name: tailwind-v4-shadcn description: | Set up Tailwind v4 with shadcn/ui using @theme inline pattern and CSS variable architecture. Four-step mandatory pattern: define CSS variables at root, map to Tailwind utilities, apply base styles, get automatic dark mode.

Use when: initializing React projects with Tailwind v4, setting up shadcn/ui dark mode, or fixing colors not working, theme not applying, CSS variables broken, tw-animate-css errors, or migrating from v3.

Tailwind v4 + shadcn/ui Production Stack

Production-tested: WordPress Auditor (https://wordpress-auditor.webfonts.workers.dev) Last Updated: 2026-01-03 Versions: tailwindcss@4.1.18, @tailwindcss/vite@4.1.18 Status: Production Ready ✅

Quick Start (Follow This Exact Order)

# 1. Install dependencies
pnpm add tailwindcss @tailwindcss/vite
pnpm add -D @types/node tw-animate-css
pnpm dlx shadcn@latest init

# 2. Delete v3 config if exists
rm tailwind.config.ts  # v4 doesn't use this file

vite.config.ts:

import { defineConfig } from 'vite'
import react from '@vitejs/plugin-react'
import tailwindcss from '@tailwindcss/vite'
import path from 'path'

export default defineConfig({
  plugins: [react(), tailwindcss()],
  resolve: { alias: { '@': path.resolve(__dirname, './src') } }
})

components.json (CRITICAL):

{
  "tailwind": {
    "config": "",              // ← Empty for v4
    "css": "src/index.css",
    "baseColor": "slate",
    "cssVariables": true
  }
}

The Four-Step Architecture (MANDATORY)

Skipping steps will break your theme. Follow exactly:

Step 1: Define CSS Variables at Root

/* src/index.css */
@import "tailwindcss";
@import "tw-animate-css";  /* Required for shadcn/ui animations */

:root {
  --background: hsl(0 0% 100%);      /* ← hsl() wrapper required */
  --foreground: hsl(222.2 84% 4.9%);
  --primary: hsl(221.2 83.2% 53.3%);
  /* ... all light mode colors */
}

.dark {
  --background: hsl(222.2 84% 4.9%);
  --foreground: hsl(210 40% 98%);
  --primary: hsl(217.2 91.2% 59.8%);
  /* ... all dark mode colors */
}

Critical: Define at root level (NOT inside @layer base). Use hsl() wrapper.

Step 2: Map Variables to Tailwind Utilities

@theme inline {
  --color-background: var(--background);
  --color-foreground: var(--foreground);
  --color-primary: var(--primary);
  /* ... map ALL CSS variables */
}

Why: Generates utility classes (bg-background, text-primary). Without this, utilities won't exist.

Step 3: Apply Base Styles

@layer base {
  body {
    background-color: var(--background);  /* NO hsl() wrapper here */
    color: var(--foreground);
  }
}

Critical: Reference variables directly. Never double-wrap: hsl(var(--background)).

Step 4: Result - Automatic Dark Mode

<div className="bg-background text-foreground">
  {/* No dark: variants needed - theme switches automatically */}
</div>

Dark Mode Setup

1. Create ThemeProvider (see templates/theme-provider.tsx)

2. Wrap App:

// src/main.tsx
import { ThemeProvider } from '@/components/theme-provider'

ReactDOM.createRoot(document.getElementById('root')!).render(
  <ThemeProvider defaultTheme="dark" storageKey="vite-ui-theme">
    <App />
  </ThemeProvider>
)

3. Add Theme Toggle:

pnpm dlx shadcn@latest add dropdown-menu

See reference/dark-mode.md for ModeToggle component.

Critical Rules

✅ Always Do:

1. Wrap colors with hsl() in :root/.dark: --bg: hsl(0 0% 100%);
2. Use @theme inline to map all CSS variables
3. Set "tailwind.config": "" in components.json
4. Delete tailwind.config.ts if exists
5. Use @tailwindcss/vite plugin (NOT PostCSS)

❌ Never Do:

1. Put :root/.dark inside @layer base
2. Use .dark { @theme { } } pattern (v4 doesn't support nested @theme)
3. Double-wrap colors: hsl(var(--background))
4. Use tailwind.config.ts for theme (v4 ignores it)
5. Use @apply directive (deprecated in v4)
6. Use dark: variants for semantic colors (auto-handled)

Common Errors & Solutions

This skill prevents 5 common errors.

1. ❌ tw-animate-css Import Error

Error: "Cannot find module 'tailwindcss-animate'"

Cause: shadcn/ui deprecated tailwindcss-animate for v4.

Solution:

# ✅ DO
pnpm add -D tw-animate-css

# Add to src/index.css:
@import "tailwindcss";
@import "tw-animate-css";

# ❌ DON'T
npm install tailwindcss-animate  # v3 only

2. ❌ Colors Not Working

Error: bg-primary doesn't apply styles

Cause: Missing @theme inline mapping

Solution:

@theme inline {
  --color-background: var(--background);
  --color-foreground: var(--foreground);
  --color-primary: var(--primary);
  /* ... map ALL CSS variables */
}

3. ❌ Dark Mode Not Switching

Error: Theme stays light/dark

Cause: Missing ThemeProvider

Solution:

1. Create ThemeProvider (see templates/theme-provider.tsx)
2. Wrap app in main.tsx
3. Verify .dark class toggles on <html> element

4. ❌ Duplicate @layer base

Error: "Duplicate @layer base" in console

Cause: shadcn init adds @layer base - don't add another

Solution:

/* ✅ Correct - single @layer base */
@import "tailwindcss";

:root { --background: hsl(0 0% 100%); }

@theme inline { --color-background: var(--background); }

@layer base { body { background-color: var(--background); } }

5. ❌ Build Fails with tailwind.config.ts

Error: "Unexpected config file"

Cause: v4 doesn't use tailwind.config.ts (v3 legacy)

Solution:

rm tailwind.config.ts

v4 configuration happens in src/index.css using @theme directive.

Quick Reference

Tailwind v4 Plugins

Use @plugin directive (NOT require() or @import):

Typography (for Markdown/CMS content):

pnpm add -D @tailwindcss/typography

@import "tailwindcss";
@plugin "@tailwindcss/typography";

<article class="prose dark:prose-invert">{{ content }}</article>

Forms (cross-browser form styling):

pnpm add -D @tailwindcss/forms

@import "tailwindcss";
@plugin "@tailwindcss/forms";

Container Queries (built-in, no plugin needed):

<div className="@container">
  <div className="@md:text-lg">Responds to container width</div>
</div>

Common Plugin Errors:

/* ❌ WRONG - v3 syntax */
@import "@tailwindcss/typography";

/* ✅ CORRECT - v4 syntax */
@plugin "@tailwindcss/typography";

Setup Checklist

• @tailwindcss/vite installed (NOT postcss)
• vite.config.ts uses tailwindcss() plugin
• components.json has "config": ""
• NO tailwind.config.ts exists
• src/index.css follows 4-step pattern:
  • :root/.dark at root level (not in @layer)
  • Colors wrapped with hsl()
  • @theme inline maps all variables
  • @layer base uses unwrapped variables
• ThemeProvider wraps app
• Theme toggle works

File Templates

Available in templates/ directory:

• index.css - Complete CSS with all color variables
• components.json - shadcn/ui v4 config
• vite.config.ts - Vite + Tailwind plugin
• theme-provider.tsx - Dark mode provider
• utils.ts - cn() utility

Migration from v3

See reference/migration-guide.md for complete guide.

Key Changes:

• Delete tailwind.config.ts
• Move theme to CSS with @theme inline
• Replace @tailwindcss/line-clamp (now built-in: line-clamp-*)
• Replace tailwindcss-animate with tw-animate-css
• Update plugins: require() → @plugin

Reference Documentation

• architecture.md - Deep dive into 4-step pattern
• dark-mode.md - Complete dark mode implementation
• common-gotchas.md - Troubleshooting guide
• migration-guide.md - v3 → v4 migration

Official Documentation

• shadcn/ui Vite Setup: https://ui.shadcn.com/docs/installation/vite
• shadcn/ui Tailwind v4: https://ui.shadcn.com/docs/tailwind-v4
• Tailwind v4 Docs: https://tailwindcss.com/docs

Last Updated: 2026-01-03 Skill Version: 2.0.1 Tailwind v4: 4.1.18 (Latest) Production: WordPress Auditor (https://wordpress-auditor.webfonts.workers.dev)