next-app-router-patternslisted

# Next.js App Router patterns Default assumption: Next.js 16 (current stable as of writing) with the App Router. Pages Router patterns are out of scope. Cache Components is the new caching model in 16 (opt-in via `cacheComponents: true`); the previous caching model is still supported when the flag is off. Verify via `package.json` or lockfile; caching model and `cacheComponents` flag differ between 15.x and 16.x. ## Severity rubric - `failure`: a concrete defect or violation that should not ship. - `warning`: a smell or pattern that compounds with other findings. - `info`: a hardening opportunity or note, not a defect. ## Reference files | File | Covers | | ---------------------------------------------------------------- | --------------------------------------------------------------------------------------- | | [reference/anti-patterns.md](reference/anti-patterns.md) | Severity-labeled anti-patterns: cache scoping, server/client boundary, streaming errors | | [reference/server-and-client.md](reference/server-and-client.md) | `"use client"` propagation, server vs client constraints, serialization, `server-only` | | [reference/caching.md](reference/caching.md) | Cache Components vs previous model, `fetch` defaults, segment config, revalidation | | [reference/server-actions.md](reference/server-actio