diff --git a/core/src/tools/google_search_tool.ts b/core/src/tools/google_search_tool.ts
index 69408fdf9..3ee46be27 100644
--- a/core/src/tools/google_search_tool.ts
+++ b/core/src/tools/google_search_tool.ts
@@ -5,7 +5,11 @@
  */
 import {GenerateContentConfig} from '@google/genai';
 
-import {isGemini1Model, isGeminiModel} from '../utils/model_name.js';
+import {
+  isGemini1Model,
+  isGeminiModel,
+  isGeminiModelIdCheckDisabled,
+} from '../utils/model_name.js';
 
 import {BaseTool, ToolProcessLlmRequest} from './base_tool.js';
 
@@ -34,6 +38,7 @@ export class GoogleSearchTool extends BaseTool {
       return;
     }
 
+    const modelCheckDisabled = isGeminiModelIdCheckDisabled();
     llmRequest.config = llmRequest.config || ({} as GenerateContentConfig);
     llmRequest.config.tools = llmRequest.config.tools || [];
 
@@ -51,7 +56,7 @@ export class GoogleSearchTool extends BaseTool {
       return;
     }
 
-    if (isGeminiModel(llmRequest.model)) {
+    if (isGeminiModel(llmRequest.model) || modelCheckDisabled) {
       llmRequest.config.tools.push({
         googleSearch: {},
       });
diff --git a/core/test/tools/google_search_tool_test.ts b/core/test/tools/google_search_tool_test.ts
index f304d94ba..e51044e82 100644
--- a/core/test/tools/google_search_tool_test.ts
+++ b/core/test/tools/google_search_tool_test.ts
@@ -4,8 +4,19 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {GOOGLE_SEARCH, GoogleSearchTool, LlmRequest} from '@google/adk';
-import {describe, expect, it} from 'vitest';
+import {
+  Context,
+  createSession,
+  GOOGLE_SEARCH,
+  GoogleSearchTool,
+  InvocationContext,
+  LlmAgent,
+  LlmRequest,
+  PluginManager,
+} from '@google/adk';
+import {afterEach, describe, expect, it, vi} from 'vitest';
+
+const MODEL_ID_CHECK_ENV_VAR = 'ADK_DISABLE_GEMINI_MODEL_ID_CHECK';
 
 function makeRequest(model?: string, tools = []): LlmRequest {
   return {
@@ -17,6 +28,18 @@ function makeRequest(model?: string, tools = []): LlmRequest {
   } as unknown as LlmRequest;
 }
 
+/** Builds a real `Context` backed by real ADK plumbing, with no stubs. */
+function makeToolContext(): Context {
+  return new Context({
+    invocationContext: new InvocationContext({
+      invocationId: 'test-invocation',
+      agent: new LlmAgent({name: 'test_agent'}),
+      session: createSession({id: 'test-session', appName: 'test-app'}),
+      pluginManager: new PluginManager([]),
+    }),
+  });
+}
+
 describe('GoogleSearchTool', () => {
   describe('processLlmRequest', () => {
     it('returns early when model is not set', async () => {
@@ -91,6 +114,53 @@ describe('GoogleSearchTool', () => {
 
       expect(req.config!.tools).toEqual([{googleSearch: {}}]);
     });
+
+    describe('ADK_DISABLE_GEMINI_MODEL_ID_CHECK', () => {
+      afterEach(() => {
+        vi.unstubAllEnvs();
+      });
+
+      it('adds googleSearch for a non-Gemini model when the check is disabled', async () => {
+        vi.stubEnv(MODEL_ID_CHECK_ENV_VAR, 'true');
+        const tool = new GoogleSearchTool();
+        const req = makeRequest('internal-model-v1');
+
+        await tool.processLlmRequest({
+          llmRequest: req,
+          toolContext: makeToolContext(),
+        });
+
+        expect(req.config!.tools).toEqual([{googleSearch: {}}]);
+      });
+
+      it('keeps Gemini 1.x handling when the check is disabled', async () => {
+        vi.stubEnv(MODEL_ID_CHECK_ENV_VAR, 'true');
+        const tool = new GoogleSearchTool();
+        const req = makeRequest('gemini-1.5-pro');
+
+        await tool.processLlmRequest({
+          llmRequest: req,
+          toolContext: makeToolContext(),
+        });
+
+        expect(req.config!.tools).toEqual([{googleSearchRetrieval: {}}]);
+      });
+
+      it('still throws for a non-Gemini model when the value is falsy', async () => {
+        vi.stubEnv(MODEL_ID_CHECK_ENV_VAR, 'false');
+        const tool = new GoogleSearchTool();
+        const req = makeRequest('internal-model-v1');
+
+        await expect(
+          tool.processLlmRequest({
+            llmRequest: req,
+            toolContext: makeToolContext(),
+          }),
+        ).rejects.toThrow(
+          'Google search tool is not supported for model internal-model-v1',
+        );
+      });
+    });
   });
 
   it('has a global instance GOOGLE_SEARCH', () => {