diff --git a/src/oauth/kiro.ts b/src/oauth/kiro.ts
index 42ecff1340f..9d1ea73237a 100644
--- a/src/oauth/kiro.ts
+++ b/src/oauth/kiro.ts
@@ -45,6 +45,10 @@ const KIRO_TERMINAL_REFRESH_ERRORS = new Set([
   "access_denied",
   "expired_token",
 ]);
+// The desktop refresh endpoint rejects a dead refresh token with HTTP 401 and a bare
+// `{"message":"Bad credentials"}` body, without an OAuth `error` code. Only that exact
+// pair is a terminal verdict; it is surfaced under this fixed code, never the raw text.
+const KIRO_DESKTOP_BAD_CREDENTIALS = "bad_credentials";
 
 interface ImportedKiroToken {
   access: string;
@@ -545,12 +549,14 @@ async function kiroTokenRefreshError(response: Response, awsSsoRefresh = false):
   let oauthError: string | undefined;
   let refreshAttention = false;
   try {
-    const payload = await response.json() as { error?: unknown };
+    const payload = await response.json() as { error?: unknown; message?: unknown };
     // This input-error code is attention evidence only for our AWS SSO refresh request,
     // never a terminal grant verdict. Do not surface arbitrary upstream descriptions.
     refreshAttention = awsSsoRefresh && response.status === 400 && payload.error === "invalid_request";
     if (typeof payload.error === "string" && KIRO_TERMINAL_REFRESH_ERRORS.has(payload.error)) {
       oauthError = payload.error;
+    } else if (!awsSsoRefresh && response.status === 401 && payload.message === "Bad credentials") {
+      oauthError = KIRO_DESKTOP_BAD_CREDENTIALS;
     }
   } catch {
     // Error bodies are untrusted and intentionally excluded from the surfaced message.
diff --git a/structure/providers-and-adapters.md b/structure/providers-and-adapters.md
index 7d3aa123b26..c7c9665547a 100644
--- a/structure/providers-and-adapters.md
+++ b/structure/providers-and-adapters.md
@@ -140,7 +140,7 @@ are tried before the failure reaches `src/oauth/index.ts`. `src/oauth/store.ts`
 and operator pause. Once that generation's access token expires, account summaries project `needsReauth: true` and the active login projects `loggedIn: false`. `src/oauth/health.ts` uses
 the same generation/expiry predicate with its supplied observation time, so account-list health and CLI diagnostics project `reauth_required` with `refresh_failed`; `ocx doctor` warns with a
 login action. The internal terminal flag stays clear so a later refresh remains eligible; successful refresh or credential replacement
-clears the evidence. Desktop input errors, network failures, and 5xx responses create no evidence. No upstream description or credential metadata enters the status response.
+clears the evidence. Desktop input errors, network failures, and 5xx responses create no evidence. No upstream description or credential metadata enters the status response. The desktop refresh endpoint answers a dead refresh token with HTTP 401 and a bare `{"message":"Bad credentials"}` body; only that exact pair on the desktop endpoint is a terminal grant refusal, surfaced as the fixed `bad_credentials` code and quarantined like an allowlisted OAuth error.
 
 Kiro's account quota cache persists quota and an optional exhaustion verdict under one opaque account key and a non-secret login identity. Hydration admits only matching live
 accounts and bounds quota and verdict independently by reset and ten-minute TTL; a failed probe keeps the same-login last-good display bar. The protected OAuth store rotates
diff --git a/tests/oauth/oauth-kiro-refresh-attention.test.ts b/tests/oauth/oauth-kiro-refresh-attention.test.ts
index fa0e17d42d7..c76dfb9cfb0 100644
--- a/tests/oauth/oauth-kiro-refresh-attention.test.ts
+++ b/tests/oauth/oauth-kiro-refresh-attention.test.ts
@@ -3,7 +3,7 @@ import { Database } from "bun:sqlite";
 import { mkdtempSync, readFileSync } from "node:fs";
 import { tmpdir } from "node:os";
 import { join } from "node:path";
-import { getLoginStatus, getValidAccessTokenForAccount, OAUTH_PROVIDERS, refreshGenericAccountWithLock } from "../../src/oauth";
+import { getLoginStatus, getValidAccessTokenForAccount, OAuthLoginRequiredError, OAUTH_PROVIDERS, refreshGenericAccountWithLock } from "../../src/oauth";
 import { credentialGeneration, getAccountSet, saveAccountCredential, saveCredential, setAccountPaused } from "../../src/oauth/store";
 import type { OAuthCredentials } from "../../src/oauth/types";
 import { handleManagementAPI } from "../../src/server/management-api";
@@ -114,6 +114,55 @@ describe("Kiro AWS SSO refresh attention", () => {
     expect(getAccountSet("kiro")!.accounts[0]!.needsReauth).toBeUndefined();
   });
 
+  test("desktop 401 Bad credentials quarantines the rejected generation", async () => {
+    stored = { ...stored, kiro: { profileArn, authType: "kiro_desktop" } };
+    await saveAccountCredential("kiro", accountId, stored);
+    const urls: string[] = [];
+    globalThis.fetch = (async input => {
+      urls.push(String(input));
+      return Response.json({ message: "Bad credentials" }, { status: 401 });
+    }) as typeof fetch;
+    const error = await refresh().then(() => undefined, reason => reason);
+    expect(error).toBeInstanceOf(OAuthLoginRequiredError);
+    expect(urls).toEqual(["https://prod.us-east-1.auth.desktop.kiro.dev/refreshToken"]);
+    expect(getAccountSet("kiro")!.accounts[0]!.needsReauth).toBe(true);
+    expect(getLoginStatus("kiro").loggedIn).toBe(false);
+  });
+
+  test("desktop Bad credentials during matching CLI recovery quarantines the account", async () => {
+    seedCli(profileArn, false);
+    const urls: string[] = [];
+    globalThis.fetch = (async input => {
+      const url = String(input);
+      urls.push(url);
+      return url.endsWith("/refreshToken")
+        ? Response.json({ message: "Bad credentials" }, { status: 401 })
+        : Response.json(rejection, { status: 400 });
+    }) as typeof fetch;
+    const error = await refresh().then(() => undefined, reason => reason);
+    expect(urls).toEqual(["https://oidc.us-east-1.amazonaws.com/token", "https://prod.us-east-1.auth.desktop.kiro.dev/refreshToken"]);
+    expect(error).toBeInstanceOf(OAuthLoginRequiredError);
+    expect(getAccountSet("kiro")!.accounts[0]!.needsReauth).toBe(true);
+  });
+
+  for (const [label, status, payload, authType] of [
+    ["desktop 401 with another message", 401, { message: "Unauthorized" }, "kiro_desktop"],
+    ["desktop 400 Bad credentials", 400, { message: "Bad credentials" }, "kiro_desktop"],
+    ["AWS SSO 401 Bad credentials", 401, { message: "Bad credentials" }, "aws_sso_oidc"],
+  ] as const) {
+    test(`${label} does not quarantine`, async () => {
+      if (authType === "kiro_desktop") {
+        stored = { ...stored, kiro: { profileArn, authType } };
+        await saveAccountCredential("kiro", accountId, stored);
+      }
+      rejectRefresh(status, payload);
+      const error = await refresh().then(() => undefined, reason => reason);
+      expect(error).toBeDefined();
+      expect(error).not.toBeInstanceOf(OAuthLoginRequiredError);
+      expect(getAccountSet("kiro")!.accounts[0]!.needsReauth).toBeUndefined();
+    });
+  }
+
   for (const [label, status, payload] of [
     ["5xx", 503, rejection], ["different input error", 400, { error: "invalid_client" }],
     ["unallowlisted error text", 400, { error: "invalid_request arbitrary-secret-text" }],