Tailwind v4 Shadcn

Configures Tailwind v4 with shadcn/ui using a mandatory four-step CSS variable theming to enable automatic dark mode and prevent common errors.

Tailwind v4 + shadcn/ui Stack

Production-tested setup for Tailwind v4 with shadcn/ui. Prevents 8 documented errors through a mandatory four-step architecture.

WHAT

Complete Tailwind v4 + shadcn/ui configuration:

• Four-step theming architecture (mandatory)
• CSS variable-based color system
• Automatic dark mode switching
• Error prevention for 8 common mistakes
• Migration guide from v3
• Production-ready templates

WHEN

• Starting a new React/Vite project with Tailwind v4
• Migrating from Tailwind v3 to v4
• Setting up shadcn/ui with Tailwind v4
• Debugging: colors not working, dark mode broken, build failures
• Fixing @theme inline, @apply, or @layer base issues

KEYWORDS

tailwind v4, tailwindcss 4, shadcn, shadcn/ui, @theme inline, dark mode, css variables, vite, tw-animate-css, tailwind config, migration

Production verified: WordPress Auditor (https://wordpress-auditor.webfonts.workers.dev)
Versions: tailwindcss@4.1.18, @tailwindcss/vite@4.1.18

Installation

OpenClaw / Moltbot / Clawbot

npx clawhub@latest install tailwind-v4-shadcn

---

Quick Start

# 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 (v4 doesn't use it)
rm tailwind.config.ts

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": "",
    "css": "src/index.css",
    "baseColor": "slate",
    "cssVariables": true
  }
}

---

The Four-Step Architecture (MANDATORY)

Skipping steps breaks theming. Follow exactly:

Step 1: Define CSS Variables at Root

/* src/index.css */
@import "tailwindcss";
@import "tw-animate-css";

:root {
  --background: hsl(0 0% 100%);
  --foreground: hsl(222.2 84% 4.9%);
  --primary: hsl(221.2 83.2% 53.3%);
  --primary-foreground: hsl(210 40% 98%);
  /* ... all light mode colors with hsl() wrapper */
}

.dark {
  --background: hsl(222.2 84% 4.9%);
  --foreground: hsl(210 40% 98%);
  --primary: hsl(217.2 91.2% 59.8%);
  --primary-foreground: hsl(222.2 47.4% 11.2%);
  /* ... all dark mode colors */
}

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

Step 2: Map Variables to Tailwind

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

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

Step 3: Apply Base Styles

@layer base {
  body {
    background-color: var(--background);
    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">
  {/* Theme switches automatically via .dark class */}
</div>

No dark: variants needed for semantic colors.

---

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 { } } (v4 doesn't support nested @theme)
3. Double-wrap: hsl(var(--background))
4. Use tailwind.config.ts for theme
5. Use @apply with @layer base/components classes
6. Use dark: variants for semantic colors

---

Common Errors & Solutions

Error 1: tw-animate-css Import

Error: Cannot find module 'tailwindcss-animate'

# Wrong (v3 package)
npm install tailwindcss-animate

# Correct (v4 package)
pnpm add -D tw-animate-css

@import "tailwindcss";
@import "tw-animate-css";

Error 2: Colors Not Working

Error: bg-primary doesn't apply styles

Cause: Missing @theme inline mapping

@theme inline {
  --color-primary: var(--primary);
  /* Map ALL variables */
}

Error 3: Dark Mode Not Switching

Cause: Missing ThemeProvider

See templates/theme-provider.tsx and wrap your app.

Error 4: Build Fails

Error: Unexpected config file

rm tailwind.config.ts  # v4 doesn't use this

Error 5: @theme inline Breaks Multi-Theme

Cause: @theme inline bakes values at build time

Use @theme (without inline) for multi-theme systems:

/* For multi-theme (not just light/dark) */
@theme {
  --color-text-primary: var(--color-slate-900);
}

@layer theme {
  [data-theme="dark"] {
    --color-text-primary: var(--color-white);
  }
}

Error 6: @apply Breaking

Error: Cannot apply unknown utility class

v4 changed @apply behavior:

/* Wrong (v3 pattern) */
@layer components {
  .custom-button { @apply px-4 py-2; }
}

/* Correct (v4 pattern) */
@utility custom-button {
  @apply px-4 py-2;
}

Error 7: @layer base Styles Ignored

Cause: CSS layer cascade issues

/* Better: Don't use @layer base for critical styles */
body {
  background-color: var(--background);
}

---

Quick Reference

Symptom	Cause	Fix
bg-primary doesn't work	Missing @theme inline	Add mapping
Colors black/white	Double hsl()	Use var(--color) not hsl(var(--color))
Dark mode stuck	Missing ThemeProvider	Wrap app
Build fails	tailwind.config.ts exists	Delete file
Animation errors	Wrong package	Use tw-animate-css

---

Tailwind v4 New Features

OKLCH Color Space

v4 uses OKLCH for perceptually uniform colors. Automatic sRGB fallbacks generated.

@theme {
  /* Modern approach */
  --color-brand: oklch(0.7 0.15 250);
  
  /* Legacy (still works) */
  --color-brand: hsl(240 80% 60%);
}

Container Queries (Built-in)

<div className="@container">
  <div className="@md:text-lg @lg:grid-cols-2">
    Content responds to container width
  </div>
</div>

Line Clamp (Built-in)

<p className="line-clamp-3">Truncate to 3 lines...</p>

Plugins

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

---

Migration from v3

Key Changes

1. Delete tailwind.config.ts
2. Move theme to CSS with @theme inline
3. Replace tailwindcss-animate → tw-animate-css
4. Replace require() → @plugin
5. @apply in @layer components → @utility

Color Migration

// Before: Hardcoded + dark variants
<div className="bg-blue-50 dark:bg-blue-950 text-blue-700 dark:text-blue-300">

// After: Semantic + automatic
<div className="bg-info/10 text-info">

Visual Changes

• Ring width default: 3px → 1px (use ring-3 to match v3)
• Heading styles removed from Preflight (add via @tailwindcss/typography or custom)

---

Files

• templates/index.css - Complete CSS with all variables
• templates/theme-provider.tsx - Dark mode provider
• templates/vite.config.ts - Vite configuration
• templates/components.json - shadcn/ui v4 config
• templates/utils.ts - cn() utility
• references/architecture.md - Deep dive on four-step pattern
• references/migration-guide.md - Semantic color migration
• references/dark-mode.md - Complete dark mode setup

---

Setup Checklist

• @tailwindcss/vite installed
• vite.config.ts uses tailwindcss() plugin
• components.json has "config": ""
• NO tailwind.config.ts exists
• src/index.css follows 4-step pattern
• ThemeProvider wraps app
• Theme toggle works

---

NEVER

• Put :root or .dark inside @layer base
• Use tailwind.config.ts with v4 (it's ignored)
• Double-wrap colors: hsl(var(--background))
• Use tailwindcss-animate (use tw-animate-css)
• Use @apply on @layer base/components classes in v4
• Skip the @theme inline step