Styling with Tailwind CSS

Always pair bg-* with text-*-foreground. Extend with success/warning/info in theming.md.

Never Build Class Names Dynamically

// WRONG - breaks Tailwind scanner
<div className={`bg-${color}-500`}>

// CORRECT - complete strings via lookup
const colorMap = { red: "bg-red-500", blue: "bg-blue-500" } as const
<div className={colorMap[color]}>

cn() Merge Order

Defaults first, consumer className last (tailwind-merge last-wins):

className={cn(buttonVariants({ variant, size }), className)}  // correct
className={cn(className, buttonVariants({ variant, size }))}  // wrong

Animation Performance

// WRONG - transition-all causes layout thrashing
<div className="transition-all duration-300">

// CORRECT - transition only what changes
<div className="transition-colors duration-200">

// CORRECT - respect reduced motion
<div className="motion-safe:animate-fade-in">

@theme vs @theme inline

• @theme - static tokens, overridable by plugins
• @theme inline - references CSS variables, follows dark mode changes

@theme { --color-brand: oklch(0.6 0.2 250); }          /* static */
@theme inline { --color-primary: var(--primary); }       /* dynamic */

See components.md for more pitfalls and theming.md for color system reference.

Core Patterns

CSS Variables for Theming

shadcn/ui uses semantic CSS variables mapped to Tailwind utilities:

/* globals.css - Light mode */
:root {
  --background: oklch(1 0 0);
  --foreground: oklch(0.145 0 0);
  --primary: oklch(0.205 0 0);
  --primary-foreground: oklch(0.985 0 0);
  --muted: oklch(0.97 0 0);
  --muted-foreground: oklch(0.556 0 0);
  --border: oklch(0.922 0 0);
  --radius: 0.5rem;
}

/* Dark mode */
.dark {
  --background: oklch(0.145 0 0);
  --foreground: oklch(0.985 0 0);
  --primary: oklch(0.922 0 0);
  --primary-foreground: oklch(0.205 0 0);
}

/* Tailwind v4: Map variables */
@theme inline {
  --color-background: var(--background);
  --color-foreground: var(--foreground);
  --color-primary: var(--primary);
}

Usage in components:

// Background colors omit the "-background" suffix
<div className="bg-primary text-primary-foreground">
<div className="bg-muted text-muted-foreground">
<div className="bg-destructive text-destructive-foreground">

Component Authoring Pattern

Components use plain functions with data-slot attributes (React 19 - no forwardRef):

import { cva, type VariantProps } from "class-variance-authority"
import { cn } from "@/lib/utils"

const buttonVariants = cva(
  "inline-flex items-center justify-center gap-2 rounded-md text-sm font-medium transition-colors focus-visible:outline-none focus-visible:ring-1 disabled:pointer-events-none disabled:opacity-50",
  {
    variants: {
      variant: {
        default: "bg-primary text-primary-foreground shadow hover:bg-primary/90",
        destructive: "bg-destructive text-destructive-foreground hover:bg-destructive/90",
        outline: "border border-input bg-background hover:bg-accent",
        ghost: "hover:bg-accent hover:text-accent-foreground",
        link: "text-primary underline-offset-4 hover:underline",
      },
      size: {
        default: "h-9 px-4 py-2",
        sm: "h-8 px-3 text-xs",
        lg: "h-10 px-8",
        icon: "size-9",
      },
    },
    defaultVariants: { variant: "default", size: "default" },
  }
)

// Plain function with React.ComponentProps (not forwardRef)
function Button({
  className,
  variant,
  size,
  ...props
}: React.ComponentProps<"button"> & VariantProps<typeof buttonVariants>) {
  return (
    <button
      data-slot="button"
      className={cn(buttonVariants({ variant, size, className }))}
      {...props}
    />
  )
}

// Usage
<Button variant="outline" size="sm">Click me</Button>

Icon spacing with data-icon:

<Button>
  <Spinner data-icon="inline-start" />
  Generating...
</Button>

<Button>
  <CheckIcon data-slot="icon" />
  Save Changes
</Button>

Responsive Design

Mobile-first breakpoints:

// Stack on mobile, grid on tablet+
<div className="grid gap-4 md:grid-cols-2 lg:grid-cols-4">

// Hide on mobile
<div className="hidden md:block">

// Different layouts per breakpoint
<div className="flex flex-col md:flex-row lg:gap-8">
  <aside className="w-full md:w-64">
  <main className="flex-1">
</div>

// Responsive text sizes
<h1 className="text-3xl md:text-4xl lg:text-5xl">

Container Queries

First-class in Tailwind v4, no plugin needed:

<div className="@container">
  <div className="grid gap-4 @sm:grid-cols-2 @lg:grid-cols-3">
    Responds to container width, not viewport
  </div>
</div>

// Named containers
<div className="@container/sidebar">
  <nav className="hidden @md/sidebar:block">

Dark Mode

// Use dark: prefix - but prefer semantic colors over manual dark: overrides
<div className="bg-background text-foreground">          // auto dark mode
<div className="bg-white dark:bg-black">                 // manual override

// Use next-themes for toggle: useTheme() → setTheme("dark" | "light")
// Always add suppressHydrationWarning to <html> to prevent flash

Common Component Patterns

Card

<div className="rounded-xl border bg-card text-card-foreground shadow">
  <div className="flex flex-col space-y-1.5 p-6">
    <h3 className="font-semibold leading-none tracking-tight">Title</h3>
    <p className="text-sm text-muted-foreground">Description</p>
  </div>
  <div className="p-6 pt-0">Content</div>
  <div className="flex items-center p-6 pt-0">Footer</div>
</div>

Form Field

<div className="space-y-2">
  <label className="text-sm font-medium leading-none peer-disabled:cursor-not-allowed peer-disabled:opacity-70">
    Email
  </label>
  <input
    type="email"
    className="flex h-9 w-full rounded-md border border-input bg-transparent px-3 py-1 text-sm shadow-sm transition-colors placeholder:text-muted-foreground focus-visible:outline-none focus-visible:ring-1 focus-visible:ring-ring disabled:cursor-not-allowed disabled:opacity-50"
  />
  <p className="text-sm text-muted-foreground">Helper text</p>
</div>

Badge

const badgeVariants = cva(
  "inline-flex items-center rounded-md border px-2.5 py-0.5 text-xs font-semibold transition-colors",
  {
    variants: {
      variant: {
        default: "border-transparent bg-primary text-primary-foreground shadow",
        secondary: "border-transparent bg-secondary text-secondary-foreground",
        destructive: "border-transparent bg-destructive text-destructive-foreground",
        outline: "text-foreground",
      },
    },
  }
)

Layout Patterns

Centered Layout

<div className="flex min-h-screen items-center justify-center">
  <div className="w-full max-w-md space-y-8 p-8">
    {/* Content */}
  </div>
</div>

Sidebar Layout

<div className="flex h-screen">
  <aside className="w-64 border-r bg-muted/40">Sidebar</aside>
  <main className="flex-1 overflow-auto">Content</main>
</div>

Dashboard Grid

<div className="grid gap-4 md:grid-cols-2 lg:grid-cols-4">
  <Card className="col-span-2">Wide card</Card>
  <Card>Regular</Card>
  <Card>Regular</Card>
  <Card className="col-span-4">Full width</Card>
</div>

Accessibility Patterns

Focus Visible

<button className="focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring focus-visible:ring-offset-2">

Screen Reader Only

<span className="sr-only">Close dialog</span>

Disabled States

<button className="disabled:cursor-not-allowed disabled:opacity-50" disabled>

Tailwind v4 Features

CSS-First Configuration

@import "tailwindcss";

/* Custom utilities (replaces @layer utilities) */
@utility tab-highlight-none {
  -webkit-tap-highlight-color: transparent;
}

/* Custom variants */
@custom-variant pointer-fine (@media (pointer: fine));

/* Source control */
@source inline("{hover:,}bg-red-{50,100,200}");
@source not "./legacy";

@theme Directive

@theme {
  --color-primary: oklch(0.205 0 0);
  --font-sans: "Inter", system-ui;
}

/* With CSS variables (shadcn/ui pattern) */
@theme inline {
  --color-primary: var(--primary);
}

Animation

@import "tw-animate-css";

<div className="animate-fade-in">
<div className="animate-slide-in-from-top">

v4.1 Features

// Text shadows
<h1 className="text-shadow-sm text-4xl font-bold">

// Gradient masks for fade effects
<div className="mask-linear-to-b">Fades to transparent at bottom</div>

// Pointer-aware sizing
<button className="pointer-fine:py-1 pointer-coarse:py-3">

// Form validation after user interaction
<input className="user-valid:border-success user-invalid:border-destructive" />

// Overflow wrap for long strings
<p className="overflow-wrap-anywhere">verylongwordthatneedstowrap</p>

v4.2 Features (February 2026)

// Logical block properties (RTL/writing-mode aware)
<div className="pbs-4 pbe-8 mbs-2">
<div className="border-bs-2 border-be">

// Logical sizing (replaces w-*/h-* for logical layouts)
<div className="inline-full block-screen">

// Font feature settings
<p className="font-features-['tnum','liga']">Tabular numbers</p>

// New color palettes: mauve, olive, mist, taupe
<div className="bg-mauve-100 text-olive-900">

Deprecation: start-*/end-* deprecated in favor of inset-s-*/inset-e-*.

OKLCH Colors

All shadcn/ui colors use OKLCH format: oklch(lightness chroma hue). Lightness 0-1, chroma 0-0.4 (0 = gray), hue 0-360. Base palettes: Neutral, Zinc, Slate, Stone, Gray. See theming.md for complete palettes and OKLCH reference.

Best Practices

Prefer Semantic Colors

// Good - uses theme
<div className="bg-background text-foreground">

// Avoid - hardcoded
<div className="bg-white text-black dark:bg-zinc-950">

Group Related Utilities

<div className="
  flex items-center justify-between
  rounded-lg border
  bg-card text-card-foreground
  p-4 shadow-sm
  hover:bg-accent
">

Avoid Arbitrary Values

// Prefer design tokens
<div className="p-4 text-sm">

// Avoid when unnecessary
<div className="p-[17px] text-[13px]">

Installation & CLI

# Create new project with visual style + primitive selection
npx shadcn create

# Initialize in existing project
pnpm dlx shadcn@latest init

# Add components
pnpm dlx shadcn@latest add button card form

# Add from community registries
npx shadcn add @acme/button @internal/auth-system

# View/search registries
npx shadcn view @acme/auth-system
npx shadcn search @tweakcn -q "dark"
npx shadcn list @acme

# Add MCP server for AI integration
npx shadcn@latest mcp init

# Update existing components
pnpm dlx shadcn@latest add button --overwrite

Visual Styles

npx shadcn create offers 5 built-in visual styles:

• Vega - Classic shadcn/ui look
• Nova - Compact, reduced padding
• Maia - Soft and rounded, generous spacing
• Lyra - Boxy and sharp, pairs with mono fonts
• Mira - Dense, for data-heavy interfaces

These rewrite component code (not just CSS variables) to match the selected style.

Troubleshooting

Colors not updating: Check CSS variable in globals.css → verify @theme inline includes the mapping → clear build cache.

Dark mode flash on load: Add suppressHydrationWarning to <html> tag and ensure ThemeProvider wraps app with attribute="class".

Found tailwind.config.js: Delete it. Run npx @tailwindcss/upgrade to auto-migrate to CSS-first config. All customization belongs in your CSS file via @theme, @utility, @plugin.

Classes not detected: Check @source directives cover your component paths. Never construct class names dynamically (see Critical Rules).

Component Patterns

For detailed component patterns see components.md:

• Composition: asChild pattern, data-slot attributes
• Typography: Heading scales, prose styles, inline code
• Forms: React Hook Form + Zod, Field component with FieldSet/FieldGroup
• Icons: Lucide icons with data-icon attributes
• Inputs: OTP, file, grouped inputs
• Dialogs: Modal patterns and composition
• Data Tables: TanStack table integration
• Toasts: Sonner notifications
• Pitfalls: cn() order, form defaultValues, dialog nesting, sticky, server/client

Resources

See theming.md for complete color system reference:

• @theme vs @theme inline (critical for dark mode)
• Status color extensions (success, warning, info)
• Z-index scale and animation tokens
• All base palettes (Neutral, Zinc, Slate, Stone, Gray)

Summary

Key concepts:

• v4 CSS-first only - no tailwind.config.js, all config in CSS
• Semantic colors only - never use raw palette (bg-blue-500), always bg-primary
• Always pair bg-* with text-*-foreground
• Never build class names dynamically - use object lookup with complete strings
• cn() order - defaults first, consumer className last
• No transition-all - transition only specific properties
• @theme inline for dynamic theming, @theme for static tokens
• Author components as plain functions with data-slot (React 19)
• Apply CVA for component variants
• Use motion-safe: / motion-reduce: for animations
• Choose Radix UI or Base UI as primitive library

This skill targets Tailwind CSS v4.2 with shadcn/ui. For component-specific examples, see components.md. For color system, see theming.md.