From b368ab9da07aac3f172aa22afbec175cf3fde030 Mon Sep 17 00:00:00 2001
From: Danil Valov <danilvalov@gmail.com>
Date: Sat, 27 Dec 2025 14:32:21 +0300
Subject: [PATCH] feat: Add support for Fetch Implementation

---
 api-report/genai-node.api.md |  1 +
 api-report/genai-web.api.md  |  1 +
 api-report/genai.api.md      |  1 +
 src/_api_client.ts           | 12 +++++++++++-
 src/client.ts                |  8 ++++++++
 src/node/node_client.ts      |  1 +
 src/web/web_client.ts        |  1 +
 7 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/api-report/genai-node.api.md b/api-report/genai-node.api.md
index bac11aebb..5f21bb54d 100644
--- a/api-report/genai-node.api.md
+++ b/api-report/genai-node.api.md
@@ -1624,6 +1624,7 @@ export class GoogleGenAI {
 export interface GoogleGenAIOptions {
     apiKey?: string;
     apiVersion?: string;
+    fetchImplementation?: typeof fetch;
     googleAuthOptions?: GoogleAuthOptions;
     httpOptions?: HttpOptions;
     location?: string;
diff --git a/api-report/genai-web.api.md b/api-report/genai-web.api.md
index bac11aebb..5f21bb54d 100644
--- a/api-report/genai-web.api.md
+++ b/api-report/genai-web.api.md
@@ -1624,6 +1624,7 @@ export class GoogleGenAI {
 export interface GoogleGenAIOptions {
     apiKey?: string;
     apiVersion?: string;
+    fetchImplementation?: typeof fetch;
     googleAuthOptions?: GoogleAuthOptions;
     httpOptions?: HttpOptions;
     location?: string;
diff --git a/api-report/genai.api.md b/api-report/genai.api.md
index bac11aebb..5f21bb54d 100644
--- a/api-report/genai.api.md
+++ b/api-report/genai.api.md
@@ -1624,6 +1624,7 @@ export class GoogleGenAI {
 export interface GoogleGenAIOptions {
     apiKey?: string;
     apiVersion?: string;
+    fetchImplementation?: typeof fetch;
     googleAuthOptions?: GoogleAuthOptions;
     httpOptions?: HttpOptions;
     location?: string;
diff --git a/src/_api_client.ts b/src/_api_client.ts
index fe4b2cbe1..bec294ad8 100644
--- a/src/_api_client.ts
+++ b/src/_api_client.ts
@@ -78,6 +78,13 @@ export interface ApiClientInitOptions {
    * This can be used to e.g specify the runtime and its version.
    */
   userAgentExtra?: string;
+  /**
+   * Optional. A custom fetch implementation to use for all HTTP requests made by the SDK.
+   *
+   * @remarks
+   * If unset, the SDK will use the default `fetch` implementation available in the runtime environment.
+   */
+  fetchImplementation?: typeof fetch;
 }
 
 /**
@@ -630,7 +637,10 @@ export class ApiClient implements GeminiNextGenAPIClientAdapter {
     url: string,
     requestInit: RequestInit,
   ): Promise<Response> {
-    return fetch(url, requestInit).catch((e) => {
+    return (this.clientOptions.fetchImplementation || fetch)(
+      url,
+      requestInit,
+    ).catch((e) => {
       throw new Error(`exception ${e} sending request`);
     });
   }
diff --git a/src/client.ts b/src/client.ts
index c3987cdeb..d550b9c13 100644
--- a/src/client.ts
+++ b/src/client.ts
@@ -89,6 +89,13 @@ export interface GoogleGenAIOptions {
    * Optional. A set of customizable configuration for HTTP requests.
    */
   httpOptions?: HttpOptions;
+  /**
+   * Optional. A custom fetch implementation to use for all HTTP requests made by the SDK.
+   *
+   * @remarks
+   * If unset, the SDK will use the default `fetch` implementation available in the runtime environment.
+   */
+  fetchImplementation?: typeof fetch;
 }
 
 /**
@@ -197,6 +204,7 @@ export class GoogleGenAI {
       userAgentExtra: LANGUAGE_LABEL_PREFIX + 'cross',
       uploader: new CrossUploader(),
       downloader: new CrossDownloader(),
+      fetchImplementation: options.fetchImplementation,
     });
     this.models = new Models(this.apiClient);
     this.live = new Live(this.apiClient, auth, new CrossWebSocketFactory());
diff --git a/src/node/node_client.ts b/src/node/node_client.ts
index f03218244..903b24fbe 100644
--- a/src/node/node_client.ts
+++ b/src/node/node_client.ts
@@ -210,6 +210,7 @@ export class GoogleGenAI {
       userAgentExtra: LANGUAGE_LABEL_PREFIX + process.version,
       uploader: new NodeUploader(),
       downloader: new NodeDownloader(),
+      fetchImplementation: options.fetchImplementation,
     });
     this.models = new Models(this.apiClient);
     this.live = new Live(this.apiClient, auth, new NodeWebSocketFactory());
diff --git a/src/web/web_client.ts b/src/web/web_client.ts
index b3ac1a914..63547625f 100644
--- a/src/web/web_client.ts
+++ b/src/web/web_client.ts
@@ -151,6 +151,7 @@ export class GoogleGenAI {
       userAgentExtra: LANGUAGE_LABEL_PREFIX + 'web',
       uploader: new BrowserUploader(),
       downloader: new BrowserDownloader(),
+      fetchImplementation: options.fetchImplementation,
     });
     this.models = new Models(this.apiClient);
     this.live = new Live(this.apiClient, auth, new BrowserWebSocketFactory());