Optimise SEO

• IS: crawlability, metadata, structured data, canonicals, redirects, status codes, hreflang, AI-crawler policy and extractable page structure, Core Web Vitals, programmatic SEO, security and privacy headers, and error-page behaviour, implemented in a Next.js App Router codebase.
• IS NOT: visual redesign, layout, or page-level UI quality (ui-design Direction, Build, and Audit modes), demand research, briefs, question maps, or Search Console monitoring (seo-program), tenant routing for robots.txt and sitemap.xml (multi-tenant-architecture), or writing the article (external ghostwriter).

Allowed surface: metadata and generateMetadata, JSON-LD, semantic HTML, internal links, alt text, app/sitemap.ts, app/robots.ts, app/feed.xml/route.ts, app/llms.txt/route.ts, proxy.ts, next.config.ts redirects and headers, error pages, and performance work. Component styling and layout stay as they are; when a fix needs a layout change, name it as a handoff to ui-design.

Before writing code, read the matching guide in node_modules/next/dist/docs/ (resolved from the app directory; in a monorepo the next package is not visible from the repo root). The bundled docs match the installed version; the notes in references/nextjs-implementation.md were checked against 16.3 and say where behaviour changed.

References