          ),
 
             // Service section
             const SliverToBoxAdapter(
@@ -196,6 +196,19 @@ class DownloadSettingsPage extends ConsumerWidget {
                         .read(settingsProvider.notifier)
                         .setSeparateSingles(value),
                   ),
+                  if (settings.separateSingles)
+                    SettingsItem(
+                      icon: Icons.folder_outlined,
+                      title: 'Album Folder Structure',
+                      subtitle: settings.albumFolderStructure == 'album_only'
+                          ? 'Albums/Album Name/'
+                          : 'Albums/Artist/Album Name/',
+                      onTap: () => _showAlbumFolderStructurePicker(
+                        context,
+                        ref,
+                        settings.albumFolderStructure,
+                      ),
+                    ),
                   if (!settings.separateSingles)
                     SettingsItem(
                       icon: Icons.create_new_folder_outlined,
@@ -221,6 +234,39 @@ class DownloadSettingsPage extends ConsumerWidget {
     );
   }
 
+  void _showAlbumFolderStructurePicker(BuildContext context, WidgetRef ref, String current) {
+    showModalBottomSheet(
+      context: context,
+      builder: (context) => SafeArea(
+        child: Column(
+          mainAxisSize: MainAxisSize.min,
+          children: [
+            ListTile(
+              leading: const Icon(Icons.folder_outlined),
+              title: const Text('Artist / Album'),
+              subtitle: const Text('Albums/Artist Name/Album Name/'),
+              trailing: current == 'artist_album' ? const Icon(Icons.check) : null,
+              onTap: () {
+                ref.read(settingsProvider.notifier).setAlbumFolderStructure('artist_album');
+                Navigator.pop(context);
+              },
+            ),
+            ListTile(
+              leading: const Icon(Icons.album_outlined),
+              title: const Text('Album Only'),
+              subtitle: const Text('Albums/Album Name/'),
+              trailing: current == 'album_only' ? const Icon(Icons.check) : null,
+              onTap: () {
+                ref.read(settingsProvider.notifier).setAlbumFolderStructure('album_only');
+                Navigator.pop(context);
+              },
+            ),
+          ],
+        ),
+      ),
+    );
+  }
+
   void _showFormatEditor(BuildContext context, WidgetRef ref, String current) {
     final controller = TextEditingController(text: current);
     final colorScheme = Theme.of(context).colorScheme;
@@ -527,74 +573,80 @@ class DownloadSettingsPage extends ConsumerWidget {
     showModalBottomSheet(
       context: context,
       backgroundColor: colorScheme.surfaceContainerHigh,
+      isScrollControlled: true,
       shape: const RoundedRectangleBorder(
         borderRadius: BorderRadius.vertical(top: Radius.circular(28)),
       ),
+      constraints: BoxConstraints(
+        maxHeight: MediaQuery.of(context).size.height * 0.7,
+      ),
       builder: (context) => SafeArea(
-        child: Column(
-          mainAxisSize: MainAxisSize.min,
-          crossAxisAlignment: CrossAxisAlignment.start,
-          children: [
-            Padding(
-              padding: const EdgeInsets.fromLTRB(24, 24, 24, 8),
-              child: Text(
-                'Folder Organization',
-                style: Theme.of(
-                  context,
-                ).textTheme.titleLarge?.copyWith(fontWeight: FontWeight.bold),
-              ),
-            ),
-            Padding(
-              padding: const EdgeInsets.fromLTRB(24, 0, 24, 16),
-              child: Text(
-                'Organize downloaded files into folders',
-                style: Theme.of(context).textTheme.bodyMedium?.copyWith(
-                  color: colorScheme.onSurfaceVariant,
+        child: SingleChildScrollView(
+          child: Column(
+            mainAxisSize: MainAxisSize.min,
+            crossAxisAlignment: CrossAxisAlignment.start,
+            children: [
+              Padding(
+                padding: const EdgeInsets.fromLTRB(24, 24, 24, 8),
+                child: Text(
+                  'Folder Organization',
+                  style: Theme.of(
+                    context,
+                  ).textTheme.titleLarge?.copyWith(fontWeight: FontWeight.bold),
                 ),
               ),
-            ),
-            _FolderOption(
-              title: 'None',
-              subtitle: 'All files in download folder',
-              example: 'SpotiFLAC/Track.flac',
-              isSelected: current == 'none',
-              onTap: () {
-                ref.read(settingsProvider.notifier).setFolderOrganization('none');
-                Navigator.pop(context);
-              },
-            ),
-            _FolderOption(
-              title: 'By Artist',
-              subtitle: 'Separate folder for each artist',
-              example: 'SpotiFLAC/Artist Name/Track.flac',
-              isSelected: current == 'artist',
-              onTap: () {
-                ref.read(settingsProvider.notifier).setFolderOrganization('artist');
-                Navigator.pop(context);
-              },
-            ),
-            _FolderOption(
-              title: 'By Album',
-              subtitle: 'Separate folder for each album',
-              example: 'SpotiFLAC/Album Name/Track.flac',
-              isSelected: current == 'album',
-              onTap: () {
-                ref.read(settingsProvider.notifier).setFolderOrganization('album');
-                Navigator.pop(context);
-              },
-            ),
-            _FolderOption(
-              title: 'By Artist & Album',
-              subtitle: 'Nested folders for artist and album',
-              example: 'SpotiFLAC/Artist/Album/Track.flac',
-              isSelected: current == 'artist_album',
-              onTap: () {
-                ref.read(settingsProvider.notifier).setFolderOrganization('artist_album');
-                Navigator.pop(context);
-              },
-            ),
-            const SizedBox(height: 16),
-          ],
+              Padding(
+                padding: const EdgeInsets.fromLTRB(24, 0, 24, 16),
+                child: Text(
+                  'Organize downloaded files into folders',
+                  style: Theme.of(context).textTheme.bodyMedium?.copyWith(
+                    color: colorScheme.onSurfaceVariant,
+                  ),
+                ),
+              ),
+              _FolderOption(
+                title: 'None',
+                subtitle: 'All files in download folder',
+                example: 'SpotiFLAC/Track.flac',
+                isSelected: current == 'none',
+                onTap: () {
+                  ref.read(settingsProvider.notifier).setFolderOrganization('none');
+                  Navigator.pop(context);
+                },
+              ),
+              _FolderOption(
+                title: 'By Artist',
+                subtitle: 'Separate folder for each artist',
+                example: 'SpotiFLAC/Artist Name/Track.flac',
+                isSelected: current == 'artist',
+                onTap: () {
+                  ref.read(settingsProvider.notifier).setFolderOrganization('artist');
+                  Navigator.pop(context);
+                },
+              ),
+              _FolderOption(
+                title: 'By Album',
+                subtitle: 'Separate folder for each album',
+                example: 'SpotiFLAC/Album Name/Track.flac',
+                isSelected: current == 'album',
+                onTap: () {
+                  ref.read(settingsProvider.notifier).setFolderOrganization('album');
+                  Navigator.pop(context);
+                },
+              ),
+              _FolderOption(
+                title: 'By Artist & Album',
+                subtitle: 'Nested folders for artist and album',
+                example: 'SpotiFLAC/Artist/Album/Track.flac',
+                isSelected: current == 'artist_album',
+                onTap: () {
+                  ref.read(settingsProvider.notifier).setFolderOrganization('artist_album');
+                  Navigator.pop(context);
+                },
+              ),
+              const SizedBox(height: 16),
+            ],
+          ),
         ),
       ),
     );

lib/screens/settings/extension_detail_page.dart

@@ -3,6 +3,7 @@ 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 {
@@ -55,11 +56,13 @@ class _ExtensionDetailPageState extends ConsumerState<ExtensionDetailPage> {
     final topPadding = MediaQuery.of(context).padding.top;
     final hasError = extension.status == 'error';
 
-    return Scaffold(
-      body: CustomScrollView(
-        slivers: [
-          // App Bar
-          SliverAppBar(
+    return PopScope(
+      canPop: true, // Always allow back gesture
+      child: Scaffold(
+        body: CustomScrollView(
+          slivers: [
+            // App Bar
+            SliverAppBar(
             expandedHeight: 120 + topPadding,
             collapsedHeight: kToolbarHeight,
             floating: false,
@@ -185,6 +188,7 @@ class _ExtensionDetailPageState extends ConsumerState<ExtensionDetailPage> {
                     const SizedBox(height: 16),
                     _InfoRow(label: 'Author', value: extension.author),
                     _InfoRow(label: 'ID', value: extension.id),
+                    _InfoRow(label: 'Version', value: 'v${extension.version}'),
                     if (hasError && extension.errorMessage != null)
                       _InfoRow(
                         label: 'Error',
@@ -235,28 +239,57 @@ class _ExtensionDetailPageState extends ConsumerState<ExtensionDetailPage> {
                   subtitle: extension.postProcessing?.hooks.isNotEmpty == true
                       ? '${extension.postProcessing!.hooks.length} hook(s) available'
                       : null,
+                ),
+                _CapabilityItem(
+                  icon: Icons.link,
+                  title: 'URL Handler',
+                  enabled: extension.hasURLHandler,
+                  subtitle: extension.urlHandler?.patterns.isNotEmpty == true
+                      ? '${extension.urlHandler!.patterns.length} pattern(s)'
+                      : null,
                   showDivider: false,
                 ),
               ],
             ),
           ),
 
-          // Search Provider Section (if extension has custom search)
-          if (extension.hasCustomSearch) ...[
+
+
+          // URL Handler Section (if extension handles URLs)
+          if (extension.hasURLHandler && extension.urlHandler!.patterns.isNotEmpty) ...[
             const SliverToBoxAdapter(
-              child: SettingsSectionHeader(title: 'Search Provider'),
+              child: SettingsSectionHeader(title: 'URL Handler'),
             ),
             SliverToBoxAdapter(
               child: SettingsGroup(
                 children: [
-                  _SearchProviderInfo(
-                    extension: extension,
+                  _URLHandlerInfo(
+                    patterns: extension.urlHandler!.patterns,
                   ),
                 ],
               ),
             ),
           ],
 
+          // Quality Options Section (for download providers)
+          if (extension.hasDownloadProvider && extension.qualityOptions.isNotEmpty) ...[
+            const SliverToBoxAdapter(
+              child: SettingsSectionHeader(title: 'Quality Options'),
+            ),
+            SliverToBoxAdapter(
+              child: SettingsGroup(
+                children: extension.qualityOptions.asMap().entries.map((entry) {
+                  final index = entry.key;
+                  final quality = entry.value;
+                  return _QualityOptionItem(
+                    quality: quality,
+                    showDivider: index < extension.qualityOptions.length - 1,
+                  );
+                }).toList(),
+              ),
+            ),
+          ],
+
           // Post-Processing Hooks (if available)
           if (extension.hasPostProcessing && extension.postProcessing!.hooks.isNotEmpty) ...[
             const SliverToBoxAdapter(
@@ -347,6 +380,7 @@ class _ExtensionDetailPageState extends ConsumerState<ExtensionDetailPage> {
           const SliverToBoxAdapter(child: SizedBox(height: 32)),
         ],
       ),
+    ),
     );
   }
 
@@ -390,6 +424,8 @@ class _ExtensionDetailPageState extends ConsumerState<ExtensionDetailPage> {
           .read(extensionProvider.notifier)
           .removeExtension(widget.extensionId);
       if (success && mounted) {
+        // Refresh store to update isInstalled status
+        ref.read(storeProvider.notifier).refresh();
         Navigator.pop(this.context);
       }
     }
@@ -814,17 +850,18 @@ class _PostProcessingHookItem extends StatelessWidget {
   }
 }
 
-class _SearchProviderInfo extends StatelessWidget {
-  final Extension extension;
 
-  const _SearchProviderInfo({
-    required this.extension,
+
+class _URLHandlerInfo extends StatelessWidget {
+  final List<String> patterns;
+
+  const _URLHandlerInfo({
+    required this.patterns,
   });
 
   @override
   Widget build(BuildContext context) {
     final colorScheme = Theme.of(context).colorScheme;
-    final searchBehavior = extension.searchBehavior;
     
     return Padding(
       padding: const EdgeInsets.all(16),
@@ -837,12 +874,12 @@ class _SearchProviderInfo extends StatelessWidget {
                 width: 48,
                 height: 48,
                 decoration: BoxDecoration(
-                  color: colorScheme.secondaryContainer,
+                  color: colorScheme.tertiaryContainer,
                   borderRadius: BorderRadius.circular(12),
                 ),
                 child: Icon(
-                  Icons.manage_search,
-                  color: colorScheme.onSecondaryContainer,
+                  Icons.link,
+                  color: colorScheme.onTertiaryContainer,
                   size: 24,
                 ),
               ),
@@ -852,14 +889,14 @@ class _SearchProviderInfo extends StatelessWidget {
                   crossAxisAlignment: CrossAxisAlignment.start,
                   children: [
                     Text(
-                      'Custom Search Available',
+                      'Custom URL Handling',
                       style: Theme.of(context).textTheme.titleMedium?.copyWith(
                         fontWeight: FontWeight.w600,
                       ),
                     ),
                     const SizedBox(height: 2),
                     Text(
-                      'This extension provides its own search functionality',
+                      'This extension can handle links from these sites',
                       style: Theme.of(context).textTheme.bodySmall?.copyWith(
                         color: colorScheme.onSurfaceVariant,
                       ),
@@ -870,25 +907,38 @@ class _SearchProviderInfo extends StatelessWidget {
             ],
           ),
           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',
+          Wrap(
+            spacing: 8,
+            runSpacing: 8,
+            children: patterns.map((pattern) {
+              return Container(
+                padding: const EdgeInsets.symmetric(horizontal: 12, vertical: 6),
+                decoration: BoxDecoration(
+                  color: colorScheme.surfaceContainerHighest,
+                  borderRadius: BorderRadius.circular(8),
+                ),
+                child: Row(
+                  mainAxisSize: MainAxisSize.min,
+                  children: [
+                    Icon(
+                      Icons.language,
+                      size: 16,
+                      color: colorScheme.primary,
+                    ),
+                    const SizedBox(width: 6),
+                    Text(
+                      pattern,
+                      style: Theme.of(context).textTheme.bodySmall?.copyWith(
+                        color: colorScheme.onSurface,
+                        fontWeight: FontWeight.w500,
+                      ),
+                    ),
+                  ],
+                ),
+              );
+            }).toList(),
           ),
           const SizedBox(height: 16),
-          // Usage instructions
           Container(
             padding: const EdgeInsets.all(12),
             decoration: BoxDecoration(
@@ -905,7 +955,7 @@ class _SearchProviderInfo extends StatelessWidget {
                 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.',
+                    'Share links from these sites to SpotiFLAC and this extension will handle them.',
                     style: Theme.of(context).textTheme.bodySmall?.copyWith(
                       color: colorScheme.onSurfaceVariant,
                     ),
@@ -920,44 +970,95 @@ class _SearchProviderInfo extends StatelessWidget {
   }
 }
 
-class _InfoTile extends StatelessWidget {
-  final IconData icon;
-  final String label;
-  final String value;
+class _QualityOptionItem extends StatelessWidget {
+  final QualityOption quality;
+  final bool showDivider;
 
-  const _InfoTile({
-    required this.icon,
-    required this.label,
-    required this.value,
+  const _QualityOptionItem({
+    required this.quality,
+    this.showDivider = true,
   });
 
   @override
   Widget build(BuildContext context) {
     final colorScheme = Theme.of(context).colorScheme;
     
-    return Row(
+    return Column(
+      mainAxisSize: MainAxisSize.min,
       children: [
-        Icon(
-          icon,
-          size: 18,
-          color: colorScheme.onSurfaceVariant,
-        ),
-        const SizedBox(width: 8),
-        Text(
-          '$label: ',
-          style: Theme.of(context).textTheme.bodySmall?.copyWith(
-            color: colorScheme.onSurfaceVariant,
+        Padding(
+          padding: const EdgeInsets.symmetric(horizontal: 16, vertical: 12),
+          child: Row(
+            children: [
+              Container(
+                width: 40,
+                height: 40,
+                decoration: BoxDecoration(
+                  color: colorScheme.secondaryContainer,
+                  borderRadius: BorderRadius.circular(10),
+                ),
+                child: Icon(
+                  Icons.high_quality,
+                  color: colorScheme.onSecondaryContainer,
+                  size: 20,
+                ),
+              ),
+              const SizedBox(width: 16),
+              Expanded(
+                child: Column(
+                  crossAxisAlignment: CrossAxisAlignment.start,
+                  children: [
+                    Text(
+                      quality.label,
+                      style: Theme.of(context).textTheme.bodyLarge?.copyWith(
+                        fontWeight: FontWeight.w500,
+                      ),
+                    ),
+                    if (quality.description != null && quality.description!.isNotEmpty) ...[
+                      const SizedBox(height: 2),
+                      Text(
+                        quality.description!,
+                        style: Theme.of(context).textTheme.bodySmall?.copyWith(
+                          color: colorScheme.onSurfaceVariant,
+                        ),
+                      ),
+                    ],
+                    const SizedBox(height: 4),
+                    Text(
+                      quality.id,
+                      style: Theme.of(context).textTheme.labelSmall?.copyWith(
+                        color: colorScheme.primary,
+                        fontFamily: 'monospace',
+                      ),
+                    ),
+                  ],
+                ),
+              ),
+              if (quality.settings.isNotEmpty)
+                Container(
+                  padding: const EdgeInsets.symmetric(horizontal: 8, vertical: 4),
+                  decoration: BoxDecoration(
+                    color: colorScheme.surfaceContainerHighest,
+                    borderRadius: BorderRadius.circular(8),
+                  ),
+                  child: Text(
+                    '${quality.settings.length} setting${quality.settings.length > 1 ? 's' : ''}',
+                    style: Theme.of(context).textTheme.labelSmall?.copyWith(
+                      color: colorScheme.onSurfaceVariant,
+                    ),
+                  ),
+                ),
+            ],
           ),
         ),
-        Expanded(
-          child: Text(
-            value,
-            style: Theme.of(context).textTheme.bodySmall?.copyWith(
-              color: colorScheme.onSurface,
-              fontWeight: FontWeight.w500,
-            ),
+        if (showDivider)
+          Divider(
+            height: 1,
+            thickness: 1,
+            indent: 72,
+            endIndent: 16,
+            color: colorScheme.outlineVariant.withValues(alpha: 0.3),
           ),
-        ),
       ],
     );
   }

lib/screens/settings/extensions_page.dart

@@ -45,9 +45,11 @@ class _ExtensionsPageState extends ConsumerState<ExtensionsPage> {
     final colorScheme = Theme.of(context).colorScheme;
     final topPadding = MediaQuery.of(context).padding.top;
 
-    return Scaffold(
-      body: CustomScrollView(
-        slivers: [
+    return PopScope(
+      canPop: true, // Always allow back gesture
+      child: Scaffold(
+        body: CustomScrollView(
+          slivers: [
           // App Bar
           SliverAppBar(
             expandedHeight: 120 + topPadding,
@@ -248,6 +250,7 @@ class _ExtensionsPageState extends ConsumerState<ExtensionsPage> {
           ),
         ],
       ),
+    ),
     );
   }
 

lib/screens/settings/log_screen.dart

@@ -125,59 +125,59 @@ class _LogScreenState extends State<LogScreen> {
     final logs = _filteredLogs;
 
     return PopScope(
-      canPop: true,
+      canPop: true, // Always allow back gesture
       child: Scaffold(
         body: CustomScrollView(
           controller: _scrollController,
           slivers: [
             // Collapsing App Bar with back button - same as other settings pages
             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),
+            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),
+            ),
+            actions: [
+              IconButton(
+                icon: Icon(_autoScroll ? Icons.vertical_align_bottom : Icons.vertical_align_center),
+                tooltip: _autoScroll ? 'Auto-scroll ON' : 'Auto-scroll OFF',
+                onPressed: () => setState(() => _autoScroll = !_autoScroll),
               ),
-              actions: [
-                IconButton(
-                  icon: Icon(_autoScroll ? Icons.vertical_align_bottom : Icons.vertical_align_center),
-                  tooltip: _autoScroll ? 'Auto-scroll ON' : 'Auto-scroll OFF',
-                  onPressed: () => setState(() => _autoScroll = !_autoScroll),
-                ),
-                IconButton(
-                  icon: const Icon(Icons.copy),
-                  tooltip: 'Copy logs',
-                  onPressed: _copyLogs,
-                ),
-                PopupMenuButton<String>(
-                  icon: const Icon(Icons.more_vert),
-                  onSelected: (value) {
-                    switch (value) {
-                      case 'share':
-                        _shareLogs();
-                        break;
-                      case 'clear':
-                        _clearLogs();
-                        break;
-                    }
-                  },
-                  itemBuilder: (context) => [
-                    const PopupMenuItem(
-                      value: 'share',
-                      child: ListTile(
-                        leading: Icon(Icons.share),
-                        title: Text('Share logs'),
-                        contentPadding: EdgeInsets.zero,
-                      ),
+              IconButton(
+                icon: const Icon(Icons.copy),
+                tooltip: 'Copy logs',
+                onPressed: _copyLogs,
+              ),
+              PopupMenuButton<String>(
+                icon: const Icon(Icons.more_vert),
+                onSelected: (value) {
+                  switch (value) {
+                    case 'share':
+                      _shareLogs();
+                      break;
+                    case 'clear':
+                      _clearLogs();
+                      break;
+                  }
+                },
+                itemBuilder: (context) => [
+                  const PopupMenuItem(
+                    value: 'share',
+                    child: ListTile(
+                      leading: Icon(Icons.share),
+                      title: Text('Share logs'),
+                      contentPadding: EdgeInsets.zero,
                     ),
-                    const PopupMenuItem(
-                      value: 'clear',
-                      child: ListTile(
-                        leading: Icon(Icons.delete_outline),
+                  ),
+                  const PopupMenuItem(
+                    value: 'clear',
+                    child: ListTile(
+                      leading: Icon(Icons.delete_outline),
                         title: Text('Clear logs'),
                         contentPadding: EdgeInsets.zero,
                       ),

lib/screens/settings/options_settings_page.dart

@@ -18,49 +18,49 @@ class OptionsSettingsPage extends ConsumerWidget {
     final topPadding = MediaQuery.of(context).padding.top;
 
     return PopScope(
-      canPop: true,
+      canPop: true, // Always allow back gesture
       child: Scaffold(
         body: CustomScrollView(
           slivers: [
             // Collapsing App Bar with back button
             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); // 56 -> 24
-                  return FlexibleSpaceBar(
-                    expandedTitleScale: 1.0,
-                    titlePadding: EdgeInsets.only(
-                      left: leftPadding,
-                      bottom: 16,
-                    ),
-                    title: Text(
-                      'Options',
-                      style: TextStyle(
-                        fontSize: 20 + (8 * expandRatio), // 20 -> 28
-                        fontWeight: FontWeight.bold,
-                        color: colorScheme.onSurface,
-                      ),
-                    ),
-                  );
-                },
-              ),
+            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); // 56 -> 24
+                return FlexibleSpaceBar(
+                  expandedTitleScale: 1.0,
+                  titlePadding: EdgeInsets.only(
+                    left: leftPadding,
+                    bottom: 16,
+                  ),
+                  title: Text(
+                    'Options',
+                    style: TextStyle(
+                      fontSize: 20 + (8 * expandRatio), // 20 -> 28
+                      fontWeight: FontWeight.bold,
+                      color: colorScheme.onSurface,
+                    ),
+                  ),
+                );
+              },
+            ),
+          ),
 
             // Search Source section
             const SliverToBoxAdapter(
@@ -202,6 +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',
@@ -836,8 +845,6 @@ class _MetadataSourceSelector extends ConsumerWidget {
               _SourceChip(
                 icon: Icons.graphic_eq,
                 label: 'Deezer',
-                badge: 'Free',
-                badgeColor: colorScheme.tertiary,
                 // Not selected if extension is active
                 isSelected: currentSource == 'deezer' && !hasExtensionSearch,
                 onTap: () {
@@ -852,8 +859,6 @@ class _MetadataSourceSelector extends ConsumerWidget {
               _SourceChip(
                 icon: Icons.music_note,
                 label: 'Spotify',
-                badge: 'API Key',
-                badgeColor: colorScheme.secondary,
                 // Not selected if extension is active
                 isSelected: currentSource == 'spotify' && !hasExtensionSearch,
                 onTap: () {

lib/screens/settings/settings_tab.dart

@@ -116,6 +116,27 @@ class SettingsTab extends ConsumerWidget {
   }
 
   void _navigateTo(BuildContext context, Widget page) {
-    Navigator.of(context).push(MaterialPageRoute(builder: (_) => page));
+    Navigator.of(context).push(
+      // Use PageRouteBuilder for better predictive back gesture support
+      // MaterialPageRoute can cause freeze on some devices with gesture navigation
+      PageRouteBuilder(
+        pageBuilder: (context, animation, secondaryAnimation) => page,
+        transitionsBuilder: (context, animation, secondaryAnimation, child) {
+          // Use slide transition similar to MaterialPageRoute
+          const begin = Offset(1.0, 0.0);
+          const end = Offset.zero;
+          const curve = Curves.easeInOut;
+          var tween = Tween(begin: begin, end: end).chain(
+            CurveTween(curve: curve),
+          );
+          return SlideTransition(
+            position: animation.drive(tween),
+            child: child,
+          );
+        },
+        transitionDuration: const Duration(milliseconds: 300),
+        reverseTransitionDuration: const Duration(milliseconds: 250),
+      ),
+    );
   }
 }

lib/screens/store/extension_details_screen.dart

@@ -0,0 +1,751 @@
+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/providers/extension_provider.dart';
+
+class ExtensionDetailsScreen extends ConsumerStatefulWidget {
+  final StoreExtension extension;
+
+  const ExtensionDetailsScreen({super.key, required this.extension});
+
+  @override
+  ConsumerState<ExtensionDetailsScreen> createState() =>
+      _ExtensionDetailsScreenState();
+}
+
+class _ExtensionDetailsScreenState
+    extends ConsumerState<ExtensionDetailsScreen> {
+
+  @override
+  Widget build(BuildContext context) {
+    // Watch store provider to get latest state of this extension (e.g. if updated/installed)
+    final storeState = ref.watch(storeProvider);
+
+    // Find our extension in the store state to get the latest status
+    // If not found in current store state (rare), fallback to widget.extension
+    final liveExtension =
+        storeState.extensions
+            .where((e) => e.id == widget.extension.id)
+            .firstOrNull ??
+        widget.extension;
+
+    final isDownloading = storeState.downloadingId == liveExtension.id;
+    final colorScheme = Theme.of(context).colorScheme;
+
+    return Scaffold(
+      body: CustomScrollView(
+        slivers: [
+          _buildAppBar(context, liveExtension, colorScheme),
+          _buildInfoCard(context, liveExtension, colorScheme, isDownloading),
+          _buildSectionHeader(
+            context,
+            'About',
+            Icons.info_outline,
+            colorScheme,
+          ),
+          _buildDescription(context, liveExtension, colorScheme),
+
+          if (liveExtension.tags.isNotEmpty) ...[
+            _buildSectionHeader(context, 'Tags', Icons.tag, colorScheme),
+            _buildTags(context, liveExtension, colorScheme),
+          ],
+
+          _buildSectionHeader(
+            context,
+            'Information',
+            Icons.table_chart_outlined,
+            colorScheme,
+          ),
+          _buildMetadataTable(context, liveExtension, colorScheme),
+
+          _buildSectionHeader(
+            context,
+            'Capabilities',
+            Icons.extension_outlined,
+            colorScheme,
+          ),
+          _buildCapabilities(context, liveExtension, colorScheme),
+
+          const SliverToBoxAdapter(child: SizedBox(height: 32)),
+        ],
+      ),
+    );
+  }
+
+  Widget _buildAppBar(
+    BuildContext context,
+    StoreExtension ext,
+    ColorScheme colorScheme,
+  ) {
+    return SliverAppBar(
+      expandedHeight: 200,
+      pinned: true,
+      stretch: true,
+      backgroundColor: colorScheme.surface,
+      surfaceTintColor: Colors.transparent,
+      flexibleSpace: FlexibleSpaceBar(
+        background: Center(
+          child: Padding(
+            padding: const EdgeInsets.only(top: kToolbarHeight),
+            child: Container(
+              width: 100,
+              height: 100,
+              decoration: BoxDecoration(
+                borderRadius: BorderRadius.circular(24),
+                color: colorScheme.surfaceContainerHighest,
+                boxShadow: [
+                  BoxShadow(
+                    color: Colors.black.withValues(alpha: 0.1),
+                    blurRadius: 16,
+                    offset: const Offset(0, 4),
+                  ),
+                ],
+              ),
+              child: ClipRRect(
+                borderRadius: BorderRadius.circular(24),
+                child: ext.iconUrl != null && ext.iconUrl!.isNotEmpty
+                    ? Image.network(
+                        ext.iconUrl!,
+                        fit: BoxFit.cover,
+                        errorBuilder: (context, error, stackTrace) =>
+                            _buildFallbackIcon(ext, colorScheme, 50),
+                      )
+                    : _buildFallbackIcon(ext, colorScheme, 50),
+              ),
+            ),
+          ),
+        ),
+      ),
+      leading: IconButton(
+        icon: const Icon(Icons.arrow_back),
+        onPressed: () => Navigator.pop(context),
+      ),
+    );
+  }
+
+  Widget _buildFallbackIcon(
+    StoreExtension ext,
+    ColorScheme colorScheme,
+    double size,
+  ) {
+    return Container(
+      color: colorScheme.surfaceContainerHighest,
+      child: Icon(
+        _getCategoryIcon(ext.category),
+        size: size,
+        color: colorScheme.onSurfaceVariant,
+      ),
+    );
+  }
+
+  Widget _buildInfoCard(
+    BuildContext context,
+    StoreExtension ext,
+    ColorScheme colorScheme,
+    bool isDownloading,
+  ) {
+    return SliverToBoxAdapter(
+      child: Padding(
+        padding: const EdgeInsets.all(16),
+        child: Card(
+          elevation: 0,
+          color: colorScheme.surfaceContainerLow,
+          shape: RoundedRectangleBorder(
+            borderRadius: BorderRadius.circular(20),
+          ),
+          child: Padding(
+            padding: const EdgeInsets.all(20),
+            child: Column(
+              crossAxisAlignment: CrossAxisAlignment.start,
+              children: [
+                Row(
+                  children: [
+                    Expanded(
+                      child: Column(
+                        crossAxisAlignment: CrossAxisAlignment.start,
+                        children: [
+                          Text(
+                            ext.displayName,
+                            style: Theme.of(context).textTheme.headlineSmall
+                                ?.copyWith(
+                                  fontWeight: FontWeight.bold,
+                                  color: colorScheme.onSurface,
+                                ),
+                          ),
+                          const SizedBox(height: 4),
+                          Text(
+                            'by ${ext.author}',
+                            style: Theme.of(context).textTheme.bodyLarge
+                                ?.copyWith(color: colorScheme.onSurfaceVariant),
+                          ),
+                        ],
+                      ),
+                    ),
+                  ],
+                ),
+
+                const SizedBox(height: 16),
+
+                // Badges row
+                Wrap(
+                  spacing: 8,
+                  runSpacing: 8,
+                  children: [
+                    _Badge(
+                      label: 'v${ext.version}',
+                      color: colorScheme.secondaryContainer,
+                      textColor: colorScheme.onSecondaryContainer,
+                    ),
+                    _Badge(
+                      label: _getCategoryName(ext.category),
+                      color: colorScheme.tertiaryContainer,
+                      textColor: colorScheme.onTertiaryContainer,
+                    ),
+                    if (ext.isInstalled)
+                      _Badge(
+                        label: 'Installed',
+                        color: colorScheme.primaryContainer,
+                        textColor: colorScheme.onPrimaryContainer,
+                        icon: Icons.check,
+                      ),
+                  ],
+                ),
+
+                const SizedBox(height: 24),
+
+                // Action Buttons
+                if (isDownloading)
+                  Center(
+                    child: CircularProgressIndicator(
+                      color: colorScheme.primary,
+                    ),
+                  )
+                else ...[
+                  if (ext.hasUpdate)
+                    FilledButton.icon(
+                      onPressed: () => _updateExtension(ext),
+                      icon: const Icon(Icons.update),
+                      label: Text('Update to v${ext.version}'),
+                      style: FilledButton.styleFrom(
+                        minimumSize: const Size.fromHeight(52),
+                        shape: RoundedRectangleBorder(
+                          borderRadius: BorderRadius.circular(16),
+                        ),
+                      ),
+                    )
+                  else if (ext.isInstalled)
+                    Row(
+                      children: [
+                        Expanded(
+                          child: OutlinedButton.icon(
+                            onPressed: null,
+                            icon: const Icon(Icons.check),
+                            label: const Text('Installed'),
+                            style: OutlinedButton.styleFrom(
+                              minimumSize: const Size(0, 52),
+                              shape: RoundedRectangleBorder(
+                                borderRadius: BorderRadius.circular(16),
+                              ),
+                            ),
+                          ),
+                        ),
+                        const SizedBox(width: 12),
+                        IconButton.filled(
+                          onPressed: () => _uninstallExtension(ext),
+                          icon: const Icon(Icons.delete_outline),
+                          style: IconButton.styleFrom(
+                            backgroundColor: colorScheme.errorContainer,
+                            foregroundColor: colorScheme.onErrorContainer,
+                            minimumSize: const Size(52, 52),
+                            shape: RoundedRectangleBorder(
+                              borderRadius: BorderRadius.circular(16),
+                            ),
+                          ),
+                          tooltip: 'Uninstall',
+                        ),
+                      ],
+                    )
+                  else
+                    FilledButton.icon(
+                      onPressed: () => _installExtension(ext),
+                      icon: const Icon(Icons.download),
+                      label: const Text('Install Extension'),
+                      style: FilledButton.styleFrom(
+                        minimumSize: const Size.fromHeight(52),
+                        shape: RoundedRectangleBorder(
+                          borderRadius: BorderRadius.circular(16),
+                        ),
+                      ),
+                    ),
+                ],
+              ],
+            ),
+          ),
+        ),
+      ),
+    );
+  }
+
+  Widget _buildSectionHeader(
+    BuildContext context,
+    String title,
+    IconData icon,
+    ColorScheme colorScheme,
+  ) {
+    return SliverToBoxAdapter(
+      child: Padding(
+        padding: const EdgeInsets.fromLTRB(20, 8, 20, 8),
+        child: Row(
+          children: [
+            Icon(icon, size: 20, color: colorScheme.primary),
+            const SizedBox(width: 8),
+            Text(
+              title,
+              style: Theme.of(context).textTheme.titleMedium?.copyWith(
+                fontWeight: FontWeight.w600,
+                color: colorScheme.onSurface,
+              ),
+            ),
+          ],
+        ),
+      ),
+    );
+  }
+
+  Widget _buildDescription(
+    BuildContext context,
+    StoreExtension ext,
+    ColorScheme colorScheme,
+  ) {
+    return SliverToBoxAdapter(
+      child: Padding(
+        padding: const EdgeInsets.symmetric(horizontal: 24, vertical: 8),
+        child: Text(
+          ext.description,
+          style: Theme.of(context).textTheme.bodyLarge?.copyWith(
+            height: 1.5,
+            color: colorScheme.onSurface,
+          ),
+        ),
+      ),
+    );
+  }
+
+  Widget _buildTags(
+    BuildContext context,
+    StoreExtension ext,
+    ColorScheme colorScheme,
+  ) {
+    return SliverToBoxAdapter(
+      child: Padding(
+        padding: const EdgeInsets.symmetric(horizontal: 24, vertical: 8),
+        child: Wrap(
+          spacing: 8,
+          runSpacing: 8,
+          children: ext.tags
+              .map(
+                (tag) => Chip(
+                  label: Text(tag),
+                  backgroundColor: colorScheme.surfaceContainer,
+                  labelStyle: Theme.of(context).textTheme.bodySmall?.copyWith(
+                    color: colorScheme.onSurfaceVariant,
+                  ),
+                  side: BorderSide.none,
+                  shape: RoundedRectangleBorder(
+                    borderRadius: BorderRadius.circular(20),
+                  ),
+                ),
+              )
+              .toList(),
+        ),
+      ),
+    );
+  }
+
+  Widget _buildMetadataTable(
+    BuildContext context,
+    StoreExtension ext,
+    ColorScheme colorScheme,
+  ) {
+    return SliverPadding(
+      padding: const EdgeInsets.symmetric(horizontal: 16, vertical: 8),
+      sliver: SliverToBoxAdapter(
+        child: Card(
+          elevation: 0,
+          color: colorScheme.surfaceContainer,
+          shape: RoundedRectangleBorder(
+            borderRadius: BorderRadius.circular(16),
+          ),
+          child: Column(
+            children: [
+              _MetadataRow(
+                label: 'Updated',
+                value: ext.updatedAt.isNotEmpty
+                    ? _formatDate(ext.updatedAt)
+                    : '-',
+                colorScheme: colorScheme,
+              ),
+              _MetadataRow(
+                label: 'ID',
+                value: ext.id,
+                colorScheme: colorScheme,
+              ),
+              _MetadataRow(
+                label: 'Min App Version',
+                value: ext.minAppVersion ?? 'Any',
+                colorScheme: colorScheme,
+                isLast: true,
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+
+  Widget _buildCapabilities(
+    BuildContext context,
+    StoreExtension ext,
+    ColorScheme colorScheme,
+  ) {
+    // Determine capabilities based on category
+    final isMetadataProvider = ext.category == 'metadata' || ext.category == 'integration';
+    final isDownloadProvider = ext.category == 'download';
+    final isLyricsProvider = ext.category == 'lyrics';
+    final isUtility = ext.category == 'utility';
+
+    return SliverPadding(
+      padding: const EdgeInsets.symmetric(horizontal: 16, vertical: 8),
+      sliver: SliverToBoxAdapter(
+        child: Card(
+          elevation: 0,
+          color: colorScheme.surfaceContainer,
+          shape: RoundedRectangleBorder(
+            borderRadius: BorderRadius.circular(16),
+          ),
+          child: Column(
+            children: [
+              _CapabilityRow(
+                icon: Icons.search,
+                label: 'Metadata Provider',
+                enabled: isMetadataProvider,
+                colorScheme: colorScheme,
+              ),
+              _CapabilityRow(
+                icon: Icons.download,
+                label: 'Download Provider',
+                enabled: isDownloadProvider,
+                colorScheme: colorScheme,
+              ),
+              _CapabilityRow(
+                icon: Icons.lyrics,
+                label: 'Lyrics Provider',
+                enabled: isLyricsProvider,
+                colorScheme: colorScheme,
+              ),
+              _CapabilityRow(
+                icon: Icons.build,
+                label: 'Utility Functions',
+                enabled: isUtility,
+                colorScheme: colorScheme,
+                isLast: true,
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+
+  String _formatDate(String dateStr) {
+    try {
+      final date = DateTime.parse(dateStr);
+      final now = DateTime.now();
+      final diff = now.difference(date);
+      
+      if (diff.inDays == 0) {
+        return 'Today';
+      } else if (diff.inDays == 1) {
+        return 'Yesterday';
+      } else if (diff.inDays < 7) {
+        return '${diff.inDays} days ago';
+      } else if (diff.inDays < 30) {
+        return '${(diff.inDays / 7).floor()} weeks ago';
+      } else if (diff.inDays < 365) {
+        return '${(diff.inDays / 30).floor()} months ago';
+      } else {
+        return '${date.year}-${date.month.toString().padLeft(2, '0')}-${date.day.toString().padLeft(2, '0')}';
+      }
+    } catch (_) {
+      return dateStr.split('T').first;
+    }
+  }
+
+  IconData _getCategoryIcon(String category) {
+    switch (category) {
+      case 'metadata':
+        return Icons.label_outline;
+      case 'download':
+        return Icons.download_outlined;
+      case 'utility':
+        return Icons.build_outlined;
+      case 'lyrics':
+        return Icons.lyrics_outlined;
+      case 'integration':
+        return Icons.link;
+      default:
+        return Icons.extension;
+    }
+  }
+
+  String _getCategoryName(String category) {
+    switch (category) {
+      case 'metadata':
+        return 'Metadata';
+      case 'download':
+        return 'Download';
+      case 'utility':
+        return 'Utility';
+      case 'lyrics':
+        return 'Lyrics';
+      case 'integration':
+        return 'Integration';
+      default:
+        return category;
+    }
+  }
+
+  Future<void> _installExtension(StoreExtension ext) async {
+    final tempDir = await getTemporaryDirectory();
+    final appDir = await getApplicationDocumentsDirectory();
+    final extensionsDir = '${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.'
+                : '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.'
+                : 'Failed to update ${ext.displayName}',
+          ),
+          behavior: SnackBarBehavior.floating,
+        ),
+      );
+    }
+  }
+
+  Future<void> _uninstallExtension(StoreExtension ext) async {
+    final confirm = await showDialog<bool>(
+      context: context,
+      builder: (context) => AlertDialog(
+        title: const Text('Uninstall Extension?'),
+        content: Text('Are you sure you want to remove ${ext.displayName}?'),
+        actions: [
+          TextButton(
+            onPressed: () => Navigator.pop(context, false),
+            child: const Text('Cancel'),
+          ),
+          TextButton(
+            onPressed: () => Navigator.pop(context, true),
+            child: Text(
+              'Uninstall',
+              style: TextStyle(color: Theme.of(context).colorScheme.error),
+            ),
+          ),
+        ],
+      ),
+    );
+
+    if (confirm == true) {
+      await ref.read(extensionProvider.notifier).removeExtension(ext.id);
+      await ref.read(storeProvider.notifier).refresh();
+      if (mounted) {
+        Navigator.pop(context);
+      }
+    }
+  }
+}
+
+class _Badge extends StatelessWidget {
+  final String label;
+  final Color color;
+  final Color textColor;
+  final IconData? icon;
+
+  const _Badge({
+    required this.label,
+    required this.color,
+    required this.textColor,
+    this.icon,
+  });
+
+  @override
+  Widget build(BuildContext context) {
+    return Container(
+      padding: const EdgeInsets.symmetric(horizontal: 10, vertical: 4),
+      decoration: BoxDecoration(
+        color: color,
+        borderRadius: BorderRadius.circular(8),
+      ),
+      child: Row(
+        mainAxisSize: MainAxisSize.min,
+        children: [
+          if (icon != null) ...[
+            Icon(icon, size: 14, color: textColor),
+            const SizedBox(width: 4),
+          ],
+          Text(
+            label,
+            style: TextStyle(
+              fontSize: 12,
+              fontWeight: FontWeight.w600,
+              color: textColor,
+            ),
+          ),
+        ],
+      ),
+    );
+  }
+}
+
+class _MetadataRow extends StatelessWidget {
+  final String label;
+  final String value;
+  final ColorScheme colorScheme;
+  final bool isLast;
+
+  const _MetadataRow({
+    required this.label,
+    required this.value,
+    required this.colorScheme,
+    this.isLast = false,
+  });
+
+  @override
+  Widget build(BuildContext context) {
+    return Column(
+      children: [
+        Padding(
+          padding: const EdgeInsets.symmetric(horizontal: 16, vertical: 12),
+          child: Row(
+            mainAxisAlignment: MainAxisAlignment.spaceBetween,
+            children: [
+              Text(
+                label,
+                style: TextStyle(
+                  color: colorScheme.onSurfaceVariant,
+                  fontSize: 14,
+                ),
+              ),
+              Expanded(
+                child: Text(
+                  value,
+                  textAlign: TextAlign.end,
+                  style: TextStyle(
+                    color: colorScheme.onSurface,
+                    fontWeight: FontWeight.w500,
+                    fontSize: 14,
+                  ),
+                  overflow: TextOverflow.ellipsis,
+                ),
+              ),
+            ],
+          ),
+        ),
+        if (!isLast)
+          Divider(
+            height: 1,
+            thickness: 1,
+            color: colorScheme.outlineVariant.withValues(alpha: 0.3),
+            indent: 16,
+            endIndent: 16,
+          ),
+      ],
+    );
+  }
+}
+
+class _CapabilityRow extends StatelessWidget {
+  final IconData icon;
+  final String label;
+  final bool enabled;
+  final ColorScheme colorScheme;
+  final bool isLast;
+
+  const _CapabilityRow({
+    required this.icon,
+    required this.label,
+    required this.enabled,
+    required this.colorScheme,
+    this.isLast = false,
+  });
+
+  @override
+  Widget build(BuildContext context) {
+    return Column(
+      children: [
+        Padding(
+          padding: const EdgeInsets.symmetric(horizontal: 16, vertical: 12),
+          child: Row(
+            children: [
+              Icon(
+                icon,
+                size: 20,
+                color: enabled ? colorScheme.primary : colorScheme.outline,
+              ),
+              const SizedBox(width: 12),
+              Expanded(
+                child: Text(
+                  label,
+                  style: TextStyle(
+                    color: colorScheme.onSurface,
+                    fontSize: 14,
+                  ),
+                ),
+              ),
+              Icon(
+                enabled ? Icons.check_circle : Icons.cancel_outlined,
+                size: 20,
+                color: enabled ? colorScheme.primary : colorScheme.outline,
+              ),
+            ],
+          ),
+        ),
+        if (!isLast)
+          Divider(
+            height: 1,
+            thickness: 1,
+            color: colorScheme.outlineVariant.withValues(alpha: 0.3),
+            indent: 16,
+            endIndent: 16,
+          ),
+      ],
+    );
+  }
+}

lib/screens/store_tab.dart

@@ -0,0 +1,622 @@
+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';
+import 'package:spotiflac_android/screens/store/extension_details_screen.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();
+
+    // Check if widget is still mounted after async operation
+    if (!mounted) return;
+
+    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),
+                        onTap: () => _showExtensionDetails(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'),
+            ),
+          ],
+        ],
+      ),
+    );
+  }
+
+  void _showExtensionDetails(StoreExtension ext) {
+    Navigator.of(context).push(
+      MaterialPageRoute(
+        builder: (context) => ExtensionDetailsScreen(extension: ext),
+      ),
+    );
+  }
+
+  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;
+  final VoidCallback? onTap;
+
+  const _ExtensionItem({
+    required this.extension,
+    required this.showDivider,
+    required this.isDownloading,
+    required this.onInstall,
+    required this.onUpdate,
+    this.onTap,
+  });
+
+  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: [
+        InkWell(
+          onTap: onTap,
+          child: 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/screens/track_metadata_screen.dart

@@ -34,7 +34,13 @@ class _TrackMetadataScreenState extends ConsumerState<TrackMetadataScreen> {
   }
 
   Future<void> _checkFile() async {
-    final file = File(widget.item.filePath);
+    // Strip EXISTS: prefix from legacy history items
+    var filePath = widget.item.filePath;
+    if (filePath.startsWith('EXISTS:')) {
+      filePath = filePath.substring(7);
+    }
+    
+    final file = File(filePath);
     final exists = await file.exists();
     int? size;
     
@@ -67,6 +73,12 @@ class _TrackMetadataScreenState extends ConsumerState<TrackMetadataScreen> {
   int? get discNumber => item.discNumber;
   String? get releaseDate => item.releaseDate;
   String? get isrc => item.isrc;
+  
+  // Clean filePath - strip EXISTS: prefix from legacy history items
+  String get cleanFilePath {
+    final path = item.filePath;
+    return path.startsWith('EXISTS:') ? path.substring(7) : path;
+  }
   int? get bitDepth => item.bitDepth;
   int? get sampleRate => item.sampleRate;
 
@@ -515,7 +527,7 @@ class _TrackMetadataScreenState extends ConsumerState<TrackMetadataScreen> {
   }
 
   Widget _buildFileInfoCard(BuildContext context, ColorScheme colorScheme, bool fileExists, int? fileSize) {
-    final fileName = item.filePath.split(Platform.pathSeparator).last;
+    final fileName = cleanFilePath.split(Platform.pathSeparator).last;
     final fileExtension = fileName.contains('.') ? fileName.split('.').last.toUpperCase() : 'Unknown';
     
     return Card(
@@ -631,7 +643,7 @@ class _TrackMetadataScreenState extends ConsumerState<TrackMetadataScreen> {
             
             // File path
             InkWell(
-              onTap: () => _copyToClipboard(context, item.filePath),
+              onTap: () => _copyToClipboard(context, cleanFilePath),
               borderRadius: BorderRadius.circular(12),
               child: Container(
                 padding: const EdgeInsets.all(12),
@@ -643,7 +655,7 @@ class _TrackMetadataScreenState extends ConsumerState<TrackMetadataScreen> {
                   children: [
                     Expanded(
                       child: Text(
-                        item.filePath,
+                        cleanFilePath,
                         style: Theme.of(context).textTheme.bodySmall?.copyWith(
                           fontFamily: 'monospace',
                           color: colorScheme.onSurfaceVariant,
@@ -776,7 +788,7 @@ class _TrackMetadataScreenState extends ConsumerState<TrackMetadataScreen> {
         item.spotifyId ?? '',
         item.trackName,
         item.artistName,
-        filePath: _fileExists ? item.filePath : null, // Try embedded lyrics first
+        filePath: _fileExists ? cleanFilePath : null, // Try embedded lyrics first
       ).timeout(
         const Duration(seconds: 20),
         onTimeout: () => '', // Return empty string on timeout
@@ -833,7 +845,7 @@ class _TrackMetadataScreenState extends ConsumerState<TrackMetadataScreen> {
         Expanded(
           flex: 2,
           child: FilledButton.icon(
-            onPressed: fileExists ? () => _openFile(context, item.filePath) : null,
+            onPressed: fileExists ? () => _openFile(context, cleanFilePath) : null,
             icon: const Icon(Icons.play_arrow),
             label: const Text('Play'),
             style: FilledButton.styleFrom(
@@ -890,7 +902,7 @@ class _TrackMetadataScreenState extends ConsumerState<TrackMetadataScreen> {
               title: const Text('Copy file path'),
               onTap: () {
                 Navigator.pop(context);
-                _copyToClipboard(context, item.filePath);
+                _copyToClipboard(context, cleanFilePath);
               },
             ),
             ListTile(
@@ -933,7 +945,7 @@ class _TrackMetadataScreenState extends ConsumerState<TrackMetadataScreen> {
             onPressed: () async {
               // Delete the file first
               try {
-                final file = File(item.filePath);
+                final file = File(cleanFilePath);
                 if (await file.exists()) {
                   await file.delete();
                 }
@@ -984,7 +996,7 @@ class _TrackMetadataScreenState extends ConsumerState<TrackMetadataScreen> {
   }
 
   Future<void> _shareFile(BuildContext context) async {
-    final file = File(item.filePath);
+    final file = File(cleanFilePath);
     if (!await file.exists()) {
       if (context.mounted) {
         ScaffoldMessenger.of(context).showSnackBar(
@@ -996,7 +1008,7 @@ class _TrackMetadataScreenState extends ConsumerState<TrackMetadataScreen> {
     
     await SharePlus.instance.share(
       ShareParams(
-        files: [XFile(item.filePath)],
+        files: [XFile(cleanFilePath)],
         text: '${item.trackName} - ${item.artistName}',
       ),
     );

lib/services/platform_bridge.dart

@@ -753,6 +753,40 @@ class PlatformBridge {
     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
@@ -773,4 +807,56 @@ class PlatformBridge {
     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/settings_group.dart

@@ -72,7 +72,7 @@ class SettingsItem extends StatelessWidget {
         InkWell(
           onTap: onTap,
           splashColor: colorScheme.primary.withValues(alpha: 0.12),
-          highlightColor: colorScheme.primary.withValues(alpha: 0.08),
+          highlightColor: Colors.transparent,
           child: Padding(
             padding: const EdgeInsets.symmetric(horizontal: 20, vertical: 16),
             child: Row(
@@ -159,7 +159,7 @@ class SettingsSwitchItem extends StatelessWidget {
           child: InkWell(
             onTap: isDisabled ? null : () => onChanged!(!value),
             splashColor: colorScheme.primary.withValues(alpha: 0.12),
-            highlightColor: colorScheme.primary.withValues(alpha: 0.08),
+            highlightColor: Colors.transparent,
             child: Padding(
               padding: const EdgeInsets.symmetric(horizontal: 20, vertical: 12),
               child: Row(

pubspec.yaml

@@ -1,7 +1,7 @@
 name: spotiflac_android
 description: Download Spotify tracks in FLAC from Tidal, Qobuz & Amazon Music
 publish_to: "none"
-version: 3.0.0-alpha.3+52
+version: 3.0.0+57
 
 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: 3.0.0-alpha.2+51
+version: 3.0.0+57
 
 environment:
   sdk: ^3.10.0