Mintlify's @mintlify/mdx is a thin TypeScript library that wraps next-mdx-remote-client to provide a simplified MDX rendering experience for Next.js applications. It adds rich syntax highlighting via Shiki, including support for language-specific highlighting, line highlights, diffs, and twoslash-powered TypeScript type hover popups. The library exposes three main APIs: `serialize` (server-side compilation), `MDXClient` (client-side rendering), and `MDXRemote` (RSC component that combines both). It includes pre-configured remark plugins (GFM, Smartypants, Math) and rehype plugins (Katex, syntax highlighting) with the ability to extend with custom plugins. The package also provides UI components for twoslash popups and a Shiki transformer for shell placeholder highlighting. The codebase is well-structured with clear separation of concerns, though test coverage is limited to the shell placeholder transformer.