fix(ai-gemini): send requests through httpOptions.fetch again

.changeset/gemini-custom-fetch.md

@@ -0,0 +1,5 @@
+---
+'@tanstack/ai-gemini': patch
+---
+
+Send Gemini API requests through `httpOptions.fetch` again when the client has an `apiKey`. Since 1.1.1 the adapters called the global `fetch` and ignored a custom one, also for image generation through the Interactions API. The `httpOptions.fetch` type is in `@google/genai` 2.23.0 and later.

docs/adapters/gemini-advanced.md

@@ -41,7 +41,7 @@ const adapter = createGeminiChat("gemini-3.8-flash", process.env.GEMINI_API_KEY!
 ```
 
 - `baseURL` sets `httpOptions.baseUrl`, and `defaultHeaders` sets `httpOptions.headers`. If you set both forms, `baseURL` and `defaultHeaders` win.
-- This adapter ignores [`wrapFetch`](../advanced/middleware#change-the-http-requests-of-a-call), because the `@google/genai` SDK does not take a custom fetch.
+- This adapter ignores [`wrapFetch`](../advanced/middleware#change-the-http-requests-of-a-call). To send the requests through your own `fetch`, set `httpOptions.fetch`. This option needs `@google/genai` 2.23.0 or later.
 
 ## Video understanding options
 

packages/ai-gemini/src/client/api.ts

@@ -71,6 +71,9 @@ export function usesVertexAI(options: GoogleGenAIOptions) {
   return flag?.toLowerCase() === 'true'
 }
 
+/** `HttpOptions` plus `fetch`, which the SDK 2.10.0 types do not have. */
+export type ClientHttpOptions = HttpOptions & { fetch?: typeof fetch }
+
 // Port of `ApiClient.patchHttpOptions`: an object value is merged one level
 // deep, any other defined value replaces the old one.
 function patchHttpOptions(base: HttpOptions, patch: HttpOptions) {
@@ -172,7 +175,7 @@ export function createApiClient(options: GoogleGenAIOptions) {
   const { apiKey } = options
   const baseUrl =
     options.httpOptions?.baseUrl ?? readEnv('GOOGLE_GEMINI_BASE_URL')
-  const clientHttpOptions = patchHttpOptions(
+  const clientHttpOptions: ClientHttpOptions = patchHttpOptions(
     {
       apiVersion: options.apiVersion ?? 'v1beta',
       baseUrl: DEFAULT_BASE_URL,
@@ -185,12 +188,15 @@ export function createApiClient(options: GoogleGenAIOptions) {
   // `retryOptions`, with the p-retry backoff (1 s, 2 s, 4 s, ...).
   const apiCall = async (url: string, init: RequestInit) => {
     const { retryOptions } = clientHttpOptions
-    if (!retryOptions) return fetch(url, init)
+    // ponytail: the client fetch only. Add a per-call fetch when a caller
+    // needs one.
+    const fetchFn = clientHttpOptions.fetch ?? fetch
+    if (!retryOptions) return fetchFn(url, init)
     const retries = (retryOptions.attempts ?? 5) - 1
     for (let attempt = 0; ; attempt++) {
       let error: unknown
       try {
-        const response = await fetch(url, init)
+        const response = await fetchFn(url, init)
         if (response.ok) return response
         if (!RETRY_STATUS_CODES.includes(response.status)) {
           throw new Error(

packages/ai-gemini/src/client/interactions.ts

@@ -2,7 +2,8 @@
 // the Gemini Developer API with an API key. Same URL, headers, body, retries,
 // response shape (`steps`, `output_text`, ...), and error fields.
 import { createHttpClient, parseSSE } from '@tanstack/ai-utils/http'
-import type { HttpOptions, Interactions } from '@google/genai'
+import type { Interactions } from '@google/genai'
+import type { ClientHttpOptions } from './api'
 
 type Interaction = Interactions.Interaction
 type InteractionSSEEvent = Interactions.InteractionSSEEvent
@@ -192,11 +193,12 @@ async function* readEvents(response: Response, signal?: AbortSignal | null) {
  */
 export function createInteractions(client: {
   apiKey: string
-  httpOptions: HttpOptions
+  httpOptions: ClientHttpOptions
 }) {
   const { apiKey, httpOptions } = client
   const http = createHttpClient({
     baseURL: (httpOptions.baseUrl ?? '').replace(/\/+$/, ''),
+    fetch: httpOptions.fetch,
     // The SDK sends its own default headers here, not `httpOptions.headers`.
     headers: {
       'Content-Type': 'application/json',

packages/ai-gemini/tests/custom-fetch-wire.test.ts

@@ -0,0 +1,62 @@
+import { afterEach, describe, expect, it, vi } from 'vitest'
+import { createGoogleGenAI } from '../src/client'
+import type { HttpOptions } from '@google/genai'
+
+// @google/genai 2.23.0 and later have `httpOptions.fetch`. The repo installs
+// 2.10.0, whose `HttpOptions` type does not have it yet.
+type HttpOptionsWithFetch = HttpOptions & { fetch: typeof fetch }
+
+/**
+ * A client whose `httpOptions.fetch` answers `body`. Global `fetch` answers a
+ * 400, which no client retries.
+ */
+function clientWithFetch(body: unknown) {
+  vi.stubGlobal(
+    'fetch',
+    vi.fn(() =>
+      Promise.resolve(
+        Response.json(
+          { error: { message: 'global fetch was called' } },
+          { status: 400 },
+        ),
+      ),
+    ),
+  )
+  const customFetch = vi.fn<typeof fetch>(() =>
+    Promise.resolve(Response.json(body)),
+  )
+  const httpOptions: HttpOptionsWithFetch = { fetch: customFetch }
+  const client = createGoogleGenAI({ apiKey: 'test-key', httpOptions })
+  return { client, customFetch }
+}
+
+afterEach(() => {
+  vi.unstubAllGlobals()
+})
+
+describe('httpOptions.fetch', () => {
+  it('sends models.generateContent through it', async () => {
+    const { client, customFetch } = clientWithFetch({ candidates: [] })
+
+    await client.models.generateContent({
+      model: 'gemini-2.5-flash',
+      contents: 'Hi',
+    })
+    // Per-call httpOptions are merged over the client options.
+    await client.models.generateContent({
+      model: 'gemini-2.5-flash',
+      contents: 'Hi',
+      config: { httpOptions: { headers: { 'x-call': '1' } } },
+    })
+
+    expect(customFetch).toHaveBeenCalledTimes(2)
+  })
+
+  it('sends interactions.create through it', async () => {
+    const { client, customFetch } = clientWithFetch({ id: 'int_1', steps: [] })
+
+    await client.interactions.create({ model: 'gemini-2.5-flash', input: 'Hi' })
+
+    expect(customFetch).toHaveBeenCalledOnce()
+  })
+})

testing/e2e/src/routeTree.gen.ts

@@ -105,6 +105,7 @@ import { Route as ApiFileSourceWireRouteImport } from './routes/api.file-source-
 import { Route as ApiForeignChunkEventsRouteImport } from './routes/api.foreign-chunk-events'
 import { Route as ApiForeignClientToolRouteImport } from './routes/api.foreign-client-tool'
 import { Route as ApiForeignInterruptRouteImport } from './routes/api.foreign-interrupt'
+import { Route as ApiGeminiCustomFetchWireRouteImport } from './routes/api.gemini-custom-fetch-wire'
 import { Route as ApiGeminiImageGaModelsRouteImport } from './routes/api.gemini-image-ga-models'
 import { Route as ApiGeminiNativeImageWireRouteImport } from './routes/api.gemini-native-image-wire'
 import { Route as ApiGeminiServerToolsWireRouteImport } from './routes/api.gemini-server-tools-wire'
@@ -723,6 +724,12 @@ const ApiForeignInterruptRoute = ApiForeignInterruptRouteImport.update({
   path: '/api/foreign-interrupt',
   getParentRoute: () => rootRouteImport,
 } as any)
+const ApiGeminiCustomFetchWireRoute =
+  ApiGeminiCustomFetchWireRouteImport.update({
+    id: '/api/gemini-custom-fetch-wire',
+    path: '/api/gemini-custom-fetch-wire',
+    getParentRoute: () => rootRouteImport,
+  } as any)
 const ApiGeminiImageGaModelsRoute = ApiGeminiImageGaModelsRouteImport.update({
   id: '/api/gemini-image-ga-models',
   path: '/api/gemini-image-ga-models',
@@ -1419,6 +1426,7 @@ export interface FileRoutesByFullPath {
   '/api/foreign-chunk-events': typeof ApiForeignChunkEventsRoute
   '/api/foreign-client-tool': typeof ApiForeignClientToolRoute
   '/api/foreign-interrupt': typeof ApiForeignInterruptRoute
+  '/api/gemini-custom-fetch-wire': typeof ApiGeminiCustomFetchWireRoute
   '/api/gemini-image-ga-models': typeof ApiGeminiImageGaModelsRoute
   '/api/gemini-native-image-wire': typeof ApiGeminiNativeImageWireRoute
   '/api/gemini-server-tools-wire': typeof ApiGeminiServerToolsWireRoute
@@ -1631,6 +1639,7 @@ export interface FileRoutesByTo {
   '/api/foreign-chunk-events': typeof ApiForeignChunkEventsRoute
   '/api/foreign-client-tool': typeof ApiForeignClientToolRoute
   '/api/foreign-interrupt': typeof ApiForeignInterruptRoute
+  '/api/gemini-custom-fetch-wire': typeof ApiGeminiCustomFetchWireRoute
   '/api/gemini-image-ga-models': typeof ApiGeminiImageGaModelsRoute
   '/api/gemini-native-image-wire': typeof ApiGeminiNativeImageWireRoute
   '/api/gemini-server-tools-wire': typeof ApiGeminiServerToolsWireRoute
@@ -1844,6 +1853,7 @@ export interface FileRoutesById {
   '/api/foreign-chunk-events': typeof ApiForeignChunkEventsRoute
   '/api/foreign-client-tool': typeof ApiForeignClientToolRoute
   '/api/foreign-interrupt': typeof ApiForeignInterruptRoute
+  '/api/gemini-custom-fetch-wire': typeof ApiGeminiCustomFetchWireRoute
   '/api/gemini-image-ga-models': typeof ApiGeminiImageGaModelsRoute
   '/api/gemini-native-image-wire': typeof ApiGeminiNativeImageWireRoute
   '/api/gemini-server-tools-wire': typeof ApiGeminiServerToolsWireRoute
@@ -2058,6 +2068,7 @@ export interface FileRouteTypes {
     | '/api/foreign-chunk-events'
     | '/api/foreign-client-tool'
     | '/api/foreign-interrupt'
+    | '/api/gemini-custom-fetch-wire'
     | '/api/gemini-image-ga-models'
     | '/api/gemini-native-image-wire'
     | '/api/gemini-server-tools-wire'
@@ -2270,6 +2281,7 @@ export interface FileRouteTypes {
     | '/api/foreign-chunk-events'
     | '/api/foreign-client-tool'
     | '/api/foreign-interrupt'
+    | '/api/gemini-custom-fetch-wire'
     | '/api/gemini-image-ga-models'
     | '/api/gemini-native-image-wire'
     | '/api/gemini-server-tools-wire'
@@ -2482,6 +2494,7 @@ export interface FileRouteTypes {
     | '/api/foreign-chunk-events'
     | '/api/foreign-client-tool'
     | '/api/foreign-interrupt'
+    | '/api/gemini-custom-fetch-wire'
     | '/api/gemini-image-ga-models'
     | '/api/gemini-native-image-wire'
     | '/api/gemini-server-tools-wire'
@@ -2695,6 +2708,7 @@ export interface RootRouteChildren {
   ApiForeignChunkEventsRoute: typeof ApiForeignChunkEventsRoute
   ApiForeignClientToolRoute: typeof ApiForeignClientToolRoute
   ApiForeignInterruptRoute: typeof ApiForeignInterruptRoute
+  ApiGeminiCustomFetchWireRoute: typeof ApiGeminiCustomFetchWireRoute
   ApiGeminiImageGaModelsRoute: typeof ApiGeminiImageGaModelsRoute
   ApiGeminiNativeImageWireRoute: typeof ApiGeminiNativeImageWireRoute
   ApiGeminiServerToolsWireRoute: typeof ApiGeminiServerToolsWireRoute
@@ -3481,6 +3495,13 @@ declare module '@tanstack/react-router' {
       preLoaderRoute: typeof ApiForeignInterruptRouteImport
       parentRoute: typeof rootRouteImport
     }
+    '/api/gemini-custom-fetch-wire': {
+      id: '/api/gemini-custom-fetch-wire'
+      path: '/api/gemini-custom-fetch-wire'
+      fullPath: '/api/gemini-custom-fetch-wire'
+      preLoaderRoute: typeof ApiGeminiCustomFetchWireRouteImport
+      parentRoute: typeof rootRouteImport
+    }
     '/api/gemini-image-ga-models': {
       id: '/api/gemini-image-ga-models'
       path: '/api/gemini-image-ga-models'
@@ -4441,6 +4462,7 @@ const rootRouteChildren: RootRouteChildren = {
   ApiForeignChunkEventsRoute: ApiForeignChunkEventsRoute,
   ApiForeignClientToolRoute: ApiForeignClientToolRoute,
   ApiForeignInterruptRoute: ApiForeignInterruptRoute,
+  ApiGeminiCustomFetchWireRoute: ApiGeminiCustomFetchWireRoute,
   ApiGeminiImageGaModelsRoute: ApiGeminiImageGaModelsRoute,
   ApiGeminiNativeImageWireRoute: ApiGeminiNativeImageWireRoute,
   ApiGeminiServerToolsWireRoute: ApiGeminiServerToolsWireRoute,

testing/e2e/src/routes/api.gemini-custom-fetch-wire.ts

@@ -0,0 +1,105 @@
+import { createFileRoute } from '@tanstack/react-router'
+import { chat, generateImage } from '@tanstack/ai'
+import { createGeminiChat, createGeminiImage } from '@tanstack/ai-gemini'
+import type { GeminiTextConfig } from '@tanstack/ai-gemini'
+
+// @google/genai 2.23.0 and later have `httpOptions.fetch`. The repo installs
+// 2.10.0, whose `HttpOptions` type does not have it yet.
+type HttpOptionsWithFetch = NonNullable<GeminiTextConfig['httpOptions']> & {
+  fetch: typeof fetch
+}
+
+const TINY_PNG_BASE64 =
+  'iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAQAAAC1HAwCAAAAC0lEQVR42mNkYAAAAAYAAjCB0C8AAAAASUVORK5CYII='
+
+/** A fake `fetch` that records each URL and answers like the Gemini API. */
+function fakeGeminiFetch() {
+  const urls: Array<string> = []
+  const fetch = (input: RequestInfo | URL) => {
+    const url = input instanceof Request ? input.url : String(input)
+    urls.push(url)
+    if (url.includes(':streamGenerateContent')) {
+      const chunk = {
+        candidates: [
+          {
+            content: { role: 'model', parts: [{ text: 'Hi from fetch.' }] },
+            finishReason: 'STOP',
+          },
+        ],
+      }
+      return Promise.resolve(
+        new Response(`data: ${JSON.stringify(chunk)}\n\n`, {
+          headers: { 'Content-Type': 'text/event-stream' },
+        }),
+      )
+    }
+    const image = {
+      type: 'image',
+      mime_type: 'image/png',
+      data: TINY_PNG_BASE64,
+    }
+    return Promise.resolve(
+      Response.json({
+        id: 'int_custom_fetch',
+        object: 'interaction',
+        status: 'completed',
+        steps: [{ type: 'model_output', content: [image] }],
+      }),
+    )
+  }
+  return { urls, fetch }
+}
+
+/**
+ * The real Gemini chat and image adapters with `httpOptions.fetch` set to a
+ * fake `fetch`. Returns the URLs that fetch got and the results. A request
+ * that goes to the global `fetch` instead fails, because `.invalid` never
+ * resolves.
+ */
+export const Route = createFileRoute('/api/gemini-custom-fetch-wire')({
+  server: {
+    handlers: {
+      POST: async () => {
+        try {
+          const wire = fakeGeminiFetch()
+          const httpOptions: HttpOptionsWithFetch = {
+            baseUrl: 'https://gemini.invalid',
+            fetch: wire.fetch,
+          }
+
+          let text = ''
+          for await (const chunk of chat({
+            threadId: 'gemini-custom-fetch-wire',
+            adapter: createGeminiChat('gemini-2.5-flash', 'e2e-key', {
+              httpOptions,
+            }),
+            messages: [{ role: 'user', content: 'Hi' }],
+          })) {
+            if (chunk.type === 'TEXT_MESSAGE_CONTENT') text += chunk.delta
+          }
+
+          const image = await generateImage({
+            threadId: 'gemini-custom-fetch-wire',
+            adapter: createGeminiImage('gemini-3.1-flash-image', 'e2e-key', {
+              httpOptions,
+            }),
+            prompt: 'a guitar',
+            stream: false,
+          })
+
+          return Response.json({
+            ok: true,
+            text,
+            images: image.images.length,
+            urls: wire.urls,
+          })
+        } catch (error) {
+          return Response.json({
+            ok: false,
+            error: error instanceof Error ? error.message : String(error),
+          })
+        }
+      },
+    },
+  },
+})

testing/e2e/tests/gemini-custom-fetch-wire.spec.ts

@@ -0,0 +1,33 @@
+import { test, expect } from './fixtures'
+
+/**
+ * `/api/gemini-custom-fetch-wire` runs the real Gemini chat and image
+ * adapters with `httpOptions.fetch` set to a fake `fetch`, and returns the
+ * URLs that fetch got. The base URL is `https://gemini.invalid`, so a request
+ * sent with the global `fetch` instead fails and never reaches the fake.
+ */
+test.describe('gemini -- httpOptions.fetch', () => {
+  test('chat and image requests go through the custom fetch', async ({
+    request,
+  }) => {
+    const response = await request.post('/api/gemini-custom-fetch-wire')
+    expect(response.ok()).toBe(true)
+    const result: {
+      ok: boolean
+      error?: string
+      text?: string
+      images?: number
+      urls?: Array<string>
+    } = await response.json()
+    if (!result.ok) throw new Error(`Route failed: ${result.error}`)
+
+    expect(result.text).toBe('Hi from fetch.')
+    expect(result.images).toBe(1)
+    expect(result.urls).toEqual([
+      expect.stringContaining(
+        '/v1beta/models/gemini-2.5-flash:streamGenerateContent',
+      ),
+      expect.stringContaining('/v1beta/interactions'),
+    ])
+  })
+})