diff --git a/packages/pi-coding-agent/src/core/auth-storage.test.ts b/packages/pi-coding-agent/src/core/auth-storage.test.ts
index a0d2cab20..819cc092b 100644
--- a/packages/pi-coding-agent/src/core/auth-storage.test.ts
+++ b/packages/pi-coding-agent/src/core/auth-storage.test.ts
@@ -423,3 +423,111 @@ describe("AuthStorage — getAll()", () => {
 		assert.equal((all["openai"] as any).key, "sk-openai");
 	});
 });
+
+// ─── getEarliestBackoffExpiry ─────────────────────────────────────────────────
+
+describe("AuthStorage — getEarliestBackoffExpiry", () => {
+	it("returns undefined when no credentials are configured for the provider", () => {
+		const storage = inMemory({});
+		assert.equal(storage.getEarliestBackoffExpiry("anthropic"), undefined);
+	});
+
+	it("returns undefined when credentials exist but none are backed off", () => {
+		const storage = inMemory({ anthropic: makeKey("sk-only") });
+		// No markUsageLimitReached call — credentialBackoff map is empty
+		assert.equal(storage.getEarliestBackoffExpiry("anthropic"), undefined);
+	});
+
+	it("returns a future timestamp when a single credential is backed off", async () => {
+		const storage = inMemory({ anthropic: makeKey("sk-only") });
+		await storage.getApiKey("anthropic");
+		storage.markUsageLimitReached("anthropic");
+
+		const expiry = storage.getEarliestBackoffExpiry("anthropic");
+		assert.ok(expiry !== undefined, "should return a timestamp");
+		assert.ok(expiry > Date.now(), "expiry should be in the future");
+	});
+
+	it("returns the earliest expiry when multiple credentials are backed off", async () => {
+		const storage = inMemory({
+			anthropic: [makeKey("sk-1"), makeKey("sk-2")],
+		});
+
+		// Back off both credentials with the default rate_limit backoff (30 s)
+		await storage.getApiKey("anthropic"); // uses index 0
+		storage.markUsageLimitReached("anthropic"); // backs off index 0
+		await storage.getApiKey("anthropic"); // uses index 1
+		storage.markUsageLimitReached("anthropic"); // backs off index 1
+
+		const expiry = storage.getEarliestBackoffExpiry("anthropic");
+		assert.ok(expiry !== undefined, "should return a timestamp");
+		assert.ok(expiry > Date.now(), "expiry should be in the future");
+	});
+
+	it("returns undefined after backed-off credentials expire (cleans up entries)", () => {
+		// Manually inject an already-expired backoff entry so we can test
+		// the cleanup path without actually waiting 30 seconds.
+		const storage = inMemory({ anthropic: makeKey("sk-only") });
+
+		// Access private credentialBackoff map via type assertion to inject expired entry
+		const credentialBackoff: Map<string, Map<number, number>> =
+			(storage as any).credentialBackoff;
+		const providerMap = new Map<number, number>();
+		// expiresAt in the past
+		providerMap.set(0, Date.now() - 1_000);
+		credentialBackoff.set("anthropic", providerMap);
+
+		// getEarliestBackoffExpiry should clean up the expired entry and return undefined
+		const expiry = storage.getEarliestBackoffExpiry("anthropic");
+		assert.equal(expiry, undefined);
+
+		// Confirm the expired entry was removed from the map
+		assert.equal(providerMap.size, 0, "expired entry should have been deleted");
+	});
+
+	it("returns undefined when provider is not in credentialBackoff map at all", () => {
+		const storage = inMemory({ openai: makeKey("sk-openai") });
+		// anthropic has no backoff map entry at all
+		assert.equal(storage.getEarliestBackoffExpiry("anthropic"), undefined);
+	});
+
+	it("only returns expiry for the requested provider, not other providers", async () => {
+		const storage = inMemory({
+			anthropic: makeKey("sk-ant"),
+			openai: makeKey("sk-oai"),
+		});
+
+		// Back off anthropic
+		await storage.getApiKey("anthropic");
+		storage.markUsageLimitReached("anthropic");
+
+		// openai is not backed off
+		assert.equal(storage.getEarliestBackoffExpiry("openai"), undefined);
+
+		// anthropic is backed off
+		const expiry = storage.getEarliestBackoffExpiry("anthropic");
+		assert.ok(expiry !== undefined);
+		assert.ok(expiry > Date.now());
+	});
+
+	it("returns the minimum expiry when one credential expires sooner than another", () => {
+		const storage = inMemory({
+			anthropic: [makeKey("sk-1"), makeKey("sk-2")],
+		});
+
+		const now = Date.now();
+		const nearExpiry = now + 5_000;   // expires in 5 s
+		const farExpiry  = now + 30_000;  // expires in 30 s
+
+		// Inject two different backoff expiries manually
+		const credentialBackoff: Map<string, Map<number, number>> =
+			(storage as any).credentialBackoff;
+		const providerMap = new Map<number, number>();
+		providerMap.set(0, nearExpiry);
+		providerMap.set(1, farExpiry);
+		credentialBackoff.set("anthropic", providerMap);
+
+		const expiry = storage.getEarliestBackoffExpiry("anthropic");
+		assert.equal(expiry, nearExpiry, "should return the nearest (smallest) expiry");
+	});
+});
diff --git a/packages/pi-coding-agent/src/core/auth-storage.ts b/packages/pi-coding-agent/src/core/auth-storage.ts
index fb1532252..02e2f3103 100644
--- a/packages/pi-coding-agent/src/core/auth-storage.ts
+++ b/packages/pi-coding-agent/src/core/auth-storage.ts
@@ -559,6 +559,36 @@ export class AuthStorage {
 		return remaining;
 	}
 
+	/**
+	 * Get the earliest timestamp at which any credential for this provider
+	 * will become available again.  Returns `undefined` when no credentials
+	 * are backed off (i.e. all are immediately available).
+	 *
+	 * Callers can use this to sleep exactly long enough for the cooldown to
+	 * clear instead of using a fixed retry delay that may be shorter than the
+	 * backoff window.
+	 */
+	getEarliestBackoffExpiry(provider: string): number | undefined {
+		const providerMap = this.credentialBackoff.get(provider);
+		if (!providerMap || providerMap.size === 0) return undefined;
+
+		const now = Date.now();
+		let earliest: number | undefined;
+
+		for (const [index, expiresAt] of providerMap) {
+			if (expiresAt <= now) {
+				// Already expired — clean up
+				providerMap.delete(index);
+				continue;
+			}
+			if (earliest === undefined || expiresAt < earliest) {
+				earliest = expiresAt;
+			}
+		}
+
+		return earliest;
+	}
+
 	/**
 	 * Check if a credential index is currently backed off.
 	 */
diff --git a/packages/pi-coding-agent/src/core/sdk.test.ts b/packages/pi-coding-agent/src/core/sdk.test.ts
new file mode 100644
index 000000000..cebb41490
--- /dev/null
+++ b/packages/pi-coding-agent/src/core/sdk.test.ts
@@ -0,0 +1,89 @@
+// pi-coding-agent / CredentialCooldownError unit tests
+// Copyright (c) 2026 Jeremy McSpadden <jeremy@fluxlabs.net>
+
+import { describe, it } from "node:test";
+import assert from "node:assert/strict";
+import { CredentialCooldownError } from "./sdk.js";
+
+// ─── CredentialCooldownError ──────────────────────────────────────────────────
+
+describe("CredentialCooldownError", () => {
+	it("is an instance of Error", () => {
+		const err = new CredentialCooldownError("anthropic");
+		assert.ok(err instanceof Error);
+	});
+
+	it("has name set to CredentialCooldownError", () => {
+		const err = new CredentialCooldownError("anthropic");
+		assert.equal(err.name, "CredentialCooldownError");
+	});
+
+	it("has code set to AUTH_COOLDOWN", () => {
+		const err = new CredentialCooldownError("anthropic");
+		assert.equal(err.code, "AUTH_COOLDOWN");
+	});
+
+	it("message includes the provider name", () => {
+		const err = new CredentialCooldownError("openai");
+		assert.ok(
+			err.message.includes("openai"),
+			`Expected message to include provider "openai", got: ${err.message}`,
+		);
+	});
+
+	it("message mentions cooldown window", () => {
+		const err = new CredentialCooldownError("anthropic");
+		assert.ok(
+			/cooldown window/i.test(err.message),
+			`Expected message to mention "cooldown window", got: ${err.message}`,
+		);
+	});
+
+	it("retryAfterMs is undefined when not provided", () => {
+		const err = new CredentialCooldownError("anthropic");
+		assert.equal(err.retryAfterMs, undefined);
+	});
+
+	it("retryAfterMs holds the provided value when specified", () => {
+		const err = new CredentialCooldownError("anthropic", 30_000);
+		assert.equal(err.retryAfterMs, 30_000);
+	});
+
+	it("retryAfterMs is 0 when explicitly passed as 0", () => {
+		const err = new CredentialCooldownError("anthropic", 0);
+		assert.equal(err.retryAfterMs, 0);
+	});
+
+	it("code property is readonly and always AUTH_COOLDOWN regardless of provider", () => {
+		for (const provider of ["anthropic", "openai", "google", "openrouter"]) {
+			const err = new CredentialCooldownError(provider);
+			assert.equal(err.code, "AUTH_COOLDOWN", `code should be AUTH_COOLDOWN for provider "${provider}"`);
+		}
+	});
+
+	it("different providers produce different messages", () => {
+		const err1 = new CredentialCooldownError("anthropic");
+		const err2 = new CredentialCooldownError("openai");
+		assert.notEqual(err1.message, err2.message);
+	});
+
+	it("can be caught as an Error in a try/catch", () => {
+		let caught: unknown;
+		try {
+			throw new CredentialCooldownError("anthropic", 5_000);
+		} catch (e) {
+			caught = e;
+		}
+		assert.ok(caught instanceof Error);
+		assert.ok(caught instanceof CredentialCooldownError);
+		assert.equal((caught as CredentialCooldownError).retryAfterMs, 5_000);
+	});
+
+	it("code property is detectable via plain object check (cross-process pattern)", () => {
+		const err = new CredentialCooldownError("anthropic", 15_000);
+		// Simulate cross-process serialization: only plain properties survive JSON round-trip
+		const plain = { code: err.code, retryAfterMs: err.retryAfterMs, message: err.message };
+		assert.equal(plain.code, "AUTH_COOLDOWN");
+		assert.equal(plain.retryAfterMs, 15_000);
+	});
+});
diff --git a/packages/pi-coding-agent/src/core/sdk.ts b/packages/pi-coding-agent/src/core/sdk.ts
index 07ed24c53..12da38d16 100644
--- a/packages/pi-coding-agent/src/core/sdk.ts
+++ b/packages/pi-coding-agent/src/core/sdk.ts
@@ -1,4 +1,24 @@
 import { join } from "node:path";
+
+/**
+ * Structured error thrown when all credentials for a provider are in a
+ * backoff window.  Carries typed metadata so callers (e.g. the auto-loop)
+ * can make informed retry decisions instead of string-matching the message.
+ */
+export class CredentialCooldownError extends Error {
+	readonly code = "AUTH_COOLDOWN" as const;
+	/** Milliseconds until the earliest credential becomes available, or undefined if unknown. */
+	readonly retryAfterMs: number | undefined;
+
+	constructor(provider: string, retryAfterMs?: number) {
+		super(
+			`All credentials for "${provider}" are in a cooldown window. ` +
+				`Please wait a moment and try again, or switch to a different provider.`,
+		);
+		this.name = "CredentialCooldownError";
+		this.retryAfterMs = retryAfterMs;
+	}
+}
 import { Agent, type AgentMessage, type ThinkingLevel } from "@gsd/pi-agent-core";
 import type { Message, Model } from "@gsd/pi-ai";
 import { getAgentDir, getDocsPath } from "../config.js";
@@ -363,8 +383,12 @@ export async function createAgentSession(options: CreateAgentSessionOptions = {}
 
 			// Retry key resolution with backoff to handle transient network failures
 			// (e.g., OAuth token refresh failing due to brief connectivity loss).
+			// When credentials are in a cooldown window (e.g., after a 429), wait
+			// for the backoff to expire instead of using fixed delays that are
+			// shorter than the cooldown duration.
 			const maxAttempts = 3;
 			const baseDelayMs = 2000;
+			const maxCooldownWaitMs = 60_000; // Don't wait longer than 60s (skip quota-exhausted 30min backoffs)
 			for (let attempt = 1; attempt <= maxAttempts; attempt++) {
 				const key = await modelRegistry.getApiKeyForProvider(resolvedProvider);
 				if (key) return key;
@@ -379,7 +403,21 @@ export async function createAgentSession(options: CreateAgentSessionOptions = {}
 				const isOAuth = model && modelRegistry.isUsingOAuth(model);
 				if (!hasAuth && !isOAuth) break;
 
-				// Wait with exponential backoff before retrying
+				// If credentials are in a cooldown window, wait for the earliest
+				// one to expire rather than using a fixed delay that's too short.
+				const backoffExpiry = modelRegistry.authStorage.getEarliestBackoffExpiry(resolvedProvider);
+				if (backoffExpiry !== undefined) {
+					const waitMs = backoffExpiry - Date.now() + 500; // 500ms buffer
+					if (waitMs > 0 && waitMs <= maxCooldownWaitMs) {
+						await new Promise(resolve => setTimeout(resolve, waitMs));
+						continue; // Retry immediately after cooldown clears
+					}
+					if (waitMs > maxCooldownWaitMs) {
+						break; // Quota-exhausted or very long backoff — don't block
+					}
+				}
+
+				// Standard exponential backoff for non-cooldown transient failures
 				await new Promise(resolve => setTimeout(resolve, baseDelayMs * attempt));
 			}
 
@@ -390,10 +428,9 @@ export async function createAgentSession(options: CreateAgentSessionOptions = {}
 			// the retry handler and creating cascading error entries (#3429).
 			const hasAuth = modelRegistry.authStorage.hasAuth(resolvedProvider);
 			if (hasAuth) {
-				throw new Error(
-					`All credentials for "${resolvedProvider}" are in a cooldown window. ` +
-						`Please wait a moment and try again, or switch to a different provider.`,
-				);
+				const expiry = modelRegistry.authStorage.getEarliestBackoffExpiry(resolvedProvider);
+				const retryAfterMs = expiry !== undefined ? Math.max(0, expiry - Date.now()) : undefined;
+				throw new CredentialCooldownError(resolvedProvider, retryAfterMs);
 			}
 			const model = agent.state.model;
 			const isOAuth = model && modelRegistry.isUsingOAuth(model);
@@ -401,10 +438,9 @@ export async function createAgentSession(options: CreateAgentSessionOptions = {}
 				// If credentials exist but are all in a backoff window (quota / rate-limit),
 				// surface a specific message instead of the misleading "Authentication failed".
 				if (modelRegistry.authStorage.areAllCredentialsBackedOff(resolvedProvider)) {
-					throw new Error(
-						`All credentials for "${resolvedProvider}" are in a cooldown window. ` +
-							`Please wait a moment and try again, or switch to a different provider.`,
-					);
+					const expiry = modelRegistry.authStorage.getEarliestBackoffExpiry(resolvedProvider);
+					const retryAfterMs = expiry !== undefined ? Math.max(0, expiry - Date.now()) : undefined;
+					throw new CredentialCooldownError(resolvedProvider, retryAfterMs);
 				}
 				throw new Error(
 					`Authentication failed for "${resolvedProvider}". ` +
diff --git a/packages/pi-coding-agent/src/index.ts b/packages/pi-coding-agent/src/index.ts
index ab7de8bac..54a20b846 100644
--- a/packages/pi-coding-agent/src/index.ts
+++ b/packages/pi-coding-agent/src/index.ts
@@ -176,6 +176,7 @@ export { DefaultResourceLoader } from "./core/resource-loader.js";
 export {
 	type CreateAgentSessionOptions,
 	type CreateAgentSessionResult,
+	CredentialCooldownError,
 	// Factory
 	createAgentSession,
 	createBashTool,
diff --git a/src/resources/extensions/gsd/auto/infra-errors.ts b/src/resources/extensions/gsd/auto/infra-errors.ts
index 17c1a553d..d0132724c 100644
--- a/src/resources/extensions/gsd/auto/infra-errors.ts
+++ b/src/resources/extensions/gsd/auto/infra-errors.ts
@@ -46,3 +46,41 @@ export function isInfrastructureError(err: unknown): string | null {
   if (msg.includes("database disk image is malformed")) return "SQLITE_CORRUPT";
   return null;
 }
+
+/**
+ * Default wait duration when a cooldown error is detected but no specific
+ * expiry is available from AuthStorage (e.g., error propagated across
+ * process boundary without structured backoff data).
+ */
+export const COOLDOWN_FALLBACK_WAIT_MS = 35_000; // 35s — slightly longer than the 30s rate-limit backoff
+
+/** Maximum consecutive cooldown retries before the auto-loop gives up. */
+export const MAX_COOLDOWN_RETRIES = 5;
+
+/**
+ * Detect whether an error is a transient credential cooldown that should
+ * be waited out rather than counted as a consecutive failure.
+ *
+ * Prefers the structured `CredentialCooldownError` (code: AUTH_COOLDOWN)
+ * thrown by sdk.ts. Falls back to message matching for errors that
+ * propagated across process boundaries without the typed class.
+ */
+export function isTransientCooldownError(err: unknown): boolean {
+  if (err && typeof err === "object" && (err as Record<string, unknown>).code === "AUTH_COOLDOWN") {
+    return true;
+  }
+  // Fallback: message match for cross-process error propagation
+  const msg = err instanceof Error ? err.message : String(err);
+  return /in a cooldown window/i.test(msg);
+}
+
+/**
+ * Extract retryAfterMs from a CredentialCooldownError, if available.
+ * Returns undefined for unstructured errors or when no retry hint exists.
+ */
+export function getCooldownRetryAfterMs(err: unknown): number | undefined {
+  if (err && typeof err === "object" && (err as Record<string, unknown>).code === "AUTH_COOLDOWN") {
+    return (err as Record<string, unknown>).retryAfterMs as number | undefined;
+  }
+  return undefined;
+}
diff --git a/src/resources/extensions/gsd/auto/loop.ts b/src/resources/extensions/gsd/auto/loop.ts
index 3a0c8de10..412ba1e26 100644
--- a/src/resources/extensions/gsd/auto/loop.ts
+++ b/src/resources/extensions/gsd/auto/loop.ts
@@ -27,7 +27,7 @@ import {
   runFinalize,
 } from "./phases.js";
 import { debugLog } from "../debug-logger.js";
-import { isInfrastructureError } from "./infra-errors.js";
+import { isInfrastructureError, isTransientCooldownError, getCooldownRetryAfterMs, COOLDOWN_FALLBACK_WAIT_MS, MAX_COOLDOWN_RETRIES } from "./infra-errors.js";
 import { resolveEngine } from "../engine-resolver.js";
 
 /**
@@ -48,6 +48,7 @@ export async function autoLoop(
   let iteration = 0;
   const loopState: LoopState = { recentUnits: [], stuckRecoveryAttempts: 0, consecutiveFinalizeTimeouts: 0 };
   let consecutiveErrors = 0;
+  let consecutiveCooldowns = 0;
   const recentErrorMessages: string[] = [];
 
   while (s.active) {
@@ -203,6 +204,7 @@ export async function autoLoop(
 
         deps.clearUnitTimeout();
         consecutiveErrors = 0;
+        consecutiveCooldowns = 0;
         recentErrorMessages.length = 0;
         deps.emitJournalEvent({ ts: new Date().toISOString(), flowId, seq: nextSeq(), eventType: "iteration-end", data: { iteration } });
         debugLog("autoLoop", { phase: "iteration-complete", iteration });
@@ -265,6 +267,7 @@ export async function autoLoop(
       if (finalizeResult.action === "continue") continue;
 
       consecutiveErrors = 0; // Iteration completed successfully
+      consecutiveCooldowns = 0;
       recentErrorMessages.length = 0;
       deps.emitJournalEvent({ ts: new Date().toISOString(), flowId, seq: nextSeq(), eventType: "iteration-end", data: { iteration } });
       debugLog("autoLoop", { phase: "iteration-complete", iteration });
@@ -300,6 +303,47 @@ export async function autoLoop(
         break;
       }
 
+      // ── Credential cooldown: wait and retry with bounded budget ──
+      // A 429 triggers a 30s credential backoff in AuthStorage. If the SDK's
+      // getApiKey() retries couldn't outlast the window, the error surfaces
+      // here. Wait for the cooldown to clear rather than counting it as a
+      // consecutive failure — but cap retries so we don't spin for hours
+      // on persistent quota exhaustion.
+      if (isTransientCooldownError(loopErr)) {
+        consecutiveCooldowns++;
+        const retryAfterMs = getCooldownRetryAfterMs(loopErr);
+        debugLog("autoLoop", {
+          phase: "cooldown-wait",
+          iteration,
+          consecutiveCooldowns,
+          retryAfterMs,
+          error: msg,
+        });
+
+        if (consecutiveCooldowns > MAX_COOLDOWN_RETRIES) {
+          ctx.ui.notify(
+            `Auto-mode stopped: ${consecutiveCooldowns} consecutive credential cooldowns — rate limit or quota may be persistently exhausted.`,
+            "error",
+          );
+          await deps.stopAuto(
+            ctx,
+            pi,
+            `${consecutiveCooldowns} consecutive credential cooldowns exceeded retry budget`,
+          );
+          break;
+        }
+
+        const waitMs = (retryAfterMs !== undefined && retryAfterMs > 0 && retryAfterMs <= 60_000)
+          ? retryAfterMs + 500 // Use structured hint + small buffer
+          : COOLDOWN_FALLBACK_WAIT_MS;
+        ctx.ui.notify(
+          `Credentials in cooldown (${consecutiveCooldowns}/${MAX_COOLDOWN_RETRIES}) — waiting ${Math.round(waitMs / 1000)}s before retrying.`,
+          "warning",
+        );
+        await new Promise(resolve => setTimeout(resolve, waitMs));
+        continue; // Retry iteration without incrementing consecutiveErrors
+      }
+
       consecutiveErrors++;
       recentErrorMessages.push(msg.length > 120 ? msg.slice(0, 120) + "..." : msg);
       debugLog("autoLoop", {
diff --git a/src/resources/extensions/gsd/tests/infra-errors-cooldown.test.ts b/src/resources/extensions/gsd/tests/infra-errors-cooldown.test.ts
new file mode 100644
index 000000000..ebaa774a6
--- /dev/null
+++ b/src/resources/extensions/gsd/tests/infra-errors-cooldown.test.ts
@@ -0,0 +1,180 @@
+// gsd / infra-errors cooldown detection tests
+// Copyright (c) 2026 Jeremy McSpadden <jeremy@fluxlabs.net>
+
+import test, { describe } from "node:test";
+import assert from "node:assert/strict";
+
+import {
+  isTransientCooldownError,
+  getCooldownRetryAfterMs,
+  MAX_COOLDOWN_RETRIES,
+  COOLDOWN_FALLBACK_WAIT_MS,
+} from "../auto/infra-errors.js";
+
+// ─── Constants ────────────────────────────────────────────────────────────────
+
+describe("infra-errors cooldown constants", () => {
+  test("COOLDOWN_FALLBACK_WAIT_MS is a positive number greater than the 30s rate-limit backoff", () => {
+    assert.ok(typeof COOLDOWN_FALLBACK_WAIT_MS === "number");
+    assert.ok(COOLDOWN_FALLBACK_WAIT_MS > 30_000, "should exceed the 30s rate-limit window");
+  });
+
+  test("MAX_COOLDOWN_RETRIES is a positive integer", () => {
+    assert.ok(typeof MAX_COOLDOWN_RETRIES === "number");
+    assert.ok(Number.isInteger(MAX_COOLDOWN_RETRIES));
+    assert.ok(MAX_COOLDOWN_RETRIES > 0);
+  });
+
+  test("COOLDOWN_FALLBACK_WAIT_MS is 35_000", () => {
+    assert.equal(COOLDOWN_FALLBACK_WAIT_MS, 35_000);
+  });
+
+  test("MAX_COOLDOWN_RETRIES is 5", () => {
+    assert.equal(MAX_COOLDOWN_RETRIES, 5);
+  });
+});
+
+// ─── isTransientCooldownError: structured detection ──────────────────────────
+
+describe("isTransientCooldownError — structured code detection", () => {
+  test("returns true for an object with code === AUTH_COOLDOWN", () => {
+    const err = { code: "AUTH_COOLDOWN", message: "credentials in cooldown" };
+    assert.equal(isTransientCooldownError(err), true);
+  });
+
+  test("returns true for a real CredentialCooldownError-shaped error", () => {
+    // Simulate CredentialCooldownError without importing sdk.ts (leaf-module rule)
+    const err = Object.assign(new Error('All credentials for "anthropic" are in a cooldown window.'), {
+      code: "AUTH_COOLDOWN",
+      retryAfterMs: 30_000,
+      name: "CredentialCooldownError",
+    });
+    assert.equal(isTransientCooldownError(err), true);
+  });
+
+  test("returns false for an object with a different code", () => {
+    const err = { code: "ENOSPC", message: "disk full" };
+    assert.equal(isTransientCooldownError(err), false);
+  });
+
+  test("returns false for an object with no code property", () => {
+    const err = { message: "some random error" };
+    assert.equal(isTransientCooldownError(err), false);
+  });
+});
+
+// ─── isTransientCooldownError: message fallback ───────────────────────────────
+
+describe("isTransientCooldownError — message fallback (cross-process)", () => {
+  test("returns true when message contains 'in a cooldown window'", () => {
+    const err = new Error('All credentials for "openai" are in a cooldown window. Please wait.');
+    assert.equal(isTransientCooldownError(err), true);
+  });
+
+  test("returns true when message matches case-insensitively", () => {
+    const err = new Error("credentials IN A COOLDOWN WINDOW");
+    assert.equal(isTransientCooldownError(err), true);
+  });
+
+  test("returns true for a plain string containing cooldown window phrase", () => {
+    assert.equal(isTransientCooldownError("all keys in a cooldown window"), true);
+  });
+
+  test("returns false for a generic error message", () => {
+    const err = new Error("rate limit exceeded");
+    assert.equal(isTransientCooldownError(err), false);
+  });
+
+  test("returns false for an error message about auth failure without cooldown phrase", () => {
+    const err = new Error("Authentication failed: invalid API key");
+    assert.equal(isTransientCooldownError(err), false);
+  });
+});
+
+// ─── isTransientCooldownError: edge cases ────────────────────────────────────
+
+describe("isTransientCooldownError — edge cases", () => {
+  test("returns false for null", () => {
+    assert.equal(isTransientCooldownError(null), false);
+  });
+
+  test("returns false for undefined", () => {
+    assert.equal(isTransientCooldownError(undefined), false);
+  });
+
+  test("returns false for a number", () => {
+    assert.equal(isTransientCooldownError(42), false);
+  });
+
+  test("returns false for an empty object", () => {
+    assert.equal(isTransientCooldownError({}), false);
+  });
+
+  test("returns false for an object with code === AUTH_COOLDOWN as a non-string", () => {
+    // code must be a string matching "AUTH_COOLDOWN" exactly
+    const err = { code: 42 };
+    assert.equal(isTransientCooldownError(err), false);
+  });
+});
+
+// ─── getCooldownRetryAfterMs: structured extraction ──────────────────────────
+
+describe("getCooldownRetryAfterMs — structured extraction", () => {
+  test("returns retryAfterMs when code is AUTH_COOLDOWN and retryAfterMs is set", () => {
+    const err = { code: "AUTH_COOLDOWN", retryAfterMs: 30_000 };
+    assert.equal(getCooldownRetryAfterMs(err), 30_000);
+  });
+
+  test("returns undefined when code is AUTH_COOLDOWN but retryAfterMs is absent", () => {
+    const err = { code: "AUTH_COOLDOWN" };
+    assert.equal(getCooldownRetryAfterMs(err), undefined);
+  });
+
+  test("returns 0 when retryAfterMs is explicitly 0", () => {
+    const err = { code: "AUTH_COOLDOWN", retryAfterMs: 0 };
+    assert.equal(getCooldownRetryAfterMs(err), 0);
+  });
+
+  test("returns undefined for an error with a different code even if retryAfterMs is set", () => {
+    const err = { code: "ENOSPC", retryAfterMs: 5_000 };
+    assert.equal(getCooldownRetryAfterMs(err), undefined);
+  });
+
+  test("returns undefined for a plain Error with no code property", () => {
+    const err = new Error("something went wrong");
+    assert.equal(getCooldownRetryAfterMs(err), undefined);
+  });
+
+  test("returns retryAfterMs from a full CredentialCooldownError-shaped object", () => {
+    const err = Object.assign(new Error('All credentials for "anthropic" are in a cooldown window.'), {
+      code: "AUTH_COOLDOWN",
+      retryAfterMs: 15_000,
+      name: "CredentialCooldownError",
+    });
+    assert.equal(getCooldownRetryAfterMs(err), 15_000);
+  });
+});
+
+// ─── getCooldownRetryAfterMs: edge cases ─────────────────────────────────────
+
+describe("getCooldownRetryAfterMs — edge cases", () => {
+  test("returns undefined for null", () => {
+    assert.equal(getCooldownRetryAfterMs(null), undefined);
+  });
+
+  test("returns undefined for undefined", () => {
+    assert.equal(getCooldownRetryAfterMs(undefined), undefined);
+  });
+
+  test("returns undefined for a plain string", () => {
+    assert.equal(getCooldownRetryAfterMs("AUTH_COOLDOWN"), undefined);
+  });
+
+  test("returns undefined for an empty object", () => {
+    assert.equal(getCooldownRetryAfterMs({}), undefined);
+  });
+
+  test("returns undefined for a number", () => {
+    assert.equal(getCooldownRetryAfterMs(42), undefined);
+  });
+});