diff --git a/gui/src/api.ts b/gui/src/api.ts
index fd6a777bb..664cde6a9 100644
--- a/gui/src/api.ts
+++ b/gui/src/api.ts
@@ -1,5 +1,12 @@
 let installed = false;
+/** Shared 401 refresh gate — concurrent waiters join one prompt / token resolution. */
 let promptInFlight: Promise<string | null> | null = null;
+/**
+ * After the user cancels (or submits blank) once, suppress further prompts for this page
+ * lifetime so a staggered 401 fan-out does not reopen the dialog N times (#647 / Codex).
+ * A full reload clears module state and allows prompting again.
+ */
+let promptCancelled = false;
 
 function needsApiAuth(input: RequestInfo | URL): boolean {
   try {
@@ -31,6 +38,11 @@ function clearToken(): void {
   memoryToken = null;
 }
 
+/** Clear memory only when it still holds `expected` (avoid wiping a newer concurrent store). */
+function clearTokenIfCurrent(expected: string | null): void {
+  if (expected != null && readToken() === expected) clearToken();
+}
+
 function clearLegacySessionToken(): void {
   try {
     sessionStorage.removeItem(LEGACY_TOKEN_KEY);
@@ -46,11 +58,31 @@ function withToken(input: RequestInfo | URL, init: RequestInit | undefined, toke
   return [input, { ...init, headers }];
 }
 
-async function promptForToken(): Promise<string | null> {
+/**
+ * Resolve a token after a 401. Concurrent callers share one in-flight resolution so a dashboard
+ * fan-out does not open one window.prompt per /api request (#647). Re-reads memoryToken before
+ * prompting so waiters that wake after another request already stored a token do not re-prompt.
+ */
+async function resolveTokenAfter401(failedToken: string | null): Promise<string | null> {
+  if (promptCancelled) return null;
   if (promptInFlight) return promptInFlight;
-  promptInFlight = Promise.resolve()
-    .then(() => window.prompt("OpenCodex API token")?.trim() || null)
-    .finally(() => { promptInFlight = null; });
+
+  promptInFlight = (async () => {
+    if (promptCancelled) return null;
+    const current = readToken();
+    if (current && current !== failedToken) return current;
+
+    const prompted = window.prompt("OpenCodex API token")?.trim() || null;
+    if (prompted) {
+      storeToken(prompted);
+      return prompted;
+    }
+    promptCancelled = true;
+    return null;
+  })().finally(() => {
+    promptInFlight = null;
+  });
+
   return promptInFlight;
 }
 
@@ -68,14 +100,23 @@ export function installApiAuthFetch(): void {
     const response = await originalFetch(firstInput, firstInit);
     if (response.status !== 401) return response;
 
-    if (token) clearToken();
-    const nextToken = await promptForToken();
+    // Another request may have stored a token while this one was in flight (or while prompt blocked).
+    const refreshed = readToken();
+    if (refreshed && refreshed !== token) {
+      const [retryInput, retryInit] = withToken(input, init, refreshed);
+      const retry = await originalFetch(retryInput, retryInit);
+      if (retry.status !== 401) return retry;
+      clearTokenIfCurrent(refreshed);
+    } else {
+      clearTokenIfCurrent(token);
+    }
+
+    const nextToken = await resolveTokenAfter401(token);
     if (!nextToken) return response;
 
-    storeToken(nextToken);
     const [retryInput, retryInit] = withToken(input, init, nextToken);
     const retry = await originalFetch(retryInput, retryInit);
-    if (retry.status === 401) clearToken();
+    if (retry.status === 401) clearTokenIfCurrent(nextToken);
     return retry;
   };
 }
@@ -85,4 +126,5 @@ export function resetApiAuthFetchForTests(): void {
   installed = false;
   memoryToken = null;
   promptInFlight = null;
+  promptCancelled = false;
 }
diff --git a/gui/tests/api-auth-memory.test.ts b/gui/tests/api-auth-memory.test.ts
index 4d27d8600..3bc008d70 100644
--- a/gui/tests/api-auth-memory.test.ts
+++ b/gui/tests/api-auth-memory.test.ts
@@ -113,6 +113,172 @@ test("cross-origin /api/* requests do not receive the API key or token prompt",
   expect(promptCalls).toBe(beforeCrossPrompts);
 });
 
+test("concurrent 401s share one token prompt and all retry with the stored token", async () => {
+  // Repro for #647: many /api/* requests start without a token (dashboard fan-out).
+  // Delivering 401s one-by-one after each auth cycle finishes matches the browser case where
+  // window.prompt blocks the main thread: each continuation still holds a captured null token
+  // and must reuse the in-memory token from an earlier request instead of prompting again.
+  let promptCalls = 0;
+  const release401: Array<() => void> = [];
+  const mockFetch = (async (_input: RequestInfo | URL, init?: RequestInit) => {
+    const headers = new Headers(init?.headers);
+    if (headers.get("X-OpenCodex-API-Key") === "shared-token") {
+      return new Response("{}", { status: 200 });
+    }
+    await new Promise<void>((resolve) => {
+      release401.push(resolve);
+    });
+    return new Response("unauthorized", { status: 401 });
+  }) as typeof fetch;
+  window.prompt = () => {
+    promptCalls += 1;
+    return "shared-token";
+  };
+  await installMockAuthFetch(mockFetch);
+
+  const endpoints = [
+    "/api/config",
+    "/api/providers",
+    "/api/models",
+    "/api/selected-models",
+    "/api/disabled-models",
+    "/api/effort-caps",
+    "/api/sidecar-settings",
+    "/api/injection-model",
+    "/api/v2",
+    "/api/keys",
+    "/api/provider-presets",
+    "/api/key-providers",
+    "/api/oauth/providers",
+    "/api/codex-auth/accounts",
+  ];
+  const pending = endpoints.map((path) => fetch(path).then((r) => r.status));
+  // Let every request reach the 401 gate before any response is delivered.
+  for (let i = 0; i < 20 && release401.length < endpoints.length; i += 1) {
+    await Promise.resolve();
+  }
+  expect(release401.length).toBe(endpoints.length);
+
+  for (let i = 0; i < endpoints.length; i += 1) {
+    const done = pending[i]!;
+    let settled = false;
+    void done.then(() => {
+      settled = true;
+    });
+    release401.shift()!();
+    for (let spin = 0; spin < 50 && !settled; spin += 1) {
+      await Promise.resolve();
+    }
+    expect(settled).toBe(true);
+  }
+
+  const statuses = await Promise.all(pending);
+  expect(promptCalls).toBe(1);
+  expect([...new Set(statuses)]).toEqual([200]);
+});
+
+test("stale concurrent 401 does not clear a token refreshed by another request", async () => {
+  // Codex/CodeRabbit race: request A prompts and stores T2; request B still holding stale T1
+  // must not wipe T2 (clearTokenIfCurrent) before its re-read / shared gate join.
+  let promptCalls = 0;
+  let acceptV1 = true;
+  const release401: Array<() => void> = [];
+  const mockFetch = (async (_input: RequestInfo | URL, init?: RequestInit) => {
+    const headers = new Headers(init?.headers);
+    const key = headers.get("X-OpenCodex-API-Key");
+    if (key === "token-v2") return new Response("{}", { status: 200 });
+    if (acceptV1 && key === "token-v1") return new Response("{}", { status: 200 });
+    if (key === "token-v1") {
+      await new Promise<void>((resolve) => {
+        release401.push(resolve);
+      });
+      return new Response("unauthorized", { status: 401 });
+    }
+    return new Response("unauthorized", { status: 401 });
+  }) as typeof fetch;
+  window.prompt = () => {
+    promptCalls += 1;
+    return "token-v1";
+  };
+  await installMockAuthFetch(mockFetch);
+  expect((await fetch("/api/config")).status).toBe(200);
+  expect(promptCalls).toBe(1);
+
+  acceptV1 = false;
+  promptCalls = 0;
+  window.prompt = () => {
+    promptCalls += 1;
+    return "token-v2";
+  };
+
+  const pending = [fetch("/api/config"), fetch("/api/providers")].map((p) => p.then((r) => r.status));
+  for (let i = 0; i < 20 && release401.length < 2; i += 1) {
+    await Promise.resolve();
+  }
+  expect(release401.length).toBe(2);
+
+  for (let i = 0; i < 2; i += 1) {
+    const done = pending[i]!;
+    let settled = false;
+    void done.then(() => {
+      settled = true;
+    });
+    release401.shift()!();
+    for (let spin = 0; spin < 50 && !settled; spin += 1) {
+      await Promise.resolve();
+    }
+    expect(settled).toBe(true);
+  }
+
+  const statuses = await Promise.all(pending);
+  expect(promptCalls).toBe(1);
+  expect([...new Set(statuses)]).toEqual([200]);
+});
+
+test("canceling the token prompt once does not reopen it for the rest of the 401 fan-out", async () => {
+  let promptCalls = 0;
+  const release401: Array<() => void> = [];
+  const mockFetch = (async (_input: RequestInfo | URL, init?: RequestInit) => {
+    const headers = new Headers(init?.headers);
+    if (headers.get("X-OpenCodex-API-Key")) {
+      return new Response("{}", { status: 200 });
+    }
+    await new Promise<void>((resolve) => {
+      release401.push(resolve);
+    });
+    return new Response("unauthorized", { status: 401 });
+  }) as typeof fetch;
+  window.prompt = () => {
+    promptCalls += 1;
+    return null;
+  };
+  await installMockAuthFetch(mockFetch);
+
+  const endpoints = ["/api/config", "/api/providers", "/api/models", "/api/keys"];
+  const pending = endpoints.map((path) => fetch(path).then((r) => r.status));
+  for (let i = 0; i < 20 && release401.length < endpoints.length; i += 1) {
+    await Promise.resolve();
+  }
+  expect(release401.length).toBe(endpoints.length);
+
+  for (let i = 0; i < endpoints.length; i += 1) {
+    const done = pending[i]!;
+    let settled = false;
+    void done.then(() => {
+      settled = true;
+    });
+    release401.shift()!();
+    for (let spin = 0; spin < 50 && !settled; spin += 1) {
+      await Promise.resolve();
+    }
+    expect(settled).toBe(true);
+  }
+
+  const statuses = await Promise.all(pending);
+  expect(promptCalls).toBe(1);
+  expect([...new Set(statuses)]).toEqual([401]);
+});
+
 test("cross-origin /v1/* requests do not receive the API key or token prompt", async () => {
   let promptCalls = 0;
   let phase: "seed" | "cross" = "seed";