diff --git a/open-sse/services/claudeUsageCooldown.ts b/open-sse/services/claudeUsageCooldown.ts
new file mode 100644
index 0000000000..01de93dec9
--- /dev/null
+++ b/open-sse/services/claudeUsageCooldown.ts
@@ -0,0 +1,51 @@
+/**
+ * Per-token cooldown for the Claude OAuth usage endpoint
+ * (`https://api.anthropic.com/api/oauth/usage`).
+ *
+ * Anthropic rate-limits this quota endpoint independently of `/v1/messages`.
+ * When polled from multiple connections at once (dashboard auto-refresh + the
+ * combo health-scheduler), it spams `429` and that surfaces as noisy provider
+ * errors plus increased upstream load. Chat with the same token still works.
+ *
+ * We track a per-access-token "skip until" timestamp. When we see a `429`,
+ * we suppress further OAuth-usage polls for that token until the cooldown
+ * expires and the caller falls back to the legacy settings/org endpoint
+ * (which is what `getClaudeUsage` does on every non-OK response).
+ *
+ * Pure helpers (no fetch, no timers) keep this TDD-friendly.
+ *
+ * Inspired-by upstream 9router commit `79df34ca`.
+ */
+
+export const OAUTH_USAGE_429_COOLDOWN_MS = 180_000; // 3 minutes
+
+const oauthCooldown = new Map<string, number>();
+
+/** Returns true while `accessToken` is still inside its 429 cooldown window. */
+export function isClaudeOauthUsageCoolingDown(
+  accessToken: string | undefined,
+  now: number = Date.now()
+): boolean {
+  if (!accessToken) return false;
+  const until = oauthCooldown.get(accessToken);
+  if (until === undefined) return false;
+  if (until > now) return true;
+  // Lazy GC of expired entries — keeps the Map bounded by active tokens.
+  oauthCooldown.delete(accessToken);
+  return false;
+}
+
+/** Record a 429 from the OAuth usage endpoint for `accessToken`. */
+export function markClaudeOauthUsage429(
+  accessToken: string | undefined,
+  now: number = Date.now(),
+  cooldownMs: number = OAUTH_USAGE_429_COOLDOWN_MS
+): void {
+  if (!accessToken) return;
+  oauthCooldown.set(accessToken, now + cooldownMs);
+}
+
+/** Test-only: clear all entries. */
+export function _resetClaudeOauthUsageCooldown(): void {
+  oauthCooldown.clear();
+}
diff --git a/open-sse/services/usage.ts b/open-sse/services/usage.ts
index edd14b8a09..5be8ab2692 100644
--- a/open-sse/services/usage.ts
+++ b/open-sse/services/usage.ts
@@ -37,6 +37,10 @@ import {
 } from "../executors/antigravity.ts";
 import { getCreditsMode } from "./antigravityCredits.ts";
 import { CLAUDE_CODE_VERSION, fetchClaudeBootstrap } from "../executors/claudeIdentity.ts";
+import {
+  isClaudeOauthUsageCoolingDown,
+  markClaudeOauthUsage429,
+} from "./claudeUsageCooldown.ts";
 import { generateAntigravityRequestId, getAntigravitySessionId } from "./antigravityIdentity.ts";
 import {
   extractCodeAssistOnboardTierId,
@@ -2564,6 +2568,12 @@ async function getClaudeUsage(accessToken?: string) {
 
   // Refresh bootstrap in parallel; best-effort, failure non-fatal.
   const bootstrapPromise = fetchClaudeBootstrap(accessToken).catch(() => null);
+  // Skip OAuth usage call while this token is cooling down from a recent 429
+  // (chat with the same token still works — only the quota endpoint is throttled).
+  if (isClaudeOauthUsageCoolingDown(accessToken)) {
+    const legacy = await getClaudeUsageLegacy(accessToken);
+    return { ...legacy, bootstrap: await bootstrapPromise };
+  }
   try {
     // Real CLI uses axios here, not Stainless — UA is `claude-code/<version>`
     // (not `claude-cli/...`) and the shape is simpler than /v1/messages.
@@ -2649,6 +2659,11 @@ async function getClaudeUsage(accessToken?: string) {
       };
     }
 
+    // Cool down OAuth usage polling after a 429 (quota endpoint only — chat is unaffected).
+    if (oauthResponse.status === 429) {
+      markClaudeOauthUsage429(accessToken);
+    }
+
     // Fallback: OAuth endpoint returned non-OK, try legacy settings/org endpoint
     console.warn(
       `[Claude Usage] OAuth endpoint returned ${oauthResponse.status}, falling back to legacy`
diff --git a/tests/unit/claude-oauth-usage-429-backoff.test.ts b/tests/unit/claude-oauth-usage-429-backoff.test.ts
new file mode 100644
index 0000000000..3406421a8b
--- /dev/null
+++ b/tests/unit/claude-oauth-usage-429-backoff.test.ts
@@ -0,0 +1,66 @@
+import { describe, it, beforeEach } from "node:test";
+import { strict as assert } from "node:assert";
+
+import {
+  OAUTH_USAGE_429_COOLDOWN_MS,
+  _resetClaudeOauthUsageCooldown,
+  isClaudeOauthUsageCoolingDown,
+  markClaudeOauthUsage429,
+} from "../../open-sse/services/claudeUsageCooldown.ts";
+
+describe("claude OAuth usage 429 backoff", () => {
+  beforeEach(() => {
+    _resetClaudeOauthUsageCooldown();
+  });
+
+  it("starts uncooled for any token", () => {
+    assert.equal(isClaudeOauthUsageCoolingDown("tok-a"), false);
+    assert.equal(isClaudeOauthUsageCoolingDown(undefined), false);
+  });
+
+  it("treats a single 429 as entering cooldown for that token only", () => {
+    const t0 = 1_000_000;
+    markClaudeOauthUsage429("tok-a", t0);
+    assert.equal(isClaudeOauthUsageCoolingDown("tok-a", t0 + 1), true);
+    // A different token is unaffected — cooldown is per-token, not global.
+    assert.equal(isClaudeOauthUsageCoolingDown("tok-b", t0 + 1), false);
+  });
+
+  it("repeated 429s on the same token do NOT spam: stays cooling once entered", () => {
+    const t0 = 2_000_000;
+    markClaudeOauthUsage429("tok-a", t0);
+    // Simulate the scheduler hitting 429 again 10s, 30s, 60s later
+    for (const dt of [10_000, 30_000, 60_000]) {
+      markClaudeOauthUsage429("tok-a", t0 + dt);
+      assert.equal(
+        isClaudeOauthUsageCoolingDown("tok-a", t0 + dt),
+        true,
+        `still cooling at +${dt}ms`
+      );
+    }
+  });
+
+  it("cooldown expires after OAUTH_USAGE_429_COOLDOWN_MS and the token becomes eligible again", () => {
+    const t0 = 3_000_000;
+    markClaudeOauthUsage429("tok-a", t0);
+    assert.equal(
+      isClaudeOauthUsageCoolingDown("tok-a", t0 + OAUTH_USAGE_429_COOLDOWN_MS - 1),
+      true
+    );
+    assert.equal(
+      isClaudeOauthUsageCoolingDown("tok-a", t0 + OAUTH_USAGE_429_COOLDOWN_MS + 1),
+      false,
+      "should be eligible again after cooldown window"
+    );
+  });
+
+  it("undefined/missing access token is a no-op (does not poison the map)", () => {
+    const t0 = 4_000_000;
+    markClaudeOauthUsage429(undefined, t0);
+    assert.equal(isClaudeOauthUsageCoolingDown(undefined, t0 + 1), false);
+  });
+
+  it("cooldown defaults to 3 minutes (matches upstream OAUTH_429_COOLDOWN_MS)", () => {
+    assert.equal(OAUTH_USAGE_429_COOLDOWN_MS, 180_000);
+  });
+});