fix: improve error message when OAuth succeeds but project ID is required (#21070)

packages/cli/src/core/auth.test.ts

@@ -9,6 +9,7 @@ import { performInitialAuth } from './auth.js';
 import {
   type Config,
   ValidationRequiredError,
+  ProjectIdRequiredError,
   AuthType,
 } from '@google/gemini-cli-core';
 
@@ -116,4 +117,22 @@ describe('auth', () => {
       AuthType.LOGIN_WITH_GOOGLE,
     );
   });
+
+  it('should return ProjectIdRequiredError message without "Failed to login" prefix', async () => {
+    const projectIdError = new ProjectIdRequiredError();
+    vi.mocked(mockConfig.refreshAuth).mockRejectedValue(projectIdError);
+    const result = await performInitialAuth(
+      mockConfig,
+      AuthType.LOGIN_WITH_GOOGLE,
+    );
+    expect(result).toEqual({
+      authError:
+        'This account requires setting the GOOGLE_CLOUD_PROJECT or GOOGLE_CLOUD_PROJECT_ID env var. See https://goo.gle/gemini-cli-auth-docs#workspace-gca',
+      accountSuspensionInfo: null,
+    });
+    expect(result.authError).not.toContain('Failed to login');
+    expect(mockConfig.refreshAuth).toHaveBeenCalledWith(
+      AuthType.LOGIN_WITH_GOOGLE,
+    );
+  });
 });

packages/cli/src/core/auth.ts

@@ -10,6 +10,7 @@ import {
   getErrorMessage,
   ValidationRequiredError,
   isAccountSuspendedError,
+  ProjectIdRequiredError,
 } from '@google/gemini-cli-core';
 
 import type { AccountSuspensionInfo } from '../ui/contexts/UIStateContext.js';
@@ -54,6 +55,14 @@ export async function performInitialAuth(
         },
       };
     }
+    if (e instanceof ProjectIdRequiredError) {
+      // OAuth succeeded but account setup requires project ID
+      // Show the error message directly without "Failed to login" prefix
+      return {
+        authError: getErrorMessage(e),
+        accountSuspensionInfo: null,
+      };
+    }
     return {
       authError: `Failed to login. Message: ${getErrorMessage(e)}`,
       accountSuspensionInfo: null,