diff --git a/packages/ai/CHANGELOG.md b/packages/ai/CHANGELOG.md
index 0e3af1a2d..02c36dea5 100644
--- a/packages/ai/CHANGELOG.md
+++ b/packages/ai/CHANGELOG.md
@@ -6,6 +6,10 @@
 
 - Fixed API-key `/login` providers replacing sibling credentials instead of appending new keys for the same provider. ([#3265](https://github.com/can1357/oh-my-pi/issues/3265))
 
+### Fixed
+
+- Fixed OpenAI Codex OAuth account rotation for quota failures that surface as bare HTTP 429 or `insufficient_quota`, so pre-content failures temporarily block only the exhausted credential and retry a healthy sibling. The 429 status-only fallback applies only to absent/opaque bodies; informative transient bodies (`Too many requests`, `Service overloaded 529`, `Please retry in 5s`, …) defer to `parseRateLimitReason` and stay in the provider's own backoff layer instead of burning sibling credentials. ([#3231](https://github.com/can1357/oh-my-pi/issues/3231))
+
 ## [16.1.14] - 2026-06-22
 
 ### Added
diff --git a/packages/ai/src/auth-gateway/server.ts b/packages/ai/src/auth-gateway/server.ts
index e41f91884..2003726ae 100644
--- a/packages/ai/src/auth-gateway/server.ts
+++ b/packages/ai/src/auth-gateway/server.ts
@@ -19,14 +19,14 @@
  */
 
 import { Effort } from "@oh-my-pi/pi-catalog/effort";
-import { extractRetryHint, logger } from "@oh-my-pi/pi-utils";
+import { extractHttpStatusFromError, extractRetryHint, logger } from "@oh-my-pi/pi-utils";
 import type { ApiKeyResolver } from "../auth-retry";
 import type { AuthStorage } from "../auth-storage";
 import * as anthropicMessages from "../providers/anthropic-messages-server";
 import * as openaiChat from "../providers/openai-chat-server";
 import * as openaiResponses from "../providers/openai-responses-server";
 import * as piNative from "../providers/pi-native-server";
-import { isUsageLimitError } from "../rate-limit-utils";
+import { isUsageLimitError, isUsageLimitOutcome } from "../rate-limit-utils";
 import { streamSimple } from "../stream";
 import type { Api, AssistantMessageEventStream, Context, Model, SimpleStreamOptions } from "../types";
 import { deterministicUuid } from "../utils/deterministic-id";
@@ -315,7 +315,7 @@ async function refreshGatewayApiKeyAfterAuthError(
 	peer: string,
 ): Promise<string | undefined> {
 	const message = error instanceof Error ? error.message : String(error);
-	if (isUsageLimitError(message)) {
+	if (isUsageLimitOutcome(extractHttpStatusFromError(error), message)) {
 		const retryAfterMs = extractRetryHint(undefined, message);
 		const { switched, retryAtMs } = await storage.markUsageLimitReached(provider, sessionId, {
 			retryAfterMs,
diff --git a/packages/ai/src/auth-retry.ts b/packages/ai/src/auth-retry.ts
index 12bc14cc7..d4a45bf87 100644
--- a/packages/ai/src/auth-retry.ts
+++ b/packages/ai/src/auth-retry.ts
@@ -1,6 +1,6 @@
 import { extractHttpStatusFromError } from "@oh-my-pi/pi-utils";
 import type { OAuthAccess } from "./auth-storage";
-import { isUsageLimitError } from "./rate-limit-utils";
+import { isUsageLimitOutcome } from "./rate-limit-utils";
 
 /**
  * Context passed to an {@link ApiKeyResolver} on each resolution attempt.
@@ -72,15 +72,20 @@ export function seedApiKeyResolver(seed: string | undefined, resolver: ApiKeyRes
 
 /**
  * Classifies whether an error should trigger a credential refresh/rotation
- * retry: a hard `401`, or a rotatable usage-limit ("usage_limit_reached",
- * Codex's "you have hit your ChatGPT usage limit", etc.).
+ * retry: a hard `401`, body-classified usage limit (Codex
+ * `usage_limit_reached`, Anthropic account rate-limit, Google
+ * `resource_exhausted`, OpenAI `insufficient_quota`, …), or a bare `429`
+ * whose payload did not preserve a richer quota code. Transient 429s
+ * (`Too many requests`, per-minute caps) classify as `RATE_LIMIT_EXCEEDED`
+ * via {@link parseRateLimitReason} and stay in the upstream-backoff lane.
  */
 export function isAuthRetryableError(error: unknown): boolean {
-	if (extractHttpStatusFromError(error) === 401) return true;
+	const status = extractHttpStatusFromError(error);
+	if (status === 401) return true;
 	const message = error instanceof Error ? error.message : typeof error === "string" ? error : undefined;
-	if (!message) return false;
-	if (extractHttpStatusFromError({ message }) === 401) return true;
-	return isUsageLimitError(message);
+	const embeddedStatus = message ? extractHttpStatusFromError({ message }) : undefined;
+	if (embeddedStatus === 401) return true;
+	return isUsageLimitOutcome(status ?? embeddedStatus, message);
 }
 
 /**
diff --git a/packages/ai/src/auth-storage.ts b/packages/ai/src/auth-storage.ts
index 7ecf412ad..45a909167 100644
--- a/packages/ai/src/auth-storage.ts
+++ b/packages/ai/src/auth-storage.ts
@@ -10,9 +10,9 @@
 import { Database, type Statement } from "bun:sqlite";
 import * as fs from "node:fs/promises";
 import * as path from "node:path";
-import { getAgentDbPath, logger } from "@oh-my-pi/pi-utils";
+import { extractHttpStatusFromError, getAgentDbPath, logger } from "@oh-my-pi/pi-utils";
 import type { ApiKeyResolver } from "./auth-retry";
-import { isUsageLimitError } from "./rate-limit-utils";
+import { isUsageLimitOutcome } from "./rate-limit-utils";
 import { getProviderDefinition } from "./registry";
 import { getOAuthApiKey, getOAuthProvider, refreshOAuthToken } from "./registry/oauth";
 import type { OAuthController, OAuthCredentials, OAuthProvider, OAuthProviderId } from "./registry/oauth/types";
@@ -4084,8 +4084,9 @@ export class AuthStorage {
 		if (!sessionCredential) return false;
 
 		const error = options?.error;
+		const status = extractHttpStatusFromError(error);
 		const message = error instanceof Error ? error.message : typeof error === "string" ? error : undefined;
-		if (message && isUsageLimitError(message)) {
+		if (isUsageLimitOutcome(status, message)) {
 			return (
 				await this.markUsageLimitReached(provider, sessionId, {
 					modelId: options?.modelId,
diff --git a/packages/ai/src/rate-limit-utils.ts b/packages/ai/src/rate-limit-utils.ts
index fed913b47..b2772cec1 100644
--- a/packages/ai/src/rate-limit-utils.ts
+++ b/packages/ai/src/rate-limit-utils.ts
@@ -100,7 +100,55 @@ export function calculateRateLimitBackoffMs(reason: RateLimitReason): number {
 
 /** Detect usage/quota limit errors in error messages (persistent, requires credential switch). */
 const USAGE_LIMIT_PATTERN =
-	/usage.?limit|usage_limit_reached|usage_not_included|limit_reached|quota.?exceeded|quota.?reached|resource.?exhausted|exhausted your capacity|quota will reset|insufficient.?balance/i;
+	/usage.?limit|usage_limit_reached|usage_not_included|limit_reached|quota.?exceeded|quota.?reached|resource.?exhausted|exhausted your capacity|quota will reset|insufficient.?(?:balance|quota)/i;
+
+/**
+ * HTTP status codes that, absent richer body classification, represent an
+ * account-local usage cap rather than a bad credential or a transient blip.
+ * Always combine with {@link isUsageLimitOutcome} when a message is available
+ * — a 429 carrying transient rate-limit wording is NOT a usage cap.
+ */
+export function isUsageLimitStatus(status: number | undefined): boolean {
+	return status === 429;
+}
+
+/**
+ * Returns true for failures that should burn one credential and rotate to a
+ * sibling account. Decision tree:
+ *
+ *  1. Body matches {@link isUsageLimitError} (Codex `usage_limit_reached`,
+ *     Anthropic account rate-limit, Google `resource_exhausted`, OpenAI
+ *     `insufficient_quota`, …) → rotate.
+ *  2. Status is not 429 → backoff (caller's domain).
+ *  3. Body is absent or {@link isOpaqueStatusBody opaque} (just the status,
+ *     empty JSON, HTTP framing only) → rotate conservatively: the server
+ *     gave us nothing else to go on.
+ *  4. Body has content → defer to {@link parseRateLimitReason}. Only
+ *     `QUOTA_EXHAUSTED` rotates; `RATE_LIMIT_EXCEEDED` (`Too many requests`,
+ *     per-minute caps), `MODEL_CAPACITY_EXHAUSTED` (`Service overloaded`),
+ *     `SERVER_ERROR`, and `UNKNOWN` (`Please retry in 5s`) stay in the
+ *     provider's own backoff layer so transient 429s don't burn sibling
+ *     credentials.
+ */
+export function isUsageLimitOutcome(status: number | undefined, message: string | undefined): boolean {
+	if (message && isUsageLimitError(message)) return true;
+	if (!isUsageLimitStatus(status)) return false;
+	if (!message || isOpaqueStatusBody(message)) return true;
+	return parseRateLimitReason(message) === "QUOTA_EXHAUSTED";
+}
+
+/**
+ * A 429 body is opaque when it carries no signal beyond the status itself —
+ * empty, whitespace-only, the status digits with HTTP/JSON framing, or
+ * generic punctuation. Anything else (retry hints, capacity wording, error
+ * descriptions) is informative enough to defer to the classifier.
+ */
+function isOpaqueStatusBody(message: string): boolean {
+	const cleaned = message
+		.replace(/\b429\b/g, "")
+		.replace(/\b(?:http|https|status|error|code|response|message)\b/gi, "");
+	return !/[a-z\d]{3,}/i.test(cleaned);
+}
 
 export function isUsageLimitError(errorMessage: string): boolean {
 	return USAGE_LIMIT_PATTERN.test(errorMessage) || ACCOUNT_RATE_LIMIT_PATTERN.test(errorMessage);
diff --git a/packages/ai/src/stream.ts b/packages/ai/src/stream.ts
index 2dce95b30..14ff913ac 100644
--- a/packages/ai/src/stream.ts
+++ b/packages/ai/src/stream.ts
@@ -48,7 +48,7 @@ import {
 	streamOpenAIResponses,
 } from "./providers/register-builtins";
 import { isSyntheticModel, streamSynthetic } from "./providers/synthetic";
-import { isUsageLimitError } from "./rate-limit-utils";
+import { isUsageLimitOutcome } from "./rate-limit-utils";
 import { PROVIDER_REGISTRY } from "./registry";
 import type {
 	Api,
@@ -384,13 +384,18 @@ function extractStatusFromAssistantError(message: AssistantMessage): number | un
 function isRetryableUpstreamError(error: unknown, status: number | undefined, message: string | undefined): boolean {
 	// 401 means the credential is bad. Usage-limit phrasing (Codex's
 	// "You have hit your ChatGPT usage limit", Anthropic's "usage_limit_reached",
-	// Google's "resource_exhausted") means this account is parked but a
-	// sibling credential can usually pick the request up. Both are
-	// rotatable via `onAuthError` — the auth-gateway maps the former to
-	// `invalidateCredentialMatching` and the latter to `markUsageLimitReached`.
+	// Google's "resource_exhausted", OpenAI's "insufficient_quota") and 429s
+	// without transient rate-limit wording mean this account is parked but a
+	// sibling credential can usually pick the request up. Both are rotatable
+	// via `onAuthError` — the auth-gateway maps the former to
+	// `invalidateCredentialMatching` and the latter to
+	// `markUsageLimitReached`. Transient 429s ("Too many requests",
+	// per-minute caps) classify as RATE_LIMIT_EXCEEDED in
+	// `parseRateLimitReason` and stay in the provider's own backoff layer
+	// instead of burning siblings.
 	if (status === 401) return true;
 	void error;
-	return !!message && isUsageLimitError(message);
+	return isUsageLimitOutcome(status, message);
 }
 
 function createAssistantAuthError(message: AssistantMessage): Error {
diff --git a/packages/ai/test/auth-storage-codex-selection.test.ts b/packages/ai/test/auth-storage-codex-selection.test.ts
index e98fd6443..2f61b1ac6 100644
--- a/packages/ai/test/auth-storage-codex-selection.test.ts
+++ b/packages/ai/test/auth-storage-codex-selection.test.ts
@@ -267,6 +267,59 @@ describe("AuthStorage codex oauth ranking", () => {
 		expect(apiKey).toBe("api-acct-healthy");
 	});
 
+	test("temporarily blocks only the exhausted Codex OAuth credential after a quota 429", async () => {
+		if (!authStorage) throw new Error("test setup failed");
+
+		await authStorage.set("openai-codex", [
+			{ type: "oauth", ...createCredential("acct-A", "a@example.com") },
+			{ type: "oauth", ...createCredential("acct-B", "b@example.com") },
+		]);
+		usageByAccount.set(
+			"acct-A",
+			createCodexUsageReport({
+				accountId: "acct-A",
+				primary: { usedFraction: 0.1, resetInMs: HOUR_MS },
+				secondary: { usedFraction: 0.1, resetInMs: WEEK_MS },
+			}),
+		);
+		usageByAccount.set(
+			"acct-B",
+			createCodexUsageReport({
+				accountId: "acct-B",
+				primary: { usedFraction: 0.1, resetInMs: HOUR_MS },
+				secondary: { usedFraction: 0.1, resetInMs: WEEK_MS },
+			}),
+		);
+
+		const sessionId = "session-codex-quota-429";
+		const firstKey = await authStorage.getApiKey("openai-codex", sessionId);
+		if (!firstKey) throw new Error("expected initial Codex credential");
+		const exhaustedAccount = firstKey.replace(/^api-/, "");
+		const healthyAccount = exhaustedAccount === "acct-A" ? "acct-B" : "acct-A";
+		usageByAccount.set(
+			exhaustedAccount,
+			createCodexUsageReport({
+				accountId: exhaustedAccount,
+				primary: { usedFraction: 1, resetInMs: 5 * 60 * 1000 },
+				secondary: { usedFraction: 1, resetInMs: 5 * 60 * 1000 },
+			}),
+		);
+
+		const usageLimitSpy = vi.spyOn(authStorage, "markUsageLimitReached");
+		const switched = await authStorage.rotateSessionCredential("openai-codex", sessionId, {
+			error: Object.assign(new Error("insufficient_quota"), { status: 429 }),
+		});
+
+		expect(switched).toBe(true);
+		expect(usageLimitSpy).toHaveBeenCalledTimes(1);
+		expect(await authStorage.getApiKey("openai-codex", sessionId)).toBe(`api-${healthyAccount}`);
+		const activeAccounts = (await authStorage.checkCredentials())
+			.map(result => result.accountId)
+			.filter((accountId): accountId is string => accountId !== undefined)
+			.sort();
+		expect(activeAccounts).toEqual(["acct-A", "acct-B"]);
+	});
+
 	test("falls back to earliest-unblocking account when all exhausted", async () => {
 		if (!authStorage) throw new Error("test setup failed");
 
diff --git a/packages/ai/test/auth-storage-force-refresh-rotate.test.ts b/packages/ai/test/auth-storage-force-refresh-rotate.test.ts
index 62a2865ec..c6eb5d117 100644
--- a/packages/ai/test/auth-storage-force-refresh-rotate.test.ts
+++ b/packages/ai/test/auth-storage-force-refresh-rotate.test.ts
@@ -22,6 +22,14 @@ function usageLimitError(): Error & { status: number } {
 	});
 }
 
+function quotaPayloadError(message: string, status?: number): Error & { status?: number } {
+	return status === undefined ? new Error(message) : Object.assign(new Error(message), { status });
+}
+
+function invalidRequestError(): Error & { status: number } {
+	return Object.assign(new Error("400 invalid_request_error: model unsupported"), { status: 400 });
+}
+
 describe("AuthStorage forceRefresh + rotateSessionCredential", () => {
 	let tempDir = "";
 	let store: AuthCredentialStore | undefined;
@@ -141,6 +149,84 @@ describe("AuthStorage forceRefresh + rotateSessionCredential", () => {
 		expect(second).not.toBe(first);
 	});
 
+	test("rotateSessionCredential treats quota payloads as temporary usage blocks", async () => {
+		if (!authStorage) throw new Error("test setup failed");
+		registerProvider();
+		await authStorage.set(PROVIDER, [
+			{ type: "oauth", access: "acc-A", refresh: "ref-A", expires: farExpiry() },
+			{ type: "oauth", access: "acc-B", refresh: "ref-B", expires: farExpiry() },
+			{ type: "oauth", access: "acc-C", refresh: "ref-C", expires: farExpiry() },
+			{ type: "oauth", access: "acc-D", refresh: "ref-D", expires: farExpiry() },
+			{ type: "oauth", access: "acc-E", refresh: "ref-E", expires: farExpiry() },
+		]);
+
+		for (const [index, error] of [
+			[0, quotaPayloadError("429", 429)],
+			[1, quotaPayloadError("insufficient_quota")],
+			[2, quotaPayloadError("usage_limit_exceeded")],
+			[3, quotaPayloadError("usage_limit_reached")],
+		] as const) {
+			const sessionId = `quota-payload-${index}`;
+			const first = await authStorage.getApiKey(PROVIDER, sessionId);
+			const usageLimitSpy = vi.spyOn(authStorage, "markUsageLimitReached");
+
+			const rotated = await authStorage.rotateSessionCredential(PROVIDER, sessionId, { error });
+
+			expect(rotated).toBe(true);
+			expect(usageLimitSpy).toHaveBeenCalledTimes(1);
+			expect(await authStorage.getApiKey(PROVIDER, sessionId)).not.toBe(first);
+			usageLimitSpy.mockRestore();
+		}
+	});
+
+	test("rotateSessionCredential does not treat invalid requests as quota blocks", async () => {
+		if (!authStorage) throw new Error("test setup failed");
+		registerProvider();
+		await authStorage.set(PROVIDER, [
+			{ type: "oauth", access: "acc-A", refresh: "ref-A", expires: farExpiry() },
+			{ type: "oauth", access: "acc-B", refresh: "ref-B", expires: farExpiry() },
+		]);
+
+		await authStorage.getApiKey(PROVIDER, "invalid-request");
+		const usageLimitSpy = vi.spyOn(authStorage, "markUsageLimitReached");
+
+		await authStorage.rotateSessionCredential(PROVIDER, "invalid-request", { error: invalidRequestError() });
+
+		expect(usageLimitSpy).not.toHaveBeenCalled();
+	});
+
+	test("rotateSessionCredential leaves informative transient 429s out of the quota block path", async () => {
+		if (!authStorage) throw new Error("test setup failed");
+		registerProvider();
+		await authStorage.set(PROVIDER, [
+			{ type: "oauth", access: "acc-A", refresh: "ref-A", expires: farExpiry() },
+			{ type: "oauth", access: "acc-B", refresh: "ref-B", expires: farExpiry() },
+		]);
+
+		const transient429Bodies = [
+			"Cloud Code Assist API error (429): Too many requests",
+			"Please retry in 5s",
+			"Service overloaded 529",
+		];
+
+		for (const [index, body] of transient429Bodies.entries()) {
+			const sessionId = `transient-429-${index}`;
+			await authStorage.getApiKey(PROVIDER, sessionId);
+			const usageLimitSpy = vi.spyOn(authStorage, "markUsageLimitReached");
+
+			await authStorage.rotateSessionCredential(PROVIDER, sessionId, {
+				error: Object.assign(new Error(body), { status: 429 }),
+			});
+
+			// `Too many requests`, server retry hints, and capacity overload are
+			// owned by the provider's own retry layer — burning a sibling
+			// credential here would orphan a healthy account for the default
+			// backoff window.
+			expect(usageLimitSpy).not.toHaveBeenCalled();
+			usageLimitSpy.mockRestore();
+		}
+	});
+
 	test("rotateSessionCredential reports no sibling for a single-credential setup", async () => {
 		if (!authStorage) throw new Error("test setup failed");
 		registerProvider();
diff --git a/packages/ai/test/rate-limit-utils.test.ts b/packages/ai/test/rate-limit-utils.test.ts
index 387e00168..4b77a215e 100644
--- a/packages/ai/test/rate-limit-utils.test.ts
+++ b/packages/ai/test/rate-limit-utils.test.ts
@@ -1,5 +1,11 @@
 import { describe, expect, it } from "bun:test";
-import { calculateRateLimitBackoffMs, isUsageLimitError, parseRateLimitReason } from "@oh-my-pi/pi-ai/rate-limit-utils";
+import {
+	calculateRateLimitBackoffMs,
+	isUsageLimitError,
+	isUsageLimitOutcome,
+	isUsageLimitStatus,
+	parseRateLimitReason,
+} from "@oh-my-pi/pi-ai/rate-limit-utils";
 
 describe("parseRateLimitReason", () => {
 	it("classifies Google Quota exceeded as QUOTA_EXHAUSTED", () => {
@@ -118,6 +124,61 @@ describe("isUsageLimitError", () => {
 		expect(isUsageLimitError("quota reached")).toBe(true);
 		expect(isUsageLimitError("quota_reached")).toBe(true);
 	});
+
+	it("detects OpenAI quota payload codes as credential-rotatable usage limits", () => {
+		for (const message of ["insufficient_quota", "usage_limit_exceeded", "usage_limit_reached"]) {
+			expect(isUsageLimitError(message)).toBe(true);
+		}
+		expect(isUsageLimitStatus(429)).toBe(true);
+		expect(isUsageLimitStatus(400)).toBe(false);
+	});
+});
+
+describe("isUsageLimitOutcome", () => {
+	it("rotates on bare/opaque 429 bodies (status-only fallback)", () => {
+		expect(isUsageLimitOutcome(429, undefined)).toBe(true);
+		expect(isUsageLimitOutcome(429, "")).toBe(true);
+		expect(isUsageLimitOutcome(429, "429")).toBe(true);
+		expect(isUsageLimitOutcome(429, "HTTP 429")).toBe(true);
+		expect(isUsageLimitOutcome(429, "Error 429")).toBe(true);
+		expect(isUsageLimitOutcome(429, "{}")).toBe(true);
+	});
+
+	it("rotates on 429 carrying quota payload codes", () => {
+		for (const message of ["insufficient_quota", "usage_limit_exceeded", "usage_limit_reached"]) {
+			expect(isUsageLimitOutcome(429, message)).toBe(true);
+		}
+	});
+
+	it("keeps informative transient 429s in the upstream-backoff lane", () => {
+		// RATE_LIMIT_EXCEEDED — generic throttling.
+		expect(isUsageLimitOutcome(429, "Cloud Code Assist API error (429): Too many requests")).toBe(false);
+		expect(isUsageLimitOutcome(429, "Requests per minute limit reached")).toBe(false);
+		// MODEL_CAPACITY_EXHAUSTED — provider overload, not account quota.
+		expect(isUsageLimitOutcome(429, "Service overloaded 529")).toBe(false);
+		// UNKNOWN but carries a transient retry hint — body is informative,
+		// so we defer to parseRateLimitReason and stay out of the quota lane.
+		expect(isUsageLimitOutcome(429, "Please retry in 5s")).toBe(false);
+	});
+
+	it("still rotates on 429 with explicit account rate-limit framing", () => {
+		expect(
+			isUsageLimitOutcome(
+				429,
+				'{"type":"error","error":{"type":"rate_limit_error","message":"This request would exceed your account\'s rate limit. Please try again later."}}',
+			),
+		).toBe(true);
+	});
+
+	it("rotates on usage-limit message regardless of status", () => {
+		expect(isUsageLimitOutcome(undefined, "usage_limit_reached")).toBe(true);
+		expect(isUsageLimitOutcome(500, "insufficient_quota")).toBe(true);
+	});
+
+	it("does not rotate on auth/invalid-request statuses with unrelated bodies", () => {
+		expect(isUsageLimitOutcome(401, "Invalid API key")).toBe(false);
+		expect(isUsageLimitOutcome(400, "invalid_request_error: model unsupported")).toBe(false);
+	});
 });
 
 describe("calculateRateLimitBackoffMs", () => {
diff --git a/packages/ai/test/stream-auth-retry.test.ts b/packages/ai/test/stream-auth-retry.test.ts
index 4d27dfbd4..307b37412 100644
--- a/packages/ai/test/stream-auth-retry.test.ts
+++ b/packages/ai/test/stream-auth-retry.test.ts
@@ -350,6 +350,113 @@ describe("streamSimple resolver auth retry", () => {
 		expect(keys).toEqual(["old-key", "new-key"]);
 	});
 
+	it("rotates before emitting content for Codex quota payloads", async () => {
+		const payloads: Array<{ message: string; status?: number }> = [
+			{ message: "429", status: 429 },
+			{ message: '{"error":{"code":"insufficient_quota","message":"quota exhausted"}}' },
+			{ message: '{"error":{"code":"usage_limit_exceeded","message":"usage limit exceeded"}}' },
+			{ message: '{"error":{"code":"usage_limit_reached","message":"usage limit reached"}}' },
+		];
+		let activePayload = payloads[0]!;
+		let keys: unknown[] = [];
+		registerCustomApi(
+			API,
+			(_model: Model<Api>, _context: Context, options?: SimpleStreamOptions) => {
+				pushKey(keys, options);
+				const stream = new AssistantMessageEventStream();
+				queueMicrotask(() => {
+					if (options?.apiKey === "credential-B") {
+						ok(stream);
+						return;
+					}
+					stream.push({ type: "start", partial: assistant() });
+					stream.push({
+						type: "error",
+						reason: "error",
+						error: assistantError(activePayload.message, activePayload.status),
+					});
+				});
+				return stream;
+			},
+			SOURCE_ID,
+		);
+
+		for (const payload of payloads) {
+			activePayload = payload;
+			keys = [];
+			const eventTypes: string[] = [];
+			const retryContexts: ApiKeyResolveContext[] = [];
+			const stream = streamSimple(model(), context, {
+				apiKey: async ctx => {
+					if (ctx.error !== undefined) retryContexts.push(ctx);
+					return ctx.error === undefined ? "credential-A" : ctx.lastChance ? "credential-B" : "credential-A";
+				},
+			});
+			for await (const event of stream) {
+				eventTypes.push(event.type);
+			}
+
+			expect((await stream.result()).content).toEqual([{ type: "text", text: "ok" }]);
+			expect(keys).toEqual(["credential-A", "credential-B"]);
+			expect(eventTypes).toEqual(["start", "done"]);
+			expect(retryContexts.map(ctx => ctx.lastChance)).toEqual([false, true]);
+		}
+	});
+
+	it("does not rotate or refresh on informative transient 429 bodies", async () => {
+		const transient429Bodies = [
+			"Cloud Code Assist API error (429): Too many requests",
+			"Please retry in 5s",
+			"Service overloaded 529",
+		];
+		let active = transient429Bodies[0]!;
+		const keys: unknown[] = [];
+		const retryResolves: ApiKeyResolveContext[] = [];
+		registerCustomApi(
+			API,
+			(_model: Model<Api>, _context: Context, options?: SimpleStreamOptions) => {
+				pushKey(keys, options);
+				const stream = new AssistantMessageEventStream();
+				queueMicrotask(() => {
+					stream.push({ type: "start", partial: assistant() });
+					stream.push({
+						type: "error",
+						reason: "error",
+						error: assistantError(active, 429),
+					});
+				});
+				return stream;
+			},
+			SOURCE_ID,
+		);
+
+		for (const body of transient429Bodies) {
+			active = body;
+			keys.length = 0;
+			retryResolves.length = 0;
+			const eventTypes: string[] = [];
+			const stream = streamSimple(model(), context, {
+				apiKey: async ctx => {
+					if (ctx.error !== undefined) retryResolves.push(ctx);
+					return ctx.error === undefined ? "credential-A" : "credential-B";
+				},
+			});
+
+			for await (const event of stream) {
+				eventTypes.push(event.type);
+			}
+			const result = await stream.result();
+
+			// The provider's own retry/backoff layer owns these — the auth
+			// retry loop must NOT capture, refresh, or burn a sibling.
+			expect(retryResolves).toEqual([]);
+			expect(keys).toEqual(["credential-A"]);
+			expect(eventTypes).toEqual(["start", "error"]);
+			expect(result.stopReason).toBe("error");
+			expect(result.errorMessage).toContain(body);
+		}
+	});
+
 	it("rotates on the exact Google Resource exhausted 429 error before content", async () => {
 		const keys: unknown[] = [];
 		const retryContexts: ApiKeyResolveContext[] = [];