perf: lazy extension VM init, incremental startup maintenance, and UI optimizations

- Defer extension VM initialization until first use with lockReadyVM() pattern to eliminate TOCTOU races and reduce startup overhead
- Add validateExtensionLoad() to catch JS errors at install time without keeping VM alive
- Teardown VM on extension disable to free resources; re-init lazily on re-enable
- Replace full orphan cleanup with incremental cursor-based pagination across launches
- Batch DB writes (upsertBatch, replaceAll) with transactions for atomicity
- Parse JSON natively on Kotlin side to avoid double-serialization over MethodChannel
- Add identity-based memoization caches for unified items and path match keys in queue tab
- Use ValueListenableBuilder for targeted embedded cover refreshes instead of full setState
- Extract shared widgets (_buildAlbumGridItemCore, _buildFilterButton, _navigateWithUnfocus)
- Use libraryCollectionsProvider selector and MediaQuery.paddingOf for fewer rebuilds
- Simplify supporter chip tiers and localize remaining hardcoded strings

go_backend/exports.go

@@ -2187,12 +2187,6 @@ func LoadExtensionFromPath(filePath string) (string, error) {
 		return "", err
 	}
 
-	settingsStore := GetExtensionSettingsStore()
-	settings := settingsStore.GetAll(ext.ID)
-	if len(settings) > 0 {
-		manager.InitializeExtension(ext.ID, settings)
-	}
-
 	result := map[string]interface{}{
 		"id":           ext.ID,
 		"name":         ext.Manifest.Name,
@@ -2226,12 +2220,6 @@ func UpgradeExtensionFromPath(filePath string) (string, error) {
 		return "", err
 	}
 
-	settingsStore := GetExtensionSettingsStore()
-	settings := settingsStore.GetAll(ext.ID)
-	if len(settings) > 0 {
-		manager.InitializeExtension(ext.ID, settings)
-	}
-
 	result := map[string]interface{}{
 		"id":           ext.ID,
 		"display_name": ext.Manifest.DisplayName,
@@ -3324,12 +3312,14 @@ func callExtensionFunctionJSON(extensionID, functionName string, timeout time.Du
 	if !ext.Enabled {
 		return "", fmt.Errorf("extension '%s' is disabled", extensionID)
 	}
+	vm, err := ext.lockReadyVM()
+	if err != nil {
+		return "", err
+	}
+	defer ext.VMMu.Unlock()
 
 	// Goja runtime is not thread-safe; guard direct extension.*() calls with VMMu
 	// to avoid races with other provider calls (e.g. getAlbum/getPlaylist).
-	ext.VMMu.Lock()
-	defer ext.VMMu.Unlock()
-
 	script := fmt.Sprintf(`
 		(function() {
 			if (typeof extension !== 'undefined' && typeof extension.%s === 'function') {
@@ -3339,7 +3329,7 @@ func callExtensionFunctionJSON(extensionID, functionName string, timeout time.Du
 		})()
 	`, functionName, functionName)
 
-	result, err := RunWithTimeoutAndRecover(ext.VM, script, timeout)
+	result, err := RunWithTimeoutAndRecover(vm, script, timeout)
 	if err != nil {
 		return "", fmt.Errorf("%s failed: %w", functionName, err)
 	}

go_backend/extension_manager.go

@@ -44,16 +44,76 @@ func compareVersions(v1, v2 string) int {
 }
 
 type LoadedExtension struct {
-	ID        string             `json:"id"`
-	Manifest  *ExtensionManifest `json:"manifest"`
-	VM        *goja.Runtime      `json:"-"`
-	VMMu      sync.Mutex         `json:"-"`
-	runtime   *ExtensionRuntime
-	Enabled   bool   `json:"enabled"`
-	Error     string `json:"error,omitempty"`
-	DataDir   string `json:"data_dir"`
-	SourceDir string `json:"source_dir"`
-	IconPath  string `json:"icon_path"`
+	ID          string             `json:"id"`
+	Manifest    *ExtensionManifest `json:"manifest"`
+	VM          *goja.Runtime      `json:"-"`
+	VMMu        sync.Mutex         `json:"-"`
+	runtime     *ExtensionRuntime
+	initialized bool
+	Enabled     bool   `json:"enabled"`
+	Error       string `json:"error,omitempty"`
+	DataDir     string `json:"data_dir"`
+	SourceDir   string `json:"source_dir"`
+	IconPath    string `json:"icon_path"`
+}
+
+func getExtensionInitSettings(extensionID string) map[string]interface{} {
+	settings := GetExtensionSettingsStore().GetAll(extensionID)
+	if len(settings) == 0 {
+		return settings
+	}
+
+	filtered := make(map[string]interface{}, len(settings))
+	for key, value := range settings {
+		if strings.HasPrefix(key, "_") {
+			continue
+		}
+		filtered[key] = value
+	}
+	return filtered
+}
+
+func ensureRuntimeReadyLocked(ext *LoadedExtension, applyStoredSettings bool) error {
+	if ext.VM == nil || ext.runtime == nil {
+		if err := initializeVMLocked(ext); err != nil {
+			ext.Error = err.Error()
+			ext.Enabled = false
+			return err
+		}
+	}
+
+	if applyStoredSettings && !ext.initialized {
+		settings := getExtensionInitSettings(ext.ID)
+		if len(settings) > 0 {
+			if err := initializeExtensionWithSettingsLocked(ext, settings); err != nil {
+				teardownVMLocked(ext)
+				ext.Error = err.Error()
+				ext.Enabled = false
+				return err
+			}
+		} else {
+			ext.initialized = true
+		}
+	}
+
+	ext.Error = ""
+	return nil
+}
+
+func (ext *LoadedExtension) ensureRuntimeReady() error {
+	ext.VMMu.Lock()
+	defer ext.VMMu.Unlock()
+
+	return ensureRuntimeReadyLocked(ext, true)
+}
+
+func (ext *LoadedExtension) lockReadyVM() (*goja.Runtime, error) {
+	ext.VMMu.Lock()
+	if err := ensureRuntimeReadyLocked(ext, true); err != nil {
+		ext.VMMu.Unlock()
+		return nil, err
+	}
+	return ext.VM, nil
 }
 
 type ExtensionManager struct {
@@ -220,10 +280,10 @@ func (m *ExtensionManager) LoadExtensionFromFile(filePath string) (*LoadedExtens
 		SourceDir: extDir,
 	}
 
-	if err := m.initializeVM(ext); err != nil {
+	if err := validateExtensionLoad(ext); err != nil {
 		ext.Error = err.Error()
 		ext.Enabled = false
-		GoLog("[Extension] Failed to initialize VM for %s: %v\n", manifest.Name, err)
+		GoLog("[Extension] Failed to validate extension %s: %v\n", manifest.Name, err)
 	}
 
 	m.extensions[manifest.Name] = ext
@@ -232,7 +292,10 @@ func (m *ExtensionManager) LoadExtensionFromFile(filePath string) (*LoadedExtens
 	return ext, nil
 }
 
-func (m *ExtensionManager) initializeVM(ext *LoadedExtension) error {
+func initializeVMLocked(ext *LoadedExtension) error {
+	ext.VM = nil
+	ext.runtime = nil
+	ext.initialized = false
 	vm := goja.New()
 	ext.VM = vm
 
@@ -279,6 +342,136 @@ func (m *ExtensionManager) initializeVM(ext *LoadedExtension) error {
 	return nil
 }
 
+func (m *ExtensionManager) initializeVM(ext *LoadedExtension) error {
+	ext.VMMu.Lock()
+	defer ext.VMMu.Unlock()
+	return initializeVMLocked(ext)
+}
+
+func initializeExtensionWithSettingsLocked(
+	ext *LoadedExtension,
+	settings map[string]interface{},
+) error {
+	if ext.VM == nil {
+		return fmt.Errorf("Extension failed to load. Please reinstall the extension")
+	}
+
+	settingsJSON, err := json.Marshal(settings)
+	if err != nil {
+		return fmt.Errorf("Failed to save settings")
+	}
+
+	script := fmt.Sprintf(`
+		(function() {
+			var settings = %s;
+			if (typeof extension !== 'undefined' && typeof extension.initialize === 'function') {
+				try {
+					extension.initialize(settings);
+					return { success: true };
+				} catch (e) {
+					return { success: false, error: e.toString() };
+				}
+			}
+			return { success: true, message: 'no initialize function' };
+		})()
+	`, string(settingsJSON))
+
+	result, err := ext.VM.RunString(script)
+	if err != nil {
+		ext.Error = fmt.Sprintf("initialize failed: %v", err)
+		ext.Enabled = false
+		GoLog("[Extension] Initialize error for %s: %v\n", ext.ID, err)
+		return err
+	}
+
+	if result != nil && !goja.IsUndefined(result) {
+		exported := result.Export()
+		if resultMap, ok := exported.(map[string]interface{}); ok {
+			if success, ok := resultMap["success"].(bool); ok && !success {
+				errMsg := "unknown error"
+				if e, ok := resultMap["error"].(string); ok {
+					errMsg = e
+				}
+				ext.Error = errMsg
+				ext.Enabled = false
+				GoLog("[Extension] Initialize failed for %s: %s\n", ext.ID, errMsg)
+				return fmt.Errorf("initialize failed: %s", errMsg)
+			}
+		}
+	}
+
+	ext.initialized = true
+	GoLog("[Extension] Initialized %s\n", ext.ID)
+	return nil
+}
+
+func runCleanupLocked(ext *LoadedExtension) error {
+	if ext.VM != nil {
+		script := `
+			(function() {
+				if (typeof extension !== 'undefined' && typeof extension.cleanup === 'function') {
+					try {
+						extension.cleanup();
+						return { success: true };
+					} catch (e) {
+						return { success: false, error: e.toString() };
+					}
+				}
+				return { success: true, message: 'no cleanup function' };
+			})()
+		`
+
+		result, err := ext.VM.RunString(script)
+		if err != nil {
+			return err
+		}
+
+		if result != nil && !goja.IsUndefined(result) {
+			exported := result.Export()
+			if resultMap, ok := exported.(map[string]interface{}); ok {
+				if success, ok := resultMap["success"].(bool); ok && !success {
+					errMsg := "unknown error"
+					if e, ok := resultMap["error"].(string); ok {
+						errMsg = e
+					}
+					return fmt.Errorf("cleanup failed: %s", errMsg)
+				}
+			}
+		}
+
+		if result != nil && !goja.IsUndefined(result) && !goja.IsNull(result) {
+			GoLog("[Extension] Cleanup called for %s\n", ext.ID)
+		}
+	}
+	return nil
+}
+
+func teardownVMLocked(ext *LoadedExtension) {
+	if err := runCleanupLocked(ext); err != nil {
+		GoLog("[Extension] Error calling cleanup for %s: %v\n", ext.ID, err)
+	}
+	if ext.runtime != nil {
+		if err := ext.runtime.flushStorageNow(); err != nil {
+			GoLog("[Extension] Failed to flush storage for %s: %v\n", ext.ID, err)
+		}
+		ext.runtime.closeStorageFlusher()
+	}
+	ext.runtime = nil
+	ext.VM = nil
+	ext.initialized = false
+}
+
+func validateExtensionLoad(ext *LoadedExtension) error {
+	ext.VMMu.Lock()
+	defer ext.VMMu.Unlock()
+
+	if err := initializeVMLocked(ext); err != nil {
+		return err
+	}
+	teardownVMLocked(ext)
+	return nil
+}
+
 func (m *ExtensionManager) UnloadExtension(extensionID string) error {
 	m.mu.Lock()
 	defer m.mu.Unlock()
@@ -288,21 +481,9 @@ func (m *ExtensionManager) UnloadExtension(extensionID string) error {
 		return fmt.Errorf("Extension not found")
 	}
 
-	if ext.VM != nil {
-		cleanup, err := ext.VM.RunString("typeof extension !== 'undefined' && typeof extension.cleanup === 'function' ? extension.cleanup() : null")
-		if err != nil {
-			GoLog("[Extension] Error calling cleanup for %s: %v\n", extensionID, err)
-		} else if cleanup != nil && !goja.IsUndefined(cleanup) && !goja.IsNull(cleanup) {
-			GoLog("[Extension] Cleanup called for %s\n", extensionID)
-		}
-	}
-	if ext.runtime != nil {
-		if err := ext.runtime.flushStorageNow(); err != nil {
-			GoLog("[Extension] Failed to flush storage for %s: %v\n", extensionID, err)
-		}
-		ext.runtime.closeStorageFlusher()
-		ext.runtime = nil
-	}
+	ext.VMMu.Lock()
+	teardownVMLocked(ext)
+	ext.VMMu.Unlock()
 
 	delete(m.extensions, extensionID)
 	GoLog("[Extension] Unloaded extension: %s\n", extensionID)
@@ -341,7 +522,21 @@ func (m *ExtensionManager) SetExtensionEnabled(extensionID string, enabled bool)
 		return fmt.Errorf("Extension not found")
 	}
 
-	ext.Enabled = enabled
+	if enabled {
+		ext.Enabled = true
+		if err := ext.ensureRuntimeReady(); err != nil {
+			store := GetExtensionSettingsStore()
+			ext.Enabled = false
+			_ = store.Set(extensionID, "_enabled", false)
+			return err
+		}
+	} else {
+		ext.Enabled = false
+		ext.Error = ""
+		ext.VMMu.Lock()
+		teardownVMLocked(ext)
+		ext.VMMu.Unlock()
+	}
 	GoLog("[Extension] %s %s\n", extensionID, map[bool]string{true: "enabled", false: "disabled"}[enabled])
 
 	store := GetExtensionSettingsStore()
@@ -436,10 +631,10 @@ func (m *ExtensionManager) loadExtensionFromDirectory(dirPath string) (*LoadedEx
 		}
 	}
 
-	if err := m.initializeVM(ext); err != nil {
+	if err := validateExtensionLoad(ext); err != nil {
 		ext.Error = err.Error()
 		ext.Enabled = false
-		GoLog("[Extension] Failed to initialize VM for %s: %v\n", manifest.Name, err)
+		GoLog("[Extension] Failed to validate extension %s: %v\n", manifest.Name, err)
 	}
 
 	m.extensions[manifest.Name] = ext
@@ -590,10 +785,14 @@ func (m *ExtensionManager) UpgradeExtension(filePath string) (*LoadedExtension,
 		SourceDir: extDir,
 	}
 
-	if err := m.initializeVM(ext); err != nil {
+	if wasEnabled {
+		if err := ext.ensureRuntimeReady(); err != nil {
+			GoLog("[Extension] Failed to initialize upgraded extension %s: %v\n", newManifest.Name, err)
+		}
+	} else if err := validateExtensionLoad(ext); err != nil {
 		ext.Error = err.Error()
 		ext.Enabled = false
-		GoLog("[Extension] Failed to initialize VM for %s: %v\n", newManifest.Name, err)
+		GoLog("[Extension] Failed to validate upgraded extension %s: %v\n", newManifest.Name, err)
 	}
 
 	m.mu.Lock()
@@ -790,56 +989,13 @@ func (m *ExtensionManager) InitializeExtension(extensionID string, settings map[
 		return fmt.Errorf("Extension not found")
 	}
 
-	if ext.VM == nil {
-		return fmt.Errorf("Extension failed to load. Please reinstall the extension")
-	}
+	ext.VMMu.Lock()
+	defer ext.VMMu.Unlock()
 
-	settingsJSON, err := json.Marshal(settings)
-	if err != nil {
-		return fmt.Errorf("Failed to save settings")
-	}
-
-	script := fmt.Sprintf(`
-		(function() {
-			var settings = %s;
-			if (typeof extension !== 'undefined' && typeof extension.initialize === 'function') {
-				try {
-					extension.initialize(settings);
-					return { success: true };
-				} catch (e) {
-					return { success: false, error: e.toString() };
-				}
-			}
-			return { success: true, message: 'no initialize function' };
-		})()
-	`, string(settingsJSON))
-
-	result, err := ext.VM.RunString(script)
-	if err != nil {
-		ext.Error = fmt.Sprintf("initialize failed: %v", err)
-		ext.Enabled = false
-		GoLog("[Extension] Initialize error for %s: %v\n", extensionID, err)
+	if err := ensureRuntimeReadyLocked(ext, false); err != nil {
 		return err
 	}
-
-	if result != nil && !goja.IsUndefined(result) {
-		exported := result.Export()
-		if resultMap, ok := exported.(map[string]interface{}); ok {
-			if success, ok := resultMap["success"].(bool); ok && !success {
-				errMsg := "unknown error"
-				if e, ok := resultMap["error"].(string); ok {
-					errMsg = e
-				}
-				ext.Error = errMsg
-				ext.Enabled = false
-				GoLog("[Extension] Initialize failed for %s: %s\n", extensionID, errMsg)
-				return fmt.Errorf("initialize failed: %s", errMsg)
-			}
-		}
-	}
-
-	GoLog("[Extension] Initialized %s\n", extensionID)
-	return nil
+	return initializeExtensionWithSettingsLocked(ext, settings)
 }
 
 func (m *ExtensionManager) CleanupExtension(extensionID string) error {
@@ -854,41 +1010,12 @@ func (m *ExtensionManager) CleanupExtension(extensionID string) error {
 	if ext.VM == nil {
 		return nil
 	}
-
-	script := `
-		(function() {
-			if (typeof extension !== 'undefined' && typeof extension.cleanup === 'function') {
-				try {
-					extension.cleanup();
-					return { success: true };
-				} catch (e) {
-					return { success: false, error: e.toString() };
-				}
-			}
-			return { success: true, message: 'no cleanup function' };
-		})()
-	`
-
-	result, err := ext.VM.RunString(script)
-	if err != nil {
+	ext.VMMu.Lock()
+	defer ext.VMMu.Unlock()
+	if err := runCleanupLocked(ext); err != nil {
 		GoLog("[Extension] Cleanup error for %s: %v\n", extensionID, err)
 		return err
 	}
-
-	if result != nil && !goja.IsUndefined(result) {
-		exported := result.Export()
-		if resultMap, ok := exported.(map[string]interface{}); ok {
-			if success, ok := resultMap["success"].(bool); ok && !success {
-				errMsg := "unknown error"
-				if e, ok := resultMap["error"].(string); ok {
-					errMsg = e
-				}
-				GoLog("[Extension] Cleanup failed for %s: %s\n", extensionID, errMsg)
-				return fmt.Errorf("cleanup failed: %s", errMsg)
-			}
-		}
-	}
-
 	GoLog("[Extension] Cleaned up %s\n", extensionID)
 	return nil
 }
@@ -917,8 +1044,8 @@ func (m *ExtensionManager) InvokeAction(extensionID string, actionName string) (
 		return nil, fmt.Errorf("extension not found: %s", extensionID)
 	}
 
-	if ext.VM == nil {
-		return nil, fmt.Errorf("extension VM not initialized")
+	if err := ext.ensureRuntimeReady(); err != nil {
+		return nil, err
 	}
 
 	if !ext.Enabled {

go_backend/extension_providers.go

@@ -125,6 +125,15 @@ func NewExtensionProviderWrapper(ext *LoadedExtension) *ExtensionProviderWrapper
 	}
 }
 
+func (p *ExtensionProviderWrapper) lockReadyVM() error {
+	vm, err := p.extension.lockReadyVM()
+	if err != nil {
+		return err
+	}
+	p.vm = vm
+	return nil
+}
+
 func (p *ExtensionProviderWrapper) SearchTracks(query string, limit int) (*ExtSearchResult, error) {
 	if !p.extension.Manifest.IsMetadataProvider() {
 		return nil, fmt.Errorf("extension '%s' is not a metadata provider", p.extension.ID)
@@ -133,8 +142,9 @@ func (p *ExtensionProviderWrapper) SearchTracks(query string, limit int) (*ExtSe
 	if !p.extension.Enabled {
 		return nil, fmt.Errorf("extension '%s' is disabled", p.extension.ID)
 	}
-
-	p.extension.VMMu.Lock()
+	if err := p.lockReadyVM(); err != nil {
+		return nil, err
+	}
 	defer p.extension.VMMu.Unlock()
 
 	script := fmt.Sprintf(`
@@ -192,8 +202,9 @@ func (p *ExtensionProviderWrapper) GetTrack(trackID string) (*ExtTrackMetadata,
 	if !p.extension.Enabled {
 		return nil, fmt.Errorf("extension '%s' is disabled", p.extension.ID)
 	}
-
-	p.extension.VMMu.Lock()
+	if err := p.lockReadyVM(); err != nil {
+		return nil, err
+	}
 	defer p.extension.VMMu.Unlock()
 
 	script := fmt.Sprintf(`
@@ -240,8 +251,9 @@ func (p *ExtensionProviderWrapper) GetAlbum(albumID string) (*ExtAlbumMetadata,
 	if !p.extension.Enabled {
 		return nil, fmt.Errorf("extension '%s' is disabled", p.extension.ID)
 	}
-
-	p.extension.VMMu.Lock()
+	if err := p.lockReadyVM(); err != nil {
+		return nil, err
+	}
 	defer p.extension.VMMu.Unlock()
 
 	script := fmt.Sprintf(`
@@ -291,8 +303,9 @@ func (p *ExtensionProviderWrapper) GetArtist(artistID string) (*ExtArtistMetadat
 	if !p.extension.Enabled {
 		return nil, fmt.Errorf("extension '%s' is disabled", p.extension.ID)
 	}
-
-	p.extension.VMMu.Lock()
+	if err := p.lockReadyVM(); err != nil {
+		return nil, err
+	}
 	defer p.extension.VMMu.Unlock()
 
 	script := fmt.Sprintf(`
@@ -345,8 +358,10 @@ func (p *ExtensionProviderWrapper) EnrichTrack(track *ExtTrackMetadata) (*ExtTra
 	if !p.extension.Enabled {
 		return track, nil
 	}
-
-	p.extension.VMMu.Lock()
+	if err := p.lockReadyVM(); err != nil {
+		GoLog("[Extension] EnrichTrack init error for %s: %v\n", p.extension.ID, err)
+		return track, nil
+	}
 	defer p.extension.VMMu.Unlock()
 
 	trackJSON, err := json.Marshal(track)
@@ -405,8 +420,9 @@ func (p *ExtensionProviderWrapper) CheckAvailability(isrc, trackName, artistName
 	if !p.extension.Enabled {
 		return nil, fmt.Errorf("extension '%s' is disabled", p.extension.ID)
 	}
-
-	p.extension.VMMu.Lock()
+	if err := p.lockReadyVM(); err != nil {
+		return nil, err
+	}
 	defer p.extension.VMMu.Unlock()
 
 	script := fmt.Sprintf(`
@@ -452,8 +468,9 @@ func (p *ExtensionProviderWrapper) GetDownloadURL(trackID, quality string) (*Ext
 	if !p.extension.Enabled {
 		return nil, fmt.Errorf("extension '%s' is disabled", p.extension.ID)
 	}
-
-	p.extension.VMMu.Lock()
+	if err := p.lockReadyVM(); err != nil {
+		return nil, err
+	}
 	defer p.extension.VMMu.Unlock()
 
 	script := fmt.Sprintf(`
@@ -501,8 +518,13 @@ func (p *ExtensionProviderWrapper) Download(trackID, quality, outputPath string,
 	if !p.extension.Enabled {
 		return nil, fmt.Errorf("extension '%s' is disabled", p.extension.ID)
 	}
-
-	p.extension.VMMu.Lock()
+	if err := p.lockReadyVM(); err != nil {
+		return &ExtDownloadResult{
+			Success:      false,
+			ErrorMessage: err.Error(),
+			ErrorType:    "init_error",
+		}, nil
+	}
 	defer p.extension.VMMu.Unlock()
 
 	p.vm.Set("__onProgress", func(call goja.FunctionCall) goja.Value {
@@ -1626,8 +1648,9 @@ func (p *ExtensionProviderWrapper) CustomSearch(query string, options map[string
 	if !p.extension.Enabled {
 		return nil, fmt.Errorf("extension '%s' is disabled", p.extension.ID)
 	}
-
-	p.extension.VMMu.Lock()
+	if err := p.lockReadyVM(); err != nil {
+		return nil, err
+	}
 	defer p.extension.VMMu.Unlock()
 
 	if options == nil {
@@ -1707,8 +1730,9 @@ func (p *ExtensionProviderWrapper) HandleURL(url string) (*ExtURLHandleResult, e
 	if !p.extension.Enabled {
 		return nil, fmt.Errorf("extension '%s' is disabled", p.extension.ID)
 	}
-
-	p.extension.VMMu.Lock()
+	if err := p.lockReadyVM(); err != nil {
+		return nil, err
+	}
 	defer p.extension.VMMu.Unlock()
 
 	script := fmt.Sprintf(`
@@ -1792,8 +1816,9 @@ func (p *ExtensionProviderWrapper) MatchTrack(sourceTrack map[string]interface{}
 	if !p.extension.Enabled {
 		return nil, fmt.Errorf("extension '%s' is disabled", p.extension.ID)
 	}
-
-	p.extension.VMMu.Lock()
+	if err := p.lockReadyVM(); err != nil {
+		return nil, err
+	}
 	defer p.extension.VMMu.Unlock()
 
 	sourceJSON, _ := json.Marshal(sourceTrack)
@@ -1862,8 +1887,9 @@ func (p *ExtensionProviderWrapper) PostProcess(filePath string, metadata map[str
 	if !p.extension.Enabled {
 		return nil, fmt.Errorf("extension '%s' is disabled", p.extension.ID)
 	}
-
-	p.extension.VMMu.Lock()
+	if err := p.lockReadyVM(); err != nil {
+		return &PostProcessResult{Success: false, Error: err.Error()}, nil
+	}
 	defer p.extension.VMMu.Unlock()
 
 	metadataJSON, _ := json.Marshal(metadata)
@@ -1924,8 +1950,9 @@ func (p *ExtensionProviderWrapper) PostProcessV2(input PostProcessInput, metadat
 	if !p.extension.Enabled {
 		return nil, fmt.Errorf("extension '%s' is disabled", p.extension.ID)
 	}
-
-	p.extension.VMMu.Lock()
+	if err := p.lockReadyVM(); err != nil {
+		return &PostProcessResult{Success: false, Error: err.Error()}, nil
+	}
 	defer p.extension.VMMu.Unlock()
 
 	metadataJSON, _ := json.Marshal(metadata)
@@ -2182,8 +2209,9 @@ func (p *ExtensionProviderWrapper) FetchLyrics(trackName, artistName, albumName
 	if !p.extension.Enabled {
 		return nil, fmt.Errorf("extension '%s' is disabled", p.extension.ID)
 	}
-
-	p.extension.VMMu.Lock()
+	if err := p.lockReadyVM(); err != nil {
+		return nil, err
+	}
 	defer p.extension.VMMu.Unlock()
 
 	// Use global variables to avoid JS injection issues with special characters in track/artist names