diff --git a/web/src/components/Chat/MessageList.test.tsx b/web/src/components/Chat/MessageList.test.tsx
new file mode 100644
index 0000000..685d69c
--- /dev/null
+++ b/web/src/components/Chat/MessageList.test.tsx
@@ -0,0 +1,62 @@
+import { render } from '@testing-library/react';
+import { describe, it, expect } from 'vitest';
+import { MessageList } from './MessageList';
+import type { ChatMessage } from '../../types/protocol';
+
+function makeMessage(
+  id: string,
+  role: 'user' | 'assistant' = 'assistant',
+  content = 'hello',
+): ChatMessage {
+  return {
+    id,
+    role,
+    content,
+    timestamp: Math.floor(Date.now() / 1000),
+    type: 'message',
+  };
+}
+
+describe('MessageList (virtualized)', () => {
+  it('1. renders empty state when no messages', () => {
+    const { getByText } = render(<MessageList messages={[]} />);
+    expect(getByText('开始新的对话')).toBeDefined();
+  });
+
+  it('2. renders without crash with many messages (virtualization smoke test)', () => {
+    const messages = Array.from({ length: 100 }, (_, i) =>
+      makeMessage(`m${i}`, 'assistant', `content ${i}`),
+    );
+    const { container } = render(<MessageList messages={messages} />);
+    // 虚拟化下 DOM 节点数应远少于 100（jsdom 下可能渲染部分或全部，但不崩溃）
+    expect(container.firstChild).not.toBeNull();
+  });
+
+  it('3. highlightedMessageId does not crash when target is virtualized out', () => {
+    const messages = Array.from({ length: 50 }, (_, i) => makeMessage(`m${i}`));
+    const { rerender } = render(<MessageList messages={messages} />);
+    // 高亮一条靠后的消息（可能在视口外），不应崩溃
+    expect(() =>
+      rerender(<MessageList messages={messages} highlightedMessageId="m45" />),
+    ).not.toThrow();
+  });
+
+  it('4. viewKey switch does not crash', () => {
+    const messages = Array.from({ length: 10 }, (_, i) => makeMessage(`m${i}`));
+    const { rerender } = render(<MessageList messages={messages} viewKey="view-a" />);
+    expect(() => rerender(<MessageList messages={messages} viewKey="view-b" />)).not.toThrow();
+  });
+
+  it('5. streaming (content grows on rerender) does not crash', () => {
+    // 注意：jsdom 下 getBoundingClientRect 返回 0 + rAF 同步化，virtualizer 测量后
+    // 可见范围可能变空（textContent 不可靠）。本用例只验证流式 rerender 不崩溃，
+    // 内容渲染的正确性由浏览器真实布局保证，jsdom 无法可靠断言。
+    const base = Array.from({ length: 5 }, (_, i) => makeMessage(`m${i}`));
+    const { rerender } = render(<MessageList messages={base} />);
+    const streamed = [...base];
+    streamed[4] = { ...streamed[4], content: 'streaming part1' };
+    expect(() => rerender(<MessageList messages={streamed} />)).not.toThrow();
+    streamed[4] = { ...streamed[4], content: 'streaming part1 part2' };
+    expect(() => rerender(<MessageList messages={streamed} />)).not.toThrow();
+  });
+});