Meta released Astryx this week, an open-source React design system currently in Beta that grew inside Meta’s monorepo over eight years. Astryx is built on React and StyleX, Meta’s compile-time CSS engine, and provides foundations, components, templates, and themes. The official repository documents more than 90 React components, while Meta’s docs site counts over 150. The license is MIT, and TypeScript makes up about three-quarters of the codebase. Astryx ships ten ready-made themes named default, neutral, daily, butter, chocolate, matcha, stone, gothic, brutalist, and y2k, all fully customizable via a CSS variable cascade. A CLI and MCP server allow AI agents to scaffold, browse, and document UIs; the CLI returns a self-describing manifest as JSON listing every command, argument, flag, and response type. Components carry JSDoc annotations with composition hints. Astryx is production-tested inside Meta but young as a public project.