feat(workers-ai-provider): add custom fetch option for credentials mode

.changeset/add-custom-fetch.md

@@ -0,0 +1,5 @@
+---
+"workers-ai-provider": patch
+---
+
+Add optional `fetch` parameter to credentials mode for request interception and testing. Available when using `accountId + apiKey` (not with bindings). Matches the pattern used by `@ai-sdk/openai` and `@ai-sdk/anthropic`.

demos/mcp-server-bearer-auth/src/utils.ts

@@ -314,8 +314,8 @@ export const renderApproveContent = async (
 		<div class="max-w-md mx-auto bg-white p-8 rounded-lg shadow-md text-center">
 			<div class="mb-4">
 				<span class="inline-block p-3 ${status === "success"
-																									? "bg-green-100 text-green-800"
-																									: "bg-red-100 text-red-800"} rounded-full">
+																											? "bg-green-100 text-green-800"
+																											: "bg-red-100 text-red-800"} rounded-full">
 					${status === "success" ? "✓" : "✗"}
 				</span>
 			</div>

demos/remote-mcp-cf-access/src/access-handler.ts

@@ -117,7 +117,11 @@ export async function handleAccessRequest(
 		let codeVerifier: string;
 
 		try {
-			const result = await validateOAuthState(request, env.OAUTH_KV, env.COOKIE_ENCRYPTION_KEY);
+			const result = await validateOAuthState(
+				request,
+				env.OAUTH_KV,
+				env.COOKIE_ENCRYPTION_KEY,
+			);
 			oauthReqInfo = result.oauthReqInfo;
 			codeVerifier = result.codeVerifier;
 		} catch (error: any) {

demos/remote-mcp-cf-access/src/workers-oauth-utils.ts

@@ -751,7 +751,6 @@ async function generatePKCE(): Promise<{ codeVerifier: string; codeChallenge: st
 	return { codeVerifier, codeChallenge };
 }
 
-
 async function getApprovedClientsFromCookie(
 	request: Request,
 	cookieSecret: string,

demos/remote-mcp-server-autorag/src/utils.ts

@@ -314,8 +314,8 @@ export const renderApproveContent = async (
 		<div class="max-w-md mx-auto bg-white p-8 rounded-lg shadow-md text-center">
 			<div class="mb-4">
 				<span class="inline-block p-3 ${status === "success"
-																									? "bg-green-100 text-green-800"
-																									: "bg-red-100 text-red-800"} rounded-full">
+																											? "bg-green-100 text-green-800"
+																											: "bg-red-100 text-red-800"} rounded-full">
 					${status === "success" ? "✓" : "✗"}
 				</span>
 			</div>

demos/remote-mcp-server/src/utils.ts

@@ -314,8 +314,8 @@ export const renderApproveContent = async (
 		<div class="max-w-md mx-auto bg-white p-8 rounded-lg shadow-md text-center">
 			<div class="mb-4">
 				<span class="inline-block p-3 ${status === "success"
-																									? "bg-green-100 text-green-800"
-																									: "bg-red-100 text-red-800"} rounded-full">
+																											? "bg-green-100 text-green-800"
+																											: "bg-red-100 text-red-800"} rounded-full">
 					${status === "success" ? "✓" : "✗"}
 				</span>
 			</div>

packages/workers-ai-provider/src/index.ts

@@ -67,6 +67,13 @@ export type WorkersAISettings = (
 			 * Both binding must be absent if credentials are used directly.
 			 */
 			binding?: never;
+
+			/**
+			 * Custom fetch implementation. You can use it as a middleware to
+			 * intercept requests, or to provide a custom fetch implementation
+			 * for e.g. testing. Only available in credentials mode.
+			 */
+			fetch?: typeof globalThis.fetch;
 	  }
 ) & {
 	/**
@@ -159,7 +166,7 @@ export function createWorkersAI(options: WorkersAISettings): WorkersAI {
 	} else {
 		const { accountId, apiKey } = options;
 		binding = {
-			run: createRun({ accountId, apiKey }),
+			run: createRun({ accountId, apiKey, fetch: options.fetch }),
 		} as Ai;
 	}
 

packages/workers-ai-provider/src/utils.ts

@@ -60,6 +60,8 @@ export interface CreateRunConfig {
 	accountId: string;
 	/** Cloudflare API token/key with appropriate permissions. */
 	apiKey: string;
+	/** Custom fetch implementation for intercepting requests. */
+	fetch?: typeof globalThis.fetch;
 }
 
 /**
@@ -68,6 +70,7 @@ export interface CreateRunConfig {
  */
 export function createRun(config: CreateRunConfig): AiRun {
 	const { accountId, apiKey } = config;
+	const fetchFn = config.fetch ?? globalThis.fetch;
 
 	return async function run<Name extends keyof AiModels>(
 		model: Name,
@@ -141,7 +144,7 @@ export function createRun(config: CreateRunConfig): AiRun {
 
 		const body = JSON.stringify(inputs);
 
-		const response = await fetch(url, {
+		const response = await fetchFn(url, {
 			body,
 			headers,
 			method: "POST",
@@ -180,7 +183,7 @@ export function createRun(config: CreateRunConfig): AiRun {
 			// Retry without streaming so doStream's graceful degradation path can
 			// wrap the complete response as a synthetic stream.
 			// Use the same URL (gateway or direct) as the original request.
-			const retryResponse = await fetch(url, {
+			const retryResponse = await fetchFn(url, {
 				body: JSON.stringify({
 					...(inputs as Record<string, unknown>),
 					stream: false,

packages/workers-ai-provider/test/utils.test.ts

@@ -639,4 +639,53 @@ describe("createRun", () => {
 			}),
 		);
 	});
+
+	it("should use custom fetch when provided", async () => {
+		const customFetch = vi.fn().mockResolvedValue({
+			ok: true,
+			json: vi.fn().mockResolvedValue({ result: { response: "Hello" } }),
+			headers: new Headers({ "content-type": "application/json" }),
+		});
+
+		const run = createRun({
+			accountId: "test-account",
+			apiKey: "test-key",
+			fetch: customFetch as typeof globalThis.fetch,
+		});
+		await run("@cf/meta/llama-3.1-8b-instruct" as any, { prompt: "Hi" });
+
+		expect(customFetch).toHaveBeenCalledWith(
+			"https://api.cloudflare.com/client/v4/accounts/test-account/ai/run/@cf/meta/llama-3.1-8b-instruct",
+			expect.objectContaining({ method: "POST" }),
+		);
+		expect(globalThis.fetch).not.toHaveBeenCalled();
+	});
+
+	it("should use custom fetch for streaming retry fallback", async () => {
+		const customFetch = vi
+			.fn()
+			// First call: streaming request returns JSON instead of SSE (triggers retry)
+			.mockResolvedValueOnce({
+				ok: true,
+				headers: new Headers({ "content-type": "application/json" }),
+				body: null,
+				json: vi.fn().mockResolvedValue({ result: { response: "" } }),
+			})
+			// Second call: non-streaming retry
+			.mockResolvedValueOnce({
+				ok: true,
+				headers: new Headers({ "content-type": "application/json" }),
+				json: vi.fn().mockResolvedValue({ result: { response: "Hello" } }),
+			});
+
+		const run = createRun({
+			accountId: "test-account",
+			apiKey: "test-key",
+			fetch: customFetch as typeof globalThis.fetch,
+		});
+		await run("@cf/meta/llama-3.1-8b-instruct" as any, { prompt: "Hi", stream: true } as any);
+
+		expect(customFetch).toHaveBeenCalledTimes(2);
+		expect(globalThis.fetch).not.toHaveBeenCalled();
+	});
 });