feat(firebaseai): add responseJsonSchema to GenerationConfig

packages/firebase_ai/firebase_ai/example/lib/main.dart

@@ -12,24 +12,25 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-import 'package:firebase_core/firebase_core.dart';
-import 'package:firebase_auth/firebase_auth.dart';
 import 'package:firebase_ai/firebase_ai.dart';
+import 'package:firebase_auth/firebase_auth.dart';
+import 'package:firebase_core/firebase_core.dart';
 import 'package:flutter/material.dart';
 
 // Import after file is generated through flutterfire_cli.
 // import 'package:firebase_ai_example/firebase_options.dart';
 
-import 'pages/chat_page.dart';
 import 'pages/audio_page.dart';
+import 'pages/bidi_page.dart';
+import 'pages/chat_page.dart';
+import 'pages/document.dart';
 import 'pages/function_calling_page.dart';
 import 'pages/image_prompt_page.dart';
-import 'pages/token_count_page.dart';
-import 'pages/schema_page.dart';
 import 'pages/imagen_page.dart';
-import 'pages/document.dart';
+import 'pages/json_schema_page.dart';
+import 'pages/schema_page.dart';
+import 'pages/token_count_page.dart';
 import 'pages/video_page.dart';
-import 'pages/bidi_page.dart';
 
 void main() async {
   WidgetsFlutterBinding.ensureInitialized();
@@ -64,11 +65,11 @@ class _GenerativeAISampleState extends State<GenerativeAISample> {
   void _initializeModel(bool useVertexBackend) {
     if (useVertexBackend) {
       final vertexInstance = FirebaseAI.vertexAI(auth: FirebaseAuth.instance);
-      _currentModel = vertexInstance.generativeModel(model: 'gemini-1.5-flash');
+      _currentModel = vertexInstance.generativeModel(model: 'gemini-2.5-flash');
       _currentImagenModel = _initializeImagenModel(vertexInstance);
     } else {
       final googleAI = FirebaseAI.googleAI(auth: FirebaseAuth.instance);
-      _currentModel = googleAI.generativeModel(model: 'gemini-2.0-flash');
+      _currentModel = googleAI.generativeModel(model: 'gemini-2.5-flash');
       _currentImagenModel = _initializeImagenModel(googleAI);
     }
   }
@@ -184,10 +185,12 @@ class _HomeScreenState extends State<HomeScreen> {
       case 6:
         return SchemaPromptPage(title: 'Schema Prompt', model: currentModel);
       case 7:
-        return DocumentPage(title: 'Document Prompt', model: currentModel);
+        return JsonSchemaPage(title: 'JSON Schema', model: currentModel);
       case 8:
-        return VideoPage(title: 'Video Prompt', model: currentModel);
+        return DocumentPage(title: 'Document Prompt', model: currentModel);
       case 9:
+        return VideoPage(title: 'Video Prompt', model: currentModel);
+      case 10:
         return BidiPage(
           title: 'Live Stream',
           model: currentModel,
@@ -230,6 +233,9 @@ class _HomeScreenState extends State<HomeScreen> {
                   onChanged: widget.onBackendChanged,
                   activeTrackColor: Colors.green.withValues(alpha: 0.5),
                   inactiveTrackColor: Colors.blueGrey.withValues(alpha: 0.5),
+                  // Ignore until activeThumbColor is available on Flutter
+                  // stable.
+                  // ignore: deprecated_member_use
                   activeColor: Colors.green,
                   inactiveThumbColor: Colors.blueGrey,
                 ),
@@ -302,6 +308,11 @@ class _HomeScreenState extends State<HomeScreen> {
             label: 'Schema',
             tooltip: 'Schema Prompt',
           ),
+          BottomNavigationBarItem(
+            icon: Icon(Icons.data_object),
+            label: 'JSON',
+            tooltip: 'JSON Schema',
+          ),
           BottomNavigationBarItem(
             icon: Icon(Icons.edit_document),
             label: 'Document',

packages/firebase_ai/firebase_ai/example/lib/pages/json_schema_page.dart

@@ -0,0 +1,200 @@
+// Copyright 2025 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// 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:flutter/material.dart';
+import 'package:firebase_ai/firebase_ai.dart';
+import '../widgets/message_widget.dart';
+
+class JsonSchemaPage extends StatefulWidget {
+  const JsonSchemaPage({super.key, required this.title, required this.model});
+
+  final String title;
+  final GenerativeModel model;
+
+  @override
+  State<JsonSchemaPage> createState() => _JsonSchemaPageState();
+}
+
+class _JsonSchemaPageState extends State<JsonSchemaPage> {
+  final ScrollController _scrollController = ScrollController();
+  final TextEditingController _textController = TextEditingController();
+  final FocusNode _textFieldFocus = FocusNode();
+  final List<MessageData> _messages = <MessageData>[];
+  bool _loading = false;
+
+  void _scrollDown() {
+    WidgetsBinding.instance.addPostFrameCallback(
+      (_) => _scrollController.animateTo(
+        _scrollController.position.maxScrollExtent,
+        duration: const Duration(
+          milliseconds: 750,
+        ),
+        curve: Curves.easeOutCirc,
+      ),
+    );
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      appBar: AppBar(
+        title: Text(widget.title),
+      ),
+      body: Padding(
+        padding: const EdgeInsets.all(8),
+        child: Column(
+          mainAxisAlignment: MainAxisAlignment.center,
+          crossAxisAlignment: CrossAxisAlignment.start,
+          children: [
+            Expanded(
+              child: ListView.builder(
+                controller: _scrollController,
+                itemBuilder: (context, idx) {
+                  return MessageWidget(
+                    text: _messages[idx].text,
+                    isFromUser: _messages[idx].fromUser ?? false,
+                  );
+                },
+                itemCount: _messages.length,
+              ),
+            ),
+            Padding(
+              padding: const EdgeInsets.symmetric(
+                vertical: 25,
+                horizontal: 15,
+              ),
+              child: Row(
+                children: [
+                  Expanded(
+                    child: ElevatedButton(
+                      onPressed: !_loading
+                          ? () async {
+                              await _promptJsonSchemaTest();
+                            }
+                          : null,
+                      child: const Text('JSON Schema Prompt'),
+                    ),
+                  ),
+                ],
+              ),
+            ),
+          ],
+        ),
+      ),
+    );
+  }
+
+  Future<void> _promptJsonSchemaTest() async {
+    setState(() {
+      _loading = true;
+    });
+    try {
+      final content = [
+        Content.text(
+          'Generate a widget hierarchy with a column containing two text widgets ',
+        ),
+      ];
+
+      final jsonSchema = {
+        r'$defs': {
+          'text_widget': {
+            r'$anchor': 'text_widget',
+            'type': 'object',
+            'properties': {
+              'type': {'const': 'Text'},
+              'text': {'type': 'string'},
+            },
+            'required': ['type', 'text'],
+          },
+        },
+        'type': 'object',
+        'properties': {
+          'type': {'const': 'Column'},
+          'children': {
+            'type': 'array',
+            'items': {
+              'anyOf': [
+                {r'$ref': '#text_widget'},
+                {
+                  'type': 'object',
+                  'properties': {
+                    'type': {'const': 'Row'},
+                    'children': {
+                      'type': 'array',
+                      'items': {r'$ref': '#text_widget'},
+                    },
+                  },
+                  'required': ['type', 'children'],
+                }
+              ],
+            },
+          },
+        },
+        'required': ['type', 'children'],
+      };
+
+      final response = await widget.model.generateContent(
+        content,
+        generationConfig: GenerationConfig(
+          responseMimeType: 'application/json',
+          responseJsonSchema: jsonSchema,
+        ),
+      );
+
+      var text = const JsonEncoder.withIndent('  ')
+          .convert(json.decode(response.text ?? '') as Object?);
+      _messages.add(MessageData(text: '```json$text```', fromUser: false));
+
+      setState(() {
+        _loading = false;
+        _scrollDown();
+      });
+    } catch (e) {
+      _showError(e.toString());
+      setState(() {
+        _loading = false;
+      });
+    } finally {
+      _textController.clear();
+      setState(() {
+        _loading = false;
+      });
+      _textFieldFocus.requestFocus();
+    }
+  }
+
+  void _showError(String message) {
+    showDialog<void>(
+      context: context,
+      builder: (context) {
+        return AlertDialog(
+          title: const Text('Something went wrong'),
+          content: SingleChildScrollView(
+            child: SelectableText(message),
+          ),
+          actions: [
+            TextButton(
+              onPressed: () {
+                Navigator.of(context).pop();
+              },
+              child: const Text('OK'),
+            ),
+          ],
+        );
+      },
+    );
+  }
+}

packages/firebase_ai/firebase_ai/example/lib/pages/schema_page.dart

@@ -12,6 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+import 'dart:convert';
+
 import 'package:flutter/material.dart';
 import 'package:firebase_ai/firebase_ai.dart';
 import '../widgets/message_widget.dart';
@@ -132,13 +134,14 @@ class _SchemaPromptPageState extends State<SchemaPromptPage> {
         ),
       );
 
-      var text = response.text;
-      _messages.add(MessageData(text: text, fromUser: false));
-
-      if (text == null) {
+      if (response.text == null) {
         _showError('No response from API.');
         return;
       } else {
+        final text = const JsonEncoder.withIndent('  ')
+            .convert(json.decode(response.text!) as Object?);
+        _messages
+            .add(MessageData(text: '```json\n$text\n```', fromUser: false));
         setState(() {
           _loading = false;
           _scrollDown();

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(),
       };