fix(ai): retry transient provider errors in Google adapters (#7471)

The google-vertex and google-generative-ai adapters called
client.models.generateContentStream bare, so a transient 429/5xx before
the first token became a terminal errored assistant message instead of
being retried like in the Anthropic, OpenAI, Azure, and OpenRouter
adapters. Wrap the initial request in the shared retryProviderRequest
via a new retryGoogleRequest helper that also normalizes @google/genai's
ApiError, which has a status property but no headers property, so
retryProviderRequest's provider-error guard recognizes it.

Opt-in via the existing maxRetries stream option; default behavior is
unchanged.

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

packages/ai/src/api/google-generative-ai.ts

@@ -32,6 +32,7 @@ import {
 	mapStopReason,
 	resolveGoogleFunctionCallingMode,
 	retainThoughtSignature,
+	retryGoogleRequest,
 	supportsGoogleStrictToolSampling,
 } from "./google-shared.ts";
 import { buildBaseOptions } from "./simple-options.ts";
@@ -88,7 +89,7 @@ export const stream: StreamFunction<"google-generative-ai", GoogleOptions> = (
 			if (nextParams !== undefined) {
 				params = nextParams as GenerateContentParameters;
 			}
-			const googleStream = await client.models.generateContentStream(params);
+			const googleStream = await retryGoogleRequest(() => client.models.generateContentStream(params), options);
 
 			stream.push({ type: "start", partial: output });
 			let currentBlock: TextContent | ThinkingContent | null = null;

packages/ai/src/api/google-shared.ts

@@ -3,7 +3,8 @@
  */
 
 import { type Content, FinishReason, FunctionCallingConfigMode, type Part } from "@google/genai";
-import type { Context, ImageContent, Model, StopReason, TextContent, Tool } from "../types.ts";
+import type { Context, ImageContent, Model, StopReason, StreamOptions, TextContent, Tool } from "../types.ts";
+import { retryProviderRequest } from "../utils/provider-retry.ts";
 import { sanitizeSurrogates } from "../utils/sanitize-unicode.ts";
 import { resolveJsonSchemaStrictSampling } from "./constrained-sampling.ts";
 import { transformMessages } from "./transform-messages.ts";
@@ -374,3 +375,35 @@ export function mapStopReasonString(reason: string): StopReason {
 			return "error";
 	}
 }
+
+/**
+ * Run a Google GenAI SDK request with the shared provider retry policy
+ * (408/409/429/5xx with backoff, honoring retry-after), mirroring how the
+ * Anthropic and OpenAI adapters wrap their initial request in
+ * retryProviderRequest. The SDK's ApiError has a `status` property but no
+ * `headers` property, and retryProviderRequest only retries errors that carry
+ * both, so normalize the error by adding the missing `headers` before
+ * rethrowing.
+ */
+export function retryGoogleRequest<T>(
+	request: () => Promise<T>,
+	options?: Pick<StreamOptions, "maxRetries" | "maxRetryDelayMs" | "signal">,
+): Promise<T> {
+	return retryProviderRequest(
+		async () => {
+			try {
+				return await request();
+			} catch (error) {
+				if (error instanceof Error && "status" in error && !("headers" in error)) {
+					(error as { headers?: Headers }).headers = undefined;
+				}
+				throw error;
+			}
+		},
+		{
+			maxRetries: options?.maxRetries,
+			maxRetryDelayMs: options?.maxRetryDelayMs,
+			signal: options?.signal,
+		},
+	);
+}

packages/ai/src/api/google-vertex.ts

@@ -37,6 +37,7 @@ import {
 	mapStopReason,
 	resolveGoogleFunctionCallingMode,
 	retainThoughtSignature,
+	retryGoogleRequest,
 	supportsGoogleStrictToolSampling,
 } from "./google-shared.ts";
 import { buildBaseOptions } from "./simple-options.ts";
@@ -106,7 +107,7 @@ export const stream: StreamFunction<"google-vertex", GoogleVertexOptions> = (
 			if (nextParams !== undefined) {
 				params = nextParams as GenerateContentParameters;
 			}
-			const googleStream = await client.models.generateContentStream(params);
+			const googleStream = await retryGoogleRequest(() => client.models.generateContentStream(params), options);
 
 			stream.push({ type: "start", partial: output });
 			let currentBlock: TextContent | ThinkingContent | null = null;

packages/ai/test/google-shared-retry.test.ts

@@ -0,0 +1,40 @@
+import { afterEach, describe, expect, it, vi } from "vitest";
+import { retryGoogleRequest } from "../src/api/google-shared.ts";
+
+/** Shaped like @google/genai's ApiError: has `status`, but no `headers`. */
+function googleApiError(status: number): Error {
+	return Object.assign(new Error(`got status: ${status}`), { status });
+}
+
+describe("google request retries", () => {
+	afterEach(() => {
+		vi.useRealTimers();
+	});
+
+	it("retries a headers-less SDK error with a retryable status", async () => {
+		vi.useFakeTimers();
+		const request = vi.fn<() => Promise<string>>().mockRejectedValueOnce(googleApiError(429)).mockResolvedValue("ok");
+
+		const result = retryGoogleRequest(request, { maxRetries: 1 });
+		await vi.advanceTimersByTimeAsync(500);
+
+		await expect(result).resolves.toBe("ok");
+		expect(request).toHaveBeenCalledTimes(2);
+	});
+
+	it("does not retry when maxRetries is unset", async () => {
+		const error = googleApiError(429);
+		const request = vi.fn<() => Promise<string>>().mockRejectedValue(error);
+
+		await expect(retryGoogleRequest(request)).rejects.toBe(error);
+		expect(request).toHaveBeenCalledTimes(1);
+	});
+
+	it("does not retry a non-retryable status", async () => {
+		const error = googleApiError(400);
+		const request = vi.fn<() => Promise<string>>().mockRejectedValue(error);
+
+		await expect(retryGoogleRequest(request, { maxRetries: 2 })).rejects.toBe(error);
+		expect(request).toHaveBeenCalledTimes(1);
+	});
+});