feat(firebase_ai): add thinking level to ThinkingConfig

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

@@ -49,8 +49,12 @@ class _ChatPageState extends State<ChatPage> {
 
   void _initializeChat() {
     final generationConfig = GenerationConfig(
-      thinkingConfig:
-          _enableThinking ? ThinkingConfig(includeThoughts: true) : null,
+      thinkingConfig: _enableThinking
+          ? ThinkingConfig.withThinkingLevel(
+              ThinkingLevel.high,
+              includeThoughts: true,
+            )
+          : null,
     );
     if (widget.useVertexBackend) {
       _model = FirebaseAI.vertexAI(auth: FirebaseAuth.instance).generativeModel(

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

@@ -53,8 +53,12 @@ class _FunctionCallingPageState extends State<FunctionCallingPage> {
 
   void _initializeModel() {
     final generationConfig = GenerationConfig(
-      thinkingConfig:
-          _enableThinking ? ThinkingConfig(includeThoughts: true) : null,
+      thinkingConfig: _enableThinking
+          ? ThinkingConfig.withThinkingLevel(
+              ThinkingLevel.high,
+              includeThoughts: true,
+            )
+          : null,
     );
     if (widget.useVertexBackend) {
       var vertexAI = FirebaseAI.vertexAI(auth: FirebaseAuth.instance);

packages/firebase_ai/firebase_ai/lib/firebase_ai.dart

@@ -23,6 +23,7 @@ export 'src/api.dart'
         GenerateContentResponse,
         GenerationConfig,
         ThinkingConfig,
+        ThinkingLevel,
         HarmBlockThreshold,
         HarmCategory,
         HarmProbability,

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

@@ -962,21 +962,92 @@ enum ResponseModalities {
   String toJson() => _jsonString;
 }
 
+/// A preset that balances the trade-off between reasoning quality and response
+/// speed for a model's "thinking" process.
+///
+/// Note, not all models support every level.
+enum ThinkingLevel {
+  /// Minimal thinking level.
+  minimal('MINIMAL'),
+
+  /// Low thinking level.
+  low('LOW'),
+
+  /// Medium thinking level.
+  medium('MEDIUM'),
+
+  /// High thinking level.
+  high('HIGH');
+
+  const ThinkingLevel(this._jsonString);
+  final String _jsonString;
+
+  // ignore: public_member_api_docs
+  String toJson() => _jsonString;
+}
+
 /// Config for thinking features.
 class ThinkingConfig {
-  // ignore: public_member_api_docs
-  ThinkingConfig({this.thinkingBudget, this.includeThoughts});
+  /// Deprecated public constructor of [ThinkingConfig].
+  ///
+  /// Keep for backwards compatibility.
+  /// [thinkingBudget] and [thinkingLevel] cannot be set at the same time.
+  @Deprecated(
+      'Use ThinkingConfig.withThinkingBudget() or ThinkingConfig.withThinkingLevel() instead.')
+  ThinkingConfig(
+      {this.thinkingBudget, this.thinkingLevel, this.includeThoughts})
+      : assert(
+          !(thinkingBudget != null && thinkingLevel != null),
+          'thinkingBudget and thinkingLevel cannot be set at the same time.',
+        );
+
+  // Private constructor
+  ThinkingConfig._(
+      {this.thinkingBudget, this.thinkingLevel, this.includeThoughts});
+
+  /// Initializes [ThinkingConfig] with [thinkingBudget].
+  ///
+  /// Used for Gemini models 2.5 and earlier.
+  factory ThinkingConfig.withThinkingBudget(int? thinkingBudget,
+          {bool? includeThoughts}) =>
+      ThinkingConfig._(
+          thinkingBudget: thinkingBudget, includeThoughts: includeThoughts);
+
+  /// Initializes [ThinkingConfig] with [thinkingLevel].
+  ///
+  /// Used for Gemini models 3.0 and newer.
+  /// See https://ai.google.dev/gemini-api/docs/thinking#thinking-levels
+  factory ThinkingConfig.withThinkingLevel(ThinkingLevel? thinkingLevel,
+          {bool? includeThoughts}) =>
+      ThinkingConfig._(
+          thinkingLevel: thinkingLevel, includeThoughts: includeThoughts);
 
   /// The number of thoughts tokens that the model should generate.
+  ///
+  /// The range of supported thinking budget values depends on the model.
+  /// https://firebase.google.com/docs/ai-logic/thinking?api=dev#supported-thinking-budget-values
+  /// To use the default thinking budget or thinking level for a model, set this
+  /// value to null or omit it.
+  /// To disable thinking, when supported by the model, set this value to `0`.
+  /// To use dynamic thinking, allowing the model to decide on the thinking
+  /// budget based on the task, set this value to `-1`.
   final int? thinkingBudget;
 
   /// Whether to include thoughts in the response.
   final bool? includeThoughts;
 
+  /// A preset that controls the model's "thinking" process.
+  ///
+  /// Use [ThinkingLevel.low] for faster responses on less complex tasks, and
+  /// [ThinkingLevel.high] for better reasoning on more complex tasks.
+  final ThinkingLevel? thinkingLevel;
+
   // ignore: public_member_api_docs
   Map<String, Object?> toJson() => {
         if (thinkingBudget case final thinkingBudget?)
           'thinkingBudget': thinkingBudget,
+        if (thinkingLevel case final thinkingLevel?)
+          'thinkingLevel': thinkingLevel.toJson(),
         if (includeThoughts case final includeThoughts?)
           'includeThoughts': includeThoughts,
       };

packages/firebase_ai/firebase_ai/test/api_test.dart

@@ -12,6 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+// ignore_for_file: deprecated_member_use_from_same_package
 import 'dart:convert';
 
 import 'package:firebase_ai/src/api.dart';
@@ -527,22 +528,81 @@ void main() {
   group('ThinkingConfig', () {
     test('toJson with thinkingBudget set', () {
       final config = ThinkingConfig(thinkingBudget: 123);
+
       expect(config.toJson(), {'thinkingBudget': 123});
     });
 
-    test('toJson with thinkingBudget null', () {
+    test('toJson with thinkingLevel set', () {
+      final config = ThinkingConfig.withThinkingLevel(ThinkingLevel.high,
+          includeThoughts: true);
+
+      expect(
+          config.toJson(), {'thinkingLevel': 'HIGH', 'includeThoughts': true});
+    });
+
+    test('toJson with includeThoughts set', () {
+      final config = ThinkingConfig(includeThoughts: true);
+
+      expect(config.toJson(), {'includeThoughts': true});
+    });
+
+    test('toJson with thinkingBudget and thinkingLevel null', () {
       final config = ThinkingConfig();
+
       // Expecting the key to be absent or the value to be explicitly null,
       // depending on implementation. Current implementation omits the key.
       expect(config.toJson(), {});
     });
 
     test('constructor initializes thinkingBudget', () {
       final config = ThinkingConfig(thinkingBudget: 456);
+
       expect(config.thinkingBudget, 456);
+      expect(config.thinkingLevel, isNull);
+      expect(config.includeThoughts, isNull);
+    });
+
+    test('constructor initializes thinkingLevel', () {
+      final config = ThinkingConfig(thinkingLevel: ThinkingLevel.low);
+
+      expect(config.thinkingBudget, isNull);
+      expect(config.thinkingLevel, ThinkingLevel.low);
+      expect(config.includeThoughts, isNull);
+    });
 
-      final configNull = ThinkingConfig();
-      expect(configNull.thinkingBudget, isNull);
+    test('constructor initializes includeThoughts', () {
+      final config = ThinkingConfig(includeThoughts: true);
+
+      expect(config.thinkingBudget, isNull);
+      expect(config.thinkingLevel, isNull);
+      expect(config.includeThoughts, isTrue);
+    });
+
+    test('withThinkingBudget factory initializes correctly', () {
+      final config =
+          ThinkingConfig.withThinkingBudget(789, includeThoughts: false);
+
+      expect(config.thinkingBudget, 789);
+      expect(config.thinkingLevel, isNull);
+      expect(config.includeThoughts, isFalse);
+    });
+
+    test('withThinkingLevel factory initializes correctly', () {
+      final config = ThinkingConfig.withThinkingLevel(ThinkingLevel.medium,
+          includeThoughts: true);
+
+      expect(config.thinkingBudget, isNull);
+      expect(config.thinkingLevel, ThinkingLevel.medium);
+      expect(config.includeThoughts, isTrue);
+    });
+
+    test(
+        'deprecated constructor throws AssertionError if both thinkingBudget and thinkingLevel are provided',
+        () {
+      expect(
+          () => ThinkingConfig(
+              thinkingBudget: 100, thinkingLevel: ThinkingLevel.high),
+          throwsA(isA<AssertionError>()));
     });
   });