An old PostCSS config broke the Astro build

I rebuilt my company site in Astro and moved it into the repo of the old Jekyll site, so the old build files were still at the root. The first build failed:

[astro:build] Failed to load PostCSS config (searchPath: <repo>): [ReferenceError] module is not defined in ES module scope

The new site uses Tailwind v4 through @tailwindcss/vite, which doesn’t need PostCSS at all. But Vite looks for a PostCSS config on its own, and it found the Jekyll site’s postcss.config.js, which used module.exports and require. The new package.json has "type": "module", so Node loads every .js file as an ES module, and module doesn’t exist there.

I didn’t need that config anymore, so I deleted it, and later the old tailwind.config.js and the rest of the Jekyll files. The build finished with no warnings.

If you still need the PostCSS config in a "type": "module" package, rename it to postcss.config.cjs or change it to export default { ... }.