Tailwind 4 was producing only theme variables (oklch colors)
without any utility classes because Astro had no astro.config.mjs
wiring the @tailwindcss/vite plugin. Result: site rendered
unstyled despite all components and HTML being correct.
Verified locally after fix:
- CSS bundle grew from 21 KB (theme only) to 36 KB (theme + utilities)
- 23 utility-class definitions present (bg-neutral-900, text-white,
min-h-screen, backdrop-blur, font-bold, flex etc)
Also adds @source directive in global.css to ensure Tailwind
scans .astro files for class usage.
