Streamdown

This handles React markdown rendering optimized for AI streaming responses. Built as a drop-in replacement for react-markdown, it includes syntax highlighting via Shiki, Mermaid diagrams, LaTeX math, and streaming-friendly features like animated carets and copy buttons that disable during active streaming. Works directly with Vercel AI SDK's useChat hook. The Tailwind setup is mandatory and commonly missed, you need to add source directives for the dist files or styles won't load. Security defaults are solid with link confirmation modals and URL sanitization built in. Good for AI chat interfaces where you're rendering streamed markdown and want polish without building everything from scratch.