Next.js 16 App Router Best Practices Comprehensive Next.js 16 App Router guide for AI agents. Contains 45 rules across 9 categories , prioritized by impact from critical (build optimization, caching strategy) through to cross-cutting codebase hygiene (dedup, dead routes, boundary coherence). Reflects Next.js 16 changes: directive replacing implicit caching, requirement, replacing , Turbopack persistent caching, App Router conventions. Rule files describe pattern shapes (not API names) and open with a "Shapes to recognize" section listing 2–4 syntactic disguises the same break can wear. Select…