Next.js Core (App Router)

• Server Components by default; minimal "use client".
• Mutations in Server Actions (validate/authz; revalidate tags/paths).
• Route handlers for APIs/webhooks; add loading/error boundaries.

Anti-patterns:

• ❌ Fetch initial data in useEffect.
• ❌ Cache or revalidate too broadly.
• ❌ Client-only authz.

References: see references/ (server actions, fetching, caching, routing, auth, testing).