Nextjs

name: nextjs description: Next.js 16 with App Router, Server Components, Server Actions, Cache Components. Use for React 19.2 apps, SSR, or encountering async params, proxy.ts migration, use cache errors.

Keywords: Next.js 16, Next.js App Router, Next.js Pages Router, Server Components, React Server Components, Server Actions, Cache Components, use cache, Next.js 16 breaking changes, async params nextjs, proxy.ts migration, React 19.2, Next.js metadata, Next.js SEO, generateMetadata, static generation, dynamic rendering, streaming SSR, Suspense, parallel routes, intercepting routes, route groups, Next.js middleware, Next.js API routes, Route Handlers, revalidatePath, revalidateTag, next/navigation, useSearchParams, turbopack, next.config license: MIT metadata: version: 1.0.0 last_verified: 2025-11-21 nextjs_version: 16.0.3 react_version: 19.2.0 node_version: 20.9+ author: Claude Skills Maintainers repository: https://github.com/secondsky/claude-skills production_tested: true token_savings: 65-70% errors_prevented: 18+ allowed-tools: ["Read", "Write", "Edit", "Bash", "Glob", "Grep"]

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
2. When NOT to Use This Skill
3. Next.js 16 Breaking Changes
4. Cache Components & Caching APIs
5. Server Components
6. Server Actions
7. Route Handlers
8. React 19.2 Features
9. Metadata API
10. Image & Font Optimization
11. Top 5 Critical Errors
12. Performance Patterns
13. TypeScript Configuration

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 Skill

Do NOT use this skill for:

• Cloudflare Workers deployment → Use cloudflare-nextjs skill instead
• Pages Router patterns → This skill covers App Router ONLY (Pages Router is legacy)
• Authentication libraries → Use clerk-auth, auth-js, or other auth-specific skills
• Database integration → Use cloudflare-d1, drizzle-orm-d1, or database-specific skills
• UI component libraries → Use tailwind-v4-shadcn skill for Tailwind + shadcn/ui
• State management → Use zustand-state-management, tanstack-query skills
• Form libraries → Use react-hook-form-zod skill

Next.js 16 Breaking Changes

CRITICAL: Next.js 16 has multiple breaking changes. For detailed migration steps, see references/next-16-migration-guide.md.

Quick Fix for Async Params:

// ✅ Next.js 16 pattern
export default async function Page({ params }: { params: Promise<{ id: string }> }) {
  const { id } = await params
  return <div>{id}</div>
}

Codemod: bunx @next/codemod@canary upgrade latest

See: references/next-16-migration-guide.md for complete migration guide with examples.

Cache Components & Caching APIs

"use cache" Directive (NEW in Next.js 16)

'use cache'

export async function BlogPosts() {
  const posts = await db.posts.findMany()
  return posts.map(post => <article key={post.id}>{post.title}</article>)
}

Caching APIs Summary

PPR (Partial Prerendering)

// next.config.ts
const config = { experimental: { ppr: true } }

// page.tsx
export const experimental_ppr = true

export default function Page() {
  return (
    <>
      <StaticHeader />
      <Suspense fallback={<Skeleton />}>
        <DynamicContent />
      </Suspense>
    </>
  )
}

See: references/caching-apis.md for complete caching API reference with ISR, tag-based revalidation, and advanced patterns.

Server Components

Server Components are the default in App Router. They run on the server and can fetch data, access databases, and keep logic server-side.

// app/posts/page.tsx (Server Component by default)
export default async function PostsPage() {
  const posts = await db.posts.findMany()
  return <div>{posts.map(p => <article key={p.id}>{p.title}</article>)}</div>
}

Streaming with Suspense

import { Suspense } from 'react'

export default function Page() {
  return (
    <div>
      <Header />
      <Suspense fallback={<Skeleton />}>
        <Posts />
      </Suspense>
    </div>
  )
}

Server vs Client Components

Client Component (requires 'use client'):

'use client'
import { useState } from 'react'
export function Counter() {
  const [count, setCount] = useState(0)
  return <button => setCount(count + 1)}>{count}</button>
}

Server Actions

Server Actions are async functions that run on the server, callable from Client or Server Components.

Basic Server Action

// app/actions.ts
'use server'

import { revalidatePath } from 'next/cache'

export async function createPost(formData: FormData) {
  const title = formData.get('title') as string
  await db.posts.create({ data: { title } })
  revalidatePath('/posts')
}

Form Handling

// Server Component Form (simplest)
import { createPost } from './actions'

export default function NewPostPage() {
  return (
    <form action={createPost}>
      <input name="title" required />
      <button type="submit">Create</button>
    </form>
  )
}

Available Patterns

See: references/server-actions-patterns.md for error handling, optimistic updates, file uploads, and advanced patterns.

Route Handlers

Route Handlers are the App Router equivalent of API Routes.

// app/api/posts/route.ts
export async function GET(request: Request) {
  const posts = await db.posts.findMany()
  return Response.json({ posts })
}

export async function POST(request: Request) {
  const body = await request.json()
  const post = await db.posts.create({ data: body })
  return Response.json({ post }, { status: 201 })
}

Dynamic Routes (with async params):

// app/api/posts/[id]/route.ts
export async function GET(
  request: Request,
  { params }: { params: Promise<{ id: string }> }
) {
  const { id } = await params // Await in Next.js 16
  const post = await db.posts.findUnique({ where: { id } })
  return post ? Response.json({ post }) : Response.json({ error: 'Not found' }, { status: 404 })
}

See: templates/route-handler-api.ts for search params, webhooks, and streaming patterns.

React 19.2 Features

Metadata API

// Static metadata
export const metadata: Metadata = {
  title: 'My Blog',
  description: 'A blog about Next.js',
  openGraph: { title: 'My Blog', images: ['/og-image.jpg'] },
}

// Dynamic metadata (await params in Next.js 16)
export async function generateMetadata({ params }: { params: Promise<{ id: string }> }) {
  const { id } = await params
  const post = await db.posts.findUnique({ where: { id } })
  return { title: post.title, description: post.excerpt }
}

Image & Font Optimization

// next/image
import Image from 'next/image'
<Image src="/profile.jpg" alt="Profile" width={500} height={500} priority />

// next/font
import { Inter } from 'next/font/google'
const inter = Inter({ subsets: ['latin'], variable: '--font-inter' })
<html className={inter.variable}>

Remote images: Configure images.remotePatterns in next.config.ts.

Top 5 Critical Errors

Error 1: params is a Promise

Error: Type 'Promise<{ id: string }>' is not assignable to type '{ id: string }'

Solution: Await params in Next.js 16:

export default async function Page({ params }: { params: Promise<{ id: string }> }) {
  const { id } = await params
}

Error 2: middleware.ts is deprecated

Warning: middleware.ts is deprecated. Use proxy.ts instead.

Solution: Rename file and function:

// Rename: middleware.ts → proxy.ts
// Rename function: middleware → proxy
export function proxy(request: NextRequest) {
  // Same logic
}

Error 3: Parallel route missing default.js

Error: Parallel route @modal was matched but no default.js was found

Solution: Add default.tsx:

// app/@modal/default.tsx
export default function ModalDefault() {
  return null
}

Error 4: Cannot use React hooks in Server Component

Error: You're importing a component that needs useState. It only works in a Client Component

Solution: Add 'use client':

'use client'

import { useState } from 'react'

export function Counter() {
  const [count, setCount] = useState(0)
  return <button => setCount(count + 1)}>{count}</button>
}

Error 5: fetch() not caching

Cause: Next.js 16 uses opt-in caching with "use cache".

Solution: Add "use cache" directive:

'use cache'

export async function getPosts() {
  const response = await fetch('/api/posts')
  return response.json()
}

See All 18 Errors: references/error-catalog.md

Performance Patterns

TypeScript Configuration

{
  "compilerOptions": {
    "strict": true,
    "baseUrl": ".",
    "paths": { "@/*": ["./*"] }
  }
}

When to Load References

Bundled Resources

Related Skills

Official Docs: https://nextjs.org/docs | App Router: https://nextjs.org/docs/app

Version: Next.js 16.0.0 | React 19.2.0 | Node.js 20.9+ | TypeScript 5.3+ Production Tested: E-commerce, SaaS, content sites | Token Savings: 65-70%