Before You Start
Quick Start
Four-Step Architecture
Dark Mode Setup
Critical Rules
Semantic Color Tokens
Common Issues & Fixes
File Templates
Setup Checklist
Advanced Topics
Dependencies
Tailwind v4 Plugins
Reference Documentation
When to Load References

⚠️ BEFORE YOU START (READ THIS!)

CRITICAL FOR AI AGENTS: If you're Claude Code helping a user set up Tailwind v4:

Explicitly state you're using this skill at the start of the conversation
Reference patterns from the skill rather than general knowledge
Prevent known issues listed in reference/common-gotchas.md
Don't guess - if unsure, check the skill documentation

USER ACTION REQUIRED: Tell Claude to check this skill first!

Say: "I'm setting up Tailwind v4 + shadcn/ui - check the tailwind-v4-shadcn skill first"

Why This Matters (Real-World Results)

Without skill activation:

❌ Setup time: ~5 minutes
❌ Errors encountered: 2-3 (tw-animate-css, duplicate @layer base)
❌ Manual fixes needed: 2+ commits
❌ Token usage: ~65k
❌ User confidence: Required debugging

With skill activation:

✅ Setup time: ~1 minute
✅ Errors encountered: 0
✅ Manual fixes needed: 0
✅ Token usage: ~20k (70% reduction)
✅ User confidence: Instant success

Known Issues This Skill Prevents

tw-animate-css import error (deprecated in v4)
Duplicate @layer base blocks (shadcn init adds its own)
Wrong template selection (vanilla TS vs React)
Missing post-init cleanup (incompatible CSS rules)
Wrong plugin syntax (using @import or require() instead of @plugin directive)

All of these are handled automatically when the skill is active.

Quick Start (5 Minutes - Follow This Exact Order)

1. Install Dependencies

bun add tailwindcss @tailwindcss/vite
# or: npm install tailwindcss @tailwindcss/vite

bun add -d @types/node

# Note: Using pnpm for shadcn init due to known Bun compatibility issues
# (bunx has "Script not found" and postinstall/msw problems)
pnpm dlx shadcn@latest init

2. Configure Vite

// 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')
    }
  }
})

3. Update components.json

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

4. Delete tailwind.config.ts

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

The Four-Step Architecture (CRITICAL)

This pattern is mandatory - skipping steps will break your theme.

Step 1: Define CSS Variables at Root Level

/* src/index.css */
@import "tailwindcss";

: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 Rules:

✅ Define at root level (NOT inside @layer base)
✅ Use hsl() wrapper on all color values
✅ Use .dark for dark mode (NOT .dark { @theme { } })

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 This Is Required:

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

Step 3: Apply Base Styles

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

Critical Rules:

✅ Reference variables directly: var(--background)
❌ 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 reference/dark-mode.md for full implementation or use template:

// Copy from: templates/theme-provider.tsx

2. Wrap Your App

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

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

3. Add Theme Toggle

pnpm dlx shadcn@latest add dropdown-menu

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

Critical Rules (MUST FOLLOW)

✅ Always Do:

Wrap color values with hsl() in :root and .dark

--background: hsl(0 0% 100%);  /* ✅ Correct */

Use @theme inline to map all CSS variables

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

Set "tailwind.config": "" in components.json
```
{ "tailwind": { "config": "" } }
```
Delete tailwind.config.ts if it exists
Use @tailwindcss/vite plugin (NOT PostCSS)

Use cn() for conditional classes

import { cn } from "@/lib/utils"
<div className={cn("base", isActive && "active")} />

❌ Never Do:

Put :root or .dark inside @layer base

/* WRONG */
@layer base {
  :root { --background: hsl(...); }
}

Use .dark { @theme { } } pattern

/* WRONG - v4 doesn't support nested @theme */
.dark {
  @theme {
    --color-primary: hsl(...);
  }
}

Double-wrap colors

/* WRONG */
body {
  background-color: hsl(var(--background));
}

Use tailwind.config.ts for theme colors

/* WRONG - v4 ignores this */
export default {
  theme: {
    extend: {
      colors: { primary: 'hsl(var(--primary))' }
    }
  }
}

Use @apply directive (deprecated in v4)

Use dark: variants for semantic colors

/* WRONG */
<div className="bg-primary dark:bg-primary-dark" />

/* CORRECT */
<div className="bg-primary" />

Semantic Color Tokens

Always use semantic names for colors:

:root {
  --destructive: hsl(0 84.2% 60.2%);        /* Red - errors, critical */
  --success: hsl(142.1 76.2% 36.3%);        /* Green - success states */
  --warning: hsl(38 92% 50%);               /* Yellow - warnings */
  --info: hsl(221.2 83.2% 53.3%);           /* Blue - info, primary */
}

Usage:

<div className="bg-destructive text-destructive-foreground">Critical</div>
<div className="bg-success text-success-foreground">Success</div>
<div className="bg-warning text-warning-foreground">Warning</div>
<div className="bg-info text-info-foreground">Info</div>

Common Issues & Quick Fixes

Symptom	Cause	Fix
`bg-primary` doesn't work	Missing `@theme inline` mapping	Add `@theme inline` block
Colors all black/white	Double `hsl()` wrapping	Use `var(--color)` not `hsl(var(--color))`
Dark mode not switching	Missing ThemeProvider	Wrap app in `<ThemeProvider>`
Build fails	`tailwind.config.ts` exists	Delete the file
Text invisible	Wrong contrast colors	Check color definitions in `:root`/`.dark`

See reference/common-gotchas.md for complete troubleshooting guide.

File Templates

All templates are available in the templates/ directory:

index.css - Complete CSS setup with all color variables
components.json - shadcn/ui v4 configuration
vite.config.ts - Vite + Tailwind plugin setup
tsconfig.app.json - TypeScript with path aliases
theme-provider.tsx - Dark mode provider with localStorage
utils.ts - cn() utility for class merging

Copy these files to your project and customize as needed.

Complete Setup Checklist

Advanced Topics

Load references/advanced-usage.md for advanced patterns including:

Custom Colors: Add semantic colors beyond default palette
v3 Migration: See references/migration-guide.md for complete guide
Component Best Practices: Semantic tokens, cn() utility, composition patterns

Quick Example:

:root { --brand: hsl(280 65% 60%); }
@theme inline { --color-brand: var(--brand); }

Usage: <div className="bg-brand">Branded</div>

For detailed patterns and component composition examples, load references/advanced-usage.md.

Dependencies

✅ Install These

{
  "dependencies": {
    "tailwindcss": "^4.1.17",
    "@tailwindcss/vite": "^4.1.17",
    "clsx": "^2.1.1",
    "tailwind-merge": "^3.3.1",
    "@radix-ui/react-*": "latest",
    "lucide-react": "^0.554.0",
    "react": "^19.2.0",
    "react-dom": "^19.2.0"
  },
  "devDependencies": {
    "@types/node": "^24.10.1",
    "@vitejs/plugin-react": "^5.1.1",
    "vite": "^7.2.4",
    "typescript": "~5.9.3"
  }
}

❌ NEVER Install These (Deprecated in v4)

# These packages will cause build errors:
bun add tailwindcss-animate  # ❌ Deprecated
# or: npm install tailwindcss-animate  # ❌ Deprecated

bun add tw-animate-css      # ❌ Doesn't exist

If you see import errors for these packages, remove them and use native CSS animations or @tailwindcss/motion instead.

Tailwind v4 Plugins

Tailwind v4 supports official plugins using the @plugin directive in CSS.

Quick Example:

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

Common Error: ❌ WRONG: @import "@tailwindcss/typography" (doesn't work) ✅ CORRECT: @plugin "@tailwindcss/typography" (use @plugin directive)

Built-in Features: Container queries are now core (no @tailwindcss/container-queries plugin needed).

Load references/plugins-reference.md for complete documentation including Typography plugin (prose classes), Forms plugin, installation steps, and common plugin errors.

Reference Documentation

For deeper understanding, see:

common-gotchas.md - All the ways it can break (and fixes)
dark-mode.md - Complete dark mode implementation
migration-guide.md - Migrating hardcoded colors to CSS variables
plugins-reference.md - Official Tailwind v4 plugins (Typography, Forms)
advanced-usage.md - Custom colors and advanced patterns

When to Load References

Load reference files based on user's specific needs:

Load `references/common-gotchas.md` when:

User reports "colors not working" or "bg-primary doesn't exist"
Dark mode not switching properly
Build fails with Tailwind errors
User encounters any CSS/configuration issue
Debugging theme problems

Load `references/dark-mode.md` when:

User asks to implement dark mode
Theme switching not working
Need ThemeProvider component code
Questions about system theme detection

Load `references/migration-guide.md` when:

Migrating from Tailwind v3 to v4
User has hardcoded colors to migrate
Questions about v3 → v4 changes
Need migration checklist

Load `references/plugins-reference.md` when:

User needs Typography plugin (prose class)
User needs Forms plugin
Questions about @plugin directive
Plugin installation errors

Load `references/advanced-usage.md` when:

User asks about custom colors beyond defaults
Need advanced component patterns
Questions about component best practices
Component composition questions

Official Documentation

shadcn/ui Vite Setup: https://ui.shadcn.com/docs/installation/vite
shadcn/ui Tailwind v4 Guide: https://ui.shadcn.com/docs/tailwind-v4
shadcn/ui Dark Mode (Vite): https://ui.shadcn.com/docs/dark-mode/vite
Tailwind v4 Docs: https://tailwindcss.com/docs
shadcn/ui Theming: https://ui.shadcn.com/docs/theming

Production Example

This skill is based on the WordPress Auditor project:

Live: https://wordpress-auditor.webfonts.workers.dev
Stack: Vite + React 19 + Tailwind v4 + shadcn/ui + Cloudflare Workers
Dark Mode: Full system/light/dark support
Version: Tailwind v4.1.17 + shadcn/ui latest (Nov 2025)

All patterns in this skill have been validated in production.

Questions? Issues?

Check reference/common-gotchas.md first
Verify all steps in the 4-step architecture
Ensure components.json has "config": ""
Delete tailwind.config.ts if it exists
Check official docs: https://ui.shadcn.com/docs/tailwind-v4

Table of Contents

secondsky-tailwind-v4-shadcn

Tailwind v4 + shadcn/ui Production Stack