diff --git a/packages/genkit_google_genai/lib/genkit_google_genai.dart b/packages/genkit_google_genai/lib/genkit_google_genai.dart
index 2c89f205..395a0807 100644
--- a/packages/genkit_google_genai/lib/genkit_google_genai.dart
+++ b/packages/genkit_google_genai/lib/genkit_google_genai.dart
@@ -32,6 +32,10 @@ class GoogleGenAiPluginHandle {
     return modelRef('googleai/$name', customOptions: GeminiOptions.$schema);
   }
 
+  ModelRef<GemmaOptions> gemma(String name) {
+    return modelRef('googleai/$name', customOptions: GemmaOptions.$schema);
+  }
+
   EmbedderRef<TextEmbedderOptions> textEmbedding(String name) {
     return embedderRef(
       'googleai/$name',
diff --git a/packages/genkit_google_genai/lib/src/common_plugin.dart b/packages/genkit_google_genai/lib/src/common_plugin.dart
index 0eebd543..491b2de5 100644
--- a/packages/genkit_google_genai/lib/src/common_plugin.dart
+++ b/packages/genkit_google_genai/lib/src/common_plugin.dart
@@ -21,6 +21,7 @@ import 'package:schemantic/schemantic.dart';
 
 import 'aggregation.dart';
 import 'api_client.dart';
+import 'gemma.dart';
 import 'generated/generativelanguage.dart' as gcl;
 import 'model.dart';
 
@@ -40,11 +41,16 @@ final commonModelInfo = ModelInfo(
 abstract class CommonGoogleGenPlugin extends GenkitPlugin {
   Future<GenerativeLanguageBaseClient> getApiClient([String? requestApiKey]);
 
-  Model createModel(String modelName, SchemanticType customOptions) {
+  Model createModel(
+    String modelName,
+    SchemanticType customOptions, {
+    ModelInfo? modelInfo,
+  }) {
+    final isGemma = isGemmaModelName(modelName);
     return Model(
       name: '$name/$modelName',
       customOptions: customOptions,
-      metadata: {'model': commonModelInfo.toJson()},
+      metadata: {'model': (modelInfo ?? commonModelInfo).toJson()},
       fn: (req, ctx) async {
         gcl.GenerationConfig generationConfig;
         List<gcl.SafetySetting>? safetySettings;
@@ -74,9 +80,9 @@ abstract class CommonGoogleGenPlugin extends GenkitPlugin {
           );
           toolConfig = toGeminiToolConfig(options.functionCallingConfig);
         } else {
-          final options = req.config == null
-              ? GeminiOptions()
-              : GeminiOptions.$schema.parse(req.config!);
+          final options = isGemma
+              ? gemmaToGeminiOptions(GemmaOptions.fromJson(req.config ?? {}))
+              : GeminiOptions.fromJson(req.config ?? {});
           apiKey = options.apiKey;
           generationConfig = toGeminiSettings(
             options,
@@ -98,9 +104,19 @@ abstract class CommonGoogleGenPlugin extends GenkitPlugin {
           final systemMessage = req.messages
               .where((m) => m.role == Role.system)
               .firstOrNull;
-          final messages = req.messages
+          final nonSystemMessages = req.messages
               .where((m) => m.role != Role.system)
               .toList();
+          final messages = isGemma
+              ? stripReasoningParts(nonSystemMessages)
+              : nonSystemMessages;
+
+          if (isGemma && messages.isEmpty) {
+            throw GenkitException(
+              'No valid messages found for the model request.',
+              status: StatusCodes.INVALID_ARGUMENT,
+            );
+          }
 
           final generateRequest = gcl.GenerateContentRequest(
             contents: toGeminiContent(messages),
@@ -189,6 +205,15 @@ abstract class CommonGoogleGenPlugin extends GenkitPlugin {
       return createEmbedder(name);
     }
     if (actionType == 'model') {
+      if (isGemmaModelName(name)) {
+        return createModel(
+          name,
+          GemmaOptions.$schema,
+          modelInfo: isGemma3ModelName(name)
+              ? gemma3ModelInfo
+              : commonGemmaModelInfo,
+        );
+      }
       if (name.contains('-tts')) {
         return createModel(name, GeminiTtsOptions.$schema);
       }
diff --git a/packages/genkit_google_genai/lib/src/gemma.dart b/packages/genkit_google_genai/lib/src/gemma.dart
new file mode 100644
index 00000000..6ed78103
--- /dev/null
+++ b/packages/genkit_google_genai/lib/src/gemma.dart
@@ -0,0 +1,88 @@
+// 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 'package:genkit/plugin.dart';
+
+import 'model.dart';
+
+final commonGemmaModelInfo = ModelInfo(
+  supports: {
+    'multiturn': true,
+    'media': true,
+    'tools': true,
+    'toolChoice': true,
+    'systemRole': true,
+    'constrained': 'no-tools',
+  },
+);
+
+final gemma3ModelInfo = ModelInfo(
+  supports: {...?commonGemmaModelInfo.supports, 'systemRole': false},
+);
+
+bool isGemmaModelName(String name) => name.startsWith('gemma-');
+
+bool isGemma3ModelName(String name) =>
+    name.startsWith('gemma-3-') || name.startsWith('gemma-3n-');
+
+/// Strips parts that the Gemma API rejects in history: reasoning parts
+/// and any text/tool parts whose metadata carries a `thoughtSignature`.
+/// Messages that become empty after filtering are dropped.
+List<Message> stripReasoningParts(List<Message> messages) {
+  return messages
+      .map(
+        (m) => Message(
+          role: m.role,
+          content: m.content
+              .where(
+                (p) =>
+                    !p.isReasoning && p.metadata?['thoughtSignature'] == null,
+              )
+              .toList(),
+          metadata: m.metadata,
+        ),
+      )
+      .where((m) => m.content.isNotEmpty)
+      .toList();
+}
+
+/// Maps a [GemmaOptions] config to its [GeminiOptions] equivalent so the
+/// shared `toGeminiSettings`/`toGeminiTools`/etc. helpers can be reused.
+/// Every Gemma field has an identical Gemini twin; the only schema-level
+/// difference is the tighter `temperature` cap on Gemma.
+GeminiOptions gemmaToGeminiOptions(GemmaOptions o) {
+  return GeminiOptions(
+    apiKey: o.apiKey,
+    safetySettings: o.safetySettings,
+    codeExecution: o.codeExecution,
+    functionCallingConfig: o.functionCallingConfig,
+    thinkingConfig: o.thinkingConfig,
+    responseModalities: o.responseModalities,
+    googleSearch: o.googleSearch,
+    fileSearch: o.fileSearch,
+    temperature: o.temperature,
+    topP: o.topP,
+    topK: o.topK,
+    candidateCount: o.candidateCount,
+    stopSequences: o.stopSequences,
+    maxOutputTokens: o.maxOutputTokens,
+    responseMimeType: o.responseMimeType,
+    responseLogprobs: o.responseLogprobs,
+    logprobs: o.logprobs,
+    presencePenalty: o.presencePenalty,
+    frequencyPenalty: o.frequencyPenalty,
+    seed: o.seed,
+    speechConfig: o.speechConfig,
+  );
+}
diff --git a/packages/genkit_google_genai/lib/src/google_api_client.dart b/packages/genkit_google_genai/lib/src/google_api_client.dart
index 60d28184..3fed4122 100644
--- a/packages/genkit_google_genai/lib/src/google_api_client.dart
+++ b/packages/genkit_google_genai/lib/src/google_api_client.dart
@@ -17,6 +17,7 @@ import 'package:meta/meta.dart';
 
 import 'api_client.dart';
 import 'common_plugin.dart';
+import 'gemma.dart';
 import 'generated/generativelanguage.dart' as gcl;
 import 'model.dart';
 
@@ -54,12 +55,23 @@ class GoogleGenAiPluginImpl extends CommonGoogleGenPlugin {
       final models = (modelsResponse.models ?? [])
           .where((model) {
             return model.name != null &&
-                model.name!.startsWith('models/gemini-');
+                (model.name!.startsWith('models/gemini-') ||
+                    model.name!.startsWith('models/gemma-'));
           })
           .map((model) {
-            final isTts = model.name!.contains('-tts');
+            final short = model.name!.split('/').last;
+            if (isGemmaModelName(short)) {
+              return modelMetadata(
+                '$name/$short',
+                customOptions: GemmaOptions.$schema,
+                modelInfo: isGemma3ModelName(short)
+                    ? gemma3ModelInfo
+                    : commonGemmaModelInfo,
+              );
+            }
+            final isTts = short.contains('-tts');
             return modelMetadata(
-              '$name/${model.name!.split('/').last}',
+              '$name/$short',
               customOptions: isTts
                   ? GeminiTtsOptions.$schema
                   : GeminiOptions.$schema,
diff --git a/packages/genkit_google_genai/lib/src/model.dart b/packages/genkit_google_genai/lib/src/model.dart
index ffb73826..43a81ba6 100644
--- a/packages/genkit_google_genai/lib/src/model.dart
+++ b/packages/genkit_google_genai/lib/src/model.dart
@@ -56,6 +56,42 @@ abstract class $GeminiOptions {
   $SpeechConfig? get speechConfig;
 }
 
+@Schema()
+abstract class $GemmaOptions {
+  String? get apiKey;
+
+  List<$SafetySettings>? get safetySettings;
+
+  bool? get codeExecution;
+  $FunctionCallingConfig? get functionCallingConfig;
+  $ThinkingConfig? get thinkingConfig;
+  List<String>? get responseModalities;
+
+  // Retrieval
+  $GoogleSearch? get googleSearch;
+  $FileSearch? get fileSearch;
+
+  @DoubleField(minimum: 0.0, maximum: 1.0)
+  double? get temperature;
+
+  @DoubleField(minimum: 0.0, maximum: 1.0)
+  double? get topP;
+
+  int? get topK;
+  int? get candidateCount;
+  List<String>? get stopSequences;
+  int? get maxOutputTokens;
+
+  String? get responseMimeType;
+  bool? get responseLogprobs;
+  int? get logprobs;
+  double? get presencePenalty;
+  double? get frequencyPenalty;
+  int? get seed;
+
+  $SpeechConfig? get speechConfig;
+}
+
 @Schema()
 abstract class $SafetySettings {
   @StringField(
diff --git a/packages/genkit_google_genai/lib/src/model.g.dart b/packages/genkit_google_genai/lib/src/model.g.dart
index a50ade23..7a6a0fd8 100644
--- a/packages/genkit_google_genai/lib/src/model.g.dart
+++ b/packages/genkit_google_genai/lib/src/model.g.dart
@@ -416,6 +416,401 @@ base class _GeminiOptionsTypeFactory extends SchemanticType<GeminiOptions> {
   );
 }
 
+base class GemmaOptions {
+  /// Creates a [GemmaOptions] from a JSON map.
+  factory GemmaOptions.fromJson(Map<String, dynamic> json) =>
+      $schema.parse(json);
+
+  GemmaOptions._(this._json);
+
+  GemmaOptions({
+    String? apiKey,
+    List<SafetySettings>? safetySettings,
+    bool? codeExecution,
+    FunctionCallingConfig? functionCallingConfig,
+    ThinkingConfig? thinkingConfig,
+    List<String>? responseModalities,
+    GoogleSearch? googleSearch,
+    FileSearch? fileSearch,
+    double? temperature,
+    double? topP,
+    int? topK,
+    int? candidateCount,
+    List<String>? stopSequences,
+    int? maxOutputTokens,
+    String? responseMimeType,
+    bool? responseLogprobs,
+    int? logprobs,
+    double? presencePenalty,
+    double? frequencyPenalty,
+    int? seed,
+    SpeechConfig? speechConfig,
+  }) {
+    _json = {
+      'apiKey': ?apiKey,
+      'safetySettings': ?safetySettings?.map((e) => e.toJson()).toList(),
+      'codeExecution': ?codeExecution,
+      'functionCallingConfig': ?functionCallingConfig?.toJson(),
+      'thinkingConfig': ?thinkingConfig?.toJson(),
+      'responseModalities': ?responseModalities,
+      'googleSearch': ?googleSearch?.toJson(),
+      'fileSearch': ?fileSearch?.toJson(),
+      'temperature': ?temperature,
+      'topP': ?topP,
+      'topK': ?topK,
+      'candidateCount': ?candidateCount,
+      'stopSequences': ?stopSequences,
+      'maxOutputTokens': ?maxOutputTokens,
+      'responseMimeType': ?responseMimeType,
+      'responseLogprobs': ?responseLogprobs,
+      'logprobs': ?logprobs,
+      'presencePenalty': ?presencePenalty,
+      'frequencyPenalty': ?frequencyPenalty,
+      'seed': ?seed,
+      'speechConfig': ?speechConfig?.toJson(),
+    };
+  }
+
+  late final Map<String, dynamic> _json;
+
+  /// The JSON schema and type descriptor for [GemmaOptions].
+  static const SchemanticType<GemmaOptions> $schema =
+      _GemmaOptionsTypeFactory();
+
+  String? get apiKey {
+    return _json['apiKey'] as String?;
+  }
+
+  set apiKey(String? value) {
+    if (value == null) {
+      _json.remove('apiKey');
+    } else {
+      _json['apiKey'] = value;
+    }
+  }
+
+  List<SafetySettings>? get safetySettings {
+    return (_json['safetySettings'] as List?)
+        ?.map((e) => SafetySettings.fromJson(e as Map<String, dynamic>))
+        .toList();
+  }
+
+  set safetySettings(List<SafetySettings>? value) {
+    if (value == null) {
+      _json.remove('safetySettings');
+    } else {
+      _json['safetySettings'] = value.toList();
+    }
+  }
+
+  bool? get codeExecution {
+    return _json['codeExecution'] as bool?;
+  }
+
+  set codeExecution(bool? value) {
+    if (value == null) {
+      _json.remove('codeExecution');
+    } else {
+      _json['codeExecution'] = value;
+    }
+  }
+
+  FunctionCallingConfig? get functionCallingConfig {
+    return _json['functionCallingConfig'] == null
+        ? null
+        : FunctionCallingConfig.fromJson(
+            _json['functionCallingConfig'] as Map<String, dynamic>,
+          );
+  }
+
+  set functionCallingConfig(FunctionCallingConfig? value) {
+    if (value == null) {
+      _json.remove('functionCallingConfig');
+    } else {
+      _json['functionCallingConfig'] = value;
+    }
+  }
+
+  ThinkingConfig? get thinkingConfig {
+    return _json['thinkingConfig'] == null
+        ? null
+        : ThinkingConfig.fromJson(
+            _json['thinkingConfig'] as Map<String, dynamic>,
+          );
+  }
+
+  set thinkingConfig(ThinkingConfig? value) {
+    if (value == null) {
+      _json.remove('thinkingConfig');
+    } else {
+      _json['thinkingConfig'] = value;
+    }
+  }
+
+  List<String>? get responseModalities {
+    return (_json['responseModalities'] as List?)?.cast<String>();
+  }
+
+  set responseModalities(List<String>? value) {
+    if (value == null) {
+      _json.remove('responseModalities');
+    } else {
+      _json['responseModalities'] = value;
+    }
+  }
+
+  GoogleSearch? get googleSearch {
+    return _json['googleSearch'] == null
+        ? null
+        : GoogleSearch.fromJson(_json['googleSearch'] as Map<String, dynamic>);
+  }
+
+  set googleSearch(GoogleSearch? value) {
+    if (value == null) {
+      _json.remove('googleSearch');
+    } else {
+      _json['googleSearch'] = value;
+    }
+  }
+
+  FileSearch? get fileSearch {
+    return _json['fileSearch'] == null
+        ? null
+        : FileSearch.fromJson(_json['fileSearch'] as Map<String, dynamic>);
+  }
+
+  set fileSearch(FileSearch? value) {
+    if (value == null) {
+      _json.remove('fileSearch');
+    } else {
+      _json['fileSearch'] = value;
+    }
+  }
+
+  double? get temperature {
+    return (_json['temperature'] as num?)?.toDouble();
+  }
+
+  set temperature(double? value) {
+    if (value == null) {
+      _json.remove('temperature');
+    } else {
+      _json['temperature'] = value;
+    }
+  }
+
+  double? get topP {
+    return (_json['topP'] as num?)?.toDouble();
+  }
+
+  set topP(double? value) {
+    if (value == null) {
+      _json.remove('topP');
+    } else {
+      _json['topP'] = value;
+    }
+  }
+
+  int? get topK {
+    return _json['topK'] as int?;
+  }
+
+  set topK(int? value) {
+    if (value == null) {
+      _json.remove('topK');
+    } else {
+      _json['topK'] = value;
+    }
+  }
+
+  int? get candidateCount {
+    return _json['candidateCount'] as int?;
+  }
+
+  set candidateCount(int? value) {
+    if (value == null) {
+      _json.remove('candidateCount');
+    } else {
+      _json['candidateCount'] = value;
+    }
+  }
+
+  List<String>? get stopSequences {
+    return (_json['stopSequences'] as List?)?.cast<String>();
+  }
+
+  set stopSequences(List<String>? value) {
+    if (value == null) {
+      _json.remove('stopSequences');
+    } else {
+      _json['stopSequences'] = value;
+    }
+  }
+
+  int? get maxOutputTokens {
+    return _json['maxOutputTokens'] as int?;
+  }
+
+  set maxOutputTokens(int? value) {
+    if (value == null) {
+      _json.remove('maxOutputTokens');
+    } else {
+      _json['maxOutputTokens'] = value;
+    }
+  }
+
+  String? get responseMimeType {
+    return _json['responseMimeType'] as String?;
+  }
+
+  set responseMimeType(String? value) {
+    if (value == null) {
+      _json.remove('responseMimeType');
+    } else {
+      _json['responseMimeType'] = value;
+    }
+  }
+
+  bool? get responseLogprobs {
+    return _json['responseLogprobs'] as bool?;
+  }
+
+  set responseLogprobs(bool? value) {
+    if (value == null) {
+      _json.remove('responseLogprobs');
+    } else {
+      _json['responseLogprobs'] = value;
+    }
+  }
+
+  int? get logprobs {
+    return _json['logprobs'] as int?;
+  }
+
+  set logprobs(int? value) {
+    if (value == null) {
+      _json.remove('logprobs');
+    } else {
+      _json['logprobs'] = value;
+    }
+  }
+
+  double? get presencePenalty {
+    return (_json['presencePenalty'] as num?)?.toDouble();
+  }
+
+  set presencePenalty(double? value) {
+    if (value == null) {
+      _json.remove('presencePenalty');
+    } else {
+      _json['presencePenalty'] = value;
+    }
+  }
+
+  double? get frequencyPenalty {
+    return (_json['frequencyPenalty'] as num?)?.toDouble();
+  }
+
+  set frequencyPenalty(double? value) {
+    if (value == null) {
+      _json.remove('frequencyPenalty');
+    } else {
+      _json['frequencyPenalty'] = value;
+    }
+  }
+
+  int? get seed {
+    return _json['seed'] as int?;
+  }
+
+  set seed(int? value) {
+    if (value == null) {
+      _json.remove('seed');
+    } else {
+      _json['seed'] = value;
+    }
+  }
+
+  SpeechConfig? get speechConfig {
+    return _json['speechConfig'] == null
+        ? null
+        : SpeechConfig.fromJson(_json['speechConfig'] as Map<String, dynamic>);
+  }
+
+  set speechConfig(SpeechConfig? value) {
+    if (value == null) {
+      _json.remove('speechConfig');
+    } else {
+      _json['speechConfig'] = value;
+    }
+  }
+
+  @override
+  String toString() {
+    return _json.toString();
+  }
+
+  /// Serializes this [GemmaOptions] to a JSON map.
+  Map<String, dynamic> toJson() {
+    return _json;
+  }
+}
+
+base class _GemmaOptionsTypeFactory extends SchemanticType<GemmaOptions> {
+  const _GemmaOptionsTypeFactory();
+
+  @override
+  GemmaOptions parse(Object? json) {
+    return GemmaOptions._(json as Map<String, dynamic>);
+  }
+
+  @override
+  JsonSchemaMetadata get schemaMetadata => JsonSchemaMetadata(
+    name: 'GemmaOptions',
+    definition: $Schema
+        .object(
+          properties: {
+            'apiKey': $Schema.string(),
+            'safetySettings': $Schema.list(
+              items: $Schema.fromMap({'\$ref': r'#/$defs/SafetySettings'}),
+            ),
+            'codeExecution': $Schema.boolean(),
+            'functionCallingConfig': $Schema.fromMap({
+              '\$ref': r'#/$defs/FunctionCallingConfig',
+            }),
+            'thinkingConfig': $Schema.fromMap({
+              '\$ref': r'#/$defs/ThinkingConfig',
+            }),
+            'responseModalities': $Schema.list(items: $Schema.string()),
+            'googleSearch': $Schema.fromMap({'\$ref': r'#/$defs/GoogleSearch'}),
+            'fileSearch': $Schema.fromMap({'\$ref': r'#/$defs/FileSearch'}),
+            'temperature': $Schema.number(minimum: 0.0, maximum: 1.0),
+            'topP': $Schema.number(minimum: 0.0, maximum: 1.0),
+            'topK': $Schema.integer(),
+            'candidateCount': $Schema.integer(),
+            'stopSequences': $Schema.list(items: $Schema.string()),
+            'maxOutputTokens': $Schema.integer(),
+            'responseMimeType': $Schema.string(),
+            'responseLogprobs': $Schema.boolean(),
+            'logprobs': $Schema.integer(),
+            'presencePenalty': $Schema.number(),
+            'frequencyPenalty': $Schema.number(),
+            'seed': $Schema.integer(),
+            'speechConfig': $Schema.fromMap({'\$ref': r'#/$defs/SpeechConfig'}),
+          },
+        )
+        .value,
+    dependencies: [
+      SafetySettings.$schema,
+      FunctionCallingConfig.$schema,
+      ThinkingConfig.$schema,
+      GoogleSearch.$schema,
+      FileSearch.$schema,
+      SpeechConfig.$schema,
+    ],
+  );
+}
+
 base class SafetySettings {
   /// Creates a [SafetySettings] from a JSON map.
   factory SafetySettings.fromJson(Map<String, dynamic> json) =>
diff --git a/packages/genkit_google_genai/test/gemma_test.dart b/packages/genkit_google_genai/test/gemma_test.dart
new file mode 100644
index 00000000..7620975c
--- /dev/null
+++ b/packages/genkit_google_genai/test/gemma_test.dart
@@ -0,0 +1,158 @@
+// 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 'package:genkit/genkit.dart';
+import 'package:genkit/src/schema.dart' show toJsonSchema;
+import 'package:genkit_google_genai/genkit_google_genai.dart';
+import 'package:genkit_google_genai/src/gemma.dart';
+import 'package:genkit_google_genai/src/google_api_client.dart';
+import 'package:test/test.dart';
+
+void main() {
+  group('GemmaOptions schema', () {
+    test('round-trips temperature at cap', () {
+      final options = GemmaOptions.$schema.parse({'temperature': 1.0});
+      expect(options.temperature, 1.0);
+    });
+
+    test('JSON schema caps temperature at 1.0', () {
+      final schema = toJsonSchema(type: GemmaOptions.$schema);
+      final defs = schema[r'$defs'] as Map<String, dynamic>;
+      final gemma = defs['GemmaOptions'] as Map<String, dynamic>;
+      final props = gemma['properties'] as Map<String, dynamic>;
+      final temp = props['temperature'] as Map<String, dynamic>;
+      expect(temp['maximum'], 1.0);
+    });
+  });
+
+  group('model family predicates', () {
+    test('isGemmaModelName', () {
+      expect(isGemmaModelName('gemma-3-1b-it'), isTrue);
+      expect(isGemmaModelName('gemma-4-31b-it'), isTrue);
+      expect(isGemmaModelName('gemini-2.5-pro'), isFalse);
+      expect(isGemmaModelName('text-embedding-004'), isFalse);
+    });
+
+    test('isGemma3ModelName', () {
+      expect(isGemma3ModelName('gemma-3-1b-it'), isTrue);
+      expect(isGemma3ModelName('gemma-3-12b-it'), isTrue);
+      expect(isGemma3ModelName('gemma-3-27b-it'), isTrue);
+      expect(isGemma3ModelName('gemma-3-4b-it'), isTrue);
+      expect(isGemma3ModelName('gemma-3n-e4b-it'), isTrue);
+      expect(isGemma3ModelName('gemma-4-31b-it'), isFalse);
+      expect(isGemma3ModelName('gemini-2.5-pro'), isFalse);
+    });
+  });
+
+  group('stripReasoningParts', () {
+    test('drops reasoning parts', () {
+      final messages = [
+        Message(
+          role: Role.model,
+          content: [
+            ReasoningPart(reasoning: 'thinking...'),
+            TextPart(text: 'answer'),
+          ],
+        ),
+      ];
+      final stripped = stripReasoningParts(messages);
+      expect(stripped, hasLength(1));
+      expect(stripped.first.content, hasLength(1));
+      expect(stripped.first.content.first.text, 'answer');
+    });
+
+    test('drops parts whose metadata carries thoughtSignature', () {
+      final messages = [
+        Message(
+          role: Role.model,
+          content: [
+            TextPart(text: 'hidden', metadata: {'thoughtSignature': 'sig'}),
+            TextPart(text: 'visible'),
+          ],
+        ),
+      ];
+      final stripped = stripReasoningParts(messages);
+      expect(stripped.first.content, hasLength(1));
+      expect(stripped.first.content.first.text, 'visible');
+    });
+
+    test('drops messages that become empty', () {
+      final messages = [
+        Message(
+          role: Role.model,
+          content: [ReasoningPart(reasoning: 'only thought')],
+        ),
+        Message(
+          role: Role.user,
+          content: [TextPart(text: 'hi')],
+        ),
+      ];
+      final stripped = stripReasoningParts(messages);
+      expect(stripped, hasLength(1));
+      expect(stripped.first.role, Role.user);
+    });
+
+    test('leaves non-gemma-affected parts alone', () {
+      final messages = [
+        Message(
+          role: Role.user,
+          content: [TextPart(text: 'hello')],
+        ),
+      ];
+      final stripped = stripReasoningParts(messages);
+      expect(stripped, hasLength(1));
+      expect(stripped.first.content.first.text, 'hello');
+    });
+  });
+
+  group('plugin handle', () {
+    test('googleAI.gemma returns a ModelRef with GemmaOptions schema', () {
+      final ref = googleAI.gemma('gemma-3-1b-it');
+      expect(ref.name, 'googleai/gemma-3-1b-it');
+      expect(ref.customOptions, same(GemmaOptions.$schema));
+    });
+  });
+
+  group('GoogleGenAiPluginImpl.resolve for gemma models', () {
+    Map<String, dynamic>? supportsOf(String modelName) {
+      final plugin = GoogleGenAiPluginImpl();
+      final action = plugin.resolve('model', modelName);
+      expect(action, isNotNull);
+      expect(action!.name, 'googleai/$modelName');
+      final model = action.metadata['model'] as Map<String, dynamic>;
+      return model['supports'] as Map<String, dynamic>?;
+    }
+
+    test('gemma-3 models advertise systemRole: false', () {
+      for (final name in const [
+        'gemma-3-1b-it',
+        'gemma-3-4b-it',
+        'gemma-3-12b-it',
+        'gemma-3-27b-it',
+        'gemma-3n-e4b-it',
+      ]) {
+        expect(supportsOf(name)?['systemRole'], isFalse, reason: name);
+      }
+    });
+
+    test('gemma-4 models keep systemRole: true', () {
+      expect(supportsOf('gemma-4-31b-it')?['systemRole'], isTrue);
+      expect(supportsOf('gemma-4-26b-a4b-it')?['systemRole'], isTrue);
+    });
+
+    test('gemma models advertise constrained: no-tools', () {
+      expect(supportsOf('gemma-3-1b-it')?['constrained'], 'no-tools');
+    });
+  });
+}