streamdown — Claude Code skill: React Markdown for AI streaming

---
name: streamdown
description: >-
  Implement, configure, and customize Streamdown — a streaming-optimized React Markdown renderer
  with syntax highlighting, Mermaid diagrams, math rendering, and CJK support. Use when working
  with Streamdown setup, configuration, plugins, styling, security, or integration with AI
  streaming (e.g., Vercel AI SDK). Triggers on: (1) Installing or setting up Streamdown,
  (2) Configuring plugins (code, mermaid, math, cjk), (3) Styling or theming Streamdown output,
  (4) Integrating with AI chat/streaming, (5) Configuring security, link safety, or custom HTML tags,
  (6) Using carets, static mode, or custom components, (7) Troubleshooting Tailwind, Shiki, or Vite issues.
---

# Streamdown

Streaming-optimized React Markdown renderer. Drop-in replacement for `react-markdown` with built-in streaming support, security, and interactive controls.

## Quick Setup

### 1. Install

```bash
npm install streamdown
```

Optional plugins (install only what's needed):
```bash
npm install @streamdown/code @streamdown/mermaid @streamdown/math @streamdown/cjk
```

### 2. Configure Tailwind CSS (Required)

**This is the most commonly missed step.** Streamdown uses Tailwind for styling and the dist files must be scanned.

**Tailwind v4** — add to `globals.css`:
```css
@source "../node_modules/streamdown/dist/*.js";
```

Add plugin `@source` lines **only for packages you have installed** (omitting uninstalled plugins avoids Tailwind errors). See plugin pages for exact paths:
- Code: `@source "../node_modules/@streamdown/code/dist/*.js";`
- CJK: `@source "../node_modules/@streamdown/cjk/dist/*.js";`
- Math: `@source "../node_modules/@streamdown/math/dist/*.js";`
- Mermaid: `@source "../node_modules/@streamdown/mermaid/dist/*.js";`


**Tailwind v3** — add to `tailwind.config.js`:
```js
module.exports = {
  content: [
    "./app/**/*.{js,ts,jsx,tsx,mdx}",
    "./node_modules/streamdown/dist/*.js",
  ],
};
```

### 3. Basic Usage

```tsx
import { Streamdown } from 'streamdown';

<Streamdown>{markdown}</Streamdown>
```

### 4. With AI Streaming (Vercel AI SDK)

```tsx
'use client';
import { useChat } from '@ai-sdk/react';
import { Streamdown } from 'streamdown';
import { code } from '@streamdown/code';

export default function Chat() {
  const { messages, input, handleInputChange, handleSubmit, isLoading } = useChat();

  return (
    <>
      {messages.map((msg, i) => (
        <Streamdown
          key={msg.id}
          plugins={{ code }}
          caret="block"
          isAnimating={isLoading && i === messages.length - 1 && msg.role === 'assistant'}
        >
          {msg.content}
        </Streamdown>
      ))}
      <form onSubmit={handleSubmit}>
        <input value={input} onChange={handleInputChange} disabled={isLoading} />
      </form>
    </>
  );
}
```

### 5. Static Mode (Blogs, Docs)

```tsx
<Streamdown mode="static" plugins={{ code }}>
  {content}
</Streamdown>
```

## Key Props

| Prop | Type | Default | Purpose |
|------|------|---------|---------|
| `children` | `string` | — | Markdown content |
| `mode` | `"streaming" \| "static"` | `"streaming"` | Rendering mode |
| `plugins` | `{ code?, mermaid?, math?, cjk? }` | — | Feature plugins |
| `isAnimating` | `boolean` | `false` | Streaming indicator |
| `caret` | `"block" \| "circle"` | — | Cursor style |
| `components` | `Components` | — | Custom element overrides |
| `controls` | `boolean \| object` | `true` | Interactive buttons; `download: { filename }` sets custom download names |
| `linkSafety` | `LinkSafetyConfig` | `{ enabled: true }` | Link confirmation modal |
| `shikiTheme` | `[light, dark]` | `['github-light', 'github-dark']` | Code themes |
| `className` | `string` | — | Container class |
| `allowedElements` | `string[]` | all | Tag names to allow |
| `disallowedElements` | `string[]` | `[]` | Tag names to disallow |
| `allowElement` | `AllowElement` | — | Custom element filter |
| `unwrapDisallowed` | `boolean` | `false` | Keep children of disallowed elements |
| `skipHtml` | `boolean` | `false` | Ignore raw HTML |
| `urlTransform` | `UrlTransform` | `defaultUrlTransform` | Transform/sanitize URLs |

For full API reference, see [references/api.md](references/api.md).

## Plugin Quick Reference

| Plugin | Package | Purpose |
|--------|---------|---------|
| Code | `@streamdown/code` | Syntax highlighting (Shiki, 200+ languages) |
| Mermaid | `@streamdown/mermaid` | Diagrams (flowcharts, sequence, etc.) |
| Math | `@streamdown/math` | LaTeX via KaTeX (requires CSS import) |
| CJK | `@streamdown/cjk` | Chinese/Japanese/Korean text support |

**Math requires CSS:**
```tsx
import 'katex/dist/katex.min.css';
```

For plugin configuration details, see [references/plugins.md](references/plugins.md).

## References

Use these for deeper implementation details:

- **[references/api.md](references/api.md)** — Complete props, types, and interfaces
- **[references/plugins.md](references/plugins.md)** — Plugin setup, configuration, and customization
- **[references/styling.md](references/styling.md)** — CSS variables, data attributes, custom components, theme examples
- **[references/security.md](references/security.md)** — Hardening, link safety, custom HTML tags, production config
- **[references/features.md](references/features.md)** — Carets, remend, static mode, controls, GFM, memoization, troubleshooting

## Example Configurations

Copy and adapt from `assets/examples/`:

- **[basic-streaming.tsx](assets/examples/basic-streaming.tsx)** — Minimal AI chat with Vercel AI SDK
- **[with-caret.tsx](assets/examples/with-caret.tsx)** — Streaming with block caret cursor
- **[full-featured.tsx](assets/examples/full-featured.tsx)** — All plugins, carets, link safety, controls
- **[static-mode.tsx](assets/examples/static-mode.tsx)** — Blog/docs rendering
- **[custom-security.tsx](assets/examples/custom-security.tsx)** — Strict security for AI content

## Common Gotchas

1. **Tailwind styles missing** — Add `@source` directive or `content` entry for `node_modules/streamdown/dist/*.js`
2. **Math not rendering** — Import `katex/dist/katex.min.css`
3. **Caret not showing** — Both `caret` prop AND `isAnimating={true}` are required
4. **Copy buttons during streaming** — Disabled automatically when `isAnimating={true}`
5. **Link safety modal appearing** — Enabled by default; disable with `linkSafety={{ enabled: false }}`
6. **Shiki warning in Next.js** — Install `shiki` explicitly, add to `transpilePackages`
7. **`allowedTags` not working** — Only works with default rehype plugins
8. **Math uses `$$` not `$`** — Single dollar is disabled by default to avoid currency conflicts