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name: nextjs-styling description: Implement zero-runtime CSS with Tailwind, CSS Modules, and the cn() utility for RSC-compatible styling in Next.js. Use when choosing a styling library, creating dynamic class utilities, or optimizing fonts with next/font. metadata: triggers: files: - '/*.css' - 'tailwind.config.ts' - '/components/ui/*.tsx' keywords: - tailwind - css modules - styled-components - clsx - cn

Styling & UI Performance

Priority: P1 (HIGH)

Prioritize Zero-Runtime CSS for Server Components.

Workflow: Set Up Styling

1. Choose library — Tailwind/shadcn (preferred), CSS Modules (scoped), or Ant Design (with client wrappers).
2. Create cn utility — Combine clsx + tailwind-merge for dynamic classes.
3. Configure fonts — Use next/font for zero-CLS self-hosted fonts.
4. Set image dimensions — Always specify width/height or fill on <Image>.

cn Utility Example

See implementation examples

Library Selection

Library	Verdict	Reason
Tailwind / shadcn	Preferred (P1)	Zero-runtime, RSC compatible. Best for App Router.
CSS Modules / SCSS	Recommended	Scoped, zero-runtime. Good for legacy projects.
Ant Design	Supported	Use with Client Component wrappers for RSCs.
MUI / Chakra (Runtime)	Avoid	Forces use client widely. Degrades performance.

Library Patterns

For specific library setups, see:

• references/scss.md
• references/ant-design.md
• references/tailwind.md (Tailwind/shadcn)

Patterns

1. Dynamic Classes: Use clsx + tailwind-merge (cn utility).

• Reference: Dynamic Classes & Button Example

2. Font Optimization: Use next/font to prevent Cumulative Layout Shift (CLS).

• Reference: Font Setup

3. CLS Prevention: Always specify width/height on images.

Anti-Patterns

• No runtime CSS-in-JS with RSC: MUI/Chakra force 'use client'; prefer Tailwind or CSS Modules.
• No <img> without dimensions: Always set width/height or use fill to prevent CLS.
• No hardcoded conditional classes: Use clsx+tailwind-merge (cn) for dynamic styles.
• No Google Fonts <link> tag: Use next/font for zero-CLS self-hosted fonts.

Canonical response anchors

When this skill applies, preserve the following domain terminology or equivalent concrete examples in the answer when relevant:

• Fix with next/image — always specify width and height or use fill prop,always