diff --git a/packages/ai/src/auth-retry.ts b/packages/ai/src/auth-retry.ts
index 87da67210..22a8f8e55 100644
--- a/packages/ai/src/auth-retry.ts
+++ b/packages/ai/src/auth-retry.ts
@@ -1,6 +1,7 @@
 import type { OAuthAccess } from "./auth-storage";
 import * as AIError from "./error";
 import { isAuthRetryableError } from "./error/auth-classify";
+import { isUsageLimit } from "./error/flags";
 
 /**
  * Context passed to an {@link ApiKeyResolver} on each resolution attempt.
@@ -92,7 +93,8 @@ export async function resolveRetryKey(
 	previousKey?: string,
 ): Promise<string | undefined> {
 	try {
-		return (await resolver({ lastChance, error, signal, previousKey })) || undefined;
+		const rotateSibling = lastChance || (!lastChance && isUsageLimit(error));
+		return (await resolver({ lastChance: rotateSibling, error, signal, previousKey })) || undefined;
 	} catch {
 		return undefined;
 	}
diff --git a/packages/ai/src/auth-storage.ts b/packages/ai/src/auth-storage.ts
index 3d0ef1262..67b698838 100644
--- a/packages/ai/src/auth-storage.ts
+++ b/packages/ai/src/auth-storage.ts
@@ -1390,12 +1390,14 @@ export class AuthStorage {
 
 		const credentialId = this.#getStoredCredentials(provider)[credentialIndex]?.id;
 		if (credentialId === undefined) return blockedUntil;
-		const persistedGlobalBlockedUntil = this.#readPersistedCredentialBlock(credentialId, providerKey, "");
-		if (
-			persistedGlobalBlockedUntil !== undefined &&
-			(blockedUntil === undefined || persistedGlobalBlockedUntil > blockedUntil)
-		) {
-			blockedUntil = persistedGlobalBlockedUntil;
+		if (!blockScope || provider !== "openai-codex") {
+			const persistedGlobalBlockedUntil = this.#readPersistedCredentialBlock(credentialId, providerKey, "");
+			if (
+				persistedGlobalBlockedUntil !== undefined &&
+				(blockedUntil === undefined || persistedGlobalBlockedUntil > blockedUntil)
+			) {
+				blockedUntil = persistedGlobalBlockedUntil;
+			}
 		}
 		if (blockScope) {
 			const persistedScopedBlockedUntil = this.#readPersistedCredentialBlock(credentialId, providerKey, blockScope);
diff --git a/packages/ai/src/usage/openai-codex.ts b/packages/ai/src/usage/openai-codex.ts
index 355744208..c7adebb4c 100644
--- a/packages/ai/src/usage/openai-codex.ts
+++ b/packages/ai/src/usage/openai-codex.ts
@@ -505,6 +505,9 @@ export const openaiCodexUsageProvider: UsageProvider = {
 const FIVE_HOUR_MS = 5 * 60 * 60 * 1000;
 
 export const codexRankingStrategy: CredentialRankingStrategy = {
+	blockScope() {
+		return "shared";
+	},
 	findWindowLimits(report) {
 		const findLimit = (key: "primary" | "secondary"): UsageLimit | undefined => {
 			const direct = report.limits.find(l => l.id === `openai-codex:${key}`);
diff --git a/packages/ai/test/auth-retry.test.ts b/packages/ai/test/auth-retry.test.ts
index 73b1f66d1..44a4a9f89 100644
--- a/packages/ai/test/auth-retry.test.ts
+++ b/packages/ai/test/auth-retry.test.ts
@@ -99,6 +99,28 @@ describe("withAuth", () => {
 		]);
 	});
 
+	it("switches accounts before refreshing the same account on usage limits", async () => {
+		const keys: string[] = [];
+		const contexts: ApiKeyResolveContext[] = [];
+		const result = await withAuth(
+			ctx => {
+				contexts.push(ctx);
+				return ctx.error === undefined ? "k0" : ctx.lastChance ? "k2" : "k1";
+			},
+			async key => {
+				keys.push(key);
+				if (key === "k2") return "success";
+				throw usageLimitError();
+			},
+		);
+		expect(result).toBe("success");
+		expect(keys).toEqual(["k0", "k2"]);
+		expect(contexts.map(ctx => ({ lastChance: ctx.lastChance, hasError: ctx.error !== undefined }))).toEqual([
+			{ lastChance: false, hasError: false },
+			{ lastChance: true, hasError: true },
+		]);
+	});
+
 	it("stops retrying when the resolver returns undefined", async () => {
 		const keys: string[] = [];
 		const original = authError();
diff --git a/packages/ai/test/auth-storage-codex-selection.test.ts b/packages/ai/test/auth-storage-codex-selection.test.ts
index 3dd0a169f..b6aa79847 100644
--- a/packages/ai/test/auth-storage-codex-selection.test.ts
+++ b/packages/ai/test/auth-storage-codex-selection.test.ts
@@ -643,6 +643,52 @@ describe("AuthStorage codex oauth ranking", () => {
 
 		expect(await authStorage.getApiKey("openai-codex", sessionId)).toBe("api-acct-plus");
 	});
+
+	test("ignores legacy global Codex blocks when a scoped quota window has fresh siblings", async () => {
+		if (!authStorage || !store) throw new Error("test setup failed");
+		await authStorage.set("openai-codex", [
+			{ type: "oauth", ...createCredential("acct-k12", "k12@example.com") },
+			{ type: "oauth", ...createCredential("acct-plus", "plus@example.com") },
+		]);
+		usageByAccount.set(
+			"acct-k12",
+			createCodexUsageReport({
+				accountId: "acct-k12",
+				primary: { usedFraction: 1, resetInMs: FIVE_HOUR_MS },
+				secondary: { usedFraction: 1, resetInMs: WEEK_MS },
+			}),
+		);
+		usageByAccount.set(
+			"acct-plus",
+			createCodexUsageReport({
+				accountId: "acct-plus",
+				primary: { usedFraction: 0.2, resetInMs: FIVE_HOUR_MS },
+				secondary: { usedFraction: 0.74, resetInMs: WEEK_MS },
+			}),
+		);
+		const plus = store
+			.listAuthCredentials("openai-codex")
+			.find(row => row.credential.type === "oauth" && row.credential.accountId === "acct-plus");
+		if (!plus || !store.upsertCredentialBlock) throw new Error("missing plus credential row");
+		store.upsertCredentialBlock({
+			credentialId: plus.id,
+			providerKey: "openai-codex:oauth",
+			blockScope: "",
+			blockedUntilMs: Date.now() + WEEK_MS,
+		});
+		const k12 = store
+			.listAuthCredentials("openai-codex")
+			.find(row => row.credential.type === "oauth" && row.credential.accountId === "acct-k12");
+		if (!k12 || !store.upsertCredentialBlock) throw new Error("missing k12 credential row");
+		store.upsertCredentialBlock({
+			credentialId: k12.id,
+			providerKey: "openai-codex:oauth",
+			blockScope: "shared",
+			blockedUntilMs: Date.now() + HOUR_MS,
+		});
+
+		expect(await authStorage.getApiKey("openai-codex", "session-with-legacy-global-block")).toBe("api-acct-plus");
+	});
 });
 
 // ─────────────────────────────────────────────────────────────────────────────