feat(firebaseai): add responseJsonSchema to GenerationConfig

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

@@ -998,8 +998,10 @@ final class GenerationConfig extends BaseGenerationConfig {
     super.responseModalities,
     this.responseMimeType,
     this.responseSchema,
+    this.responseJsonSchema,
     this.thinkingConfig,
-  });
+  }) : assert(responseSchema == null || responseJsonSchema == null,
+            'responseSchema and responseJsonSchema cannot both be set.');
 
   /// The set of character sequences (up to 5) that will stop output generation.
   ///
@@ -1018,8 +1020,28 @@ final class GenerationConfig extends BaseGenerationConfig {
   ///
   /// - Note: This only applies when the [responseMimeType] supports
   ///   a schema; currently this is limited to `application/json`.
+  ///
+  /// Only one of [responseSchema] or [responseJsonSchema] may be specified at
+  /// the same time.
   final Schema? responseSchema;
 
+  /// The response schema as a JSON-compatible map.
+  ///
+  /// - Note: This only applies when the [responseMimeType] supports a schema;
+  ///   currently this is limited to `application/json`.
+  ///
+  /// This schema can include more advanced features of JSON than the [Schema]
+  /// class taken by [responseSchema] supports.  See the [Gemini
+  /// documentation](https://ai.google.dev/api/generate-content#FIELDS.response_json_schema)
+  /// about the limitations of this feature.
+  ///
+  /// Notably, this feature is only supported on Gemini 2.5 and later. Use
+  /// [responseSchema] for earlier models.
+  ///
+  /// Only one of [responseSchema] or [responseJsonSchema] may be specified at
+  /// the same time.
+  final Map<String, Object?>? responseJsonSchema;
+
   /// Config for thinking features.
   ///
   /// An error will be returned if this field is set for models that don't
@@ -1036,6 +1058,8 @@ final class GenerationConfig extends BaseGenerationConfig {
           'responseMimeType': responseMimeType,
         if (responseSchema case final responseSchema?)
           'responseSchema': responseSchema.toJson(),
+        if (responseJsonSchema case final responseJsonSchema?)
+          'responseJsonSchema': responseJsonSchema,
         if (thinkingConfig case final thinkingConfig?)
           'thinkingConfig': thinkingConfig.toJson(),
       };

packages/firebase_ai/firebase_ai/test/api_test.dart

@@ -11,6 +11,9 @@
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.
+
+import 'dart:convert';
+
 import 'package:firebase_ai/firebase_ai.dart';
 import 'package:firebase_ai/src/api.dart';
 
@@ -442,6 +445,38 @@ void main() {
       });
     });
 
+    test('GenerationConfig toJson with responseJsonSchema', () {
+      final jsonSchema = {
+        'type': 'object',
+        'properties': {
+          'recipeName': {'type': 'string'}
+        },
+        'required': ['recipeName']
+      };
+      final config = GenerationConfig(
+        responseMimeType: 'application/json',
+        responseJsonSchema: jsonSchema,
+      );
+      final json = config.toJson();
+      expect(json['responseMimeType'], 'application/json');
+      final dynamic responseSchema = json['responseJsonSchema'];
+      expect(responseSchema, isA<Map<String, Object?>>());
+      expect(responseSchema, equals(jsonSchema));
+    });
+
+    test(
+        'throws assertion if both responseSchema and responseJsonSchema are provided',
+        () {
+      final schema = Schema.object(properties: {});
+      final jsonSchema =
+          (json.decode('{"type": "string", "title": "MyString"}') as Map)
+              .cast<String, Object?>();
+      expect(
+          () => GenerationConfig(
+              responseSchema: schema, responseJsonSchema: jsonSchema),
+          throwsA(isA<AssertionError>()));
+    });
+
     test('GenerationConfig toJson with empty stopSequences (omitted)', () {
       final config = GenerationConfig(stopSequences: []);
       expect(config.toJson(), {}); // Empty list for stopSequences is omitted