feat(firebaseai): Add app check limited use token

packages/firebase_ai/firebase_ai/lib/src/base_model.dart

@@ -169,14 +169,20 @@ abstract class BaseModel {
 
   /// Returns a function that generates Firebase auth tokens.
   static FutureOr<Map<String, String>> Function() firebaseTokens(
-      FirebaseAppCheck? appCheck, FirebaseAuth? auth, FirebaseApp? app) {
+    FirebaseAppCheck? appCheck,
+    FirebaseAuth? auth,
+    FirebaseApp? app,
+    bool? useLimitedUseAppCheckTokens,
+  ) {
     return () async {
       Map<String, String> headers = {};
       // Override the client name in Google AI SDK
       headers['x-goog-api-client'] =
           'gl-dart/$packageVersion fire/$packageVersion';
       if (appCheck != null) {
-        final appCheckToken = await appCheck.getToken();
+        final appCheckToken = useLimitedUseAppCheckTokens == true
+            ? await appCheck.getLimitedUseToken()
+            : await appCheck.getToken();
         if (appCheckToken != null) {
           headers['X-Firebase-AppCheck'] = appCheckToken;
         }

packages/firebase_ai/firebase_ai/lib/src/firebase_ai.dart

@@ -26,13 +26,14 @@ const _defaultLocation = 'us-central1';
 
 /// The entrypoint for generative models.
 class FirebaseAI extends FirebasePluginPlatform {
-  FirebaseAI._(
-      {required this.app,
-      required this.location,
-      required bool useVertexBackend,
-      this.appCheck,
-      this.auth})
-      : _useVertexBackend = useVertexBackend,
+  FirebaseAI._({
+    required this.app,
+    required this.location,
+    required bool useVertexBackend,
+    this.appCheck,
+    this.auth,
+    this.useLimitedUseAppCheckTokens = false,
+  })  : _useVertexBackend = useVertexBackend,
         super(app.name, 'plugins.flutter.io/firebase_vertexai');
 
   /// The [FirebaseApp] for this current [FirebaseAI] instance.
@@ -48,6 +49,9 @@ class FirebaseAI extends FirebasePluginPlatform {
   /// The service location for this [FirebaseAI] instance.
   String location;
 
+  /// Whether to use App Check limited use tokens. Defaults to false.
+  final bool useLimitedUseAppCheckTokens;
+
   final bool _useVertexBackend;
 
   static final Map<String, FirebaseAI> _cachedInstances = {};
@@ -61,6 +65,7 @@ class FirebaseAI extends FirebasePluginPlatform {
     FirebaseAppCheck? appCheck,
     FirebaseAuth? auth,
     String? location,
+    bool? useLimitedUseAppCheckTokens,
   }) {
     app ??= Firebase.app();
     var instanceKey = '${app.name}::vertexai';
@@ -77,6 +82,7 @@ class FirebaseAI extends FirebasePluginPlatform {
       appCheck: appCheck,
       auth: auth,
       useVertexBackend: true,
+      useLimitedUseAppCheckTokens: useLimitedUseAppCheckTokens ?? false,
     );
     _cachedInstances[instanceKey] = newInstance;
 
@@ -91,6 +97,7 @@ class FirebaseAI extends FirebasePluginPlatform {
     FirebaseApp? app,
     FirebaseAppCheck? appCheck,
     FirebaseAuth? auth,
+    bool? useLimitedUseAppCheckTokens,
   }) {
     app ??= Firebase.app();
     var instanceKey = '${app.name}::googleai';
@@ -105,6 +112,7 @@ class FirebaseAI extends FirebasePluginPlatform {
       appCheck: appCheck,
       auth: auth,
       useVertexBackend: false,
+      useLimitedUseAppCheckTokens: useLimitedUseAppCheckTokens ?? false,
     );
     _cachedInstances[instanceKey] = newInstance;
 
@@ -142,6 +150,7 @@ class FirebaseAI extends FirebasePluginPlatform {
       tools: tools,
       toolConfig: toolConfig,
       systemInstruction: systemInstruction,
+      useLimitedUseAppCheckTokens: useLimitedUseAppCheckTokens,
     );
   }
 
@@ -162,7 +171,8 @@ class FirebaseAI extends FirebasePluginPlatform {
         generationConfig: generationConfig,
         safetySettings: safetySettings,
         appCheck: appCheck,
-        auth: auth);
+        auth: auth,
+        useLimitedUseAppCheckTokens: useLimitedUseAppCheckTokens);
   }
 
   /// Create a [LiveGenerativeModel] for real-time interaction.
@@ -185,6 +195,7 @@ class FirebaseAI extends FirebasePluginPlatform {
       systemInstruction: systemInstruction,
       appCheck: appCheck,
       auth: auth,
+      useLimitedUseAppCheckTokens: useLimitedUseAppCheckTokens,
     );
   }
 }

packages/firebase_ai/firebase_ai/lib/src/generative_model.dart

@@ -37,6 +37,7 @@ final class GenerativeModel extends BaseApiClientModel {
     required String location,
     required FirebaseApp app,
     required bool useVertexBackend,
+    bool? useLimitedUseAppCheckTokens,
     FirebaseAppCheck? appCheck,
     FirebaseAuth? auth,
     List<SafetySetting>? safetySettings,
@@ -60,13 +61,15 @@ final class GenerativeModel extends BaseApiClientModel {
             client: HttpApiClient(
                 apiKey: app.options.apiKey,
                 httpClient: httpClient,
-                requestHeaders: BaseModel.firebaseTokens(appCheck, auth, app)));
+                requestHeaders: BaseModel.firebaseTokens(
+                    appCheck, auth, app, useLimitedUseAppCheckTokens)));
 
   GenerativeModel._constructTestModel({
     required String model,
     required String location,
     required FirebaseApp app,
     required useVertexBackend,
+    bool? useLimitedUseAppCheckTokens,
     FirebaseAppCheck? appCheck,
     FirebaseAuth? auth,
     List<SafetySetting>? safetySettings,
@@ -90,8 +93,8 @@ final class GenerativeModel extends BaseApiClientModel {
             client: apiClient ??
                 HttpApiClient(
                     apiKey: app.options.apiKey,
-                    requestHeaders:
-                        BaseModel.firebaseTokens(appCheck, auth, app)));
+                    requestHeaders: BaseModel.firebaseTokens(
+                        appCheck, auth, app, useLimitedUseAppCheckTokens)));
 
   final List<SafetySetting> _safetySettings;
   final GenerationConfig? _generationConfig;
@@ -199,6 +202,7 @@ GenerativeModel createGenerativeModel({
   required String location,
   required String model,
   required bool useVertexBackend,
+  bool? useLimitedUseAppCheckTokens,
   FirebaseAppCheck? appCheck,
   FirebaseAuth? auth,
   GenerationConfig? generationConfig,
@@ -212,6 +216,7 @@ GenerativeModel createGenerativeModel({
       app: app,
       appCheck: appCheck,
       useVertexBackend: useVertexBackend,
+      useLimitedUseAppCheckTokens: useLimitedUseAppCheckTokens,
       auth: auth,
       location: location,
       safetySettings: safetySettings,
@@ -230,6 +235,7 @@ GenerativeModel createModelWithClient({
   required String model,
   required ApiClient client,
   required bool useVertexBackend,
+  bool? useLimitedUseAppCheckTokens,
   Content? systemInstruction,
   FirebaseAppCheck? appCheck,
   FirebaseAuth? auth,
@@ -243,6 +249,7 @@ GenerativeModel createModelWithClient({
         app: app,
         appCheck: appCheck,
         useVertexBackend: useVertexBackend,
+        useLimitedUseAppCheckTokens: useLimitedUseAppCheckTokens,
         auth: auth,
         location: location,
         safetySettings: safetySettings,

packages/firebase_ai/firebase_ai/lib/src/imagen/imagen_model.dart

@@ -31,6 +31,7 @@ final class ImagenModel extends BaseApiClientModel {
       required String model,
       required String location,
       required bool useVertexBackend,
+      bool? useLimitedUseAppCheckTokens,
       FirebaseAppCheck? appCheck,
       FirebaseAuth? auth,
       ImagenGenerationConfig? generationConfig,
@@ -45,7 +46,8 @@ final class ImagenModel extends BaseApiClientModel {
                 : _GoogleAIUri(app: app, model: model),
             client: HttpApiClient(
                 apiKey: app.options.apiKey,
-                requestHeaders: BaseModel.firebaseTokens(appCheck, auth, app)));
+                requestHeaders: BaseModel.firebaseTokens(
+                    appCheck, auth, app, useLimitedUseAppCheckTokens)));
 
   final ImagenGenerationConfig? _generationConfig;
   final ImagenSafetySettings? _safetySettings;
@@ -198,6 +200,7 @@ ImagenModel createImagenModel({
   required String location,
   required String model,
   required bool useVertexBackend,
+  bool? useLimitedUseAppCheckTokens,
   FirebaseAppCheck? appCheck,
   FirebaseAuth? auth,
   ImagenGenerationConfig? generationConfig,
@@ -210,6 +213,7 @@ ImagenModel createImagenModel({
       auth: auth,
       location: location,
       useVertexBackend: useVertexBackend,
+      useLimitedUseAppCheckTokens: useLimitedUseAppCheckTokens,
       safetySettings: safetySettings,
       generationConfig: generationConfig,
     );

packages/firebase_ai/firebase_ai/lib/src/live_model.dart

@@ -34,6 +34,7 @@ final class LiveGenerativeModel extends BaseModel {
       required String location,
       required FirebaseApp app,
       required bool useVertexBackend,
+      bool? useLimitedUseAppCheckTokens,
       FirebaseAppCheck? appCheck,
       FirebaseAuth? auth,
       LiveGenerationConfig? liveGenerationConfig,
@@ -47,6 +48,7 @@ final class LiveGenerativeModel extends BaseModel {
         _liveGenerationConfig = liveGenerationConfig,
         _tools = tools,
         _systemInstruction = systemInstruction,
+        _useLimitedUseAppCheckTokens = useLimitedUseAppCheckTokens,
         super._(
           serializationStrategy: VertexSerialization(),
           modelUri: useVertexBackend
@@ -69,6 +71,7 @@ final class LiveGenerativeModel extends BaseModel {
   final LiveGenerationConfig? _liveGenerationConfig;
   final List<Tool>? _tools;
   final Content? _systemInstruction;
+  final bool? _useLimitedUseAppCheckTokens;
 
   String _vertexAIUri() => 'wss://${_modelUri.baseAuthority}/'
       '$_apiUrl.${_modelUri.apiVersion}.$_apiUrlSuffixVertexAI/'
@@ -107,7 +110,12 @@ final class LiveGenerativeModel extends BaseModel {
     };
 
     final request = jsonEncode(setupJson);
-    final headers = await BaseModel.firebaseTokens(_appCheck, _auth, _app)();
+    final headers = await BaseModel.firebaseTokens(
+      _appCheck,
+      _auth,
+      _app,
+      _useLimitedUseAppCheckTokens,
+    )();
 
     var ws = kIsWeb
         ? WebSocketChannel.connect(Uri.parse(uri))
@@ -126,6 +134,7 @@ LiveGenerativeModel createLiveGenerativeModel({
   required String location,
   required String model,
   required bool useVertexBackend,
+  bool? useLimitedUseAppCheckTokens,
   FirebaseAppCheck? appCheck,
   FirebaseAuth? auth,
   LiveGenerationConfig? liveGenerationConfig,
@@ -139,6 +148,7 @@ LiveGenerativeModel createLiveGenerativeModel({
       auth: auth,
       location: location,
       useVertexBackend: useVertexBackend,
+      useLimitedUseAppCheckTokens: useLimitedUseAppCheckTokens,
       liveGenerationConfig: liveGenerationConfig,
       tools: tools,
       systemInstruction: systemInstruction,

packages/firebase_ai/firebase_ai/test/base_model_test.dart

@@ -45,6 +45,10 @@ class MockFirebaseAppCheck extends Mock implements FirebaseAppCheck {
   @override
   Future<String?> getToken([bool? forceRefresh = false]) async =>
       super.noSuchMethod(Invocation.method(#getToken, [forceRefresh]));
+
+  @override
+  Future<String> getLimitedUseToken() async =>
+      super.noSuchMethod(Invocation.method(#getLimitedUseToken, [])) ?? '';
 }
 
 // Mock Firebase Auth
@@ -72,7 +76,7 @@ class MockApiClient extends Mock implements ApiClient {
 void main() {
   group('BaseModel', () {
     test('firebaseTokens returns a function that generates headers', () async {
-      final tokenFunction = BaseModel.firebaseTokens(null, null, null);
+      final tokenFunction = BaseModel.firebaseTokens(null, null, null, false);
       final headers = await tokenFunction();
       expect(headers['x-goog-api-client'], contains('gl-dart'));
       expect(headers['x-goog-api-client'], contains('fire'));
@@ -83,7 +87,8 @@ void main() {
       final mockAppCheck = MockFirebaseAppCheck();
       when(mockAppCheck.getToken())
           .thenAnswer((_) async => 'test-app-check-token');
-      final tokenFunction = BaseModel.firebaseTokens(mockAppCheck, null, null);
+      final tokenFunction =
+          BaseModel.firebaseTokens(mockAppCheck, null, null, false);
       final headers = await tokenFunction();
       expect(headers['X-Firebase-AppCheck'], 'test-app-check-token');
       expect(headers['x-goog-api-client'], contains('gl-dart'));
@@ -96,7 +101,8 @@ void main() {
       final mockUser = MockUser();
       when(mockUser.getIdToken()).thenAnswer((_) async => 'test-id-token');
       when(mockAuth.currentUser).thenReturn(mockUser);
-      final tokenFunction = BaseModel.firebaseTokens(null, mockAuth, null);
+      final tokenFunction =
+          BaseModel.firebaseTokens(null, mockAuth, null, false);
       final headers = await tokenFunction();
       expect(headers['Authorization'], 'Firebase test-id-token');
       expect(headers['x-goog-api-client'], contains('gl-dart'));
@@ -109,7 +115,8 @@ void main() {
         () async {
       final mockApp = MockFirebaseApp();
 
-      final tokenFunction = BaseModel.firebaseTokens(null, null, mockApp);
+      final tokenFunction =
+          BaseModel.firebaseTokens(null, null, mockApp, false);
       final headers = await tokenFunction();
       expect(headers['X-Firebase-AppId'], 'test-app-id');
       expect(headers['x-goog-api-client'], contains('gl-dart'));
@@ -128,7 +135,7 @@ void main() {
       final mockApp = MockFirebaseApp();
 
       final tokenFunction =
-          BaseModel.firebaseTokens(mockAppCheck, mockAuth, mockApp);
+          BaseModel.firebaseTokens(mockAppCheck, mockAuth, mockApp, false);
       final headers = await tokenFunction();
       expect(headers['X-Firebase-AppCheck'], 'test-app-check-token');
       expect(headers['Authorization'], 'Firebase test-id-token');
@@ -137,5 +144,20 @@ void main() {
       expect(headers['x-goog-api-client'], contains('fire'));
       expect(headers.length, 4);
     });
+
+    test('firebaseTokens includes limited use App Check token if specified',
+        () async {
+      final mockAppCheck = MockFirebaseAppCheck();
+      when(mockAppCheck.getLimitedUseToken())
+          .thenAnswer((_) async => 'test-limited-use-app-check-token');
+      final tokenFunction =
+          BaseModel.firebaseTokens(mockAppCheck, null, null, true);
+      final headers = await tokenFunction();
+      expect(
+          headers['X-Firebase-AppCheck'], 'test-limited-use-app-check-token');
+      expect(headers['x-goog-api-client'], contains('gl-dart'));
+      expect(headers['x-goog-api-client'], contains('fire'));
+      expect(headers.length, 2);
+    });
   });
 }

packages/firebase_ai/firebase_ai/test/firebase_vertexai_test.dart

@@ -26,7 +26,9 @@ void main() {
   // ignore: unused_local_variable
   late FirebaseAppCheck appCheck;
   late FirebaseApp customApp;
+  late FirebaseApp limitTokenApp;
   late FirebaseAppCheck customAppCheck;
+  late FirebaseAppCheck limitTokenAppCheck;
 
   group('FirebaseAI Tests', () {
     late FirebaseApp app;
@@ -38,8 +40,13 @@ void main() {
         name: 'custom-app',
         options: Firebase.app().options,
       );
+      limitTokenApp = await Firebase.initializeApp(
+        name: 'limit-token-app',
+        options: Firebase.app().options,
+      );
       appCheck = FirebaseAppCheck.instance;
       customAppCheck = FirebaseAppCheck.instanceFor(app: customApp);
+      limitTokenAppCheck = FirebaseAppCheck.instanceFor(app: limitTokenApp);
     });
 
     test('Singleton behavior', () {
@@ -76,6 +83,19 @@ void main() {
       expect(model, isA<GenerativeModel>());
     });
 
+    test('Instance creation with useLimitedUseAppCheckTokens', () {
+      final vertexAIAppCheck = FirebaseAI.vertexAI(
+        app: limitTokenApp,
+        appCheck: limitTokenAppCheck,
+        location: 'limit-token-location',
+        useLimitedUseAppCheckTokens: true,
+      );
+      expect(vertexAIAppCheck.app, equals(limitTokenApp));
+      expect(vertexAIAppCheck.appCheck, equals(limitTokenAppCheck));
+      expect(vertexAIAppCheck.location, equals('limit-token-location'));
+      expect(vertexAIAppCheck.useLimitedUseAppCheckTokens, true);
+    });
+
     // ... other tests (e.g., with different parameters)
   });
 }