Astryx
Meta's design system, opened as a beta under the MIT licence after eight years of internal use across more than 13,000 apps. It ships 150+ accessible React components, themes, dark mode, page templates and an `astryx` command line tool. You import pre-built CSS and typed components, with no build plugin. Docs, templates and theme generation are reachable from the command line or MCP, which means by an agent.
Strengths
- Docs an agent can read from the command line or MCP: the agent looks the component up instead of guessing it
- 150+ accessible components and page templates, the result of eight years of use across more than 13,000 of Meta's internal apps
- No styling lock-in: StyleX stays invisible and you override with Tailwind, CSS modules or plain CSS
Limitations
- Beta: charts published on canary only, experimental components unpublished, API still moving
- Requires React 19 or later, so out of reach for a project still on React 18
- A component whose source you pull out (the `swizzle` command) leaves the update stream: it is yours to maintain
Best for
- A new React app built with an agent, with no in-house design system to respect
- A design system lead who wants to see how a major player makes its docs readable by an agent