@stylexjs/unplugin

Universal bundler plugin for StyleX built on top of unplugin. It compiles StyleX at build time, aggregates CSS from all transformed modules, and appends the result into an existing CSS asset produced by your bundler (or emits a stable fallback when none exists).

• Adapters for Vite/Rollup, Webpack/Rspack, and esbuild.
• Designed to keep StyleX output consolidated and deterministic.
• Dev helpers expose virtual modules for hot CSS reloads: virtual:stylex:runtime (JS) and /virtual:stylex.css (CSS) or virtual:stylex:css-only (JS shim).

Install

npm i -D @stylexjs/unplugin

Usage by bundler

Vite

// vite.config.ts
import { defineConfig } from 'vite';
import react from '@vitejs/plugin-react';
import stylex from '@stylexjs/unplugin';

export default defineConfig({
  plugins: [
    // devMode: 'full' | 'css-only' | 'off'
    // externalPackages: ['lib-using-stylex'] // optional manual include
    stylex.vite(),
    react(),
  ],
});

Notes:

• The plugin auto-discovers installed packages that depend on @stylexjs/stylex (or any configured importSources) and excludes them from optimizeDeps/ssr.optimizeDeps so their StyleX code is transformed. Use externalPackages to force-deopt additional deps.
• devMode: 'full' injects a lightweight runtime that refetches the dev CSS endpoint on HMR. css-only serves just the CSS endpoint. off disables dev middleware/virtual modules.
• In dev, inject the virtual CSS + runtime from your HTML shell. If a <script src="/@id/virtual:stylex:runtime"> tag is blocked by CORS (some frameworks proxy assets differently), call import('virtual:stylex:runtime') or import('virtual:stylex:css-only') from a tiny client shim instead.
• Ensure your app produces a CSS asset (default Vite behavior). If none exists, the plugin writes stylex.css in the output.

Dev HTML injection (baseline):

<!-- Add in your HTML shell when import.meta.env.DEV -->
<link rel="stylesheet" href="/virtual:stylex.css" />
<script type="module">
  import('virtual:stylex:runtime'); // or 'virtual:stylex:css-only' if you only need CSS
</script>

If your environment can safely load the runtime via a virtual module ID, replace the inline script with <script type="module" src="/@id/virtual:stylex:runtime">.

Rollup

// rollup.config.mjs
import stylex from '@stylexjs/unplugin';

export default {
  plugins: [stylex.rollup()],
};

Webpack

// webpack.config.js
const stylex = require('@stylexjs/unplugin').default;
const MiniCssExtractPlugin = require('mini-css-extract-plugin');

module.exports = {
  module: {
    rules: [
      // your JS/TS loader here
      { test: /\.css$/, use: [MiniCssExtractPlugin.loader, 'css-loader'] },
    ],
  },
  plugins: [stylex.webpack({ useCSSLayers: true }), new MiniCssExtractPlugin()],
};

Rspack

const rspack = require('@rspack/core');
const stylex = require('@stylexjs/unplugin').default;

module.exports = {
  plugins: [
    stylex.rspack(),
    new rspack.CssExtractRspackPlugin({ filename: 'index.css' }),
  ],
};

esbuild

import esbuild from 'esbuild';
import stylex from '@stylexjs/unplugin';

esbuild.build({
  entryPoints: ['src/App.jsx'],
  bundle: true,
  metafile: true, // lets the plugin locate CSS outputs if any
  plugins: [
    stylex.esbuild({
      importSources: ['@stylexjs/stylex'],
      useCSSLayers: true,
    }),
  ],
});

Options (shared)

• dev: boolean, defaults based on NODE_ENV/BABEL_ENV.
• importSources: array of import sources to scan, default ['stylex', '@stylexjs/stylex'].
• useCSSLayers: boolean, emit CSS layers.
• babelConfig: { plugins, presets } to merge into the internal Babel call.
• unstable_moduleResolution: forwarded to the StyleX Babel plugin.
• lightningcssOptions: pass-through options for lightningcss.
• cssInjectionTarget: (fileName: string) => boolean to pick a CSS asset to append to. Defaults to index.css, style.css, or the first .css asset.
• externalPackages: package names inside node_modules that should be treated like app code (useful if they ship StyleX). They are excluded from Vite dependency optimization.
• devMode: 'full' | 'css-only' | 'off' (Vite only).
• devPersistToDisk: persist collected rules to node_modules/.stylex/rules.json in dev so multiple Vite environments can share CSS.

Notes

• With multiple outputs (e.g. client/SSR), each output gets its own aggregated StyleX CSS.
• If the bundler produces no CSS assets, the plugin emits a fallback stylex.css (often in assets/ for Rollup/Vite or alongside esbuild outputs).
• When using extraction plugins (Webpack/Rspack), ensure they run so there is a CSS asset to append to; otherwise the fallback file is created.
• Dev HMR CSS hookup: add <link rel="stylesheet" href="/virtual:stylex.css" /> to your shell in dev. For the JS runtime, prefer import('virtual:stylex:runtime') (or virtual:stylex:css-only if you only need CSS) from a local client shim when direct <script src="/@id/virtual:stylex:runtime"> fails due to CORS/proxying.