diff --git a/packages/vertexai/src/methods/count-tokens.test.ts b/packages/vertexai/src/methods/count-tokens.test.ts
index a3d7c99b4ba..9eccbf702fe 100644
--- a/packages/vertexai/src/methods/count-tokens.test.ts
+++ b/packages/vertexai/src/methods/count-tokens.test.ts
@@ -45,7 +45,10 @@ describe('countTokens()', () => {
     restore();
   });
   it('total tokens', async () => {
-    const mockResponse = getMockResponse('unary-success-total-tokens.json');
+    const mockResponse = getMockResponse(
+      'vertexAI',
+      'unary-success-total-tokens.json'
+    );
     const makeRequestStub = stub(request, 'makeRequest').resolves(
       mockResponse as Response
     );
@@ -69,6 +72,7 @@ describe('countTokens()', () => {
   });
   it('total tokens with modality details', async () => {
     const mockResponse = getMockResponse(
+      'vertexAI',
       'unary-success-detailed-token-response.json'
     );
     const makeRequestStub = stub(request, 'makeRequest').resolves(
@@ -96,6 +100,7 @@ describe('countTokens()', () => {
   });
   it('total tokens no billable characters', async () => {
     const mockResponse = getMockResponse(
+      'vertexAI',
       'unary-success-no-billable-characters.json'
     );
     const makeRequestStub = stub(request, 'makeRequest').resolves(
@@ -120,7 +125,10 @@ describe('countTokens()', () => {
     );
   });
   it('model not found', async () => {
-    const mockResponse = getMockResponse('unary-failure-model-not-found.json');
+    const mockResponse = getMockResponse(
+      'vertexAI',
+      'unary-failure-model-not-found.json'
+    );
     const mockFetch = stub(globalThis, 'fetch').resolves({
       ok: false,
       status: 404,
diff --git a/packages/vertexai/src/methods/generate-content.test.ts b/packages/vertexai/src/methods/generate-content.test.ts
index 426bd5176db..1d15632f828 100644
--- a/packages/vertexai/src/methods/generate-content.test.ts
+++ b/packages/vertexai/src/methods/generate-content.test.ts
@@ -61,6 +61,7 @@ describe('generateContent()', () => {
   });
   it('short response', async () => {
     const mockResponse = getMockResponse(
+      'vertexAI',
       'unary-success-basic-reply-short.json'
     );
     const makeRequestStub = stub(request, 'makeRequest').resolves(
@@ -84,7 +85,10 @@ describe('generateContent()', () => {
     );
   });
   it('long response', async () => {
-    const mockResponse = getMockResponse('unary-success-basic-reply-long.json');
+    const mockResponse = getMockResponse(
+      'vertexAI',
+      'unary-success-basic-reply-long.json'
+    );
     const makeRequestStub = stub(request, 'makeRequest').resolves(
       mockResponse as Response
     );
@@ -105,6 +109,7 @@ describe('generateContent()', () => {
   });
   it('long response with token details', async () => {
     const mockResponse = getMockResponse(
+      'vertexAI',
       'unary-success-basic-response-long-usage-metadata.json'
     );
     const makeRequestStub = stub(request, 'makeRequest').resolves(
@@ -138,7 +143,10 @@ describe('generateContent()', () => {
     );
   });
   it('citations', async () => {
-    const mockResponse = getMockResponse('unary-success-citations.json');
+    const mockResponse = getMockResponse(
+      'vertexAI',
+      'unary-success-citations.json'
+    );
     const makeRequestStub = stub(request, 'makeRequest').resolves(
       mockResponse as Response
     );
@@ -163,6 +171,7 @@ describe('generateContent()', () => {
   });
   it('blocked prompt', async () => {
     const mockResponse = getMockResponse(
+      'vertexAI',
       'unary-failure-prompt-blocked-safety.json'
     );
     const makeRequestStub = stub(request, 'makeRequest').resolves(
@@ -184,6 +193,7 @@ describe('generateContent()', () => {
   });
   it('finishReason safety', async () => {
     const mockResponse = getMockResponse(
+      'vertexAI',
       'unary-failure-finish-reason-safety.json'
     );
     const makeRequestStub = stub(request, 'makeRequest').resolves(
@@ -204,7 +214,10 @@ describe('generateContent()', () => {
     );
   });
   it('empty content', async () => {
-    const mockResponse = getMockResponse('unary-failure-empty-content.json');
+    const mockResponse = getMockResponse(
+      'vertexAI',
+      'unary-failure-empty-content.json'
+    );
     const makeRequestStub = stub(request, 'makeRequest').resolves(
       mockResponse as Response
     );
@@ -224,6 +237,7 @@ describe('generateContent()', () => {
   });
   it('unknown enum - should ignore', async () => {
     const mockResponse = getMockResponse(
+      'vertexAI',
       'unary-success-unknown-enum-safety-ratings.json'
     );
     const makeRequestStub = stub(request, 'makeRequest').resolves(
@@ -244,7 +258,10 @@ describe('generateContent()', () => {
     );
   });
   it('image rejected (400)', async () => {
-    const mockResponse = getMockResponse('unary-failure-image-rejected.json');
+    const mockResponse = getMockResponse(
+      'vertexAI',
+      'unary-failure-image-rejected.json'
+    );
     const mockFetch = stub(globalThis, 'fetch').resolves({
       ok: false,
       status: 400,
@@ -257,6 +274,7 @@ describe('generateContent()', () => {
   });
   it('api not enabled (403)', async () => {
     const mockResponse = getMockResponse(
+      'vertexAI',
       'unary-failure-firebasevertexai-api-not-enabled.json'
     );
     const mockFetch = stub(globalThis, 'fetch').resolves({
diff --git a/packages/vertexai/src/models/generative-model.test.ts b/packages/vertexai/src/models/generative-model.test.ts
index 26dff4e04c6..987f9b115e2 100644
--- a/packages/vertexai/src/models/generative-model.test.ts
+++ b/packages/vertexai/src/models/generative-model.test.ts
@@ -60,6 +60,7 @@ describe('GenerativeModel', () => {
     );
     expect(genModel.systemInstruction?.parts[0].text).to.equal('be friendly');
     const mockResponse = getMockResponse(
+      'vertexAI',
       'unary-success-basic-reply-short.json'
     );
     const makeRequestStub = stub(request, 'makeRequest').resolves(
@@ -89,6 +90,7 @@ describe('GenerativeModel', () => {
     });
     expect(genModel.systemInstruction?.parts[0].text).to.equal('be friendly');
     const mockResponse = getMockResponse(
+      'vertexAI',
       'unary-success-basic-reply-short.json'
     );
     const makeRequestStub = stub(request, 'makeRequest').resolves(
@@ -129,6 +131,7 @@ describe('GenerativeModel', () => {
     );
     expect(genModel.systemInstruction?.parts[0].text).to.equal('be friendly');
     const mockResponse = getMockResponse(
+      'vertexAI',
       'unary-success-basic-reply-short.json'
     );
     const makeRequestStub = stub(request, 'makeRequest').resolves(
@@ -177,6 +180,7 @@ describe('GenerativeModel', () => {
     );
     expect(genModel.systemInstruction?.parts[0].text).to.equal('be friendly');
     const mockResponse = getMockResponse(
+      'vertexAI',
       'unary-success-basic-reply-short.json'
     );
     const makeRequestStub = stub(request, 'makeRequest').resolves(
@@ -206,6 +210,7 @@ describe('GenerativeModel', () => {
     });
     expect(genModel.systemInstruction?.parts[0].text).to.equal('be friendly');
     const mockResponse = getMockResponse(
+      'vertexAI',
       'unary-success-basic-reply-short.json'
     );
     const makeRequestStub = stub(request, 'makeRequest').resolves(
@@ -239,6 +244,7 @@ describe('GenerativeModel', () => {
     );
     expect(genModel.systemInstruction?.parts[0].text).to.equal('be friendly');
     const mockResponse = getMockResponse(
+      'vertexAI',
       'unary-success-basic-reply-short.json'
     );
     const makeRequestStub = stub(request, 'makeRequest').resolves(
@@ -277,7 +283,10 @@ describe('GenerativeModel', () => {
   });
   it('calls countTokens', async () => {
     const genModel = new GenerativeModel(fakeVertexAI, { model: 'my-model' });
-    const mockResponse = getMockResponse('unary-success-total-tokens.json');
+    const mockResponse = getMockResponse(
+      'vertexAI',
+      'unary-success-total-tokens.json'
+    );
     const makeRequestStub = stub(request, 'makeRequest').resolves(
       mockResponse as Response
     );
diff --git a/packages/vertexai/src/models/imagen-model.test.ts b/packages/vertexai/src/models/imagen-model.test.ts
index c566a88e5b0..9e534f2195a 100644
--- a/packages/vertexai/src/models/imagen-model.test.ts
+++ b/packages/vertexai/src/models/imagen-model.test.ts
@@ -47,6 +47,7 @@ const fakeVertexAI: VertexAI = {
 describe('ImagenModel', () => {
   it('generateImages makes a request to predict with default parameters', async () => {
     const mockResponse = getMockResponse(
+      'vertexAI',
       'unary-success-generate-images-base64.json'
     );
     const makeRequestStub = stub(request, 'makeRequest').resolves(
@@ -90,6 +91,7 @@ describe('ImagenModel', () => {
     });
 
     const mockResponse = getMockResponse(
+      'vertexAI',
       'unary-success-generate-images-base64.json'
     );
     const makeRequestStub = stub(request, 'makeRequest').resolves(
@@ -133,6 +135,7 @@ describe('ImagenModel', () => {
   });
   it('throws if prompt blocked', async () => {
     const mockResponse = getMockResponse(
+      'vertexAI',
       'unary-failure-generate-images-prompt-blocked.json'
     );
 
diff --git a/packages/vertexai/src/requests/request.test.ts b/packages/vertexai/src/requests/request.test.ts
index 499f06c848b..cd39a0f8ae5 100644
--- a/packages/vertexai/src/requests/request.test.ts
+++ b/packages/vertexai/src/requests/request.test.ts
@@ -414,6 +414,7 @@ describe('request methods', () => {
   });
   it('Network error, API not enabled', async () => {
     const mockResponse = getMockResponse(
+      'vertexAI',
       'unary-failure-firebasevertexai-api-not-enabled.json'
     );
     const fetchStub = stub(globalThis, 'fetch').resolves(
diff --git a/packages/vertexai/src/requests/response-helpers.test.ts b/packages/vertexai/src/requests/response-helpers.test.ts
index 4cab8cde047..5371d040253 100644
--- a/packages/vertexai/src/requests/response-helpers.test.ts
+++ b/packages/vertexai/src/requests/response-helpers.test.ts
@@ -257,6 +257,7 @@ describe('response-helpers methods', () => {
   describe('handlePredictResponse', () => {
     it('returns base64 images', async () => {
       const mockResponse = getMockResponse(
+        'vertexAI',
         'unary-success-generate-images-base64.json'
       ) as Response;
       const res = await handlePredictResponse<ImagenInlineImage>(mockResponse);
@@ -270,6 +271,7 @@ describe('response-helpers methods', () => {
   });
   it('returns GCS images', async () => {
     const mockResponse = getMockResponse(
+      'vertexAI',
       'unary-success-generate-images-gcs.json'
     ) as Response;
     const res = await handlePredictResponse<ImagenGCSImage>(mockResponse);
@@ -284,6 +286,7 @@ describe('response-helpers methods', () => {
   });
   it('has filtered reason and no images if all images were filtered', async () => {
     const mockResponse = getMockResponse(
+      'vertexAI',
       'unary-failure-generate-images-all-filtered.json'
     ) as Response;
     const res = await handlePredictResponse<ImagenInlineImage>(mockResponse);
@@ -294,6 +297,7 @@ describe('response-helpers methods', () => {
   });
   it('has filtered reason and no images if all base64 images were filtered', async () => {
     const mockResponse = getMockResponse(
+      'vertexAI',
       'unary-failure-generate-images-base64-some-filtered.json'
     ) as Response;
     const res = await handlePredictResponse<ImagenInlineImage>(mockResponse);
@@ -308,6 +312,7 @@ describe('response-helpers methods', () => {
   });
   it('has filtered reason and no images if all GCS images were filtered', async () => {
     const mockResponse = getMockResponse(
+      'vertexAI',
       'unary-failure-generate-images-gcs-some-filtered.json'
     ) as Response;
     const res = await handlePredictResponse<ImagenGCSImage>(mockResponse);
diff --git a/packages/vertexai/src/requests/stream-reader.test.ts b/packages/vertexai/src/requests/stream-reader.test.ts
index b68c2423066..bf959276a93 100644
--- a/packages/vertexai/src/requests/stream-reader.test.ts
+++ b/packages/vertexai/src/requests/stream-reader.test.ts
@@ -72,6 +72,7 @@ describe('processStream', () => {
   });
   it('streaming response - short', async () => {
     const fakeResponse = getMockResponseStreaming(
+      'vertexAI',
       'streaming-success-basic-reply-short.txt'
     );
     const result = processStream(fakeResponse as Response);
@@ -83,6 +84,7 @@ describe('processStream', () => {
   });
   it('streaming response - long', async () => {
     const fakeResponse = getMockResponseStreaming(
+      'vertexAI',
       'streaming-success-basic-reply-long.txt'
     );
     const result = processStream(fakeResponse as Response);
@@ -95,6 +97,7 @@ describe('processStream', () => {
   });
   it('streaming response - long - big chunk', async () => {
     const fakeResponse = getMockResponseStreaming(
+      'vertexAI',
       'streaming-success-basic-reply-long.txt',
       1e6
     );
@@ -107,7 +110,10 @@ describe('processStream', () => {
     expect(aggregatedResponse.text()).to.include('to their owners.');
   });
   it('streaming response - utf8', async () => {
-    const fakeResponse = getMockResponseStreaming('streaming-success-utf8.txt');
+    const fakeResponse = getMockResponseStreaming(
+      'vertexAI',
+      'streaming-success-utf8.txt'
+    );
     const result = processStream(fakeResponse as Response);
     for await (const response of result.stream) {
       expect(response.text()).to.not.be.empty;
@@ -118,6 +124,7 @@ describe('processStream', () => {
   });
   it('streaming response - functioncall', async () => {
     const fakeResponse = getMockResponseStreaming(
+      'vertexAI',
       'streaming-success-function-call-short.txt'
     );
     const result = processStream(fakeResponse as Response);
@@ -141,6 +148,7 @@ describe('processStream', () => {
   });
   it('candidate had finishReason', async () => {
     const fakeResponse = getMockResponseStreaming(
+      'vertexAI',
       'streaming-failure-finish-reason-safety.txt'
     );
     const result = processStream(fakeResponse as Response);
@@ -153,6 +161,7 @@ describe('processStream', () => {
   });
   it('prompt was blocked', async () => {
     const fakeResponse = getMockResponseStreaming(
+      'vertexAI',
       'streaming-failure-prompt-blocked-safety.txt'
     );
     const result = processStream(fakeResponse as Response);
@@ -165,6 +174,7 @@ describe('processStream', () => {
   });
   it('empty content', async () => {
     const fakeResponse = getMockResponseStreaming(
+      'vertexAI',
       'streaming-failure-empty-content.txt'
     );
     const result = processStream(fakeResponse as Response);
@@ -176,6 +186,7 @@ describe('processStream', () => {
   });
   it('unknown enum - should ignore', async () => {
     const fakeResponse = getMockResponseStreaming(
+      'vertexAI',
       'streaming-success-unknown-safety-enum.txt'
     );
     const result = processStream(fakeResponse as Response);
@@ -187,6 +198,7 @@ describe('processStream', () => {
   });
   it('recitation ending with a missing content field', async () => {
     const fakeResponse = getMockResponseStreaming(
+      'vertexAI',
       'streaming-failure-recitation-no-content.txt'
     );
     const result = processStream(fakeResponse as Response);
@@ -205,6 +217,7 @@ describe('processStream', () => {
   });
   it('handles citations', async () => {
     const fakeResponse = getMockResponseStreaming(
+      'vertexAI',
       'streaming-success-citations.txt'
     );
     const result = processStream(fakeResponse as Response);
@@ -224,6 +237,7 @@ describe('processStream', () => {
   });
   it('removes empty text parts', async () => {
     const fakeResponse = getMockResponseStreaming(
+      'vertexAI',
       'streaming-success-empty-text-part.txt'
     );
     const result = processStream(fakeResponse as Response);
diff --git a/packages/vertexai/test-utils/convert-mocks.ts b/packages/vertexai/test-utils/convert-mocks.ts
index c306bec312f..851d6017b6d 100644
--- a/packages/vertexai/test-utils/convert-mocks.ts
+++ b/packages/vertexai/test-utils/convert-mocks.ts
@@ -1,6 +1,6 @@
 /**
  * @license
- * Copyright 2024 Google LLC
+ * 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.
@@ -15,42 +15,111 @@
  * limitations under the License.
  */
 
+/* eslint-disable @typescript-eslint/no-require-imports */
+const { readdirSync, readFileSync, writeFileSync } = require('node:fs');
+const { join } = require('node:path');
+
+const MOCK_RESPONSES_DIR_PATH = join(
+  __dirname,
+  'vertexai-sdk-test-data',
+  'mock-responses'
+);
+const MOCK_LOOKUP_OUTPUT_PATH = join(__dirname, 'mocks-lookup.ts');
+
+type BackendName = 'vertexAI' | 'googleAI';
+
+const mockDirs: Record<BackendName, string> = {
+  vertexAI: join(MOCK_RESPONSES_DIR_PATH, 'vertexai'),
+  // Note: the dirname is developerapi is legacy. It should be updated to googleai.
+  googleAI: join(MOCK_RESPONSES_DIR_PATH, 'developerapi')
+};
+
 /**
- * Converts mock text files into a js file that karma can read without
- * using fs.
+ * Generates a JS file that exports maps from filenames to JSON mock responses (as strings)
+ * for each backend.
+ *
+ * This allows tests that run in a browser to access the mock responses without having to
+ * read from local disk and requiring 'fs'.
  */
+function generateMockLookupFile(): void {
+  console.log('Generating mock lookup file...');
+  const vertexAIMockLookupText = generateMockLookup('vertexAI');
+  const googleAIMockLookupText = generateMockLookup('googleAI');
 
-// eslint-disable-next-line @typescript-eslint/no-require-imports
-const fs = require('fs');
-// eslint-disable-next-line @typescript-eslint/no-require-imports
-const { join } = require('path');
+  const fileText = `
+/**
+ * DO NOT EDIT - This file was generated by the packages/vertexai/test-utils/convert-mocks.ts script.
+ * 
+ * These objects map mock response filenames to their JSON contents.
+ * 
+ * Mock response files are pulled from https://github.com/FirebaseExtended/vertexai-sdk-test-data.
+ */
 
-const mockResponseDir = join(
-  __dirname,
-  'vertexai-sdk-test-data/mock-responses/vertexai'
-);
+// Automatically generated at: ${new Date().toISOString()}
+
+${vertexAIMockLookupText}
 
-async function main(): Promise<void> {
-  const list = fs.readdirSync(mockResponseDir);
+${googleAIMockLookupText}
+`;
+  try {
+    writeFileSync(MOCK_LOOKUP_OUTPUT_PATH, fileText, 'utf-8');
+    console.log(
+      `Successfully generated mock lookup file at: ${MOCK_LOOKUP_OUTPUT_PATH}`
+    );
+  } catch (err) {
+    console.error(
+      `Error writing mock lookup file to ${MOCK_LOOKUP_OUTPUT_PATH}:`,
+      err
+    );
+    process.exit(1);
+  }
+}
+
+/**
+ * Given a directory that contains mock response files, reads through all the files,
+ * maps file names to file contents, and returns a string of typescript code
+ * that exports that map as an object.
+ */
+function generateMockLookup(backendName: BackendName): string {
   const lookup: Record<string, string> = {};
-  // eslint-disable-next-line guard-for-in
-  for (const fileName of list) {
-    const fullText = fs.readFileSync(join(mockResponseDir, fileName), 'utf-8');
-    lookup[fileName] = fullText;
+  const mockDir = mockDirs[backendName];
+  let mockFilenames: string[];
+
+  console.log(
+    `Processing mocks for "${backendName}" from directory: ${mockDir}`
+  );
+
+  try {
+    mockFilenames = readdirSync(mockDir);
+  } catch (err) {
+    console.error(
+      `Error reading directory ${mockDir} for ${backendName}:`,
+      err
+    );
+    return `export const ${backendName}MocksLookup: Record<string, string> = {};`;
   }
-  let fileText = `// Generated from mocks text files.`;
-
-  fileText += '\n\n';
-  fileText += `export const mocksLookup: Record<string, string> = ${JSON.stringify(
-    lookup,
-    null,
-    2
-  )}`;
-  fileText += ';\n';
-  fs.writeFileSync(join(__dirname, 'mocks-lookup.ts'), fileText, 'utf-8');
+
+  if (mockFilenames.length === 0) {
+    console.warn(`No .json files found in ${mockDir} for ${backendName}.`);
+  }
+
+  for (const mockFilename of mockFilenames) {
+    const mockFilepath = `${mockDir}/${mockFilename}`;
+    try {
+      const fullText = readFileSync(mockFilepath, 'utf-8');
+      lookup[mockFilename] = fullText;
+    } catch (err) {
+      console.error(
+        `Error reading mock file ${mockFilepath} for ${backendName}:`,
+        err
+      );
+    }
+  }
+
+  // Use JSON.stringify with indentation for readable output in the generated file
+  const lookupJsonString = JSON.stringify(lookup, null, 2);
+
+  return `export const ${backendName}MocksLookup: Record<string, string> = ${lookupJsonString};`;
 }
 
-main().catch(e => {
-  console.error(e);
-  process.exit(1);
-});
+generateMockLookupFile();
diff --git a/packages/vertexai/test-utils/mock-response.ts b/packages/vertexai/test-utils/mock-response.ts
index 9b42c93427b..5128ddabe74 100644
--- a/packages/vertexai/test-utils/mock-response.ts
+++ b/packages/vertexai/test-utils/mock-response.ts
@@ -1,6 +1,6 @@
 /**
  * @license
- * Copyright 2024 Google LLC
+ * 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.
@@ -15,7 +15,12 @@
  * limitations under the License.
  */
 
-import { mocksLookup } from './mocks-lookup';
+import { vertexAIMocksLookup, googleAIMocksLookup } from './mocks-lookup';
+
+const mockSetMaps: Record<BackendName, Record<string, string>> = {
+  'vertexAI': vertexAIMocksLookup,
+  'googleAI': googleAIMocksLookup
+};
 
 /**
  * Mock native Response.body
@@ -45,25 +50,33 @@ export function getChunkedStream(
 
   return stream;
 }
+
 export function getMockResponseStreaming(
+  backendName: BackendName,
   filename: string,
   chunkLength: number = 20
 ): Partial<Response> {
-  if (!(filename in mocksLookup)) {
-    throw Error(`Mock response file '${filename}' not found.`);
+  const mocksMap = mockSetMaps[backendName];
+  if (!(filename in mocksMap)) {
+    throw Error(`${backendName} mock response file '${filename}' not found.`);
   }
-  const fullText = mocksLookup[filename];
+  const fullText = mocksMap[filename];
 
   return {
     body: getChunkedStream(fullText, chunkLength)
   };
 }
 
-export function getMockResponse(filename: string): Partial<Response> {
+export function getMockResponse(
+  backendName: BackendName,
+  filename: string
+): Partial<Response> {
+  const mocksLookup = mockSetMaps[backendName];
   if (!(filename in mocksLookup)) {
-    throw Error(`Mock response file '${filename}' not found.`);
+    throw Error(`${backendName} mock response file '${filename}' not found.`);
   }
   const fullText = mocksLookup[filename];
+
   return {
     ok: true,
     json: () => Promise.resolve(JSON.parse(fullText))