feat: add configurable extension download fallback

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

@@ -2965,6 +2965,13 @@ class MainActivity: FlutterFragmentActivity() {
                             }
                             result.success(response)
                         }
+                        "setDownloadFallbackExtensionIds" -> {
+                            val extensionIdsJson = call.argument<String>("extension_ids") ?: ""
+                            withContext(Dispatchers.IO) {
+                                Gobackend.setExtensionFallbackProviderIDsJSON(extensionIdsJson)
+                            }
+                            result.success(null)
+                        }
                         "setMetadataProviderPriority" -> {
                             val priorityJson = call.argument<String>("priority") ?: "[]"
                             withContext(Dispatchers.IO) {

go_backend/exports.go

@@ -2665,6 +2665,30 @@ func GetProviderPriorityJSON() (string, error) {
 	return string(jsonBytes), nil
 }
 
+func SetExtensionFallbackProviderIDsJSON(providerIDsJSON string) error {
+	if strings.TrimSpace(providerIDsJSON) == "" {
+		SetExtensionFallbackProviderIDs(nil)
+		return nil
+	}
+
+	var providerIDs []string
+	if err := json.Unmarshal([]byte(providerIDsJSON), &providerIDs); err != nil {
+		return err
+	}
+
+	SetExtensionFallbackProviderIDs(providerIDs)
+	return nil
+}
+
+func GetExtensionFallbackProviderIDsJSON() (string, error) {
+	providerIDs := GetExtensionFallbackProviderIDs()
+	jsonBytes, err := json.Marshal(providerIDs)
+	if err != nil {
+		return "", err
+	}
+	return string(jsonBytes), nil
+}
+
 func SetMetadataProviderPriorityJSON(priorityJSON string) error {
 	var priority []string
 	if err := json.Unmarshal([]byte(priorityJSON), &priority); err != nil {

go_backend/exports_test.go

@@ -2,6 +2,21 @@ package gobackend
 
 import "testing"
 
+func TestSetExtensionFallbackProviderIDsJSONEmptyStringResetsDefault(t *testing.T) {
+	original := GetExtensionFallbackProviderIDs()
+	defer SetExtensionFallbackProviderIDs(original)
+
+	SetExtensionFallbackProviderIDs([]string{"custom-ext"})
+
+	if err := SetExtensionFallbackProviderIDsJSON(""); err != nil {
+		t.Fatalf("SetExtensionFallbackProviderIDsJSON returned error: %v", err)
+	}
+
+	if got := GetExtensionFallbackProviderIDs(); got != nil {
+		t.Fatalf("expected nil fallback provider list after reset, got %v", got)
+	}
+}
+
 func TestBuildDownloadSuccessResponsePrefersRequestedAlbumMetadata(t *testing.T) {
 	req := DownloadRequest{
 		TrackName:   "Bonus Track",

go_backend/extension_providers.go

@@ -676,6 +676,9 @@ func (m *extensionManager) SearchTracksWithExtensions(query string, limit int) (
 var providerPriority []string
 var providerPriorityMu sync.RWMutex
 
+var extensionFallbackProviderIDs []string
+var extensionFallbackProviderIDsMu sync.RWMutex
+
 var metadataProviderPriority []string
 var metadataProviderPriorityMu sync.RWMutex
 
@@ -701,6 +704,65 @@ func GetProviderPriority() []string {
 	return result
 }
 
+func SetExtensionFallbackProviderIDs(providerIDs []string) {
+	extensionFallbackProviderIDsMu.Lock()
+	defer extensionFallbackProviderIDsMu.Unlock()
+
+	if providerIDs == nil {
+		extensionFallbackProviderIDs = nil
+		GoLog("[Extension] Extension fallback providers reset to default (all enabled download extensions)\n")
+		return
+	}
+
+	sanitized := make([]string, 0, len(providerIDs))
+	seen := map[string]struct{}{}
+	for _, providerID := range providerIDs {
+		providerID = strings.TrimSpace(providerID)
+		if providerID == "" || isBuiltInProvider(strings.ToLower(providerID)) {
+			continue
+		}
+		if _, exists := seen[providerID]; exists {
+			continue
+		}
+		seen[providerID] = struct{}{}
+		sanitized = append(sanitized, providerID)
+	}
+
+	extensionFallbackProviderIDs = sanitized
+	GoLog("[Extension] Extension fallback providers set: %v\n", sanitized)
+}
+
+func GetExtensionFallbackProviderIDs() []string {
+	extensionFallbackProviderIDsMu.RLock()
+	defer extensionFallbackProviderIDsMu.RUnlock()
+
+	if extensionFallbackProviderIDs == nil {
+		return nil
+	}
+
+	result := make([]string, len(extensionFallbackProviderIDs))
+	copy(result, extensionFallbackProviderIDs)
+	return result
+}
+
+func isExtensionFallbackAllowed(providerID string) bool {
+	if isBuiltInProvider(strings.ToLower(providerID)) {
+		return true
+	}
+
+	allowed := GetExtensionFallbackProviderIDs()
+	if allowed == nil {
+		return true
+	}
+
+	for _, allowedProviderID := range allowed {
+		if allowedProviderID == providerID {
+			return true
+		}
+	}
+	return false
+}
+
 func SetMetadataProviderPriority(providerIDs []string) {
 	metadataProviderPriorityMu.Lock()
 	defer metadataProviderPriorityMu.Unlock()
@@ -1308,6 +1370,11 @@ func DownloadWithExtensionFallback(req DownloadRequest) (*DownloadResponse, erro
 			continue
 		}
 
+		if !isBuiltInProvider(providerIDNormalized) && !isExtensionFallbackAllowed(providerID) {
+			GoLog("[DownloadWithExtensionFallback] Skipping extension provider %s (not enabled for fallback)\n", providerID)
+			continue
+		}
+
 		GoLog("[DownloadWithExtensionFallback] Trying provider: %s\n", providerID)
 
 		if isBuiltInProvider(providerIDNormalized) {

go_backend/extension_providers_test.go

@@ -19,6 +19,55 @@ func TestSetMetadataProviderPriorityAddsBuiltIns(t *testing.T) {
 	}
 }
 
+func TestSetExtensionFallbackProviderIDsSkipsBuiltInsAndDuplicates(t *testing.T) {
+	original := GetExtensionFallbackProviderIDs()
+	defer SetExtensionFallbackProviderIDs(original)
+
+	SetExtensionFallbackProviderIDs([]string{"ext-a", "tidal", "ext-a", " ext-b "})
+
+	got := GetExtensionFallbackProviderIDs()
+	want := []string{"ext-a", "ext-b"}
+	if len(got) != len(want) {
+		t.Fatalf("unexpected fallback provider length: got %v want %v", got, want)
+	}
+	for i := range want {
+		if got[i] != want[i] {
+			t.Fatalf("unexpected fallback provider at %d: got %v want %v", i, got, want)
+		}
+	}
+}
+
+func TestIsExtensionFallbackAllowedDefaultsToAllExtensions(t *testing.T) {
+	original := GetExtensionFallbackProviderIDs()
+	defer SetExtensionFallbackProviderIDs(original)
+
+	SetExtensionFallbackProviderIDs(nil)
+
+	if !isExtensionFallbackAllowed("custom-ext") {
+		t.Fatal("expected custom extension to be allowed when no fallback allowlist is configured")
+	}
+	if !isExtensionFallbackAllowed("qobuz") {
+		t.Fatal("expected built-in provider to remain allowed")
+	}
+}
+
+func TestIsExtensionFallbackAllowedRespectsAllowlist(t *testing.T) {
+	original := GetExtensionFallbackProviderIDs()
+	defer SetExtensionFallbackProviderIDs(original)
+
+	SetExtensionFallbackProviderIDs([]string{"allowed-ext"})
+
+	if !isExtensionFallbackAllowed("allowed-ext") {
+		t.Fatal("expected explicitly allowed extension to be permitted")
+	}
+	if isExtensionFallbackAllowed("blocked-ext") {
+		t.Fatal("expected extension outside allowlist to be blocked")
+	}
+	if !isExtensionFallbackAllowed("deezer") {
+		t.Fatal("expected built-in provider to ignore extension allowlist")
+	}
+}
+
 func TestSearchTracksWithMetadataProvidersUsesPriorityAndDedupes(t *testing.T) {
 	originalPriority := GetMetadataProviderPriority()
 	originalSearch := searchBuiltInMetadataTracksFunc

ios/Runner/AppDelegate.swift

@@ -607,6 +607,13 @@ import Gobackend  // Import Go framework
             let response = GobackendGetProviderPriorityJSON(&error)
             if let error = error { throw error }
             return response
+
+        case "setDownloadFallbackExtensionIds":
+            let args = call.arguments as! [String: Any]
+            let extensionIdsJson = args["extension_ids"] as? String ?? ""
+            GobackendSetExtensionFallbackProviderIDsJSON(extensionIdsJson, &error)
+            if let error = error { throw error }
+            return nil
             
         case "setMetadataProviderPriority":
             let args = call.arguments as! [String: Any]

lib/l10n/app_localizations.dart

@@ -1738,6 +1738,24 @@ abstract class AppLocalizations {
   /// **'If a track is not available on the first provider, the app will automatically try the next one.'**
   String get providerPriorityInfo;
 
+  /// Section title for choosing which download extensions can be used as fallback providers
+  ///
+  /// In en, this message translates to:
+  /// **'Extension Fallback'**
+  String get providerPriorityFallbackExtensionsTitle;
+
+  /// Section description for extension fallback selection
+  ///
+  /// In en, this message translates to:
+  /// **'Choose which installed download extensions can be used during automatic fallback. Built-in providers still follow the priority order above.'**
+  String get providerPriorityFallbackExtensionsDescription;
+
+  /// Hint below the extension fallback selection list
+  ///
+  /// In en, this message translates to:
+  /// **'Only enabled extensions with download-provider capability are listed here.'**
+  String get providerPriorityFallbackExtensionsHint;
+
   /// Label for built-in providers (Tidal/Qobuz)
   ///
   /// In en, this message translates to:
@@ -2644,6 +2662,18 @@ abstract class AppLocalizations {
   /// **'Set download service order'**
   String get extensionsDownloadPrioritySubtitle;
 
+  /// Setting and page title for choosing which download extensions can be used during fallback
+  ///
+  /// In en, this message translates to:
+  /// **'Fallback Extensions'**
+  String get extensionsFallbackTitle;
+
+  /// Subtitle for download fallback extensions menu
+  ///
+  /// In en, this message translates to:
+  /// **'Choose which installed download extensions can be used as fallback'**
+  String get extensionsFallbackSubtitle;
+
   /// Empty state - no download providers
   ///
   /// In en, this message translates to:

lib/l10n/app_localizations_de.dart

@@ -940,6 +940,17 @@ class AppLocalizationsDe extends AppLocalizations {
   String get providerPriorityInfo =>
       'Wenn kein Titel bei dem ersten Anbieter nicht verfügbar ist, wird die App automatisch den nächsten versuchen.';
 
+  @override
+  String get providerPriorityFallbackExtensionsTitle => 'Extension Fallback';
+
+  @override
+  String get providerPriorityFallbackExtensionsDescription =>
+      'Choose which installed download extensions can be used during automatic fallback. Built-in providers still follow the priority order above.';
+
+  @override
+  String get providerPriorityFallbackExtensionsHint =>
+      'Only enabled extensions with download-provider capability are listed here.';
+
   @override
   String get providerBuiltIn => 'Integriert';
 
@@ -1438,6 +1449,13 @@ class AppLocalizationsDe extends AppLocalizations {
   String get extensionsDownloadPrioritySubtitle =>
       'Download-Service-Reihenfolge festlegen';
 
+  @override
+  String get extensionsFallbackTitle => 'Fallback Extensions';
+
+  @override
+  String get extensionsFallbackSubtitle =>
+      'Choose which installed download extensions can be used as fallback';
+
   @override
   String get extensionsNoDownloadProvider =>
       'Keine Erweiterungen mit Download-Provider';

lib/l10n/app_localizations_en.dart

@@ -926,6 +926,17 @@ class AppLocalizationsEn extends AppLocalizations {
   String get providerPriorityInfo =>
       'If a track is not available on the first provider, the app will automatically try the next one.';
 
+  @override
+  String get providerPriorityFallbackExtensionsTitle => 'Extension Fallback';
+
+  @override
+  String get providerPriorityFallbackExtensionsDescription =>
+      'Choose which installed download extensions can be used during automatic fallback. Built-in providers still follow the priority order above.';
+
+  @override
+  String get providerPriorityFallbackExtensionsHint =>
+      'Only enabled extensions with download-provider capability are listed here.';
+
   @override
   String get providerBuiltIn => 'Built-in';
 
@@ -1415,6 +1426,13 @@ class AppLocalizationsEn extends AppLocalizations {
   @override
   String get extensionsDownloadPrioritySubtitle => 'Set download service order';
 
+  @override
+  String get extensionsFallbackTitle => 'Fallback Extensions';
+
+  @override
+  String get extensionsFallbackSubtitle =>
+      'Choose which installed download extensions can be used as fallback';
+
   @override
   String get extensionsNoDownloadProvider =>
       'No extensions with download provider';

lib/l10n/app_localizations_es.dart

@@ -926,6 +926,17 @@ class AppLocalizationsEs extends AppLocalizations {
   String get providerPriorityInfo =>
       'If a track is not available on the first provider, the app will automatically try the next one.';
 
+  @override
+  String get providerPriorityFallbackExtensionsTitle => 'Extension Fallback';
+
+  @override
+  String get providerPriorityFallbackExtensionsDescription =>
+      'Choose which installed download extensions can be used during automatic fallback. Built-in providers still follow the priority order above.';
+
+  @override
+  String get providerPriorityFallbackExtensionsHint =>
+      'Only enabled extensions with download-provider capability are listed here.';
+
   @override
   String get providerBuiltIn => 'Built-in';
 
@@ -1415,6 +1426,13 @@ class AppLocalizationsEs extends AppLocalizations {
   @override
   String get extensionsDownloadPrioritySubtitle => 'Set download service order';
 
+  @override
+  String get extensionsFallbackTitle => 'Fallback Extensions';
+
+  @override
+  String get extensionsFallbackSubtitle =>
+      'Choose which installed download extensions can be used as fallback';
+
   @override
   String get extensionsNoDownloadProvider =>
       'No extensions with download provider';

lib/l10n/app_localizations_fr.dart

@@ -928,6 +928,17 @@ class AppLocalizationsFr extends AppLocalizations {
   String get providerPriorityInfo =>
       'If a track is not available on the first provider, the app will automatically try the next one.';
 
+  @override
+  String get providerPriorityFallbackExtensionsTitle => 'Extension Fallback';
+
+  @override
+  String get providerPriorityFallbackExtensionsDescription =>
+      'Choose which installed download extensions can be used during automatic fallback. Built-in providers still follow the priority order above.';
+
+  @override
+  String get providerPriorityFallbackExtensionsHint =>
+      'Only enabled extensions with download-provider capability are listed here.';
+
   @override
   String get providerBuiltIn => 'Built-in';
 
@@ -1417,6 +1428,13 @@ class AppLocalizationsFr extends AppLocalizations {
   @override
   String get extensionsDownloadPrioritySubtitle => 'Set download service order';
 
+  @override
+  String get extensionsFallbackTitle => 'Fallback Extensions';
+
+  @override
+  String get extensionsFallbackSubtitle =>
+      'Choose which installed download extensions can be used as fallback';
+
   @override
   String get extensionsNoDownloadProvider =>
       'No extensions with download provider';

lib/l10n/app_localizations_hi.dart

@@ -926,6 +926,17 @@ class AppLocalizationsHi extends AppLocalizations {
   String get providerPriorityInfo =>
       'If a track is not available on the first provider, the app will automatically try the next one.';
 
+  @override
+  String get providerPriorityFallbackExtensionsTitle => 'Extension Fallback';
+
+  @override
+  String get providerPriorityFallbackExtensionsDescription =>
+      'Choose which installed download extensions can be used during automatic fallback. Built-in providers still follow the priority order above.';
+
+  @override
+  String get providerPriorityFallbackExtensionsHint =>
+      'Only enabled extensions with download-provider capability are listed here.';
+
   @override
   String get providerBuiltIn => 'Built-in';
 
@@ -1415,6 +1426,13 @@ class AppLocalizationsHi extends AppLocalizations {
   @override
   String get extensionsDownloadPrioritySubtitle => 'Set download service order';
 
+  @override
+  String get extensionsFallbackTitle => 'Fallback Extensions';
+
+  @override
+  String get extensionsFallbackSubtitle =>
+      'Choose which installed download extensions can be used as fallback';
+
   @override
   String get extensionsNoDownloadProvider =>
       'No extensions with download provider';

lib/l10n/app_localizations_id.dart

@@ -930,6 +930,17 @@ class AppLocalizationsId extends AppLocalizations {
   String get providerPriorityInfo =>
       'Jika lagu tidak tersedia di provider pertama, aplikasi akan otomatis mencoba yang berikutnya.';
 
+  @override
+  String get providerPriorityFallbackExtensionsTitle => 'Fallback Ekstensi';
+
+  @override
+  String get providerPriorityFallbackExtensionsDescription =>
+      'Pilih ekstensi unduhan terpasang mana yang boleh dipakai saat fallback otomatis. Provider bawaan tetap mengikuti urutan prioritas di atas.';
+
+  @override
+  String get providerPriorityFallbackExtensionsHint =>
+      'Hanya ekstensi aktif dengan kemampuan download provider yang ditampilkan di sini.';
+
   @override
   String get providerBuiltIn => 'Bawaan';
 
@@ -1423,6 +1434,13 @@ class AppLocalizationsId extends AppLocalizations {
   String get extensionsDownloadPrioritySubtitle =>
       'Atur urutan layanan unduhan';
 
+  @override
+  String get extensionsFallbackTitle => 'Fallback Extensions';
+
+  @override
+  String get extensionsFallbackSubtitle =>
+      'Pilih ekstensi unduhan terpasang yang boleh dipakai saat fallback';
+
   @override
   String get extensionsNoDownloadProvider =>
       'Tidak ada ekstensi dengan provider unduhan';

lib/l10n/app_localizations_ja.dart

@@ -920,6 +920,17 @@ class AppLocalizationsJa extends AppLocalizations {
   String get providerPriorityInfo =>
       'If a track is not available on the first provider, the app will automatically try the next one.';
 
+  @override
+  String get providerPriorityFallbackExtensionsTitle => 'Extension Fallback';
+
+  @override
+  String get providerPriorityFallbackExtensionsDescription =>
+      'Choose which installed download extensions can be used during automatic fallback. Built-in providers still follow the priority order above.';
+
+  @override
+  String get providerPriorityFallbackExtensionsHint =>
+      'Only enabled extensions with download-provider capability are listed here.';
+
   @override
   String get providerBuiltIn => '内蔵';
 
@@ -1409,6 +1420,13 @@ class AppLocalizationsJa extends AppLocalizations {
   @override
   String get extensionsDownloadPrioritySubtitle => 'ダウンロードサービスの順序を設定';
 
+  @override
+  String get extensionsFallbackTitle => 'Fallback Extensions';
+
+  @override
+  String get extensionsFallbackSubtitle =>
+      'Choose which installed download extensions can be used as fallback';
+
   @override
   String get extensionsNoDownloadProvider => 'ダウンロードプロバイダーの拡張はありません';
 

lib/l10n/app_localizations_ko.dart

@@ -908,6 +908,17 @@ class AppLocalizationsKo extends AppLocalizations {
   String get providerPriorityInfo =>
       'If a track is not available on the first provider, the app will automatically try the next one.';
 
+  @override
+  String get providerPriorityFallbackExtensionsTitle => 'Extension Fallback';
+
+  @override
+  String get providerPriorityFallbackExtensionsDescription =>
+      'Choose which installed download extensions can be used during automatic fallback. Built-in providers still follow the priority order above.';
+
+  @override
+  String get providerPriorityFallbackExtensionsHint =>
+      'Only enabled extensions with download-provider capability are listed here.';
+
   @override
   String get providerBuiltIn => 'Built-in';
 
@@ -1395,6 +1406,13 @@ class AppLocalizationsKo extends AppLocalizations {
   @override
   String get extensionsDownloadPrioritySubtitle => 'Set download service order';
 
+  @override
+  String get extensionsFallbackTitle => 'Fallback Extensions';
+
+  @override
+  String get extensionsFallbackSubtitle =>
+      'Choose which installed download extensions can be used as fallback';
+
   @override
   String get extensionsNoDownloadProvider =>
       'No extensions with download provider';

lib/l10n/app_localizations_nl.dart

@@ -926,6 +926,17 @@ class AppLocalizationsNl extends AppLocalizations {
   String get providerPriorityInfo =>
       'If a track is not available on the first provider, the app will automatically try the next one.';
 
+  @override
+  String get providerPriorityFallbackExtensionsTitle => 'Extension Fallback';
+
+  @override
+  String get providerPriorityFallbackExtensionsDescription =>
+      'Choose which installed download extensions can be used during automatic fallback. Built-in providers still follow the priority order above.';
+
+  @override
+  String get providerPriorityFallbackExtensionsHint =>
+      'Only enabled extensions with download-provider capability are listed here.';
+
   @override
   String get providerBuiltIn => 'Built-in';
 
@@ -1415,6 +1426,13 @@ class AppLocalizationsNl extends AppLocalizations {
   @override
   String get extensionsDownloadPrioritySubtitle => 'Set download service order';
 
+  @override
+  String get extensionsFallbackTitle => 'Fallback Extensions';
+
+  @override
+  String get extensionsFallbackSubtitle =>
+      'Choose which installed download extensions can be used as fallback';
+
   @override
   String get extensionsNoDownloadProvider =>
       'No extensions with download provider';

lib/l10n/app_localizations_pt.dart

@@ -926,6 +926,17 @@ class AppLocalizationsPt extends AppLocalizations {
   String get providerPriorityInfo =>
       'If a track is not available on the first provider, the app will automatically try the next one.';
 
+  @override
+  String get providerPriorityFallbackExtensionsTitle => 'Extension Fallback';
+
+  @override
+  String get providerPriorityFallbackExtensionsDescription =>
+      'Choose which installed download extensions can be used during automatic fallback. Built-in providers still follow the priority order above.';
+
+  @override
+  String get providerPriorityFallbackExtensionsHint =>
+      'Only enabled extensions with download-provider capability are listed here.';
+
   @override
   String get providerBuiltIn => 'Built-in';
 
@@ -1415,6 +1426,13 @@ class AppLocalizationsPt extends AppLocalizations {
   @override
   String get extensionsDownloadPrioritySubtitle => 'Set download service order';
 
+  @override
+  String get extensionsFallbackTitle => 'Fallback Extensions';
+
+  @override
+  String get extensionsFallbackSubtitle =>
+      'Choose which installed download extensions can be used as fallback';
+
   @override
   String get extensionsNoDownloadProvider =>
       'No extensions with download provider';

lib/l10n/app_localizations_ru.dart

@@ -940,6 +940,17 @@ class AppLocalizationsRu extends AppLocalizations {
   String get providerPriorityInfo =>
       'Если трек не доступен у первого провайдера, приложение автоматически попробует следующий.';
 
+  @override
+  String get providerPriorityFallbackExtensionsTitle => 'Extension Fallback';
+
+  @override
+  String get providerPriorityFallbackExtensionsDescription =>
+      'Choose which installed download extensions can be used during automatic fallback. Built-in providers still follow the priority order above.';
+
+  @override
+  String get providerPriorityFallbackExtensionsHint =>
+      'Only enabled extensions with download-provider capability are listed here.';
+
   @override
   String get providerBuiltIn => 'Встроенные';
 
@@ -1439,6 +1450,13 @@ class AppLocalizationsRu extends AppLocalizations {
   String get extensionsDownloadPrioritySubtitle =>
       'Установка порядок сервисов скачивания';
 
+  @override
+  String get extensionsFallbackTitle => 'Fallback Extensions';
+
+  @override
+  String get extensionsFallbackSubtitle =>
+      'Choose which installed download extensions can be used as fallback';
+
   @override
   String get extensionsNoDownloadProvider =>
       'Нет расширений с провайдером загрузки';

lib/l10n/app_localizations_tr.dart

@@ -931,6 +931,17 @@ class AppLocalizationsTr extends AppLocalizations {
   String get providerPriorityInfo =>
       'Eğer bir şarkı ilk hizmette mevcut değilse uygulama otomatik olarak bir sonrakini deneyecektir.';
 
+  @override
+  String get providerPriorityFallbackExtensionsTitle => 'Extension Fallback';
+
+  @override
+  String get providerPriorityFallbackExtensionsDescription =>
+      'Choose which installed download extensions can be used during automatic fallback. Built-in providers still follow the priority order above.';
+
+  @override
+  String get providerPriorityFallbackExtensionsHint =>
+      'Only enabled extensions with download-provider capability are listed here.';
+
   @override
   String get providerBuiltIn => 'Dahili';
 
@@ -1421,6 +1432,13 @@ class AppLocalizationsTr extends AppLocalizations {
   @override
   String get extensionsDownloadPrioritySubtitle => 'Set download service order';
 
+  @override
+  String get extensionsFallbackTitle => 'Fallback Extensions';
+
+  @override
+  String get extensionsFallbackSubtitle =>
+      'Choose which installed download extensions can be used as fallback';
+
   @override
   String get extensionsNoDownloadProvider =>
       'No extensions with download provider';

lib/l10n/app_localizations_zh.dart

@@ -926,6 +926,17 @@ class AppLocalizationsZh extends AppLocalizations {
   String get providerPriorityInfo =>
       'If a track is not available on the first provider, the app will automatically try the next one.';
 
+  @override
+  String get providerPriorityFallbackExtensionsTitle => 'Extension Fallback';
+
+  @override
+  String get providerPriorityFallbackExtensionsDescription =>
+      'Choose which installed download extensions can be used during automatic fallback. Built-in providers still follow the priority order above.';
+
+  @override
+  String get providerPriorityFallbackExtensionsHint =>
+      'Only enabled extensions with download-provider capability are listed here.';
+
   @override
   String get providerBuiltIn => 'Built-in';
 
@@ -1415,6 +1426,13 @@ class AppLocalizationsZh extends AppLocalizations {
   @override
   String get extensionsDownloadPrioritySubtitle => 'Set download service order';
 
+  @override
+  String get extensionsFallbackTitle => 'Fallback Extensions';
+
+  @override
+  String get extensionsFallbackSubtitle =>
+      'Choose which installed download extensions can be used as fallback';
+
   @override
   String get extensionsNoDownloadProvider =>
       'No extensions with download provider';

lib/l10n/arb/app_en.arb

@@ -1203,6 +1203,18 @@
   "@providerPriorityInfo": {
     "description": "Info tip about fallback behavior"
   },
+  "providerPriorityFallbackExtensionsTitle": "Extension Fallback",
+  "@providerPriorityFallbackExtensionsTitle": {
+    "description": "Section title for choosing which download extensions can be used as fallback providers"
+  },
+  "providerPriorityFallbackExtensionsDescription": "Choose which installed download extensions can be used during automatic fallback. Built-in providers still follow the priority order above.",
+  "@providerPriorityFallbackExtensionsDescription": {
+    "description": "Section description for extension fallback selection"
+  },
+  "providerPriorityFallbackExtensionsHint": "Only enabled extensions with download-provider capability are listed here.",
+  "@providerPriorityFallbackExtensionsHint": {
+    "description": "Hint below the extension fallback selection list"
+  },
   "providerBuiltIn": "Built-in",
   "@providerBuiltIn": {
     "description": "Label for built-in providers (Tidal/Qobuz)"
@@ -1857,6 +1869,14 @@
   "@extensionsDownloadPrioritySubtitle": {
     "description": "Subtitle for download priority"
   },
+  "extensionsFallbackTitle": "Fallback Extensions",
+  "@extensionsFallbackTitle": {
+    "description": "Setting and page title for choosing which download extensions can be used during fallback"
+  },
+  "extensionsFallbackSubtitle": "Choose which installed download extensions can be used as fallback",
+  "@extensionsFallbackSubtitle": {
+    "description": "Subtitle for download fallback extensions menu"
+  },
   "extensionsNoDownloadProvider": "No extensions with download provider",
   "@extensionsNoDownloadProvider": {
     "description": "Empty state - no download providers"

lib/l10n/arb/app_id.arb

@@ -1119,6 +1119,18 @@
   "@providerPriorityInfo": {
     "description": "Info tip about fallback behavior"
   },
+  "providerPriorityFallbackExtensionsTitle": "Fallback Ekstensi",
+  "@providerPriorityFallbackExtensionsTitle": {
+    "description": "Section title for choosing which download extensions can be used as fallback providers"
+  },
+  "providerPriorityFallbackExtensionsDescription": "Pilih ekstensi unduhan terpasang mana yang boleh dipakai saat fallback otomatis. Provider bawaan tetap mengikuti urutan prioritas di atas.",
+  "@providerPriorityFallbackExtensionsDescription": {
+    "description": "Section description for extension fallback selection"
+  },
+  "providerPriorityFallbackExtensionsHint": "Hanya ekstensi aktif dengan kemampuan download provider yang ditampilkan di sini.",
+  "@providerPriorityFallbackExtensionsHint": {
+    "description": "Hint below the extension fallback selection list"
+  },
   "providerBuiltIn": "Bawaan",
   "@providerBuiltIn": {
     "description": "Label for built-in providers (Tidal/Qobuz)"
@@ -1713,6 +1725,14 @@
   "@extensionsDownloadPrioritySubtitle": {
     "description": "Subtitle for download priority"
   },
+  "extensionsFallbackTitle": "Fallback Extensions",
+  "@extensionsFallbackTitle": {
+    "description": "Setting and page title for choosing which download extensions can be used during fallback"
+  },
+  "extensionsFallbackSubtitle": "Pilih ekstensi unduhan terpasang yang boleh dipakai saat fallback",
+  "@extensionsFallbackSubtitle": {
+    "description": "Subtitle for download fallback extensions menu"
+  },
   "extensionsNoDownloadProvider": "Tidak ada ekstensi dengan provider unduhan",
   "@extensionsNoDownloadProvider": {
     "description": "Empty state - no download providers"

lib/models/settings.dart

@@ -33,6 +33,7 @@ class AppSettings {
   final bool askQualityBeforeDownload;
   final bool enableLogging;
   final bool useExtensionProviders;
+  final List<String>? downloadFallbackExtensionIds;
   final String? searchProvider;
   final String? homeFeedProvider;
   final bool separateSingles;
@@ -108,6 +109,7 @@ class AppSettings {
     this.askQualityBeforeDownload = true,
     this.enableLogging = false,
     this.useExtensionProviders = true,
+    this.downloadFallbackExtensionIds,
     this.searchProvider,
     this.homeFeedProvider,
     this.separateSingles = false,
@@ -170,6 +172,8 @@ class AppSettings {
     bool? askQualityBeforeDownload,
     bool? enableLogging,
     bool? useExtensionProviders,
+    List<String>? downloadFallbackExtensionIds,
+    bool clearDownloadFallbackExtensionIds = false,
     String? searchProvider,
     bool clearSearchProvider = false,
     String? homeFeedProvider,
@@ -232,6 +236,9 @@ class AppSettings {
       enableLogging: enableLogging ?? this.enableLogging,
       useExtensionProviders:
           useExtensionProviders ?? this.useExtensionProviders,
+      downloadFallbackExtensionIds: clearDownloadFallbackExtensionIds
+          ? null
+          : (downloadFallbackExtensionIds ?? this.downloadFallbackExtensionIds),
       searchProvider: clearSearchProvider
           ? null
           : (searchProvider ?? this.searchProvider),

lib/models/settings.g.dart

@@ -35,6 +35,10 @@ AppSettings _$AppSettingsFromJson(Map<String, dynamic> json) => AppSettings(
   askQualityBeforeDownload: json['askQualityBeforeDownload'] as bool? ?? true,
   enableLogging: json['enableLogging'] as bool? ?? false,
   useExtensionProviders: json['useExtensionProviders'] as bool? ?? true,
+  downloadFallbackExtensionIds:
+      (json['downloadFallbackExtensionIds'] as List<dynamic>?)
+          ?.map((e) => e as String)
+          .toList(),
   searchProvider: json['searchProvider'] as String?,
   homeFeedProvider: json['homeFeedProvider'] as String?,
   separateSingles: json['separateSingles'] as bool? ?? false,
@@ -105,6 +109,7 @@ Map<String, dynamic> _$AppSettingsToJson(
   'askQualityBeforeDownload': instance.askQualityBeforeDownload,
   'enableLogging': instance.enableLogging,
   'useExtensionProviders': instance.useExtensionProviders,
+  'downloadFallbackExtensionIds': instance.downloadFallbackExtensionIds,
   'searchProvider': instance.searchProvider,
   'homeFeedProvider': instance.homeFeedProvider,
   'separateSingles': instance.separateSingles,

lib/providers/settings_provider.dart

@@ -35,9 +35,19 @@ class SettingsNotifier extends Notifier<AppSettings> {
     final prefs = await _prefs;
     final json = prefs.getString(_settingsKey);
     if (json != null) {
-      state = AppSettings.fromJson(
+      final loaded = AppSettings.fromJson(
         Map<String, dynamic>.from(jsonDecode(json) as Map),
       );
+      final sanitizedDownloadFallbackExtensionIds =
+          _sanitizeDownloadFallbackExtensionIds(
+            loaded.downloadFallbackExtensionIds,
+          );
+      state = loaded.copyWith(
+        downloadFallbackExtensionIds: sanitizedDownloadFallbackExtensionIds,
+        clearDownloadFallbackExtensionIds:
+            loaded.downloadFallbackExtensionIds != null &&
+            sanitizedDownloadFallbackExtensionIds == null,
+      );
 
       await _runMigrations(prefs);
       await _normalizeIosDownloadDirectoryIfNeeded();
@@ -50,6 +60,7 @@ class SettingsNotifier extends Notifier<AppSettings> {
 
     _syncLyricsSettingsToBackend();
     _syncNetworkCompatibilitySettingsToBackend();
+    _syncExtensionFallbackSettingsToBackend();
   }
 
   void _syncLyricsSettingsToBackend() {
@@ -83,6 +94,16 @@ class SettingsNotifier extends Notifier<AppSettings> {
     });
   }
 
+  void _syncExtensionFallbackSettingsToBackend() {
+    if (!PlatformBridge.supportsCoreBackend) return;
+
+    PlatformBridge.setDownloadFallbackExtensionIds(
+      state.downloadFallbackExtensionIds,
+    ).catchError((Object e) {
+      _log.w('Failed to sync extension fallback settings to backend: $e');
+    });
+  }
+
   Future<void> _runMigrations(SharedPreferences prefs) async {
     final lastMigration = prefs.getInt(_migrationVersionKey) ?? 0;
 
@@ -172,6 +193,22 @@ class SettingsNotifier extends Notifier<AppSettings> {
     await _saveSettings();
   }
 
+  List<String>? _sanitizeDownloadFallbackExtensionIds(List<String>? ids) {
+    if (ids == null) {
+      return null;
+    }
+
+    final result = <String>[];
+    for (final id in ids) {
+      final normalized = id.trim();
+      if (normalized.isEmpty || result.contains(normalized)) {
+        continue;
+      }
+      result.add(normalized);
+    }
+    return result;
+  }
+
   Future<void> _cleanupRetiredSpotifySettings() async {
     final storedSecret = await _secureStorage.read(
       key: _spotifyClientSecretKey,
@@ -390,6 +427,17 @@ class SettingsNotifier extends Notifier<AppSettings> {
     _saveSettings();
   }
 
+  void setDownloadFallbackExtensionIds(List<String>? extensionIds) {
+    final sanitized = _sanitizeDownloadFallbackExtensionIds(extensionIds);
+    state = state.copyWith(
+      downloadFallbackExtensionIds: sanitized,
+      clearDownloadFallbackExtensionIds:
+          extensionIds == null && state.downloadFallbackExtensionIds != null,
+    );
+    _saveSettings();
+    _syncExtensionFallbackSettingsToBackend();
+  }
+
   void setSeparateSingles(bool enabled) {
     state = state.copyWith(separateSingles: enabled);
     _saveSettings();

lib/screens/settings/download_fallback_extensions_page.dart

@@ -0,0 +1,250 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:spotiflac_android/l10n/l10n.dart';
+import 'package:spotiflac_android/providers/extension_provider.dart';
+import 'package:spotiflac_android/providers/settings_provider.dart';
+import 'package:spotiflac_android/utils/app_bar_layout.dart';
+import 'package:spotiflac_android/widgets/settings_group.dart';
+
+class DownloadFallbackExtensionsPage extends ConsumerStatefulWidget {
+  const DownloadFallbackExtensionsPage({super.key});
+
+  @override
+  ConsumerState<DownloadFallbackExtensionsPage> createState() =>
+      _DownloadFallbackExtensionsPageState();
+}
+
+class _DownloadFallbackExtensionsPageState
+    extends ConsumerState<DownloadFallbackExtensionsPage> {
+  late List<Extension> _extensions;
+  late Set<String> _selectedExtensionIds;
+  bool _hasChanges = false;
+
+  @override
+  void initState() {
+    super.initState();
+    _loadExtensions();
+  }
+
+  void _loadExtensions() {
+    final extState = ref.read(extensionProvider);
+    final settings = ref.read(settingsProvider);
+
+    _extensions = extState.extensions
+        .where(
+          (extension) => extension.enabled && extension.hasDownloadProvider,
+        )
+        .toList();
+
+    final savedIds = settings.downloadFallbackExtensionIds;
+    if (savedIds == null) {
+      _selectedExtensionIds = _extensions
+          .map((extension) => extension.id)
+          .toSet();
+    } else {
+      final allowedIds = _extensions.map((extension) => extension.id).toSet();
+      _selectedExtensionIds = savedIds
+          .where((extensionId) => allowedIds.contains(extensionId))
+          .toSet();
+    }
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    final colorScheme = Theme.of(context).colorScheme;
+    final topPadding = normalizedHeaderTopPadding(context);
+
+    return PopScope(
+      canPop: !_hasChanges,
+      onPopInvokedWithResult: (didPop, result) async {
+        if (didPop) return;
+        final shouldPop = await _confirmDiscard(context);
+        if (shouldPop && context.mounted) {
+          Navigator.pop(context);
+        }
+      },
+      child: Scaffold(
+        body: CustomScrollView(
+          slivers: [
+            SliverAppBar(
+              expandedHeight: 120 + topPadding,
+              collapsedHeight: kToolbarHeight,
+              floating: false,
+              pinned: true,
+              backgroundColor: colorScheme.surface,
+              surfaceTintColor: Colors.transparent,
+              leading: IconButton(
+                tooltip: MaterialLocalizations.of(context).backButtonTooltip,
+                icon: const Icon(Icons.arrow_back),
+                onPressed: () async {
+                  if (_hasChanges) {
+                    final shouldPop = await _confirmDiscard(context);
+                    if (shouldPop && context.mounted) {
+                      Navigator.pop(context);
+                    }
+                  } else {
+                    Navigator.pop(context);
+                  }
+                },
+              ),
+              actions: [
+                if (_hasChanges)
+                  TextButton(
+                    onPressed: _saveChanges,
+                    child: Text(context.l10n.dialogSave),
+                  ),
+              ],
+              flexibleSpace: LayoutBuilder(
+                builder: (context, constraints) {
+                  final maxHeight = 120 + topPadding;
+                  final minHeight = kToolbarHeight + topPadding;
+                  final expandRatio =
+                      ((constraints.maxHeight - minHeight) /
+                              (maxHeight - minHeight))
+                          .clamp(0.0, 1.0);
+                  final leftPadding = 56 - (32 * expandRatio);
+                  return FlexibleSpaceBar(
+                    expandedTitleScale: 1.0,
+                    titlePadding: EdgeInsets.only(
+                      left: leftPadding,
+                      bottom: 16,
+                    ),
+                    title: Text(
+                      context.l10n.extensionsFallbackTitle,
+                      style: TextStyle(
+                        fontSize: 20 + (8 * expandRatio),
+                        fontWeight: FontWeight.bold,
+                        color: colorScheme.onSurface,
+                      ),
+                    ),
+                  );
+                },
+              ),
+            ),
+            SliverToBoxAdapter(
+              child: Padding(
+                padding: const EdgeInsets.all(16),
+                child: Text(
+                  context.l10n.providerPriorityFallbackExtensionsDescription,
+                  style: Theme.of(context).textTheme.bodyMedium?.copyWith(
+                    color: colorScheme.onSurfaceVariant,
+                  ),
+                ),
+              ),
+            ),
+            if (_extensions.isEmpty)
+              SliverToBoxAdapter(
+                child: Padding(
+                  padding: const EdgeInsets.symmetric(horizontal: 16),
+                  child: Container(
+                    padding: const EdgeInsets.all(20),
+                    decoration: BoxDecoration(
+                      color: colorScheme.surfaceContainerHighest.withValues(
+                        alpha: 0.4,
+                      ),
+                      borderRadius: BorderRadius.circular(16),
+                    ),
+                    child: Text(
+                      context.l10n.extensionsNoDownloadProvider,
+                      style: Theme.of(context).textTheme.bodyMedium?.copyWith(
+                        color: colorScheme.onSurfaceVariant,
+                      ),
+                    ),
+                  ),
+                ),
+              ),
+            if (_extensions.isNotEmpty)
+              SliverPadding(
+                padding: const EdgeInsets.symmetric(horizontal: 16),
+                sliver: SliverToBoxAdapter(
+                  child: SettingsGroup(
+                    margin: EdgeInsets.zero,
+                    children: List.generate(_extensions.length, (index) {
+                      final extension = _extensions[index];
+                      final isSelected = _selectedExtensionIds.contains(
+                        extension.id,
+                      );
+                      return SettingsSwitchItem(
+                        icon: Icons.extension_rounded,
+                        title: extension.displayName,
+                        subtitle: extension.id,
+                        value: isSelected,
+                        showDivider: index != _extensions.length - 1,
+                        onChanged: (value) {
+                          setState(() {
+                            if (value) {
+                              _selectedExtensionIds.add(extension.id);
+                            } else {
+                              _selectedExtensionIds.remove(extension.id);
+                            }
+                            _hasChanges = true;
+                          });
+                        },
+                      );
+                    }),
+                  ),
+                ),
+              ),
+            if (_extensions.isNotEmpty)
+              SliverToBoxAdapter(
+                child: Padding(
+                  padding: const EdgeInsets.fromLTRB(16, 8, 16, 0),
+                  child: Text(
+                    context.l10n.providerPriorityFallbackExtensionsHint,
+                    style: Theme.of(context).textTheme.bodySmall?.copyWith(
+                      color: colorScheme.onSurfaceVariant,
+                    ),
+                  ),
+                ),
+              ),
+            const SliverToBoxAdapter(child: SizedBox(height: 32)),
+          ],
+        ),
+      ),
+    );
+  }
+
+  Future<bool> _confirmDiscard(BuildContext context) async {
+    final result = await showDialog<bool>(
+      context: context,
+      builder: (context) => AlertDialog(
+        title: Text(context.l10n.dialogDiscardChanges),
+        content: Text(context.l10n.dialogUnsavedChanges),
+        actions: [
+          TextButton(
+            onPressed: () => Navigator.pop(context, false),
+            child: Text(context.l10n.dialogCancel),
+          ),
+          FilledButton(
+            onPressed: () => Navigator.pop(context, true),
+            child: Text(context.l10n.dialogDiscard),
+          ),
+        ],
+      ),
+    );
+    return result ?? false;
+  }
+
+  void _saveChanges() {
+    final allExtensionIds = _extensions
+        .map((extension) => extension.id)
+        .toList();
+    final selectedExtensionIds = allExtensionIds
+        .where(_selectedExtensionIds.contains)
+        .toList();
+    final fallbackExtensionIds =
+        selectedExtensionIds.length == allExtensionIds.length
+        ? null
+        : selectedExtensionIds;
+
+    ref
+        .read(settingsProvider.notifier)
+        .setDownloadFallbackExtensionIds(fallbackExtensionIds);
+    setState(() {
+      _hasChanges = false;
+    });
+    ScaffoldMessenger.of(context).showSnackBar(
+      SnackBar(content: Text(context.l10n.snackbarProviderPrioritySaved)),
+    );
+  }
+}

lib/screens/settings/extensions_page.dart

@@ -8,9 +8,10 @@ import 'package:spotiflac_android/models/settings.dart';
 import 'package:spotiflac_android/providers/extension_provider.dart';
 import 'package:spotiflac_android/providers/explore_provider.dart';
 import 'package:spotiflac_android/providers/settings_provider.dart';
+import 'package:spotiflac_android/screens/settings/download_fallback_extensions_page.dart';
 import 'package:spotiflac_android/screens/settings/extension_detail_page.dart';
-import 'package:spotiflac_android/screens/settings/provider_priority_page.dart';
 import 'package:spotiflac_android/screens/settings/metadata_provider_priority_page.dart';
+import 'package:spotiflac_android/screens/settings/provider_priority_page.dart';
 import 'package:spotiflac_android/utils/app_bar_layout.dart';
 import 'package:spotiflac_android/widgets/settings_group.dart';
 
@@ -151,6 +152,7 @@ class _ExtensionsPageState extends ConsumerState<ExtensionsPage> {
               child: SettingsGroup(
                 children: [
                   _DownloadPriorityItem(),
+                  _DownloadFallbackItem(),
                   _MetadataPriorityItem(),
                   _SearchProviderSelector(),
                   _HomeFeedProviderSelector(),
@@ -588,6 +590,73 @@ class _MetadataPriorityItem extends ConsumerWidget {
   }
 }
 
+class _DownloadFallbackItem extends ConsumerWidget {
+  const _DownloadFallbackItem();
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final extState = ref.watch(extensionProvider);
+    final colorScheme = Theme.of(context).colorScheme;
+
+    final hasDownloadExtensions = extState.extensions.any(
+      (e) => e.enabled && e.hasDownloadProvider,
+    );
+
+    return InkWell(
+      onTap: hasDownloadExtensions
+          ? () => Navigator.push(
+              context,
+              MaterialPageRoute<void>(
+                builder: (_) => const DownloadFallbackExtensionsPage(),
+              ),
+            )
+          : null,
+      child: Padding(
+        padding: const EdgeInsets.symmetric(horizontal: 16, vertical: 12),
+        child: Row(
+          children: [
+            Icon(
+              Icons.alt_route,
+              color: hasDownloadExtensions
+                  ? colorScheme.onSurfaceVariant
+                  : colorScheme.outline,
+            ),
+            const SizedBox(width: 16),
+            Expanded(
+              child: Column(
+                crossAxisAlignment: CrossAxisAlignment.start,
+                children: [
+                  Text(
+                    context.l10n.extensionsFallbackTitle,
+                    style: Theme.of(context).textTheme.bodyLarge?.copyWith(
+                      color: hasDownloadExtensions ? null : colorScheme.outline,
+                    ),
+                  ),
+                  const SizedBox(height: 2),
+                  Text(
+                    hasDownloadExtensions
+                        ? context.l10n.extensionsFallbackSubtitle
+                        : context.l10n.extensionsNoDownloadProvider,
+                    style: Theme.of(context).textTheme.bodySmall?.copyWith(
+                      color: colorScheme.onSurfaceVariant,
+                    ),
+                  ),
+                ],
+              ),
+            ),
+            Icon(
+              Icons.chevron_right,
+              color: hasDownloadExtensions
+                  ? colorScheme.onSurfaceVariant
+                  : colorScheme.outline,
+            ),
+          ],
+        ),
+      ),
+    );
+  }
+}
+
 class _SearchProviderSelector extends ConsumerWidget {
   const _SearchProviderSelector();
 

lib/services/platform_bridge.dart

@@ -781,6 +781,15 @@ class PlatformBridge {
     return list.map((e) => e as String).toList();
   }
 
+  static Future<void> setDownloadFallbackExtensionIds(
+    List<String>? extensionIds,
+  ) async {
+    _log.d('setDownloadFallbackExtensionIds: $extensionIds');
+    await _channel.invokeMethod('setDownloadFallbackExtensionIds', {
+      'extension_ids': extensionIds == null ? '' : jsonEncode(extensionIds),
+    });
+  }
+
   static Future<void> setMetadataProviderPriority(
     List<String> providerIds,
   ) async {