nextjs

# Next.js App Router - Production Patterns

**Version**: Next.js 16.0.3
**React Version**: 19.2.0
**Node.js**: 20.9+
**Last Verified**: 2025-11-21

## Table of Contents
1. [When to Use This Skill](#when-to-use-this-skill)
2. [When NOT to Use This Skill](#when-not-to-use-this-skill)
3. [Next.js 16 Breaking Changes](#nextjs-16-breaking-changes)
4. [Cache Components & Caching APIs](#cache-components--caching-apis)
5. [Server Components](#server-components)
6. [Server Actions](#server-actions)
7. [Route Handlers](#route-handlers)
8. [React 19.2 Features](#react-192-features)
9. [Metadata API](#metadata-api)
10. [Image & Font Optimization](#image--font-optimization)
11. [Top 5 Critical Errors](#top-5-critical-errors)
12. [Performance Patterns](#performance-patterns)
13. [TypeScript Configuration](#typescript-configuration)

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## When to Use This Skill

Use this skill when you need:

- **Next.js 16 App Router patterns** (layouts, loading, error boundaries, routing)
- **Server Components** best practices (data fetching, composition, streaming)
- **Server Actions** patterns (forms, mutations, revalidation, error handling)
- **Cache Components** with `"use cache"` directive (NEW in Next.js 16)
- **New caching APIs**: `revalidateTag()`, `updateTag()`, `refresh()` (Updated in Next.js 16)
- **Migration from Next.js 15 to 16** (async params, proxy.ts, parallel routes)
- **Route Handlers** (API endpoints, webhooks, streaming responses)
- **Proxy patterns** (`proxy.ts` replaces `middleware.ts` in Next.js 16)
- **Async route params** (`params`, `searchParams`, `cookies()`, `headers()` now async)
- **Parallel routes with default.js** (breaking change in Next.js 16)
- **React 19.2 features** (View Transitions, `useEffectEvent()`, React Compiler)
- **Metadata API** (SEO, Open Graph, Twitter Cards, sitemaps)
- **Image optimization** (`next/image` with updated defaults in Next.js 16)
- **Performance optimization** (lazy loading, code splitting, PPR, ISR)

## When NOT to Use This Skil