Что сказать
«App Router — file-system router on React Server Components. Folders URL segments, special files page, layout, loading, error — contract. Shift: Server Component default — fetch async/await in component, secrets server, most tree zero JS. 'use client' only interactivity leaves. Navigation client-side prefetched — RSC payload not full page reload — layouts persist, shared shell mounted. Gotcha: per-route data in layout — layouts don't re-run between children.»
Итог
App Router pitch: RSC default + file conventions + layout persistence gotcha.
Next.js · middle · сложность 5