diff --git a/src/cliproxy/auth/provider-refreshers/index.ts b/src/cliproxy/auth/provider-refreshers/index.ts
index 3e7c763c..07ed2bd2 100644
--- a/src/cliproxy/auth/provider-refreshers/index.ts
+++ b/src/cliproxy/auth/provider-refreshers/index.ts
@@ -26,6 +26,10 @@ export interface ProviderRefreshResult {
   delegated?: boolean;
 }
 
+function assertNever(value: never): never {
+  throw new Error(`Unhandled token refresh ownership: ${String(value)}`);
+}
+
 /**
  * Check if a provider's token refresh is delegated to CLIProxy
  */
@@ -47,24 +51,22 @@ export async function refreshToken(
     return await refreshGeminiTokenWrapper();
   }
 
-  if (isRefreshDelegated(provider)) {
-    // CLIProxyAPIPlus handles refresh for these providers automatically.
-    // No action needed from CCS — report success with delegated flag.
-    return { success: true, delegated: true };
-  }
-
   const ownership = getTokenRefreshOwnership(provider);
-  if (ownership === 'unsupported') {
-    return {
-      success: false,
-      error: `Token refresh not yet implemented for ${provider}`,
-    };
+  switch (ownership) {
+    case 'cliproxy':
+      // CLIProxyAPIPlus handles refresh for these providers automatically.
+      // No action needed from CCS — report success with delegated flag.
+      return { success: true, delegated: true };
+    case 'unsupported':
+    case 'ccs':
+      // Non-gemini CCS-owned refresh paths are not implemented yet.
+      return {
+        success: false,
+        error: `Token refresh not yet implemented for ${provider}`,
+      };
+    default:
+      return assertNever(ownership);
   }
-
-  return {
-    success: false,
-    error: `Unknown provider: ${provider}`,
-  };
 }
 
 /**
diff --git a/tests/unit/cliproxy/backend-ui-default-ports-sync.test.ts b/tests/unit/cliproxy/backend-ui-default-ports-sync.test.ts
index 751d7624..8e9bee7c 100644
--- a/tests/unit/cliproxy/backend-ui-default-ports-sync.test.ts
+++ b/tests/unit/cliproxy/backend-ui-default-ports-sync.test.ts
@@ -7,10 +7,22 @@
 import { describe, expect, test } from 'bun:test';
 import { CLIPROXY_DEFAULT_PORT as BACKEND_CLIPROXY_DEFAULT_PORT } from '../../../src/cliproxy/config/port-manager';
 import { DEFAULT_CURSOR_PORT as BACKEND_CURSOR_DEFAULT_PORT } from '../../../src/cursor/cursor-models';
+import {
+  CLIPROXY_PROVIDER_IDS as BACKEND_CLIPROXY_PROVIDER_IDS,
+  getProvidersByOAuthFlow,
+} from '../../../src/cliproxy/provider-capabilities';
 import {
   CLIPROXY_DEFAULT_PORT as UI_CLIPROXY_DEFAULT_PORT,
   DEFAULT_CURSOR_PORT as UI_CURSOR_DEFAULT_PORT,
 } from '../../../ui/src/lib/default-ports';
+import {
+  CLIPROXY_PROVIDERS as UI_CLIPROXY_PROVIDERS,
+  DEVICE_CODE_PROVIDERS as UI_DEVICE_CODE_PROVIDERS,
+} from '../../../ui/src/lib/provider-config';
+
+function sorted(values: readonly string[]): string[] {
+  return [...values].sort((a, b) => a.localeCompare(b));
+}
 
 describe('Default Port Sync', () => {
   test('CLIProxy default port is synced between backend and UI', () => {
@@ -20,4 +32,12 @@ describe('Default Port Sync', () => {
   test('Cursor default port is synced between backend and UI', () => {
     expect(UI_CURSOR_DEFAULT_PORT).toBe(BACKEND_CURSOR_DEFAULT_PORT);
   });
+
+  test('CLIProxy provider IDs are synced between backend and UI', () => {
+    expect(sorted(UI_CLIPROXY_PROVIDERS)).toEqual(sorted(BACKEND_CLIPROXY_PROVIDER_IDS));
+  });
+
+  test('Device code providers are synced between backend and UI', () => {
+    expect(sorted(UI_DEVICE_CODE_PROVIDERS)).toEqual(sorted(getProvidersByOAuthFlow('device_code')));
+  });
 });
diff --git a/ui/src/hooks/use-cursor.ts b/ui/src/hooks/use-cursor.ts
index e86d8782..2beca36f 100644
--- a/ui/src/hooks/use-cursor.ts
+++ b/ui/src/hooks/use-cursor.ts
@@ -8,8 +8,6 @@ import { useMemo } from 'react';
 import { useMutation, useQuery, useQueryClient } from '@tanstack/react-query';
 import { withApiBase } from '@/lib/api-client';
 
-export { DEFAULT_CURSOR_PORT } from '@/lib/default-ports';
-
 export interface CursorStatus {
   enabled: boolean;
   authenticated: boolean;
diff --git a/ui/src/pages/cursor.tsx b/ui/src/pages/cursor.tsx
index f66dd584..ec2da394 100644
--- a/ui/src/pages/cursor.tsx
+++ b/ui/src/pages/cursor.tsx
@@ -23,7 +23,8 @@ import {
   XCircle,
 } from 'lucide-react';
 import { cn } from '@/lib/utils';
-import { DEFAULT_CURSOR_PORT, useCursor } from '@/hooks/use-cursor';
+import { useCursor } from '@/hooks/use-cursor';
+import { DEFAULT_CURSOR_PORT } from '@/lib/default-ports';
 import { Button } from '@/components/ui/button';
 import { Input } from '@/components/ui/input';
 import { Label } from '@/components/ui/label';