/next-best-practices

name: next-best-practices
description: Next.js best practices - file conventions, RSC boundaries, data patterns, async APIs, metadata, error handling, route handlers, image/font optimization, bundling
user-invocable: false

Next.js Best Practices

Apply these rules when writing or reviewing Next.js code.

File Conventions

See [file-conventions.md](./file-conventions.md) for:

• Project structure and special files
• Route segments (dynamic, catch-all, groups)
• Parallel and intercepting routes
• Middleware rename in v16 (middleware → proxy)

RSC Boundaries

Detect invalid React Server Component patterns.

See [rsc-boundaries.md](./rsc-boundaries.md) for:

• Async client component detection (invalid)
• Non-serializable props detection
• Server Action exceptions

Async Patterns

Next.js 15+ async API changes.

See [async-patterns.md](./async-patterns.md) for:

• Async `params` and `searchParams`
• Async `cookies()` and `headers()`
• Migration codemod

Runtime Selection

See [runtime-selection.md](./runtime-selection.md) for:

• Default to Node.js runtime
• When Edge runtime is appropriate

Directives

See [directives.md](./directives.md) for:

• `'use client'`, `'use server'` (React)
• `'use cache'` (Next.js)

Functions

See [functions.md](./functions.md) for:

• Navigation hooks: `useRouter`, `usePathname`, `useSearchParams`, `useParams`
• Server functions: `cookies`, `headers`, `draftMode`, `after`
• Generate functions: `generateStaticParams`, `generateMetadata`

Error Handling

See [error-handling.md](./error-handling.md) for:

• `error.tsx`, `global-error.tsx`, `not-found.tsx`
• `redirect`, `permanentRedirect`, `notFound`
• `forbidden`, `unauthorized` (auth errors)
• `unstable_rethrow` for catch blocks

Data Patterns

See [data-patterns.md](./data-patterns.md) for:

• Server Components vs Server Actions vs Route Handlers
• Avoiding data waterfalls (`Promise.all`, Suspense, preload)
• Client component data fetching

Route Handlers

See [route-handlers.md](./route-handlers.md) for:

• `route.ts` basics
• GET handler conflicts with `page.tsx`
• Environment behavior (no React DOM)
• When to use vs Server Actions

Metadata & OG Images

See [metadata.md](./metadata.md) for:

• Static and dynamic metadata
• `generateMetadata` function
• OG image generation with `next/og`
• File-based metadata conventions

Image Optimization

See [image.md](./image.md) for:

• Always use `next/image` over `<img>`
• Remote images configuration
• Responsive `sizes` attribute
• Blur placeholders
• Priority loading for LCP

Font Optimization

See [font.md](./font.md) for:

• `next/font` setup
• Google Fonts, local fonts
• Tailwind CSS integration
• Preloading subsets

Bundling

See [bundling.md](./bundling.md) for:

• Server-incompatible packages
• CSS imports (not link tags)
• Polyfills (already included)
• ESM/CommonJS issues
• Bundle analysis

Scripts

See [scripts.md](./scripts.md) for:

• `next/script` vs native script tags
• Inline scripts need `id`
• Loading strategies
• Google Analytics with `@next/third-parties`

Hydration Errors

See [hydration-error.md](./hydration-error.md) for:

• Common causes (browser APIs, dates, invalid HTML)
• Debugging with error overlay
• Fixes for each cause

Suspense Boundaries

See [suspense-boundaries.md](./suspense-boundaries.md) for:

• CSR bailout with `useSearchParams` and `usePathname`
• Which hooks require Suspense boundaries

Parallel & Intercepting Routes

See [parallel-routes.md](./parallel-routes.md) for:

• Modal patterns with `@slot` and `(.)` interceptors
• `default.tsx` for fallbacks
• Closing modals correctly with `router.back()`

Self-Hosting

See [self-hosting.md](./self-hosting.md) for:

• `output: 'standalone'` for Docker
• Cache handlers for multi-instance ISR
• What works vs needs extra setup

Debug Tricks

See [debug-tricks.md](./debug-tricks.md) for:

• MCP endpoint for AI-assisted debugging
• Rebuild specific routes with `--debug-build-paths`