diff --git a/src/cliproxy/quota-fetcher.ts b/src/cliproxy/quota-fetcher.ts
index 06e7c392..dbe30a75 100644
--- a/src/cliproxy/quota-fetcher.ts
+++ b/src/cliproxy/quota-fetcher.ts
@@ -352,6 +352,28 @@ function buildAntigravityFailure(
   };
 }
 
+function mergeAntigravityTierEvidence(
+  entitlement: ProviderEntitlementEvidence | undefined,
+  tier: AccountTier,
+  rawTierId: string | null,
+  rawTierLabel: string | null
+): ProviderEntitlementEvidence | undefined {
+  if (tier === 'unknown' && !entitlement) {
+    return undefined;
+  }
+
+  return buildProviderEntitlementEvidence({
+    normalizedTier: tier,
+    rawTierId,
+    rawTierLabel,
+    source: rawTierId ? 'runtime_api' : (entitlement?.source ?? 'runtime_inference'),
+    confidence: rawTierId ? 'high' : (entitlement?.confidence ?? 'medium'),
+    accessState: entitlement?.accessState ?? 'unknown',
+    capacityState: entitlement?.capacityState ?? 'unknown',
+    notes: entitlement?.notes ?? null,
+  });
+}
+
 async function readManagedResponse(
   response: Response,
   viaManagement: boolean
@@ -620,6 +642,14 @@ async function getProjectId(accountId: string, accessToken: string): Promise<Pro
       error: 'Invalid quota response from provider',
       errorCode: 'provider_unavailable',
       retryable: true,
+      entitlement: buildProviderEntitlementEvidence({
+        normalizedTier: 'unknown',
+        source: 'runtime_inference',
+        confidence: 'low',
+        accessState: 'unknown',
+        capacityState: 'temporarily_unavailable',
+        notes: 'Provider returned a 2xx response with an empty or invalid project payload.',
+      }),
     };
   }
 
@@ -862,6 +892,12 @@ export async function fetchAccountQuota(
   } else {
     result.isExpired = authData.isExpired;
     result.expiresAt = authData.expiresAt || undefined;
+    result.entitlement = mergeAntigravityTierEvidence(
+      result.entitlement,
+      apiTier,
+      rawTierId,
+      rawTierLabel
+    );
   }
 
   if (verbose && result.error) {
diff --git a/tests/unit/cliproxy/quota-fetcher-antigravity-failure.test.ts b/tests/unit/cliproxy/quota-fetcher-antigravity-failure.test.ts
index 817e7f3a..fd2363ed 100644
--- a/tests/unit/cliproxy/quota-fetcher-antigravity-failure.test.ts
+++ b/tests/unit/cliproxy/quota-fetcher-antigravity-failure.test.ts
@@ -82,4 +82,134 @@ describe('Antigravity quota failure metadata', () => {
       fs.rmSync(tempHome, { recursive: true, force: true });
     }
   });
+
+  it('attaches entitlement evidence when project lookup returns an invalid 2xx payload', async () => {
+    const moduleId = Date.now() + Math.random();
+    const { fetchAccountQuota } = await import(
+      `../../../src/cliproxy/quota-fetcher?agy-invalid-project=${moduleId}`
+    );
+    const { getProviderAuthDir } = await import(
+      `../../../src/cliproxy/config-generator?agy-config=${moduleId}`
+    );
+    const fs = await import('node:fs');
+    const os = await import('node:os');
+    const path = await import('node:path');
+
+    const tempHome = fs.mkdtempSync(path.join(os.tmpdir(), 'ccs-agy-invalid-project-'));
+    const originalCcsHome = process.env.CCS_HOME;
+    process.env.CCS_HOME = tempHome;
+
+    try {
+      const authDir = getProviderAuthDir('agy');
+      fs.mkdirSync(authDir, { recursive: true });
+      fs.writeFileSync(
+        path.join(authDir, 'antigravity-user@example.com.json'),
+        JSON.stringify({
+          type: 'antigravity',
+          email: 'user@example.com',
+          access_token: 'token',
+        })
+      );
+
+      const originalFetch = globalThis.fetch;
+      globalThis.fetch = (async () =>
+        new Response('', {
+          status: 200,
+          headers: { 'Content-Type': 'application/json' },
+        })) as typeof fetch;
+
+      try {
+        const result = await fetchAccountQuota('agy', 'user@example.com');
+        expect(result.success).toBe(false);
+        expect(result.errorCode).toBe('provider_unavailable');
+        expect(result.entitlement).toMatchObject({
+          accessState: 'unknown',
+          capacityState: 'temporarily_unavailable',
+        });
+      } finally {
+        globalThis.fetch = originalFetch;
+      }
+    } finally {
+      if (originalCcsHome === undefined) {
+        delete process.env.CCS_HOME;
+      } else {
+        process.env.CCS_HOME = originalCcsHome;
+      }
+      fs.rmSync(tempHome, { recursive: true, force: true });
+    }
+  });
+
+  it('preserves live tier evidence when quota fetch fails after a successful project lookup', async () => {
+    const moduleId = Date.now() + Math.random();
+    const { fetchAccountQuota } = await import(
+      `../../../src/cliproxy/quota-fetcher?agy-invalid-models=${moduleId}`
+    );
+    const { getProviderAuthDir } = await import(
+      `../../../src/cliproxy/config-generator?agy-config=${moduleId}`
+    );
+    const fs = await import('node:fs');
+    const os = await import('node:os');
+    const path = await import('node:path');
+
+    const tempHome = fs.mkdtempSync(path.join(os.tmpdir(), 'ccs-agy-invalid-models-'));
+    const originalCcsHome = process.env.CCS_HOME;
+    process.env.CCS_HOME = tempHome;
+
+    try {
+      const authDir = getProviderAuthDir('agy');
+      fs.mkdirSync(authDir, { recursive: true });
+      fs.writeFileSync(
+        path.join(authDir, 'antigravity-user@example.com.json'),
+        JSON.stringify({
+          type: 'antigravity',
+          email: 'user@example.com',
+          access_token: 'token',
+        })
+      );
+
+      const originalFetch = globalThis.fetch;
+      let requestCount = 0;
+      globalThis.fetch = (async () => {
+        requestCount += 1;
+        if (requestCount === 1) {
+          return new Response(
+            JSON.stringify({
+              cloudaicompanionProject: { id: 'project-x' },
+              paidTier: { id: 'g1-pro-tier' },
+            }),
+            {
+              status: 200,
+              headers: { 'Content-Type': 'application/json' },
+            }
+          );
+        }
+
+        return new Response('', {
+          status: 200,
+          headers: { 'Content-Type': 'application/json' },
+        });
+      }) as typeof fetch;
+
+      try {
+        const result = await fetchAccountQuota('agy', 'user@example.com');
+        expect(result.success).toBe(false);
+        expect(result.entitlement).toMatchObject({
+          normalizedTier: 'pro',
+          rawTierId: 'g1-pro-tier',
+          rawTierLabel: 'Pro',
+          accessState: 'unknown',
+          capacityState: 'temporarily_unavailable',
+        });
+      } finally {
+        globalThis.fetch = originalFetch;
+      }
+    } finally {
+      if (originalCcsHome === undefined) {
+        delete process.env.CCS_HOME;
+      } else {
+        process.env.CCS_HOME = originalCcsHome;
+      }
+      fs.rmSync(tempHome, { recursive: true, force: true });
+    }
+  });
 });
diff --git a/ui/src/lib/api-client.ts b/ui/src/lib/api-client.ts
index 6a0e1bc4..a4fe2ed8 100644
--- a/ui/src/lib/api-client.ts
+++ b/ui/src/lib/api-client.ts
@@ -9,9 +9,11 @@ import type {
   ListAiProvidersResult,
   UpsertAiProviderEntryInput,
 } from '../../../src/cliproxy/ai-providers';
+import type { ProviderEntitlementEvidence } from '../../../src/cliproxy/provider-entitlement-types';
 
 export const API_BASE_URL = '/api';
 export const API_CONFLICT_ERROR_CODE = 'CONFLICT';
+export type { ProviderEntitlementEvidence };
 
 export class ApiConflictError extends Error {
   readonly code = API_CONFLICT_ERROR_CODE;
@@ -566,28 +568,6 @@ export interface QuotaResult {
   entitlement?: ProviderEntitlementEvidence;
 }
 
-export interface ProviderEntitlementEvidence {
-  normalizedTier: 'free' | 'pro' | 'ultra' | 'unknown';
-  rawTierId: string | null;
-  rawTierLabel: string | null;
-  source: 'runtime_api' | 'runtime_inference' | 'registry_cache' | 'official_docs';
-  confidence: 'high' | 'medium' | 'low';
-  accessState:
-    | 'entitled'
-    | 'not_entitled'
-    | 'capacity_exhausted'
-    | 'temporarily_unavailable'
-    | 'unknown';
-  capacityState:
-    | 'available'
-    | 'capacity_exhausted'
-    | 'rate_limited'
-    | 'temporarily_unavailable'
-    | 'unknown';
-  lastVerifiedAt: number;
-  notes?: string | null;
-}
-
 /** Codex rate limit window */
 export interface CodexQuotaWindow {
   /** Window label: "Primary", "Secondary", "Code Review (Primary)", "Code Review (Secondary)" */