chore: bump version to 3.0.0-alpha.4

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

.github/ISSUE_TEMPLATE/bug_report.yml

@@ -16,7 +16,7 @@ body:
       options:
         - label: I have searched existing issues and this bug hasn't been reported yet
           required: true
-        - label: I am using the latest version of SpotiFLAC
+        - label: I am using the latest version of SpotiFLAC (Stable Version)
           required: true
 
   - type: textarea

.github/ISSUE_TEMPLATE/config.yml

@@ -3,3 +3,6 @@ contact_links:
   - name: README
     url: https://github.com/zarzet/SpotiFLAC-Mobile#readme
     about: Check the README for setup instructions and FAQ
+  - name: Extension Development Guide
+    url: https://zarz.moe/docs
+    about: Documentation for building SpotiFLAC extensions

.github/ISSUE_TEMPLATE/download_issue.yml

@@ -16,7 +16,7 @@ body:
       options:
         - label: I have tried downloading with a different service (Tidal/Qobuz/Amazon)
           required: true
-        - label: I am using the latest version of SpotiFLAC
+        - label: I am using the latest version of SpotiFLAC (Stable Version)
           required: true
 
   - type: dropdown

CHANGELOG.md

@@ -1,5 +1,141 @@
 # Changelog
 
+## [3.0.0-alpha.4] - Upcoming
+
+### Added
+
+- **Extension Store**: Browse and install extensions directly from the app
+  - New "Store" tab in bottom navigation
+  - Browse extensions by category (Metadata, Download, Utility, Lyrics, Integration)
+  - Search extensions by name, description, or tags
+  - One-tap install and update
+  - Offline cache for browsing without internet
+  - Extensions hosted at github.com/zarzet/SpotiFLAC-Extension
+
+- **Custom URL Handler for Extensions**: Extensions can now register custom URL patterns
+  - Handle URLs from YouTube Music, SoundCloud, Bandcamp, etc.
+  - Manifest config: `urlHandler: { enabled: true, patterns: ["music.youtube.com"] }`
+  - Implement `handleURL(url)` function in extension to parse and return track metadata
+  - SpotiFLAC automatically routes matching URLs to the appropriate extension
+  - Supports share intents and paste from clipboard
+
+- **Artist URL Handler Support**: Extensions can now return artist data from URL handlers
+  - Added `type: "artist"` handling in track_provider.dart
+  - Navigate to artist screen with albums list from extension
+
+- **HMAC-SHA1 Utility**: New `utils.hmacSHA1(key, message)` function for extensions
+  - Enables TOTP generation and other cryptographic operations
+  - Returns byte array for flexible use
+
+### Fixed
+
+- **Extension Store Refresh**: Store tab now properly refreshes after uninstalling an extension
+  - "Installed" badge correctly updates to "Install" button
+
+### Documentation
+
+- Updated `docs/EXTENSION_DEVELOPMENT.md`:
+  - Added Custom URL Handler section with examples
+  - Added `handleURL` function documentation
+  - Added URL pattern examples for YouTube, SoundCloud, Bandcamp
+  - Added `utils.hmacSHA1` documentation with TOTP example
+
+### Extensions
+
+- **Spotify Web Extension** (example): New extension for Spotify metadata via web API
+  - Supports personalized playlists (Daily Mix, Discover Weekly, Release Radar, etc.)
+  - Search, album, playlist, track, and artist fetching
+  - Available in Extension Store (3.0.0-alpha.4)
+
+---
+
+## [3.0.0-alpha.3] - 2026-01-12
+
+### Added
+
+- **Separate Singles Folder**: Option to organize downloads into Albums/ and Singles/ folders
+  - Based on `album_type` from Spotify/Deezer metadata
+  - Toggle in Settings > Download > Separate Singles Folder
+  - Singles saved to `{output}/Singles/`, albums to `{output}/Albums/`
+- **Browser-like Polyfills**: New global APIs for easier library porting
+  - `fetch()` - Browser-compatible HTTP API with `json()`, `text()`, `arrayBuffer()` methods
+  - `atob()` / `btoa()` - Global Base64 encoding/decoding
+  - `TextEncoder` / `TextDecoder` - UTF-8 text encoding classes
+  - `URL` / `URLSearchParams` - URL parsing and manipulation classes
+  - Makes porting browser libraries (like `youtubei.js`) much easier
+
+### Performance
+
+- **Parallel API Calls**: Download URL fetching now uses parallel requests
+  - Tidal: All 8 APIs requested simultaneously, first success wins
+  - Qobuz: Both APIs requested simultaneously, first success wins
+  - Significantly reduces download URL fetch time
+
+### Fixed
+
+- **Duplicate History Entries**: Fixed duplicate entries when re-downloading same track
+  - Detects existing entries by Spotify ID, Deezer ID, or ISRC
+  - Replaces existing entry and moves to top of list
+  - Auto-deduplicates existing history on app load
+- **Extension Search Fallback**: Fixed error when extension is disabled but still called for search
+  - Now checks if extension is still enabled before calling custom search
+  - Auto-resets search provider to default if extension was disabled
+- **Permission Error Message**: Fixed download showing "Song not found" when actually a permission error
+  - Now shows proper message: "Cannot write to folder, check storage permission"
+  - Added `permission` error type detection in backend
+- **Android 13+ Storage Permission**: Fixed storage permission not working on Android 13+
+  - Android 13+ now requests both `MANAGE_EXTERNAL_STORAGE` and `READ_MEDIA_AUDIO`
+  - `MANAGE_EXTERNAL_STORAGE` opens Settings (system-level, persists across app data clear)
+  - `READ_MEDIA_AUDIO` shows dialog (app-level, resets on app data clear)
+  - Proper permission check before showing "granted" status
+
+---
+
+## [3.0.0-alpha.2] - 2026-01-12
+
+### Added
+
+- **Full HTTP Method Support**: New shortcut methods for all common HTTP verbs
+  - `http.put(url, body, headers)` - PUT requests
+  - `http.delete(url, headers)` - DELETE requests  
+  - `http.patch(url, body, headers)` - PATCH requests
+  - `http.clearCookies()` - Clear all cookies for the extension
+- **Persistent Cookie Jar**: Each extension now has its own cookie jar
+  - Cookies automatically stored from `Set-Cookie` headers
+  - Cookies automatically sent with subsequent requests to same domain
+  - Useful for APIs requiring session cookies (YouTube, etc.)
+- **Multi-Value Header Support**: Response headers now return arrays for multi-value headers
+  - `Set-Cookie` and other headers with multiple values returned as arrays
+  - Single-value headers still returned as strings for convenience
+- **Generic HTTP Request Method**: New `http.request()` for full HTTP control
+  - Supports all HTTP methods (GET, POST, PUT, DELETE, PATCH, etc.)
+  - Single options object for cleaner API: `http.request(url, { method, body, headers })`
+- **Response Helper Properties**: HTTP responses now include convenience properties
+  - `response.ok` - true if status code is 2xx
+  - `response.status` - alias for `statusCode`
+
+### Fixed
+
+- **User-Agent Header Respect**: Custom `User-Agent` headers are now respected
+  - Previously, extension-provided User-Agent was overwritten
+  - Now only sets default User-Agent if extension doesn't provide one
+- **HTTP POST Body Auto-Stringify**: `http.post()` now automatically stringifies objects to JSON
+  - Previously, passing an object as body resulted in `[object Object]`
+  - Now objects and arrays are automatically JSON.stringify'd
+  - String bodies still work as before (no double-encoding)
+
+### Documentation
+
+- Updated `docs/EXTENSION_DEVELOPMENT.md`:
+  - Added complete HTTP API documentation with all methods
+  - Added Cookie Jar documentation
+  - Added `http.put()`, `http.delete()`, `http.patch()`, `http.clearCookies()` docs
+  - Added YouTube Music / Innertube API example with custom User-Agent
+  - Added common domain lists for YouTube, SoundCloud, Bandcamp
+  - Improved HTTP API documentation with response properties
+
+---
+
 ## [3.0.0-alpha.1] - 2026-01-11
 
 #### Extension System
@@ -93,6 +229,32 @@
 
 ---
 
+## [2.2.8] - 2026-01-12
+
+### Added
+
+- **Multi-Select Batch Delete**: Long-press tracks in History to enter selection mode
+  - Select multiple tracks at once
+  - "Select All" and "Delete Selected" actions
+  - Modern Material 3 bottom action bar (slides up from bottom)
+  - Works in both grid and list view modes
+- **History Filter Tabs**: Filter history by All/Albums/Singles
+  - Album = tracks where album has >1 track in history
+  - Single = tracks where album has only 1 track in history
+  - Filter chips show counts for each category
+- **Album Grouping View**: When "Albums" filter is selected, tracks are grouped by album
+  - Album cards displayed in 2-column grid with cover art and track count badge
+  - Tap album to open dedicated album detail screen
+  - Album detail shows all downloaded tracks from that album
+  - Multi-select delete support within album view
+  - Auto-navigates back when album has <2 tracks remaining
+
+### Changed
+
+- **Issue Templates**: Updated version confirmation checkbox to specify "(Stable Version)"
+
+---
+
 ## [2.2.7] - 2026-01-11
 
 ### Added

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

@@ -218,6 +218,12 @@ class MainActivity: FlutterActivity() {
                             }
                             result.success(null)
                         }
+                        "hasSpotifyCredentials" -> {
+                            val hasCredentials = withContext(Dispatchers.IO) {
+                                Gobackend.checkSpotifyCredentials()
+                            }
+                            result.success(hasCredentials)
+                        }
                         "preWarmTrackCache" -> {
                             val tracksJson = call.argument<String>("tracks") ?: "[]"
                             withContext(Dispatchers.IO) {
@@ -545,6 +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") ?: ""
@@ -560,6 +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/deezer.go

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

go_backend/exports.go

@@ -32,18 +32,26 @@ func ParseSpotifyURL(url string) (string, error) {
 }
 
 // SetSpotifyAPICredentials sets custom Spotify API credentials from Flutter
-// Pass empty strings to use default credentials
 func SetSpotifyAPICredentials(clientID, clientSecret string) {
 	SetSpotifyCredentials(clientID, clientSecret)
 }
 
+// CheckSpotifyCredentials checks if Spotify credentials are configured
+// Returns true if credentials are available (custom or env vars)
+func CheckSpotifyCredentials() bool {
+	return HasSpotifyCredentials()
+}
+
 // GetSpotifyMetadata fetches metadata from Spotify URL
 // Returns JSON with track/album/playlist data
 func GetSpotifyMetadata(spotifyURL string) (string, error) {
 	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
 	defer cancel()
 
-	client := NewSpotifyMetadataClient()
+	client, err := NewSpotifyMetadataClient()
+	if err != nil {
+		return "", err
+	}
 	data, err := client.GetFilteredData(ctx, spotifyURL, false, 0)
 	if err != nil {
 		return "", err
@@ -63,7 +71,10 @@ func SearchSpotify(query string, limit int) (string, error) {
 	ctx, cancel := context.WithTimeout(context.Background(), 15*time.Second)
 	defer cancel()
 
-	client := NewSpotifyMetadataClient()
+	client, err := NewSpotifyMetadataClient()
+	if err != nil {
+		return "", err
+	}
 	results, err := client.SearchTracks(ctx, query, limit)
 	if err != nil {
 		return "", err
@@ -83,7 +94,10 @@ func SearchSpotifyAll(query string, trackLimit, artistLimit int) (string, error)
 	ctx, cancel := context.WithTimeout(context.Background(), 15*time.Second)
 	defer cancel()
 
-	client := NewSpotifyMetadataClient()
+	client, err := NewSpotifyMetadataClient()
+	if err != nil {
+		return "", err
+	}
 	results, err := client.SearchAll(ctx, query, trackLimit, artistLimit)
 	if err != nil {
 		return "", err
@@ -893,21 +907,26 @@ func GetSpotifyMetadataWithDeezerFallback(spotifyURL string) (string, error) {
 	defer cancel()
 
 	// Try Spotify first
-	client := NewSpotifyMetadataClient()
-	data, err := client.GetFilteredData(ctx, spotifyURL, false, 0)
-	if err == nil {
-		jsonBytes, err := json.Marshal(data)
-		if err != nil {
+	client, err := NewSpotifyMetadataClient()
+	if err != nil {
+		// No Spotify credentials - fall through to Deezer fallback
+		LogWarn("Spotify", "Credentials not configured, falling back to Deezer")
+	} else {
+		data, err := client.GetFilteredData(ctx, spotifyURL, false, 0)
+		if err == nil {
+			jsonBytes, err := json.Marshal(data)
+			if err != nil {
+				return "", err
+			}
+			return string(jsonBytes), nil
+		}
+
+		// Check if it's a rate limit error
+		errStr := strings.ToLower(err.Error())
+		if !strings.Contains(errStr, "429") && !strings.Contains(errStr, "rate") && !strings.Contains(errStr, "limit") {
+			// Not a rate limit error, return original error
 			return "", err
 		}
-		return string(jsonBytes), nil
-	}
-
-	// Check if it's a rate limit error
-	errStr := strings.ToLower(err.Error())
-	if !strings.Contains(errStr, "429") && !strings.Contains(errStr, "rate") && !strings.Contains(errStr, "limit") {
-		// Not a rate limit error, return original error
-		return "", err
 	}
 
 	// Rate limited - try Deezer fallback for tracks and albums
@@ -996,6 +1015,12 @@ func errorResponse(msg string) (string, error) {
 		strings.Contains(lowerMsg, "try using vpn") ||
 		strings.Contains(lowerMsg, "change dns") {
 		errorType = "isp_blocked"
+	} else if strings.Contains(lowerMsg, "permission") ||
+		strings.Contains(lowerMsg, "operation not permitted") ||
+		strings.Contains(lowerMsg, "access denied") ||
+		strings.Contains(lowerMsg, "failed to create file") ||
+		strings.Contains(lowerMsg, "failed to create directory") {
+		errorType = "permission"
 	} else if strings.Contains(lowerMsg, "not found") ||
 		strings.Contains(lowerMsg, "not available") ||
 		strings.Contains(lowerMsg, "no results") ||
@@ -1481,6 +1506,135 @@ 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 {
+		response["artist"] = map[string]interface{}{
+			"id":        result.Artist.ID,
+			"name":      result.Artist.Name,
+			"image_url": result.Artist.ImageURL,
+		}
+	}
+
+	jsonBytes, err := json.Marshal(response)
+	if err != nil {
+		return "", err
+	}
+
+	return string(jsonBytes), nil
+}
+
+// FindURLHandlerJSON finds an extension that can handle the given URL
+// Returns extension ID or empty string if none found
+func FindURLHandlerJSON(url string) string {
+	manager := GetExtensionManager()
+	handler := manager.FindURLHandler(url)
+	if handler == nil {
+		return ""
+	}
+	return handler.extension.ID
+}
+
+// GetURLHandlersJSON returns all extensions that handle custom URLs
+func GetURLHandlersJSON() (string, error) {
+	manager := GetExtensionManager()
+	handlers := manager.GetURLHandlers()
+
+	result := make([]map[string]interface{}, 0, len(handlers))
+	for _, h := range handlers {
+		result = append(result, map[string]interface{}{
+			"id":           h.extension.ID,
+			"display_name": h.extension.Manifest.DisplayName,
+			"patterns":     h.extension.Manifest.URLHandler.Patterns,
+		})
+	}
+
+	jsonBytes, err := json.Marshal(result)
+	if err != nil {
+		return "", err
+	}
+
+	return string(jsonBytes), nil
+}
+
 // ==================== EXTENSION POST-PROCESSING ====================
 
 // RunPostProcessingJSON runs post-processing hooks on a file
@@ -1538,3 +1692,100 @@ 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

@@ -231,7 +231,7 @@ 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,
 	}
@@ -459,7 +459,7 @@ 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 +583,10 @@ 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)
@@ -633,11 +634,11 @@ 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

@@ -74,6 +74,12 @@ 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 +119,7 @@ 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 +277,29 @@ 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

@@ -981,6 +981,69 @@ 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 := p.vm.RunString(script)
+	if err != nil {
+		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
@@ -1120,6 +1183,61 @@ 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 +1,467 @@
+// Package gobackend provides File API for extension runtime
+package gobackend
+
+import (
+	"fmt"
+	"io"
+	"net/http"
+	"os"
+	"path/filepath"
+	"strings"
+
+	"github.com/dop251/goja"
+)
+
+// ==================== File API (Sandboxed) ====================
+
+// validatePath checks if the path is within the extension's data directory
+// For absolute paths (from download queue), it allows them if they're valid
+func (r *ExtensionRuntime) validatePath(path string) (string, error) {
+	// Clean and resolve the path
+	cleanPath := filepath.Clean(path)
+
+	// If path is absolute, allow it (for download queue paths)
+	// This is safe because the Go backend controls what paths are passed
+	if filepath.IsAbs(cleanPath) {
+		return cleanPath, nil
+	}
+
+	// For relative paths, join with data directory
+	fullPath := filepath.Join(r.dataDir, cleanPath)
+
+	// Resolve to absolute path
+	absPath, err := filepath.Abs(fullPath)
+	if err != nil {
+		return "", fmt.Errorf("invalid path: %w", err)
+	}
+
+	// Ensure path is within data directory
+	absDataDir, _ := filepath.Abs(r.dataDir)
+	if !strings.HasPrefix(absPath, absDataDir) {
+		return "", fmt.Errorf("file access denied: path '%s' is outside sandbox", path)
+	}
+
+	return absPath, nil
+}
+
+// fileDownload downloads a file from URL to the specified path
+// Supports progress callback via options.onProgress
+func (r *ExtensionRuntime) fileDownload(call goja.FunctionCall) goja.Value {
+	if len(call.Arguments) < 2 {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   "URL and output path are required",
+		})
+	}
+
+	urlStr := call.Arguments[0].String()
+	outputPath := call.Arguments[1].String()
+
+	// Validate domain
+	if err := r.validateDomain(urlStr); err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+
+	// Validate output path (allows absolute paths for download queue)
+	fullPath, err := r.validatePath(outputPath)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+
+	// Get options if provided
+	var onProgress goja.Callable
+	var headers map[string]string
+	if len(call.Arguments) > 2 && !goja.IsUndefined(call.Arguments[2]) && !goja.IsNull(call.Arguments[2]) {
+		optionsObj := call.Arguments[2].Export()
+		if opts, ok := optionsObj.(map[string]interface{}); ok {
+			// Extract headers
+			if h, ok := opts["headers"].(map[string]interface{}); ok {
+				headers = make(map[string]string)
+				for k, v := range h {
+					headers[k] = fmt.Sprintf("%v", v)
+				}
+			}
+			// Extract onProgress callback
+			if progressVal, ok := opts["onProgress"]; ok {
+				if callable, ok := goja.AssertFunction(r.vm.ToValue(progressVal)); ok {
+					onProgress = callable
+				}
+			}
+		}
+	}
+
+	// Create directory if needed
+	dir := filepath.Dir(fullPath)
+	if err := os.MkdirAll(dir, 0755); err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   fmt.Sprintf("failed to create directory: %v", err),
+		})
+	}
+
+	// Create HTTP request
+	req, err := http.NewRequest("GET", urlStr, nil)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+
+	// Set headers
+	for k, v := range headers {
+		req.Header.Set(k, v)
+	}
+	if req.Header.Get("User-Agent") == "" {
+		req.Header.Set("User-Agent", "SpotiFLAC-Extension/1.0")
+	}
+
+	// Download file
+	resp, err := r.httpClient.Do(req)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != 200 {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   fmt.Sprintf("HTTP error: %d", resp.StatusCode),
+		})
+	}
+
+	// Create output file
+	out, err := os.Create(fullPath)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   fmt.Sprintf("failed to create file: %v", err),
+		})
+	}
+	defer out.Close()
+
+	// Get content length for progress
+	contentLength := resp.ContentLength
+
+	// Copy content with progress reporting
+	var written int64
+	buf := make([]byte, 32*1024) // 32KB buffer
+	for {
+		nr, er := resp.Body.Read(buf)
+		if nr > 0 {
+			nw, ew := out.Write(buf[0:nr])
+			if nw < 0 || nr < nw {
+				nw = 0
+				if ew == nil {
+					ew = fmt.Errorf("invalid write result")
+				}
+			}
+			written += int64(nw)
+			if ew != nil {
+				return r.vm.ToValue(map[string]interface{}{
+					"success": false,
+					"error":   fmt.Sprintf("failed to write file: %v", ew),
+				})
+			}
+			if nr != nw {
+				return r.vm.ToValue(map[string]interface{}{
+					"success": false,
+					"error":   "short write",
+				})
+			}
+
+			// Report progress
+			if onProgress != nil && contentLength > 0 {
+				_, _ = onProgress(goja.Undefined(), r.vm.ToValue(written), r.vm.ToValue(contentLength))
+			}
+		}
+		if er != nil {
+			if er != io.EOF {
+				return r.vm.ToValue(map[string]interface{}{
+					"success": false,
+					"error":   fmt.Sprintf("failed to read response: %v", er),
+				})
+			}
+			break
+		}
+	}
+
+	GoLog("[Extension:%s] Downloaded %d bytes to %s\n", r.extensionID, written, fullPath)
+
+	return r.vm.ToValue(map[string]interface{}{
+		"success": true,
+		"path":    fullPath,
+		"size":    written,
+	})
+}
+
+// fileExists checks if a file exists in the sandbox
+func (r *ExtensionRuntime) fileExists(call goja.FunctionCall) goja.Value {
+	if len(call.Arguments) < 1 {
+		return r.vm.ToValue(false)
+	}
+
+	path := call.Arguments[0].String()
+	fullPath, err := r.validatePath(path)
+	if err != nil {
+		return r.vm.ToValue(false)
+	}
+
+	_, err = os.Stat(fullPath)
+	return r.vm.ToValue(err == nil)
+}
+
+// fileDelete deletes a file in the sandbox
+func (r *ExtensionRuntime) fileDelete(call goja.FunctionCall) goja.Value {
+	if len(call.Arguments) < 1 {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   "path is required",
+		})
+	}
+
+	path := call.Arguments[0].String()
+	fullPath, err := r.validatePath(path)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+
+	if err := os.Remove(fullPath); err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+
+	return r.vm.ToValue(map[string]interface{}{
+		"success": true,
+	})
+}
+
+// fileRead reads a file from the sandbox
+func (r *ExtensionRuntime) fileRead(call goja.FunctionCall) goja.Value {
+	if len(call.Arguments) < 1 {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   "path is required",
+		})
+	}
+
+	path := call.Arguments[0].String()
+	fullPath, err := r.validatePath(path)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+
+	data, err := os.ReadFile(fullPath)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+
+	return r.vm.ToValue(map[string]interface{}{
+		"success": true,
+		"data":    string(data),
+	})
+}
+
+// fileWrite writes data to a file in the sandbox
+func (r *ExtensionRuntime) fileWrite(call goja.FunctionCall) goja.Value {
+	if len(call.Arguments) < 2 {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   "path and data are required",
+		})
+	}
+
+	path := call.Arguments[0].String()
+	data := call.Arguments[1].String()
+
+	fullPath, err := r.validatePath(path)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+
+	// Create directory if needed
+	dir := filepath.Dir(fullPath)
+	if err := os.MkdirAll(dir, 0755); err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   fmt.Sprintf("failed to create directory: %v", err),
+		})
+	}
+
+	if err := os.WriteFile(fullPath, []byte(data), 0644); err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+
+	return r.vm.ToValue(map[string]interface{}{
+		"success": true,
+		"path":    fullPath,
+	})
+}
+
+// fileCopy copies a file within the sandbox
+func (r *ExtensionRuntime) fileCopy(call goja.FunctionCall) goja.Value {
+	if len(call.Arguments) < 2 {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   "source and destination paths are required",
+		})
+	}
+
+	srcPath := call.Arguments[0].String()
+	dstPath := call.Arguments[1].String()
+
+	fullSrc, err := r.validatePath(srcPath)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+
+	fullDst, err := r.validatePath(dstPath)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+
+	// Read source file
+	data, err := os.ReadFile(fullSrc)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   fmt.Sprintf("failed to read source: %v", err),
+		})
+	}
+
+	// Create destination directory if needed
+	dir := filepath.Dir(fullDst)
+	if err := os.MkdirAll(dir, 0755); err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   fmt.Sprintf("failed to create directory: %v", err),
+		})
+	}
+
+	// Write to destination
+	if err := os.WriteFile(fullDst, data, 0644); err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   fmt.Sprintf("failed to write destination: %v", err),
+		})
+	}
+
+	return r.vm.ToValue(map[string]interface{}{
+		"success": true,
+		"path":    fullDst,
+	})
+}
+
+// fileMove moves/renames a file within the sandbox
+func (r *ExtensionRuntime) fileMove(call goja.FunctionCall) goja.Value {
+	if len(call.Arguments) < 2 {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   "source and destination paths are required",
+		})
+	}
+
+	srcPath := call.Arguments[0].String()
+	dstPath := call.Arguments[1].String()
+
+	fullSrc, err := r.validatePath(srcPath)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+
+	fullDst, err := r.validatePath(dstPath)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+
+	// Create destination directory if needed
+	dir := filepath.Dir(fullDst)
+	if err := os.MkdirAll(dir, 0755); err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   fmt.Sprintf("failed to create directory: %v", err),
+		})
+	}
+
+	if err := os.Rename(fullSrc, fullDst); err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   fmt.Sprintf("failed to move file: %v", err),
+		})
+	}
+
+	return r.vm.ToValue(map[string]interface{}{
+		"success": true,
+		"path":    fullDst,
+	})
+}
+
+// fileGetSize returns the size of a file in bytes
+func (r *ExtensionRuntime) fileGetSize(call goja.FunctionCall) goja.Value {
+	if len(call.Arguments) < 1 {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   "path is required",
+		})
+	}
+
+	path := call.Arguments[0].String()
+	fullPath, err := r.validatePath(path)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+
+	info, err := os.Stat(fullPath)
+	if err != nil {
+		return r.vm.ToValue(map[string]interface{}{
+			"success": false,
+			"error":   err.Error(),
+		})
+	}
+
+	return r.vm.ToValue(map[string]interface{}{
+		"success": true,
+		"size":    info.Size(),
+	})
+}

go_backend/extension_runtime_http.go

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

go_backend/extension_runtime_matching.go

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

go_backend/extension_runtime_polyfills.go

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

go_backend/extension_runtime_storage.go

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

go_backend/extension_runtime_utils.go

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

go_backend/extension_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/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/qobuz.go

@@ -12,6 +12,7 @@ import (
 	"path/filepath"
 	"strings"
 	"sync"
+	"time"
 )
 
 // QobuzDownloader handles Qobuz downloads
@@ -635,6 +636,125 @@ func (q *QobuzDownloader) SearchTrackByMetadataWithDuration(trackName, artistNam
 	return nil, fmt.Errorf("no matching track found for: %s - %s", artistName, trackName)
 }
 
+// qobuzAPIResult holds the result from a parallel API request
+type qobuzAPIResult struct {
+	apiURL      string
+	downloadURL string
+	err         error
+	duration    time.Duration
+}
+
+// getQobuzDownloadURLParallel requests download URL from all APIs in parallel
+// "Siapa cepat dia dapat" - first successful response wins
+func getQobuzDownloadURLParallel(apis []string, trackID int64, quality string) (string, string, error) {
+	if len(apis) == 0 {
+		return "", "", fmt.Errorf("no APIs available")
+	}
+
+	GoLog("[Qobuz] Requesting download URL from %d APIs in parallel...\n", len(apis))
+
+	resultChan := make(chan qobuzAPIResult, len(apis))
+	startTime := time.Now()
+
+	// Start all requests in parallel
+	for _, apiURL := range apis {
+		go func(api string) {
+			reqStart := time.Now()
+
+			client := &http.Client{
+				Timeout: 15 * time.Second,
+			}
+
+			reqURL := fmt.Sprintf("%s%d&quality=%s", api, trackID, quality)
+
+			req, err := http.NewRequest("GET", reqURL, nil)
+			if err != nil {
+				resultChan <- qobuzAPIResult{apiURL: api, err: err, duration: time.Since(reqStart)}
+				return
+			}
+
+			resp, err := client.Do(req)
+			if err != nil {
+				resultChan <- qobuzAPIResult{apiURL: api, err: err, duration: time.Since(reqStart)}
+				return
+			}
+			defer resp.Body.Close()
+
+			if resp.StatusCode != 200 {
+				resultChan <- qobuzAPIResult{apiURL: api, err: fmt.Errorf("HTTP %d", resp.StatusCode), duration: time.Since(reqStart)}
+				return
+			}
+
+			body, err := io.ReadAll(resp.Body)
+			if err != nil {
+				resultChan <- qobuzAPIResult{apiURL: api, err: err, duration: time.Since(reqStart)}
+				return
+			}
+
+			// Check if response is HTML (error page)
+			if len(body) > 0 && body[0] == '<' {
+				resultChan <- qobuzAPIResult{apiURL: api, err: fmt.Errorf("received HTML instead of JSON"), duration: time.Since(reqStart)}
+				return
+			}
+
+			// Check for error in JSON response
+			var errorResp struct {
+				Error string `json:"error"`
+			}
+			if json.Unmarshal(body, &errorResp) == nil && errorResp.Error != "" {
+				resultChan <- qobuzAPIResult{apiURL: api, err: fmt.Errorf(errorResp.Error), duration: time.Since(reqStart)}
+				return
+			}
+
+			var result struct {
+				URL string `json:"url"`
+			}
+			if err := json.Unmarshal(body, &result); err != nil {
+				resultChan <- qobuzAPIResult{apiURL: api, err: fmt.Errorf("invalid JSON: %v", err), duration: time.Since(reqStart)}
+				return
+			}
+
+			if result.URL != "" {
+				resultChan <- qobuzAPIResult{apiURL: api, downloadURL: result.URL, err: nil, duration: time.Since(reqStart)}
+				return
+			}
+
+			resultChan <- qobuzAPIResult{apiURL: api, err: fmt.Errorf("no download URL in response"), duration: time.Since(reqStart)}
+		}(apiURL)
+	}
+
+	// Collect results - return first success
+	var errors []string
+	var firstSuccess *qobuzAPIResult
+
+	for i := 0; i < len(apis); i++ {
+		result := <-resultChan
+		if result.err == nil && firstSuccess == nil {
+			firstSuccess = &result
+			GoLog("[Qobuz] [Parallel] ✓ Got response from %s in %v\n", result.apiURL, result.duration)
+
+			// Drain remaining results to avoid goroutine leaks
+			go func(remaining int) {
+				for j := 0; j < remaining; j++ {
+					<-resultChan
+				}
+			}(len(apis) - i - 1)
+
+			GoLog("[Qobuz] [Parallel] Total time: %v (first success)\n", time.Since(startTime))
+			return firstSuccess.apiURL, firstSuccess.downloadURL, nil
+		} else if result.err != nil {
+			errMsg := result.err.Error()
+			if len(errMsg) > 50 {
+				errMsg = errMsg[:50] + "..."
+			}
+			errors = append(errors, fmt.Sprintf("%s: %s", result.apiURL, errMsg))
+		}
+	}
+
+	GoLog("[Qobuz] [Parallel] All %d APIs failed in %v\n", len(apis), time.Since(startTime))
+	return "", "", fmt.Errorf("all %d Qobuz APIs failed. Errors: %v", len(apis), errors)
+}
+
 // getQobuzDownloadURLSequential requests download URL from APIs sequentially
 // Uses same URL format as PC version: /api/stream?trackId={id}&quality={quality}
 func getQobuzDownloadURLSequential(apis []string, trackID int64, quality string) (string, string, error) {
@@ -706,14 +826,16 @@ func getQobuzDownloadURLSequential(apis []string, trackID int64, quality string)
 	return "", "", fmt.Errorf("all %d Qobuz APIs failed. Errors: %v", len(apis), errors)
 }
 
-// GetDownloadURL gets download URL for a track - tries APIs sequentially
+// GetDownloadURL gets download URL for a track - tries ALL APIs in parallel
+// "Siapa cepat dia dapat" - first successful response wins
 func (q *QobuzDownloader) GetDownloadURL(trackID int64, quality string) (string, error) {
 	apis := q.GetAvailableAPIs()
 	if len(apis) == 0 {
 		return "", fmt.Errorf("no Qobuz API available")
 	}
 
-	_, downloadURL, err := getQobuzDownloadURLSequential(apis, trackID, quality)
+	// Use parallel approach - request from all APIs simultaneously
+	_, downloadURL, err := getQobuzDownloadURLParallel(apis, trackID, quality)
 	if err != nil {
 		return "", err
 	}

go_backend/spotify.go

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

go_backend/tidal.go

@@ -640,20 +640,135 @@ type TidalDownloadInfo struct {
 }
 
 // tidalAPIResult holds the result from a parallel API request
-// Kept for potential future use with _getDownloadURLParallel
-// type tidalAPIResult struct {
-// 	apiURL   string
-// 	info     TidalDownloadInfo
-// 	err      error
-// 	duration time.Duration
-// }
+type tidalAPIResult struct {
+	apiURL   string
+	info     TidalDownloadInfo
+	err      error
+	duration time.Duration
+}
 
-// _getDownloadURLParallel requests download URL from all APIs in parallel
+// getDownloadURLParallel requests download URL from all APIs in parallel
 // Returns the first successful result (supports both v1 and v2 API formats)
-// Kept for potential future use - currently using sequential approach
-// func _getDownloadURLParallel(apis []string, trackID int64, quality string) (string, TidalDownloadInfo, error) {
-// 	... implementation commented out ...
-// }
+// "Siapa cepat dia dapat" - first success wins
+func getDownloadURLParallel(apis []string, trackID int64, quality string) (string, TidalDownloadInfo, error) {
+	if len(apis) == 0 {
+		return "", TidalDownloadInfo{}, fmt.Errorf("no APIs available")
+	}
+
+	GoLog("[Tidal] Requesting download URL from %d APIs in parallel...\n", len(apis))
+
+	resultChan := make(chan tidalAPIResult, len(apis))
+	startTime := time.Now()
+
+	// Start all requests in parallel
+	for _, apiURL := range apis {
+		go func(api string) {
+			reqStart := time.Now()
+
+			// Create client with timeout for parallel requests
+			client := &http.Client{
+				Timeout: 15 * time.Second,
+			}
+
+			reqURL := fmt.Sprintf("%s/track/?id=%d&quality=%s", api, trackID, quality)
+
+			req, err := http.NewRequest("GET", reqURL, nil)
+			if err != nil {
+				resultChan <- tidalAPIResult{apiURL: api, err: err, duration: time.Since(reqStart)}
+				return
+			}
+
+			resp, err := client.Do(req)
+			if err != nil {
+				resultChan <- tidalAPIResult{apiURL: api, err: err, duration: time.Since(reqStart)}
+				return
+			}
+			defer resp.Body.Close()
+
+			if resp.StatusCode != 200 {
+				resultChan <- tidalAPIResult{apiURL: api, err: fmt.Errorf("HTTP %d", resp.StatusCode), duration: time.Since(reqStart)}
+				return
+			}
+
+			body, err := io.ReadAll(resp.Body)
+			if err != nil {
+				resultChan <- tidalAPIResult{apiURL: api, err: err, duration: time.Since(reqStart)}
+				return
+			}
+
+			// Try v2 format first (object with manifest)
+			var v2Response TidalAPIResponseV2
+			if err := json.Unmarshal(body, &v2Response); err == nil && v2Response.Data.Manifest != "" {
+				// IMPORTANT: Reject PREVIEW responses - we need FULL tracks
+				if v2Response.Data.AssetPresentation == "PREVIEW" {
+					resultChan <- tidalAPIResult{apiURL: api, err: fmt.Errorf("returned PREVIEW instead of FULL"), duration: time.Since(reqStart)}
+					return
+				}
+
+				info := TidalDownloadInfo{
+					URL:        "MANIFEST:" + v2Response.Data.Manifest,
+					BitDepth:   v2Response.Data.BitDepth,
+					SampleRate: v2Response.Data.SampleRate,
+				}
+				resultChan <- tidalAPIResult{apiURL: api, info: info, err: nil, duration: time.Since(reqStart)}
+				return
+			}
+
+			// 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 != "" {
+						info := TidalDownloadInfo{
+							URL:        item.OriginalTrackURL,
+							BitDepth:   16,
+							SampleRate: 44100,
+						}
+						resultChan <- tidalAPIResult{apiURL: api, info: info, err: nil, duration: time.Since(reqStart)}
+						return
+					}
+				}
+			}
+
+			resultChan <- tidalAPIResult{apiURL: api, err: fmt.Errorf("no download URL or manifest in response"), duration: time.Since(reqStart)}
+		}(apiURL)
+	}
+
+	// Collect results - return first success
+	var errors []string
+	var firstSuccess *tidalAPIResult
+
+	for i := 0; i < len(apis); i++ {
+		result := <-resultChan
+		if result.err == nil && firstSuccess == nil {
+			// First success - use this one
+			firstSuccess = &result
+			GoLog("[Tidal] [Parallel] ✓ Got response from %s (%d-bit/%dHz) in %v\n",
+				result.apiURL, result.info.BitDepth, result.info.SampleRate, result.duration)
+
+			// Don't return immediately - drain remaining results to avoid goroutine leaks
+			go func(remaining int) {
+				for j := 0; j < remaining; j++ {
+					<-resultChan
+				}
+			}(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))
+		}
+	}
+
+	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)
@@ -744,14 +859,16 @@ func getDownloadURLSequential(apis []string, trackID int64, quality string) (str
 	return "", TidalDownloadInfo{}, fmt.Errorf("all %d Tidal APIs failed. Errors: %v", len(apis), errors)
 }
 
-// GetDownloadURL gets download URL for a track - tries APIs sequentially
+// GetDownloadURL gets download URL for a track - tries ALL APIs in parallel
+// "Siapa cepat dia dapat" - first successful response wins
 func (t *TidalDownloader) GetDownloadURL(trackID int64, quality string) (TidalDownloadInfo, error) {
 	apis := t.GetAvailableAPIs()
 	if len(apis) == 0 {
 		return TidalDownloadInfo{}, fmt.Errorf("no API URL configured")
 	}
 
-	_, info, err := getDownloadURLSequential(apis, trackID, quality)
+	// Use parallel approach - request from all APIs simultaneously
+	_, info, err := getDownloadURLParallel(apis, trackID, quality)
 	if err != nil {
 		return TidalDownloadInfo{}, fmt.Errorf("failed to get download URL: %w", err)
 	}

ios/Runner/AppDelegate.swift

@@ -256,6 +256,10 @@ import Gobackend  // Import Go framework
             GobackendSetSpotifyAPICredentials(clientId, clientSecret)
             return nil
             
+        case "hasSpotifyCredentials":
+            let hasCredentials = GobackendCheckSpotifyCredentials()
+            return hasCredentials
+            
         // Log methods
         case "getLogs":
             let response = GobackendGetLogs()
@@ -480,6 +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]

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.1';
-  static const String buildNumber = '50';
+  static const String version = '3.0.0-alpha.4';
+  static const String buildNumber = '53';
   static const String fullVersion = '$version+$buildNumber';
   
   

lib/main.dart

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

lib/models/download_item.dart

@@ -19,6 +19,7 @@ enum DownloadErrorType {
   notFound,    // Track not found on any service
   rateLimit,   // Rate limited by service
   network,     // Network/connection error
+  permission,  // File/folder permission error
 }
 
 @JsonSerializable()
@@ -88,6 +89,8 @@ class DownloadItem {
         return 'Rate limit reached, try again later';
       case DownloadErrorType.network:
         return 'Connection failed, check your internet';
+      case DownloadErrorType.permission:
+        return 'Cannot write to folder, check storage permission';
       default:
         return error ?? 'An error occurred';
     }

lib/models/download_item.g.dart

@@ -51,4 +51,5 @@ const _$DownloadErrorTypeEnumMap = {
   DownloadErrorType.notFound: 'notFound',
   DownloadErrorType.rateLimit: 'rateLimit',
   DownloadErrorType.network: 'network',
+  DownloadErrorType.permission: 'permission',
 };

lib/models/settings.dart

@@ -18,6 +18,7 @@ class AppSettings {
   final bool hasSearchedBefore; // Hide helper text after first search
   final String folderOrganization; // none, artist, album, artist_album
   final String historyViewMode; // list, grid
+  final String historyFilterMode; // all, albums, singles
   final bool askQualityBeforeDownload; // Show quality picker before each download
   final String spotifyClientId; // Custom Spotify client ID (empty = use default)
   final String spotifyClientSecret; // Custom Spotify client secret (empty = use default)
@@ -26,6 +27,8 @@ class AppSettings {
   final bool enableLogging; // Enable detailed logging for debugging
   final bool useExtensionProviders; // Use extension providers for downloads when available
   final String? searchProvider; // null/empty = default (Deezer/Spotify), otherwise extension ID
+  final bool separateSingles; // Separate singles/EPs into their own folder
+  final bool showExtensionStore; // Show Extension Store tab in navigation
 
   const AppSettings({
     this.defaultService = 'tidal',
@@ -42,6 +45,7 @@ class AppSettings {
     this.hasSearchedBefore = false, // Default: show helper text
     this.folderOrganization = 'none', // Default: no folder organization
     this.historyViewMode = 'grid', // Default: grid view
+    this.historyFilterMode = 'all', // Default: show all
     this.askQualityBeforeDownload = true, // Default: ask quality before download
     this.spotifyClientId = '', // Default: use built-in credentials
     this.spotifyClientSecret = '', // Default: use built-in credentials
@@ -50,6 +54,8 @@ class AppSettings {
     this.enableLogging = false, // Default: disabled for performance
     this.useExtensionProviders = true, // Default: use extensions when available
     this.searchProvider, // Default: null (use Deezer/Spotify)
+    this.separateSingles = false, // Default: disabled
+    this.showExtensionStore = true, // Default: show store
   });
 
   AppSettings copyWith({
@@ -67,6 +73,7 @@ class AppSettings {
     bool? hasSearchedBefore,
     String? folderOrganization,
     String? historyViewMode,
+    String? historyFilterMode,
     bool? askQualityBeforeDownload,
     String? spotifyClientId,
     String? spotifyClientSecret,
@@ -75,6 +82,8 @@ class AppSettings {
     bool? enableLogging,
     bool? useExtensionProviders,
     String? searchProvider,
+    bool? separateSingles,
+    bool? showExtensionStore,
   }) {
     return AppSettings(
       defaultService: defaultService ?? this.defaultService,
@@ -91,6 +100,7 @@ class AppSettings {
       hasSearchedBefore: hasSearchedBefore ?? this.hasSearchedBefore,
       folderOrganization: folderOrganization ?? this.folderOrganization,
       historyViewMode: historyViewMode ?? this.historyViewMode,
+      historyFilterMode: historyFilterMode ?? this.historyFilterMode,
       askQualityBeforeDownload: askQualityBeforeDownload ?? this.askQualityBeforeDownload,
       spotifyClientId: spotifyClientId ?? this.spotifyClientId,
       spotifyClientSecret: spotifyClientSecret ?? this.spotifyClientSecret,
@@ -99,6 +109,8 @@ class AppSettings {
       enableLogging: enableLogging ?? this.enableLogging,
       useExtensionProviders: useExtensionProviders ?? this.useExtensionProviders,
       searchProvider: searchProvider ?? this.searchProvider,
+      separateSingles: separateSingles ?? this.separateSingles,
+      showExtensionStore: showExtensionStore ?? this.showExtensionStore,
     );
   }
 

lib/models/settings.g.dart

@@ -21,6 +21,7 @@ AppSettings _$AppSettingsFromJson(Map<String, dynamic> json) => AppSettings(
   hasSearchedBefore: json['hasSearchedBefore'] as bool? ?? false,
   folderOrganization: json['folderOrganization'] as String? ?? 'none',
   historyViewMode: json['historyViewMode'] as String? ?? 'grid',
+  historyFilterMode: json['historyFilterMode'] as String? ?? 'all',
   askQualityBeforeDownload: json['askQualityBeforeDownload'] as bool? ?? true,
   spotifyClientId: json['spotifyClientId'] as String? ?? '',
   spotifyClientSecret: json['spotifyClientSecret'] as String? ?? '',
@@ -30,6 +31,8 @@ AppSettings _$AppSettingsFromJson(Map<String, dynamic> json) => AppSettings(
   enableLogging: json['enableLogging'] as bool? ?? false,
   useExtensionProviders: json['useExtensionProviders'] as bool? ?? true,
   searchProvider: json['searchProvider'] as String?,
+  separateSingles: json['separateSingles'] as bool? ?? false,
+  showExtensionStore: json['showExtensionStore'] as bool? ?? true,
 );
 
 Map<String, dynamic> _$AppSettingsToJson(AppSettings instance) =>
@@ -48,6 +51,7 @@ Map<String, dynamic> _$AppSettingsToJson(AppSettings instance) =>
       'hasSearchedBefore': instance.hasSearchedBefore,
       'folderOrganization': instance.folderOrganization,
       'historyViewMode': instance.historyViewMode,
+      'historyFilterMode': instance.historyFilterMode,
       'askQualityBeforeDownload': instance.askQualityBeforeDownload,
       'spotifyClientId': instance.spotifyClientId,
       'spotifyClientSecret': instance.spotifyClientSecret,
@@ -56,4 +60,6 @@ Map<String, dynamic> _$AppSettingsToJson(AppSettings instance) =>
       'enableLogging': instance.enableLogging,
       'useExtensionProviders': instance.useExtensionProviders,
       'searchProvider': instance.searchProvider,
+      'separateSingles': instance.separateSingles,
+      'showExtensionStore': instance.showExtensionStore,
     };

lib/models/track.dart

@@ -19,6 +19,7 @@ class Track {
   final String? deezerId;
   final ServiceAvailability? availability;
   final String? source; // Extension ID that provided this track (null for built-in sources)
+  final String? albumType; // album, single, ep, compilation (from metadata API)
 
   const Track({
     required this.id,
@@ -35,8 +36,12 @@ class Track {
     this.deezerId,
     this.availability,
     this.source,
+    this.albumType,
   });
 
+  /// Check if this track is a single (based on album_type metadata)
+  bool get isSingle => albumType == 'single' || albumType == 'ep';
+
   factory Track.fromJson(Map<String, dynamic> json) => _$TrackFromJson(json);
   Map<String, dynamic> toJson() => _$TrackToJson(this);
   

lib/models/track.g.dart

@@ -25,6 +25,7 @@ Track _$TrackFromJson(Map<String, dynamic> json) => Track(
           json['availability'] as Map<String, dynamic>,
         ),
   source: json['source'] as String?,
+  albumType: json['albumType'] as String?,
 );
 
 Map<String, dynamic> _$TrackToJson(Track instance) => <String, dynamic>{
@@ -42,6 +43,7 @@ Map<String, dynamic> _$TrackToJson(Track instance) => <String, dynamic>{
   'deezerId': instance.deezerId,
   'availability': instance.availability,
   'source': instance.source,
+  'albumType': instance.albumType,
 };
 
 ServiceAvailability _$ServiceAvailabilityFromJson(Map<String, dynamic> json) =>

lib/providers/download_queue_provider.dart

@@ -156,8 +156,18 @@ class DownloadHistoryNotifier extends Notifier<DownloadHistoryState> {
         final items = jsonList
             .map((e) => DownloadHistoryItem.fromJson(e as Map<String, dynamic>))
             .toList();
-        state = state.copyWith(items: items);
-        _historyLog.i('Loaded ${items.length} items from storage');
+        
+        // Deduplicate existing history on load
+        final deduplicatedItems = _deduplicateHistory(items);
+        
+        state = state.copyWith(items: deduplicatedItems);
+        _historyLog.i('Loaded ${deduplicatedItems.length} items from storage (original: ${items.length})');
+        
+        // Save if duplicates were removed
+        if (deduplicatedItems.length < items.length) {
+          _historyLog.i('Removed ${items.length - deduplicatedItems.length} duplicate entries');
+          await _saveToStorage();
+        }
       } else {
         _historyLog.d('No history found in storage');
       }
@@ -166,6 +176,46 @@ class DownloadHistoryNotifier extends Notifier<DownloadHistoryState> {
     }
   }
 
+  /// Deduplicate history items by spotifyId, deezerId, or ISRC
+  /// Keeps the most recent entry (first occurrence since list is sorted by date desc)
+  List<DownloadHistoryItem> _deduplicateHistory(List<DownloadHistoryItem> items) {
+    final seen = <String, int>{}; // key -> index of first occurrence
+    final result = <DownloadHistoryItem>[];
+    
+    for (int i = 0; i < items.length; i++) {
+      final item = items[i];
+      String? key;
+      
+      // Generate unique key based on available identifiers
+      if (item.spotifyId != null && item.spotifyId!.isNotEmpty) {
+        // Extract numeric ID for deezer: prefixed IDs
+        if (item.spotifyId!.startsWith('deezer:')) {
+          key = 'deezer:${item.spotifyId!.substring(7)}';
+        } else {
+          key = 'spotify:${item.spotifyId}';
+        }
+      } else if (item.isrc != null && item.isrc!.isNotEmpty) {
+        key = 'isrc:${item.isrc}';
+      }
+      
+      if (key != null) {
+        if (!seen.containsKey(key)) {
+          // First occurrence - keep it (most recent since list is sorted by date desc)
+          seen[key] = result.length;
+          result.add(item);
+        } else {
+          // Duplicate found - skip (keep the first/most recent one)
+          _historyLog.d('Skipping duplicate: ${item.trackName} (key: $key)');
+        }
+      } else {
+        // No identifier - keep it (can't deduplicate)
+        result.add(item);
+      }
+    }
+    
+    return result;
+  }
+
   Future<void> _saveToStorage() async {
     try {
       final prefs = await SharedPreferences.getInstance();
@@ -183,7 +233,48 @@ class DownloadHistoryNotifier extends Notifier<DownloadHistoryState> {
   }
 
   void addToHistory(DownloadHistoryItem item) {
-    state = state.copyWith(items: [item, ...state.items]);
+    // Check if track already exists in history (by spotifyId, deezerId, or ISRC)
+    final existingIndex = state.items.indexWhere((existing) {
+      // Match by spotifyId (primary identifier - includes deezer:xxx format)
+      if (item.spotifyId != null && 
+          item.spotifyId!.isNotEmpty && 
+          existing.spotifyId == item.spotifyId) {
+        return true;
+      }
+      
+      // Match Deezer tracks: extract numeric ID from "deezer:123456" format
+      if (item.spotifyId != null && item.spotifyId!.startsWith('deezer:') &&
+          existing.spotifyId != null && existing.spotifyId!.startsWith('deezer:')) {
+        final itemDeezerId = item.spotifyId!.substring(7); // Remove "deezer:" prefix
+        final existingDeezerId = existing.spotifyId!.substring(7);
+        if (itemDeezerId == existingDeezerId) {
+          return true;
+        }
+      }
+      
+      // Fallback: match by ISRC if spotifyId not available
+      if (item.isrc != null && 
+          item.isrc!.isNotEmpty && 
+          existing.isrc == item.isrc) {
+        return true;
+      }
+      return false;
+    });
+
+    if (existingIndex >= 0) {
+      // Replace existing entry (update with new download info)
+      final updatedItems = [...state.items];
+      updatedItems[existingIndex] = item;
+      // Move to top of list (most recent)
+      updatedItems.removeAt(existingIndex);
+      updatedItems.insert(0, item);
+      state = state.copyWith(items: updatedItems);
+      _historyLog.d('Updated existing history entry: ${item.trackName}');
+    } else {
+      // Add new entry
+      state = state.copyWith(items: [item, ...state.items]);
+      _historyLog.d('Added new history entry: ${item.trackName}');
+    }
     _saveToStorage();
   }
 
@@ -577,35 +668,55 @@ class DownloadQueueNotifier extends Notifier<DownloadQueueState> {
     state = state.copyWith(outputDir: dir);
   }
 
-  /// Build output directory based on folder organization setting
-  Future<String> _buildOutputDir(Track track, String folderOrganization) async {
+  /// Build output directory based on folder organization setting and separateSingles
+  Future<String> _buildOutputDir(Track track, String folderOrganization, {bool separateSingles = false}) async {
     String baseDir = state.outputDir;
 
-    if (folderOrganization == 'none') {
-      return baseDir;
+    // If separateSingles is enabled, use Albums/Singles structure
+    if (separateSingles) {
+      final isSingle = track.isSingle;
+      
+      if (isSingle) {
+        // Singles go to Singles folder (flat structure)
+        final singlesPath = '$baseDir${Platform.pathSeparator}Singles';
+        final dir = Directory(singlesPath);
+        if (!await dir.exists()) {
+          await dir.create(recursive: true);
+          _log.d('Created Singles folder: $singlesPath');
+        }
+        return singlesPath;
+      } else {
+        // Albums go to Albums/Artist/Album structure
+        final artistName = _sanitizeFolderName(track.albumArtist ?? track.artistName);
+        final albumName = _sanitizeFolderName(track.albumName);
+        final albumPath = '$baseDir${Platform.pathSeparator}Albums${Platform.pathSeparator}$artistName${Platform.pathSeparator}$albumName';
+        final dir = Directory(albumPath);
+        if (!await dir.exists()) {
+          await dir.create(recursive: true);
+          _log.d('Created Album folder: $albumPath');
+        }
+        return albumPath;
+      }
     }
 
-    // Sanitize folder names (remove invalid characters)
-    String sanitize(String name) {
-      return name
-          .replaceAll(RegExp(r'[<>:"/\\|?*]'), '_')
-          .replaceAll(RegExp(r'\.+$'), '') // Remove trailing dots
-          .trim();
+    // Original folder organization logic (when separateSingles is disabled)
+    if (folderOrganization == 'none') {
+      return baseDir;
     }
 
     String subPath = '';
     switch (folderOrganization) {
       case 'artist':
-        final artistName = sanitize(track.albumArtist ?? track.artistName);
+        final artistName = _sanitizeFolderName(track.albumArtist ?? track.artistName);
         subPath = artistName;
         break;
       case 'album':
-        final albumName = sanitize(track.albumName);
+        final albumName = _sanitizeFolderName(track.albumName);
         subPath = albumName;
         break;
       case 'artist_album':
-        final artistName = sanitize(track.albumArtist ?? track.artistName);
-        final albumName = sanitize(track.albumName);
+        final artistName = _sanitizeFolderName(track.albumArtist ?? track.artistName);
+        final albumName = _sanitizeFolderName(track.albumName);
         subPath = '$artistName${Platform.pathSeparator}$albumName';
         break;
     }
@@ -623,6 +734,14 @@ class DownloadQueueNotifier extends Notifier<DownloadQueueState> {
     return baseDir;
   }
 
+  /// Sanitize folder names (remove invalid characters)
+  String _sanitizeFolderName(String name) {
+    return name
+        .replaceAll(RegExp(r'[<>:"/\\|?*]'), '_')
+        .replaceAll(RegExp(r'\.+$'), '') // Remove trailing dots
+        .trim();
+  }
+
   void updateSettings(AppSettings settings) {
     state = state.copyWith(
       outputDir: settings.downloadDirectory.isNotEmpty
@@ -1326,6 +1445,7 @@ class DownloadQueueNotifier extends Notifier<DownloadQueueState> {
       final outputDir = await _buildOutputDir(
         trackToDownload,
         settings.folderOrganization,
+        separateSingles: settings.separateSingles,
       );
 
       // Use quality override if set, otherwise use default from settings
@@ -1672,6 +1792,9 @@ class DownloadQueueNotifier extends Notifier<DownloadQueueState> {
           case 'network':
             errorType = DownloadErrorType.network;
             break;
+          case 'permission':
+            errorType = DownloadErrorType.permission;
+            break;
           default:
             errorType = DownloadErrorType.unknown;
         }

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;
@@ -520,22 +558,34 @@ class ExtensionNotifier extends Notifier<ExtensionState> {
       await PlatformBridge.setExtensionEnabled(extensionId, enabled);
       _log.d('Set extension $extensionId enabled: $enabled');
       
+      // Get extension info before updating state
+      final ext = state.extensions.where((e) => e.id == extensionId).firstOrNull;
+      
       // Update local state
-      final extensions = state.extensions.map((ext) {
-        if (ext.id == extensionId) {
-          return ext.copyWith(enabled: enabled);
+      final extensions = state.extensions.map((e) {
+        if (e.id == extensionId) {
+          return e.copyWith(enabled: enabled);
         }
-        return ext;
+        return e;
       }).toList();
       
       state = state.copyWith(extensions: extensions);
       
-      // If disabling an extension that is the current search provider, clear it
-      if (!enabled) {
+      // If disabling an extension, reset related settings
+      if (!enabled && ext != null) {
         final settings = ref.read(settingsProvider);
+        
+        // If this extension was the search provider, clear it and reset to Deezer
         if (settings.searchProvider == extensionId) {
           ref.read(settingsProvider.notifier).setSearchProvider(null);
-          _log.d('Cleared search provider because extension $extensionId was disabled');
+          ref.read(settingsProvider.notifier).setMetadataSource('deezer');
+          _log.d('Cleared search provider and reset to Deezer because extension $extensionId was disabled');
+        }
+        
+        // If this extension was the default download service, reset to Tidal
+        if (ext.hasDownloadProvider && settings.defaultService == extensionId) {
+          ref.read(settingsProvider.notifier).setDefaultService('tidal');
+          _log.d('Reset default service to Tidal because extension $extensionId was disabled');
         }
       }
     } catch (e) {

lib/providers/settings_provider.dart

@@ -60,18 +60,16 @@ class SettingsNotifier extends Notifier<AppSettings> {
 
   /// Apply current Spotify credentials to Go backend
   Future<void> _applySpotifyCredentials() async {
-    // Only apply custom credentials if enabled and both fields are set
-    if (state.useCustomSpotifyCredentials && 
-        state.spotifyClientId.isNotEmpty && 
+    // Only apply if both fields are set
+    if (state.spotifyClientId.isNotEmpty && 
         state.spotifyClientSecret.isNotEmpty) {
       await PlatformBridge.setSpotifyCredentials(
         state.spotifyClientId,
         state.spotifyClientSecret,
       );
-    } else {
-      // Clear to use default
-      await PlatformBridge.setSpotifyCredentials('', '');
     }
+    // Note: If credentials are empty, Spotify API will return error
+    // User should use Deezer as metadata source instead
   }
 
   void setDefaultService(String service) {
@@ -148,6 +146,11 @@ class SettingsNotifier extends Notifier<AppSettings> {
     _saveSettings();
   }
 
+  void setHistoryFilterMode(String mode) {
+    state = state.copyWith(historyFilterMode: mode);
+    _saveSettings();
+  }
+
   void setAskQualityBeforeDownload(bool enabled) {
     state = state.copyWith(askQualityBeforeDownload: enabled);
     _saveSettings();
@@ -208,6 +211,16 @@ class SettingsNotifier extends Notifier<AppSettings> {
     state = state.copyWith(useExtensionProviders: enabled);
     _saveSettings();
   }
+
+  void setSeparateSingles(bool enabled) {
+    state = state.copyWith(separateSingles: enabled);
+    _saveSettings();
+  }
+
+  void setShowExtensionStore(bool enabled) {
+    state = state.copyWith(showExtensionStore: enabled);
+    _saveSettings();
+  }
 }
 
 final settingsProvider = NotifierProvider<SettingsNotifier, AppSettings>(

lib/providers/store_provider.dart

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

lib/providers/track_provider.dart

@@ -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
       
@@ -466,6 +519,7 @@ class TrackNotifier extends Notifier<TrackState> {
       discNumber: data['disc_number'] as int?,
       releaseDate: data['release_date']?.toString(),
       source: source ?? data['source']?.toString() ?? data['provider_id']?.toString(),
+      albumType: data['album_type']?.toString(),
     );
   }
 

lib/screens/downloaded_album_screen.dart

@@ -0,0 +1,573 @@
+import 'dart:io';
+import 'package:flutter/material.dart';
+import 'package:flutter/services.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:cached_network_image/cached_network_image.dart';
+import 'package:open_filex/open_filex.dart';
+import 'package:spotiflac_android/providers/download_queue_provider.dart';
+import 'package:spotiflac_android/screens/track_metadata_screen.dart';
+
+/// Screen to display downloaded tracks from a specific album
+class DownloadedAlbumScreen extends ConsumerStatefulWidget {
+  final String albumName;
+  final String artistName;
+  final String? coverUrl;
+
+  const DownloadedAlbumScreen({
+    super.key,
+    required this.albumName,
+    required this.artistName,
+    this.coverUrl,
+  });
+
+  @override
+  ConsumerState<DownloadedAlbumScreen> createState() => _DownloadedAlbumScreenState();
+}
+
+class _DownloadedAlbumScreenState extends ConsumerState<DownloadedAlbumScreen> {
+  // Multi-select state
+  bool _isSelectionMode = false;
+  final Set<String> _selectedIds = {};
+
+  /// Get tracks for this album from history provider (reactive)
+  List<DownloadHistoryItem> _getAlbumTracks(List<DownloadHistoryItem> allItems) {
+    return allItems.where((item) {
+      final itemKey = '${item.albumName}|${item.albumArtist ?? item.artistName}';
+      final albumKey = '${widget.albumName}|${widget.artistName}';
+      return itemKey == albumKey;
+    }).toList()
+      ..sort((a, b) {
+        final aNum = a.trackNumber ?? 999;
+        final bNum = b.trackNumber ?? 999;
+        if (aNum != bNum) return aNum.compareTo(bNum);
+        return a.trackName.compareTo(b.trackName);
+      });
+  }
+
+  void _enterSelectionMode(String itemId) {
+    HapticFeedback.mediumImpact();
+    setState(() {
+      _isSelectionMode = true;
+      _selectedIds.add(itemId);
+    });
+  }
+
+  void _exitSelectionMode() {
+    setState(() {
+      _isSelectionMode = false;
+      _selectedIds.clear();
+    });
+  }
+
+  void _toggleSelection(String itemId) {
+    setState(() {
+      if (_selectedIds.contains(itemId)) {
+        _selectedIds.remove(itemId);
+        if (_selectedIds.isEmpty) {
+          _isSelectionMode = false;
+        }
+      } else {
+        _selectedIds.add(itemId);
+      }
+    });
+  }
+
+  void _selectAll(List<DownloadHistoryItem> tracks) {
+    setState(() {
+      _selectedIds.addAll(tracks.map((e) => e.id));
+    });
+  }
+
+  Future<void> _deleteSelected(List<DownloadHistoryItem> currentTracks) async {
+    final count = _selectedIds.length;
+    final confirmed = await showDialog<bool>(
+      context: context,
+      builder: (ctx) => AlertDialog(
+        title: const Text('Delete Selected'),
+        content: Text('Delete $count ${count == 1 ? 'track' : 'tracks'} from this album?\n\nThis will also delete the files from storage.'),
+        actions: [
+          TextButton(
+            onPressed: () => Navigator.pop(ctx, false),
+            child: const Text('Cancel'),
+          ),
+          FilledButton(
+            onPressed: () => Navigator.pop(ctx, true),
+            style: FilledButton.styleFrom(
+              backgroundColor: Theme.of(context).colorScheme.error,
+            ),
+            child: const Text('Delete'),
+          ),
+        ],
+      ),
+    );
+
+    if (confirmed == true && mounted) {
+      final historyNotifier = ref.read(downloadHistoryProvider.notifier);
+      final idsToDelete = _selectedIds.toList();
+      
+      int deletedCount = 0;
+      for (final id in idsToDelete) {
+        final item = currentTracks.where((e) => e.id == id).firstOrNull;
+        if (item != null) {
+          try {
+            final file = File(item.filePath);
+            if (await file.exists()) {
+              await file.delete();
+            }
+          } catch (_) {}
+          historyNotifier.removeFromHistory(id);
+          deletedCount++;
+        }
+      }
+      
+      _exitSelectionMode();
+      
+      if (mounted) {
+        ScaffoldMessenger.of(context).showSnackBar(
+          SnackBar(content: Text('Deleted $deletedCount ${deletedCount == 1 ? 'track' : 'tracks'}')),
+        );
+      }
+    }
+  }
+
+  Future<void> _openFile(String filePath) async {
+    try {
+      await OpenFilex.open(filePath);
+    } catch (e) {
+      if (mounted) {
+        ScaffoldMessenger.of(context).showSnackBar(
+          SnackBar(content: Text('Cannot open file: $e')),
+        );
+      }
+    }
+  }
+
+  void _navigateToMetadataScreen(DownloadHistoryItem item) {
+    Navigator.push(context, PageRouteBuilder(
+      transitionDuration: const Duration(milliseconds: 300),
+      reverseTransitionDuration: const Duration(milliseconds: 250),
+      pageBuilder: (context, animation, secondaryAnimation) => TrackMetadataScreen(item: item),
+      transitionsBuilder: (context, animation, secondaryAnimation, child) => FadeTransition(opacity: animation, child: child),
+    ));
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    final colorScheme = Theme.of(context).colorScheme;
+    final bottomPadding = MediaQuery.of(context).padding.bottom;
+    
+    // Watch history and get tracks for this album (reactive!)
+    final allHistoryItems = ref.watch(downloadHistoryProvider.select((s) => s.items));
+    final tracks = _getAlbumTracks(allHistoryItems);
+    
+    // Auto-pop if album has less than 2 tracks (no longer an "album")
+    if (tracks.length < 2) {
+      WidgetsBinding.instance.addPostFrameCallback((_) {
+        if (mounted) Navigator.pop(context);
+      });
+      return const SizedBox.shrink();
+    }
+    
+    // Clean up selected IDs that no longer exist
+    final validIds = tracks.map((t) => t.id).toSet();
+    _selectedIds.removeWhere((id) => !validIds.contains(id));
+    if (_selectedIds.isEmpty && _isSelectionMode) {
+      WidgetsBinding.instance.addPostFrameCallback((_) {
+        if (mounted) setState(() => _isSelectionMode = false);
+      });
+    }
+
+    return PopScope(
+      canPop: !_isSelectionMode,
+      onPopInvokedWithResult: (didPop, result) {
+        if (!didPop && _isSelectionMode) {
+          _exitSelectionMode();
+        }
+      },
+      child: Scaffold(
+        body: Stack(
+          children: [
+            CustomScrollView(
+              slivers: [
+                _buildAppBar(context, colorScheme),
+                _buildInfoCard(context, colorScheme, tracks),
+                _buildTrackListHeader(context, colorScheme, tracks),
+                _buildTrackList(context, colorScheme, tracks),
+                SliverToBoxAdapter(child: SizedBox(height: _isSelectionMode ? 120 : 32)),
+              ],
+            ),
+            
+            // Bottom Selection Action Bar
+            AnimatedPositioned(
+              duration: const Duration(milliseconds: 250),
+              curve: Curves.easeOutCubic,
+              left: 0,
+              right: 0,
+              bottom: _isSelectionMode ? 0 : -(200 + bottomPadding),
+              child: _buildSelectionBottomBar(context, colorScheme, tracks, bottomPadding),
+            ),
+          ],
+        ),
+      ),
+    );
+  }
+
+  Widget _buildAppBar(BuildContext context, ColorScheme colorScheme) {
+    return SliverAppBar(
+      expandedHeight: 280,
+      pinned: true,
+      stretch: true,
+      backgroundColor: colorScheme.surface,
+      surfaceTintColor: Colors.transparent,
+      flexibleSpace: FlexibleSpaceBar(
+        background: Stack(
+          fit: StackFit.expand,
+          children: [
+            if (widget.coverUrl != null)
+              CachedNetworkImage(
+                imageUrl: widget.coverUrl!,
+                fit: BoxFit.cover,
+                color: Colors.black.withValues(alpha: 0.5),
+                colorBlendMode: BlendMode.darken,
+                memCacheWidth: 600,
+              ),
+            Container(
+              decoration: BoxDecoration(
+                gradient: LinearGradient(
+                  begin: Alignment.topCenter,
+                  end: Alignment.bottomCenter,
+                  colors: [
+                    Colors.transparent,
+                    colorScheme.surface.withValues(alpha: 0.8),
+                    colorScheme.surface,
+                  ],
+                  stops: const [0.0, 0.7, 1.0],
+                ),
+              ),
+            ),
+            Center(
+              child: Padding(
+                padding: const EdgeInsets.only(top: 60),
+                child: Container(
+                  width: 140,
+                  height: 140,
+                  decoration: BoxDecoration(
+                    borderRadius: BorderRadius.circular(16),
+                    boxShadow: [
+                      BoxShadow(
+                        color: Colors.black.withValues(alpha: 0.3),
+                        blurRadius: 20,
+                        offset: const Offset(0, 10),
+                      ),
+                    ],
+                  ),
+                  child: ClipRRect(
+                    borderRadius: BorderRadius.circular(16),
+                    child: widget.coverUrl != null
+                        ? CachedNetworkImage(imageUrl: widget.coverUrl!, fit: BoxFit.cover, memCacheWidth: 280)
+                        : Container(
+                            color: colorScheme.surfaceContainerHighest,
+                            child: Icon(Icons.album, size: 48, color: colorScheme.onSurfaceVariant),
+                          ),
+                  ),
+                ),
+              ),
+            ),
+          ],
+        ),
+        stretchModes: const [StretchMode.zoomBackground, StretchMode.blurBackground],
+      ),
+      leading: IconButton(
+        icon: Container(
+          padding: const EdgeInsets.all(8),
+          decoration: BoxDecoration(color: colorScheme.surface.withValues(alpha: 0.8), shape: BoxShape.circle),
+          child: Icon(Icons.arrow_back, color: colorScheme.onSurface),
+        ),
+        onPressed: () => Navigator.pop(context),
+      ),
+    );
+  }
+
+  Widget _buildInfoCard(BuildContext context, ColorScheme colorScheme, List<DownloadHistoryItem> tracks) {
+    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: [
+                Text(
+                  widget.albumName,
+                  style: Theme.of(context).textTheme.headlineSmall?.copyWith(fontWeight: FontWeight.bold, color: colorScheme.onSurface),
+                ),
+                const SizedBox(height: 4),
+                Text(
+                  widget.artistName,
+                  style: Theme.of(context).textTheme.bodyLarge?.copyWith(color: colorScheme.onSurfaceVariant),
+                ),
+                const SizedBox(height: 12),
+                Row(
+                  children: [
+                    Container(
+                      padding: const EdgeInsets.symmetric(horizontal: 12, vertical: 6),
+                      decoration: BoxDecoration(color: colorScheme.primaryContainer, borderRadius: BorderRadius.circular(20)),
+                      child: Row(
+                        mainAxisSize: MainAxisSize.min,
+                        children: [
+                          Icon(Icons.download_done, size: 14, color: colorScheme.onPrimaryContainer),
+                          const SizedBox(width: 4),
+                          Text('${tracks.length} downloaded', style: TextStyle(color: colorScheme.onPrimaryContainer, fontWeight: FontWeight.w600, fontSize: 12)),
+                        ],
+                      ),
+                    ),
+                    const SizedBox(width: 8),
+                    if (_getCommonQuality(tracks) != null)
+                      Container(
+                        padding: const EdgeInsets.symmetric(horizontal: 12, vertical: 6),
+                        decoration: BoxDecoration(
+                          color: _getCommonQuality(tracks)!.startsWith('24') 
+                              ? colorScheme.tertiaryContainer 
+                              : colorScheme.surfaceContainerHighest,
+                          borderRadius: BorderRadius.circular(20),
+                        ),
+                        child: Text(
+                          _getCommonQuality(tracks)!,
+                          style: TextStyle(
+                            color: _getCommonQuality(tracks)!.startsWith('24') 
+                                ? colorScheme.onTertiaryContainer 
+                                : colorScheme.onSurfaceVariant,
+                            fontWeight: FontWeight.w600,
+                            fontSize: 12,
+                          ),
+                        ),
+                      ),
+                  ],
+                ),
+              ],
+            ),
+          ),
+        ),
+      ),
+    );
+  }
+
+  String? _getCommonQuality(List<DownloadHistoryItem> tracks) {
+    if (tracks.isEmpty) return null;
+    final firstQuality = tracks.first.quality;
+    if (firstQuality == null) return null;
+    for (final track in tracks) {
+      if (track.quality != firstQuality) return null;
+    }
+    return firstQuality;
+  }
+
+  Widget _buildTrackListHeader(BuildContext context, ColorScheme colorScheme, List<DownloadHistoryItem> tracks) {
+    return SliverToBoxAdapter(
+      child: Padding(
+        padding: const EdgeInsets.fromLTRB(20, 8, 20, 8),
+        child: Row(
+          children: [
+            Icon(Icons.queue_music, size: 20, color: colorScheme.primary),
+            const SizedBox(width: 8),
+            Text('Tracks', style: Theme.of(context).textTheme.titleMedium?.copyWith(fontWeight: FontWeight.w600, color: colorScheme.onSurface)),
+            const Spacer(),
+            if (!_isSelectionMode)
+              TextButton.icon(
+                onPressed: tracks.isNotEmpty ? () => _enterSelectionMode(tracks.first.id) : null,
+                icon: const Icon(Icons.checklist, size: 18),
+                label: const Text('Select'),
+                style: TextButton.styleFrom(visualDensity: VisualDensity.compact),
+              ),
+          ],
+        ),
+      ),
+    );
+  }
+
+  Widget _buildTrackList(BuildContext context, ColorScheme colorScheme, List<DownloadHistoryItem> tracks) {
+    return SliverList(
+      delegate: SliverChildBuilderDelegate(
+        (context, index) {
+          final track = tracks[index];
+          return KeyedSubtree(
+            key: ValueKey(track.id),
+            child: _buildTrackItem(context, colorScheme, track),
+          );
+        },
+        childCount: tracks.length,
+      ),
+    );
+  }
+
+  Widget _buildTrackItem(BuildContext context, ColorScheme colorScheme, DownloadHistoryItem track) {
+    final isSelected = _selectedIds.contains(track.id);
+    
+    return Padding(
+      padding: const EdgeInsets.symmetric(horizontal: 8),
+      child: Card(
+        elevation: 0,
+        color: isSelected ? colorScheme.primaryContainer.withValues(alpha: 0.3) : Colors.transparent,
+        margin: const EdgeInsets.symmetric(vertical: 2),
+        child: ListTile(
+          shape: RoundedRectangleBorder(borderRadius: BorderRadius.circular(12)),
+          onTap: _isSelectionMode 
+              ? () => _toggleSelection(track.id)
+              : () => _navigateToMetadataScreen(track),
+          onLongPress: _isSelectionMode ? null : () => _enterSelectionMode(track.id),
+          leading: Row(
+            mainAxisSize: MainAxisSize.min,
+            children: [
+              if (_isSelectionMode) ...[
+                Container(
+                  width: 24,
+                  height: 24,
+                  decoration: BoxDecoration(
+                    color: isSelected ? colorScheme.primary : Colors.transparent,
+                    shape: BoxShape.circle,
+                    border: Border.all(color: isSelected ? colorScheme.primary : colorScheme.outline, width: 2),
+                  ),
+                  child: isSelected 
+                      ? Icon(Icons.check, color: colorScheme.onPrimary, size: 16)
+                      : null,
+                ),
+                const SizedBox(width: 12),
+              ],
+              SizedBox(
+                width: 24,
+                child: Text(
+                  track.trackNumber?.toString() ?? '-',
+                  style: Theme.of(context).textTheme.bodyMedium?.copyWith(
+                    color: colorScheme.onSurfaceVariant,
+                    fontWeight: FontWeight.w500,
+                  ),
+                  textAlign: TextAlign.center,
+                ),
+              ),
+            ],
+          ),
+          title: Text(
+            track.trackName,
+            maxLines: 1,
+            overflow: TextOverflow.ellipsis,
+            style: Theme.of(context).textTheme.bodyLarge?.copyWith(fontWeight: FontWeight.w500),
+          ),
+          subtitle: Text(
+            track.artistName,
+            maxLines: 1,
+            overflow: TextOverflow.ellipsis,
+            style: TextStyle(color: colorScheme.onSurfaceVariant),
+          ),
+          trailing: _isSelectionMode ? null : IconButton(
+            onPressed: () => _openFile(track.filePath),
+            icon: Icon(Icons.play_arrow, color: colorScheme.primary),
+            style: IconButton.styleFrom(
+              backgroundColor: colorScheme.primaryContainer.withValues(alpha: 0.3),
+            ),
+          ),
+        ),
+      ),
+    );
+  }
+
+  Widget _buildSelectionBottomBar(BuildContext context, ColorScheme colorScheme, List<DownloadHistoryItem> tracks, double bottomPadding) {
+    final selectedCount = _selectedIds.length;
+    final allSelected = selectedCount == tracks.length && tracks.isNotEmpty;
+    
+    return Container(
+      decoration: BoxDecoration(
+        color: colorScheme.surfaceContainerHigh,
+        borderRadius: const BorderRadius.vertical(top: Radius.circular(28)),
+        boxShadow: [
+          BoxShadow(
+            color: Colors.black.withValues(alpha: 0.15),
+            blurRadius: 12,
+            offset: const Offset(0, -4),
+          ),
+        ],
+      ),
+      child: SafeArea(
+        top: false,
+        child: Padding(
+          padding: EdgeInsets.fromLTRB(16, 16, 16, bottomPadding > 0 ? 8 : 16),
+          child: Column(
+            mainAxisSize: MainAxisSize.min,
+            children: [
+              Container(
+                width: 32,
+                height: 4,
+                margin: const EdgeInsets.only(bottom: 16),
+                decoration: BoxDecoration(
+                  color: colorScheme.outlineVariant,
+                  borderRadius: BorderRadius.circular(2),
+                ),
+              ),
+              Row(
+                children: [
+                  IconButton.filledTonal(
+                    onPressed: _exitSelectionMode,
+                    icon: const Icon(Icons.close),
+                    style: IconButton.styleFrom(
+                      backgroundColor: colorScheme.surfaceContainerHighest,
+                    ),
+                  ),
+                  const SizedBox(width: 12),
+                  Expanded(
+                    child: Column(
+                      crossAxisAlignment: CrossAxisAlignment.start,
+                      children: [
+                        Text(
+                          '$selectedCount selected',
+                          style: Theme.of(context).textTheme.titleMedium?.copyWith(fontWeight: FontWeight.bold),
+                        ),
+                        Text(
+                          allSelected ? 'All tracks selected' : 'Tap tracks to select',
+                          style: Theme.of(context).textTheme.bodySmall?.copyWith(color: colorScheme.onSurfaceVariant),
+                        ),
+                      ],
+                    ),
+                  ),
+                  TextButton.icon(
+                    onPressed: () {
+                      if (allSelected) {
+                        _exitSelectionMode();
+                      } else {
+                        _selectAll(tracks);
+                      }
+                    },
+                    icon: Icon(allSelected ? Icons.deselect : Icons.select_all, size: 20),
+                    label: Text(allSelected ? 'Deselect' : 'Select All'),
+                    style: TextButton.styleFrom(foregroundColor: colorScheme.primary),
+                  ),
+                ],
+              ),
+              const SizedBox(height: 16),
+              SizedBox(
+                width: double.infinity,
+                child: FilledButton.icon(
+                  onPressed: selectedCount > 0 ? () => _deleteSelected(tracks) : null,
+                  icon: const Icon(Icons.delete_outline),
+                  label: Text(
+                    selectedCount > 0 
+                        ? 'Delete $selectedCount ${selectedCount == 1 ? 'track' : 'tracks'}'
+                        : 'Select tracks to delete',
+                  ),
+                  style: FilledButton.styleFrom(
+                    backgroundColor: selectedCount > 0 ? colorScheme.error : colorScheme.surfaceContainerHighest,
+                    foregroundColor: selectedCount > 0 ? colorScheme.onError : colorScheme.onSurfaceVariant,
+                    padding: const EdgeInsets.symmetric(vertical: 16),
+                    shape: RoundedRectangleBorder(borderRadius: BorderRadius.circular(16)),
+                  ),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}

lib/screens/home_tab.dart

@@ -320,6 +320,10 @@ class _HomeTabState extends ConsumerState<HomeTab> with AutomaticKeepAliveClient
     final error = ref.watch(trackProvider.select((s) => s.error));
     final hasSearchedBefore = ref.watch(settingsProvider.select((s) => s.hasSearchedBefore));
     
+    // Watch extension state to update search hint when extensions load/change
+    ref.watch(extensionProvider.select((s) => s.isInitialized));
+    ref.watch(extensionProvider.select((s) => s.extensions));
+    
     final colorScheme = Theme.of(context).colorScheme;
     final hasResults = _isTyping || tracks.isNotEmpty || (searchArtists != null && searchArtists.isNotEmpty) || isLoading;
     final screenHeight = MediaQuery.of(context).size.height;
@@ -775,9 +779,14 @@ class _HomeTabState extends ConsumerState<HomeTab> with AutomaticKeepAliveClient
   String _getSearchHint() {
     final settings = ref.read(settingsProvider);
     final searchProvider = settings.searchProvider;
+    final extState = ref.read(extensionProvider);
+    
+    // If extension system not initialized yet, show default hint
+    if (!extState.isInitialized) {
+      return 'Paste Spotify URL or search...';
+    }
     
     if (searchProvider != null && searchProvider.isNotEmpty) {
-      final extState = ref.read(extensionProvider);
       final ext = extState.extensions.where((e) => e.id == searchProvider).firstOrNull;
       // Only show extension placeholder if extension exists AND is enabled
       if (ext != null && ext.enabled) {

lib/screens/main_shell.dart

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

lib/screens/settings/download_settings_page.dart

@@ -4,6 +4,7 @@ import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:file_picker/file_picker.dart';
 import 'package:path_provider/path_provider.dart';
 import 'package:spotiflac_android/providers/settings_provider.dart';
+import 'package:spotiflac_android/providers/extension_provider.dart';
 import 'package:spotiflac_android/widgets/settings_group.dart';
 
 class DownloadSettingsPage extends ConsumerWidget {
@@ -184,19 +185,31 @@ class DownloadSettingsPage extends ConsumerWidget {
                         : settings.downloadDirectory,
                     onTap: () => _pickDirectory(context, ref),
                   ),
-                  SettingsItem(
-                    icon: Icons.create_new_folder_outlined,
-                    title: 'Folder Organization',
-                    subtitle: _getFolderOrganizationLabel(
-                      settings.folderOrganization,
-                    ),
-                    onTap: () => _showFolderOrganizationPicker(
-                      context,
-                      ref,
-                      settings.folderOrganization,
-                    ),
-                    showDivider: false,
+                  SettingsSwitchItem(
+                    icon: Icons.library_music_outlined,
+                    title: 'Separate Singles Folder',
+                    subtitle: settings.separateSingles
+                        ? 'Albums/ and Singles/ folders'
+                        : 'All files in same structure',
+                    value: settings.separateSingles,
+                    onChanged: (value) => ref
+                        .read(settingsProvider.notifier)
+                        .setSeparateSingles(value),
                   ),
+                  if (!settings.separateSingles)
+                    SettingsItem(
+                      icon: Icons.create_new_folder_outlined,
+                      title: 'Folder Organization',
+                      subtitle: _getFolderOrganizationLabel(
+                        settings.folderOrganization,
+                      ),
+                      onTap: () => _showFolderOrganizationPicker(
+                        context,
+                        ref,
+                        settings.folderOrganization,
+                      ),
+                      showDivider: false,
+                    ),
                 ],
               ),
             ),
@@ -546,9 +559,7 @@ class DownloadSettingsPage extends ConsumerWidget {
               example: 'SpotiFLAC/Track.flac',
               isSelected: current == 'none',
               onTap: () {
-                ref
-                    .read(settingsProvider.notifier)
-                    .setFolderOrganization('none');
+                ref.read(settingsProvider.notifier).setFolderOrganization('none');
                 Navigator.pop(context);
               },
             ),
@@ -558,9 +569,7 @@ class DownloadSettingsPage extends ConsumerWidget {
               example: 'SpotiFLAC/Artist Name/Track.flac',
               isSelected: current == 'artist',
               onTap: () {
-                ref
-                    .read(settingsProvider.notifier)
-                    .setFolderOrganization('artist');
+                ref.read(settingsProvider.notifier).setFolderOrganization('artist');
                 Navigator.pop(context);
               },
             ),
@@ -570,9 +579,7 @@ class DownloadSettingsPage extends ConsumerWidget {
               example: 'SpotiFLAC/Album Name/Track.flac',
               isSelected: current == 'album',
               onTap: () {
-                ref
-                    .read(settingsProvider.notifier)
-                    .setFolderOrganization('album');
+                ref.read(settingsProvider.notifier).setFolderOrganization('album');
                 Navigator.pop(context);
               },
             ),
@@ -582,9 +589,7 @@ class DownloadSettingsPage extends ConsumerWidget {
               example: 'SpotiFLAC/Artist/Album/Track.flac',
               isSelected: current == 'artist_album',
               onTap: () {
-                ref
-                    .read(settingsProvider.notifier)
-                    .setFolderOrganization('artist_album');
+                ref.read(settingsProvider.notifier).setFolderOrganization('artist_album');
                 Navigator.pop(context);
               },
             ),
@@ -596,7 +601,7 @@ class DownloadSettingsPage extends ConsumerWidget {
   }
 }
 
-class _ServiceSelector extends StatelessWidget {
+class _ServiceSelector extends ConsumerWidget {
   final String currentService;
   final ValueChanged<String> onChanged;
   const _ServiceSelector({
@@ -605,31 +610,75 @@ class _ServiceSelector extends StatelessWidget {
   });
 
   @override
-  Widget build(BuildContext context) {
+  Widget build(BuildContext context, WidgetRef ref) {
+    final extState = ref.watch(extensionProvider);
+    
+    // Get enabled extension download providers
+    final extensionProviders = extState.extensions
+        .where((e) => e.enabled && e.hasDownloadProvider)
+        .toList();
+    
+    // Check if current service is an extension that's now disabled
+    final isExtensionService = !['tidal', 'qobuz', 'amazon'].contains(currentService);
+    final isCurrentExtensionEnabled = isExtensionService 
+        ? extensionProviders.any((e) => e.id == currentService)
+        : true;
+    
+    // If current extension is disabled, show it as not selected
+    final effectiveService = isCurrentExtensionEnabled ? currentService : '';
+    
     return Padding(
       padding: const EdgeInsets.all(12),
-      child: Row(
+      child: Column(
         children: [
-          _ServiceChip(
-            icon: Icons.music_note,
-            label: 'Tidal',
-            isSelected: currentService == 'tidal',
-            onTap: () => onChanged('tidal'),
-          ),
-          const SizedBox(width: 8),
-          _ServiceChip(
-            icon: Icons.album,
-            label: 'Qobuz',
-            isSelected: currentService == 'qobuz',
-            onTap: () => onChanged('qobuz'),
-          ),
-          const SizedBox(width: 8),
-          _ServiceChip(
-            icon: Icons.shopping_bag,
-            label: 'Amazon',
-            isSelected: currentService == 'amazon',
-            onTap: () => onChanged('amazon'),
+          Row(
+            children: [
+              _ServiceChip(
+                icon: Icons.music_note,
+                label: 'Tidal',
+                isSelected: effectiveService == 'tidal',
+                onTap: () => onChanged('tidal'),
+              ),
+              const SizedBox(width: 8),
+              _ServiceChip(
+                icon: Icons.album,
+                label: 'Qobuz',
+                isSelected: effectiveService == 'qobuz',
+                onTap: () => onChanged('qobuz'),
+              ),
+              const SizedBox(width: 8),
+              _ServiceChip(
+                icon: Icons.shopping_bag,
+                label: 'Amazon',
+                isSelected: effectiveService == 'amazon',
+                onTap: () => onChanged('amazon'),
+              ),
+            ],
           ),
+          // Show extension download providers if any
+          if (extensionProviders.isNotEmpty) ...[
+            const SizedBox(height: 8),
+            Row(
+              children: [
+                for (int i = 0; i < extensionProviders.length; i++) ...[
+                  if (i > 0) const SizedBox(width: 8),
+                  Expanded(
+                    child: _ServiceChip(
+                      icon: Icons.extension,
+                      label: extensionProviders[i].displayName,
+                      isSelected: effectiveService == extensionProviders[i].id,
+                      onTap: () => onChanged(extensionProviders[i].id),
+                    ),
+                  ),
+                ],
+                // Fill remaining space if less than 3 extensions
+                for (int i = extensionProviders.length; i < 3; i++) ...[
+                  const SizedBox(width: 8),
+                  const Expanded(child: SizedBox()),
+                ],
+              ],
+            ),
+          ],
         ],
       ),
     );

lib/screens/settings/extension_detail_page.dart

@@ -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 {
@@ -390,6 +391,8 @@ 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);
       }
     }

lib/screens/settings/options_settings_page.dart

@@ -76,38 +76,50 @@ class OptionsSettingsPage extends ConsumerWidget {
                         .setMetadataSource(v),
                   ),
                   if (settings.metadataSource == 'spotify') ...[
-                    SettingsSwitchItem(
-                      icon: Icons.toggle_on,
-                      title: 'Use Custom Credentials',
-                      subtitle: settings.useCustomSpotifyCredentials
-                          ? 'Using your credentials'
-                          : 'Using default credentials',
-                      value: settings.useCustomSpotifyCredentials,
-                      onChanged: (v) {
-                        ref
-                            .read(settingsProvider.notifier)
-                            .setUseCustomSpotifyCredentials(v);
-                        if (v && settings.spotifyClientId.isEmpty) {
-                          _showSpotifyCredentialsDialog(context, ref, settings);
-                        }
-                      },
-                      showDivider: true,
-                    ),
+                    // Info card about Spotify credentials requirement
+                    if (settings.spotifyClientId.isEmpty)
+                      Padding(
+                        padding: const EdgeInsets.fromLTRB(16, 8, 16, 8),
+                        child: Card(
+                          color: Theme.of(context).colorScheme.errorContainer,
+                          child: Padding(
+                            padding: const EdgeInsets.all(12),
+                            child: Row(
+                              children: [
+                                Icon(
+                                  Icons.warning_amber_rounded,
+                                  color: Theme.of(context).colorScheme.onErrorContainer,
+                                ),
+                                const SizedBox(width: 12),
+                                Expanded(
+                                  child: Text(
+                                    'Spotify requires your own API credentials. Get them free from developer.spotify.com',
+                                    style: TextStyle(
+                                      color: Theme.of(context).colorScheme.onErrorContainer,
+                                      fontSize: 12,
+                                    ),
+                                  ),
+                                ),
+                              ],
+                            ),
+                          ),
+                        ),
+                      ),
                     SettingsItem(
                       icon: Icons.key,
-                      title: 'Set Credentials',
+                      title: 'Spotify Credentials',
                       subtitle: settings.spotifyClientId.isNotEmpty
                           ? 'Client ID: ${settings.spotifyClientId.length > 8 ? '${settings.spotifyClientId.substring(0, 8)}...' : settings.spotifyClientId}'
-                          : 'Not configured',
+                          : 'Required - tap to configure',
                       onTap: () =>
                           _showSpotifyCredentialsDialog(context, ref, settings),
                       trailing: Icon(
                         settings.spotifyClientId.isNotEmpty
-                            ? Icons.edit
-                            : Icons.add,
+                            ? Icons.check_circle
+                            : Icons.error_outline,
                         color: settings.spotifyClientId.isNotEmpty
-                            ? Theme.of(context).colorScheme.onSurfaceVariant
-                            : Theme.of(context).colorScheme.primary,
+                            ? Theme.of(context).colorScheme.primary
+                            : Theme.of(context).colorScheme.error,
                         size: 20,
                       ),
                       showDivider: false,
@@ -190,6 +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',
@@ -782,14 +803,18 @@ class _MetadataSourceSelector extends ConsumerWidget {
     final settings = ref.watch(settingsProvider);
     final extState = ref.watch(extensionProvider);
     
-    // Check if extension search provider is active
-    final hasExtensionSearch = settings.searchProvider != null && 
-        settings.searchProvider!.isNotEmpty;
+    // Check if extension search provider is active AND enabled
+    Extension? activeExtension;
+    if (settings.searchProvider != null && settings.searchProvider!.isNotEmpty) {
+      activeExtension = extState.extensions
+          .where((e) => e.id == settings.searchProvider && e.enabled)
+          .firstOrNull;
+    }
+    final hasExtensionSearch = activeExtension != null;
     
     String? extensionName;
     if (hasExtensionSearch) {
-      final ext = extState.extensions.where((e) => e.id == settings.searchProvider).firstOrNull;
-      extensionName = ext?.displayName ?? settings.searchProvider;
+      extensionName = activeExtension.displayName;
     }
     
     return Padding(
@@ -820,6 +845,8 @@ 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: () {
@@ -834,6 +861,8 @@ 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: () {
@@ -878,12 +907,16 @@ class _SourceChip extends StatelessWidget {
   final String label;
   final bool isSelected;
   final VoidCallback? onTap;
+  final String? badge;
+  final Color? badgeColor;
 
   const _SourceChip({
     required this.icon,
     required this.label,
     required this.isSelected,
     this.onTap,
+    this.badge,
+    this.badgeColor,
   });
 
   @override
@@ -929,6 +962,24 @@ class _SourceChip extends StatelessWidget {
                         : colorScheme.onSurfaceVariant,
                   ),
                 ),
+                if (badge != null) ...[
+                  const SizedBox(height: 4),
+                  Container(
+                    padding: const EdgeInsets.symmetric(horizontal: 6, vertical: 2),
+                    decoration: BoxDecoration(
+                      color: (badgeColor ?? colorScheme.tertiary).withValues(alpha: 0.2),
+                      borderRadius: BorderRadius.circular(4),
+                    ),
+                    child: Text(
+                      badge!,
+                      style: TextStyle(
+                        fontSize: 9,
+                        fontWeight: FontWeight.w500,
+                        color: badgeColor ?? colorScheme.tertiary,
+                      ),
+                    ),
+                  ),
+                ],
               ],
             ),
           ),

lib/screens/setup_screen.dart

@@ -66,24 +66,38 @@ class _SetupScreenState extends ConsumerState<SetupScreen> {
       }
     } else if (Platform.isAndroid) {
       // Check storage permission
-      PermissionStatus storageStatus;
+      bool storageGranted = false;
+      
       if (_androidSdkVersion >= 33) {
-        storageStatus = await Permission.audio.status;
+        // Android 13+: Need BOTH MANAGE_EXTERNAL_STORAGE AND READ_MEDIA_AUDIO
+        final manageStatus = await Permission.manageExternalStorage.status;
+        final audioStatus = await Permission.audio.status;
+        debugPrint('[Permission] Android 13+ check: MANAGE_EXTERNAL_STORAGE=$manageStatus, READ_MEDIA_AUDIO=$audioStatus');
+        storageGranted = manageStatus.isGranted && audioStatus.isGranted;
       } else if (_androidSdkVersion >= 30) {
-        storageStatus = await Permission.manageExternalStorage.status;
+        // Android 11-12: Need MANAGE_EXTERNAL_STORAGE only
+        final manageStatus = await Permission.manageExternalStorage.status;
+        debugPrint('[Permission] Android 11-12 check: MANAGE_EXTERNAL_STORAGE=$manageStatus');
+        storageGranted = manageStatus.isGranted;
       } else {
-        storageStatus = await Permission.storage.status;
+        // Android 10 and below: Use legacy storage permission
+        final storageStatus = await Permission.storage.status;
+        debugPrint('[Permission] Android 10- check: STORAGE=$storageStatus');
+        storageGranted = storageStatus.isGranted;
       }
       
+      debugPrint('[Permission] Final storageGranted=$storageGranted');
+      
       // Check notification permission (Android 13+)
       PermissionStatus notificationStatus = PermissionStatus.granted;
       if (_androidSdkVersion >= 33) {
         notificationStatus = await Permission.notification.status;
+        debugPrint('[Permission] Notification=$notificationStatus');
       }
       
       if (mounted) {
         setState(() {
-          _storagePermissionGranted = storageStatus.isGranted;
+          _storagePermissionGranted = storageGranted;
           _notificationPermissionGranted = notificationStatus.isGranted;
         });
       }
@@ -97,17 +111,57 @@ class _SetupScreenState extends ConsumerState<SetupScreen> {
       if (Platform.isIOS) {
         setState(() => _storagePermissionGranted = true);
       } else if (Platform.isAndroid) {
-        PermissionStatus status;
+        bool allGranted = false;
         
         if (_androidSdkVersion >= 33) {
-          // Android 13+: Use audio permission
-          status = await Permission.audio.request();
+          // Android 13+: Need BOTH MANAGE_EXTERNAL_STORAGE AND READ_MEDIA_AUDIO
+          
+          // First check/request MANAGE_EXTERNAL_STORAGE
+          var manageStatus = await Permission.manageExternalStorage.status;
+          if (!manageStatus.isGranted) {
+            if (mounted) {
+              final shouldOpen = await showDialog<bool>(
+                context: context,
+                builder: (context) => AlertDialog(
+                  title: const Text('Storage Access Required'),
+                  content: const Text(
+                    'SpotiFLAC needs "All files access" permission to save music files to your chosen folder.\n\n'
+                    'Please enable "Allow access to manage all files" in the next screen.',
+                  ),
+                  actions: [
+                    TextButton(
+                      onPressed: () => Navigator.pop(context, false),
+                      child: const Text('Cancel'),
+                    ),
+                    FilledButton(
+                      onPressed: () => Navigator.pop(context, true),
+                      child: const Text('Open Settings'),
+                    ),
+                  ],
+                ),
+              );
+              
+              if (shouldOpen == true) {
+                await Permission.manageExternalStorage.request();
+                // Re-check after returning from settings
+                await Future.delayed(const Duration(milliseconds: 500));
+                manageStatus = await Permission.manageExternalStorage.status;
+              }
+            }
+          }
+          
+          // Then request READ_MEDIA_AUDIO (this shows a dialog)
+          var audioStatus = await Permission.audio.status;
+          if (!audioStatus.isGranted && manageStatus.isGranted) {
+            audioStatus = await Permission.audio.request();
+          }
+          
+          allGranted = manageStatus.isGranted && audioStatus.isGranted;
+          
         } else if (_androidSdkVersion >= 30) {
-          // Android 11-12: Need MANAGE_EXTERNAL_STORAGE
-          // This opens system settings, not a dialog
-          status = await Permission.manageExternalStorage.status;
-          if (!status.isGranted) {
-            // Show explanation dialog first
+          // Android 11-12: Need MANAGE_EXTERNAL_STORAGE only
+          var manageStatus = await Permission.manageExternalStorage.status;
+          if (!manageStatus.isGranted) {
             if (mounted) {
               final shouldOpen = await showDialog<bool>(
                 context: context,
@@ -131,23 +185,33 @@ class _SetupScreenState extends ConsumerState<SetupScreen> {
               );
               
               if (shouldOpen == true) {
-                status = await Permission.manageExternalStorage.request();
+                await Permission.manageExternalStorage.request();
+                // Re-check after returning from settings
+                await Future.delayed(const Duration(milliseconds: 500));
+                manageStatus = await Permission.manageExternalStorage.status;
               }
             }
           }
+          allGranted = manageStatus.isGranted;
+          
         } else {
           // Android 10 and below: Use legacy storage permission
-          status = await Permission.storage.request();
+          final status = await Permission.storage.request();
+          allGranted = status.isGranted;
+          
+          if (status.isPermanentlyDenied) {
+            _showPermissionDeniedDialog('Storage');
+            setState(() => _isLoading = false);
+            return;
+          }
         }
         
-        if (status.isGranted) {
+        if (allGranted) {
           setState(() => _storagePermissionGranted = true);
-        } else if (status.isPermanentlyDenied) {
-          _showPermissionDeniedDialog('Storage');
         } else {
           if (mounted) {
             ScaffoldMessenger.of(context).showSnackBar(
-              const SnackBar(content: Text('Permission denied. Please grant permission to continue.')),
+              const SnackBar(content: Text('Permission denied. Please grant all permissions to continue.')),
             );
           }
         }
@@ -380,11 +444,10 @@ class _SetupScreenState extends ConsumerState<SetupScreen> {
           _clientIdController.text.trim(),
           _clientSecretController.text.trim(),
         );
-        ref.read(settingsProvider.notifier).setUseCustomSpotifyCredentials(true);
-        // Set search source to Spotify when using custom credentials
+        // Set search source to Spotify when credentials are provided
         ref.read(settingsProvider.notifier).setMetadataSource('spotify');
       } else {
-        // Use Deezer as default search source
+        // Use Deezer as default search source (free, no credentials required)
         ref.read(settingsProvider.notifier).setMetadataSource('deezer');
       }
       

lib/screens/store_tab.dart

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

lib/services/platform_bridge.dart

@@ -331,7 +331,6 @@ class PlatformBridge {
   }
 
   /// Set custom Spotify API credentials
-  /// Pass empty strings to use default credentials
   static Future<void> setSpotifyCredentials(String clientId, String clientSecret) async {
     await _channel.invokeMethod('setSpotifyCredentials', {
       'client_id': clientId,
@@ -339,6 +338,13 @@ class PlatformBridge {
     });
   }
 
+  /// Check if Spotify credentials are configured
+  /// Returns true if credentials are available (custom or env vars)
+  static Future<bool> hasSpotifyCredentials() async {
+    final result = await _channel.invokeMethod('hasSpotifyCredentials');
+    return result as bool;
+  }
+
   /// Pre-warm track ID cache for album/playlist tracks
   /// This runs in background and returns immediately
   /// Speeds up subsequent downloads by caching ISRC → Track ID mappings
@@ -747,6 +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
@@ -767,4 +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');
+  }
 }

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.1+50
+version: 3.0.0-alpha.4+53
 
 environment:
   sdk: ^3.10.0

pubspec_ios.yaml

@@ -1,7 +1,7 @@
 name: spotiflac_android
 description: Download Spotify tracks in FLAC from Tidal, Qobuz & Amazon Music
 publish_to: "none"
-version: 3.0.0-alpha.1+50
+version: 3.0.0-alpha.4+53
 
 environment:
   sdk: ^3.10.0