Meta’s Astryx Brings a CLI and MCP Server to an Open-Source React Design System Agents Can Read

Meta released Astryx this week. It is an open-source design system, currently in Beta. The project grew inside Meta’s monorepo over eight years. Astryx is built on React and StyleX. StyleX is Meta’s compile-time CSS engine.

TL;DR

• Astryx is Meta’s open-source, agent-ready React design system, now in Beta.
• It pairs StyleX styling with a CSS-variable theme cascade and ten themes.
• A CLI and MCP server lets AI agents scaffold and document UIs.
• It is production-tested inside Meta but young as a public project.

What is Astryx

Astryx is a component library and a system around it. It provides foundations, components, templates, and themes. Foundations cover typography, color, layout, and accessibility. The official repository documents more than 90 React components. Meta’s docs site counts over 150. Components ship with built-in spacing, dark mode, and flexible styling. Templates compose full pages like dashboards, settings, and forms. The license is MIT. TypeScript makes up about three-quarters of the codebase.

The styling layer is worth understanding. StyleX compiles styles to static, atomic CSS at build time. Meta open-sourced StyleX at the end of 2023. It powers Facebook, Instagram, WhatsApp, and Threads. External companies like Figma and Snowflake also use it.

Two design choices stand out. First, internals are open. All primitives are exported and composable, not hidden. You can compose at any level. Second, spacing is automatic. Astryx calls this context-aware spacing compensation. It eliminates ‘double padding’ issues without manual fixups.

The ‘Agent Ready’ Part

This is the main difference from other design systems. Astryx ships docs and tooling that AI agents can read. Components carry JSDoc annotations with composition hints. A CLI exposes the same API a developer uses. There is also an MCP server. MCP is the Model Context Protocol. Agents use it to scaffold, browse, and document.

The CLI is called via astryx or the shorthand xds. One feature is really important for automation. The CLI returns a self-describing manifest as JSON. It lists every command, argument, flag, and response type. Compareing it to an OpenAPI spec for the CLI. So an agent need not scrape --help text. It reads one structured payload instead.

npx astryx component Button        # full docs for a component
npx astryx template dashboard      # emit full page source
npx astryx manifest --json         # machine-readable command spec

Themes and the CSS-Variable Cascade

Astryx ships ten ready-made themes. They are named default, neutral, daily, butter, chocolate, matcha, stone, gothic, brutalist, and y2k. All are fully customizable. Theming uses a CSS variable cascade. You change the variables, and every component restyles. Component code stays untouched.

The interactive demo below shows this directly. Pick a theme and watch the tokens update live.

import {Button} from '@astryxdesign/core/Button';
import {Badge} from '@astryxdesign/core/Badge';

export default function Toolbar() {
  return (
    

      <Button label="Save" variant="primary" />
      <Badge>BetaBadge>
    
  );
}

# get the real component source to edit in your repo
$ npx astryx swizzle Button

# then import your local copy instead of the package
import {Button} from './components/Button';

# install core, a theme, and the CLI
npm install @astryxdesign/core @astryxdesign/theme-neutral
npm install -D @astryxdesign/cli

// providers.tsx — wrap your app once
'use client';
import type {ReactNode} from 'react';
import {Theme} from '@astryxdesign/core/theme';
import {neutralTheme} from '@astryxdesign/theme-neutral/built';

export function Providers({children}: {children: ReactNode}) {
  return <Theme theme={neutralTheme}>{children}Theme>;
}

npm install @astryxdesign/core @astryxdesign/theme-neutral
npm install -D @astryxdesign/cli

Wrap your app in the Theme provider.

'use client';
import type {ReactNode} from 'react';
import {Theme} from '@astryxdesign/core/theme';
import {neutralTheme} from '@astryxdesign/theme-neutral/built';

export function Providers({children}: {children: ReactNode}) {
  return {children};
}

import {Button} from '@astryxdesign/core/Button';

export default function Page() {
  return ;
}