Tailwind CSS v4 CSS-First Configuration

v4 moves the entire configuration surface from JavaScript into CSS. Tokens are CSS variables in @theme. Custom utilities are CSS at-rules. Plugins, variants, and content paths all declare in CSS. The JS config file is opt-in only, via @config "./tailwind.config.js", for migration.

Companion skills :

• tailwind-impl-config-v3 : the v3 JS-config surface (tailwind.config.js)
• tailwind-core-v3-vs-v4 : v3-to-v4 differences across the API
• tailwind-impl-migration-v3-v4 : automated codemod + manual steps
• tailwind-errors-v4-migration : trap catalogue when an upgrade breaks

Quick Reference : The Minimum v4 Setup