nextjs-expert

AI-consumed reference. Optimized for Claude to read during execution. Human-readable explanation: see docs/architecture/HIERARCHICAL_PLANNING.md or docs/getting-started/ depending on topic.

Next.js Expert — Gotchas & Decisions

Use Context7 for full Next.js docs.

Key Decisions

decisions[4]{choice,use_when}:
  Server vs Client,"Server by default. 'use client' ONLY for interactivity (useState/onClick). Push boundary as low as possible"
  Cache strategy,"force-cache (static) | revalidate:N (time) | revalidateTag (on-demand) | no-store (always fresh)"
  Server Actions vs API routes,"Actions for form mutations. API routes for external consumers/webhooks"
  Streaming vs blocking,"Suspense wrap for slow data. Always Promise.all for parallel fetches"

Gotchas

• Server Components can't use useState/useEffect — move interactive parts to a child Client Component
• 'use client' makes ALL imports in that file client-side — keep it at leaf components
• fetch() in Server Components is auto-deduped but only within same render pass
• Server Actions: always validate with Zod — formData comes from untrusted client
• error.tsx MUST be a Client Component ('use client'). global-error.tsx must render <html> and <body>
• loading.tsx wraps page in Suspense — don't double-wrap with manual Suspense
• Dynamic routes [slug]: params are now a Promise in Next.js 15 — await params
• revalidatePath('/') revalidates ALL pages, not just home — use revalidateTag for precision
• Image: always provide sizes prop with fill — without it, Next.js sends full-size image
• Middleware runs on Edge: no Node.js APIs (fs, Buffer, etc.)