fix: suppress duplicate extension warnings during startup (#26208)

packages/cli/src/config/skipExtensions.test.ts

@@ -0,0 +1,54 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { describe, it, expect, vi, beforeEach } from 'vitest';
+import { loadCliConfig, type CliArgs } from './config.js';
+import { ExtensionManager } from './extension-manager.js';
+import { createTestMergedSettings } from './settings.js';
+
+vi.mock('./extension-manager.js', () => ({
+  ExtensionManager: vi.fn().mockImplementation(() => ({
+    loadExtensions: vi.fn().mockResolvedValue([]),
+    getExtensions: vi.fn().mockReturnValue([]),
+  })),
+}));
+
+describe('loadCliConfig skipExtensions', () => {
+  const settings = createTestMergedSettings();
+  const argv = {
+    query: undefined,
+    model: undefined,
+    sandbox: undefined,
+    debug: undefined,
+    prompt: undefined,
+    promptInteractive: undefined,
+    yolo: undefined,
+    approvalMode: undefined,
+    policy: undefined,
+    adminPolicy: undefined,
+    allowedMcpServerNames: undefined,
+    allowedTools: undefined,
+    extensions: undefined,
+    listExtensions: undefined,
+    resume: undefined,
+    sessionId: undefined,
+    listSessions: undefined,
+  } as unknown as CliArgs;
+
+  beforeEach(() => {
+    vi.clearAllMocks();
+  });
+
+  it('should load extensions by default', async () => {
+    await loadCliConfig(settings, 'session-id', argv);
+    expect(ExtensionManager).toHaveBeenCalled();
+  });
+
+  it('should skip extensions when skipExtensions is true', async () => {
+    await loadCliConfig(settings, 'session-id', argv, { skipExtensions: true });
+    expect(ExtensionManager).not.toHaveBeenCalled();
+  });
+});