260223:1415 20260223 nextJS & nestJS Best pratices

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+---
+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`
+