feat(chat): render LaTeX math formulas in assistant messages (#886)

Co-authored-by: Cursor Agent <cursoragent@cursor.com>
Co-authored-by: Haze <hazeone@users.noreply.github.com>

tests/unit/chat-message.test.tsx

@@ -30,3 +30,52 @@ describe('ChatMessage attachment dedupe', () => {
     expect(screen.getByAltText('artifact.png')).toBeInTheDocument();
   });
 });
+
+describe('ChatMessage LaTeX rendering', () => {
+  it('renders inline `$...$` math with KaTeX', () => {
+    const message: RawMessage = {
+      role: 'assistant',
+      content: 'Mass-energy equivalence: $E=mc^2$ is famous.',
+    };
+    const { container } = render(<ChatMessage message={message} />);
+    expect(container.querySelector('.katex')).not.toBeNull();
+  });
+
+  it('renders display `$$...$$` math as a block', () => {
+    const message: RawMessage = {
+      role: 'assistant',
+      content: 'Definite integral:\n\n$$\n\\int_0^1 x\\,dx = \\frac{1}{2}\n$$\n',
+    };
+    const { container } = render(<ChatMessage message={message} />);
+    expect(container.querySelector('.katex-display')).not.toBeNull();
+  });
+
+  it('renders `\\(...\\)` inline math (OpenAI-style escaping)', () => {
+    const message: RawMessage = {
+      role: 'assistant',
+      content: 'Quadratic formula: \\(x = \\frac{-b \\pm \\sqrt{b^2-4ac}}{2a}\\).',
+    };
+    const { container } = render(<ChatMessage message={message} />);
+    expect(container.querySelector('.katex')).not.toBeNull();
+    expect(container.querySelector('.katex-display')).toBeNull();
+  });
+
+  it('renders `\\[...\\]` block math (OpenAI-style escaping)', () => {
+    const message: RawMessage = {
+      role: 'assistant',
+      content: 'Sum formula:\n\n\\[\\sum_{i=1}^n i = \\frac{n(n+1)}{2}\\]',
+    };
+    const { container } = render(<ChatMessage message={message} />);
+    expect(container.querySelector('.katex-display')).not.toBeNull();
+  });
+
+  it('does not rewrite `\\(` inside code fences', () => {
+    const message: RawMessage = {
+      role: 'assistant',
+      content: 'Code sample:\n\n```\nprintf("\\(hello\\)")\n```\n',
+    };
+    const { container } = render(<ChatMessage message={message} />);
+    expect(container.textContent).toContain('\\(hello\\)');
+    expect(container.querySelector('.katex')).toBeNull();
+  });
+});