Metadata, JSON-LD, sitemaps, robots.txt, feeds and responsive images, each rule an assert* that throws a coded SeoError naming the route file and the edit. Package @ultimat3/seo (tier 1) — the full reference is packages/seo/README.md. Route metadata itself is declared on defineRoute({ meta }) (Routes and render modes).

export const config = defineRoute({
  render: 'isr',
  meta: ({ post }) => ({
    title: post.title,
    titleTemplate: '%s — Ultimate',
    description: post.excerpt,
    og: { type: 'article', image: post.cover, publishedTime: post.publishedAt },
    ld: [ld.Article({ headline: post.title, datePublished: post.publishedAt, author: post.author })],
  }),
});

x verify's seo step runs validateMeta over every site/ route: missing, duplicate and over-long meta fail the gate. Canonical checks are skipped there, because an app declares no base URL; JSON-LD, sitemaps and robots are enforced where they are built — each builder throws. Performance budgets are not here: they are the budgets step and X_BUDGET_EXCEEDED.

meta.links puts <link> tags in <head> — a font preload, a preconnect, a feed — typed, in declaration order, for SSR and prerender alike. canonical and hreflang keep their own fields, and the surface stylesheet is the renderer's, so neither rel is spellable here.

export const config = defineRoute({
  render: 'static',
  meta: () => ({
    title: 'Notificado',
    description: 'Notificaciones electrónicas con constancia de entrega',
    links: [
      {
        rel: 'preload',
        href: asset('assets/fonts/inter-var.woff2'),
        as: 'font',
        type: 'font/woff2',
        crossorigin: 'anonymous',
      },
      { rel: 'alternate', href: '/feed.xml', type: 'application/rss+xml' },
    ],
  }),
});

Fields: rel, href, as, type, crossorigin, media. Two links of one rel are two tags: a link's href is part of its identity when the head is deduped.

Every X_SEO_* and image code is in Error codes.

One answer, served two ways. siteSeo() from @ultimat3/cli builds both from the route table. It takes the public site/ routes (no policy) and expands a dynamic route through its prerender().

prerender() answers a bare string, a params object, or an entry — the three mix freely:

import { defineRoute } from '@ultimat3/render';

declare const posts: {
  published(): Promise<readonly { slug: string; updatedAt: Date; englishReviewed: boolean }[]>;
};

export const config = defineRoute({
  render: 'isr',
  revalidate: { ttl: '10m' },
  offline: 'network-only',
  prerender: async () =>
    (await posts.published()).map((post) => ({
      params: { slug: post.slug },
      lastmod: post.updatedAt, // a Date, or ISO 8601 with a zone
      locales: post.englishReviewed ? ['es-co', 'en'] : ['es-co'],
    })),
  meta: ({ params }) => ({ title: params['slug'] ?? '', description: 'A note from the blog.' }),
});

A route with no params may answer prerender() too — () => [{ params: {}, lastmod, locales }] — which is how a page with a load (a blog index whose date is its newest post's) says either.

A key that is none of the three (lastMod) is X_PRERENDER_FAILED. The static export still lists only the pages it emitted; it asks prerender() again for what each says of itself.

The <head> is separate: a page's hreflang tags come from meta.alternates, or from every routed locale when it declares none. A page listed in one locale declares its own: alternates: [{ hreflang: 'es-CO', href: url }].

import { defineConfig } from '@ultimat3/core';

export const config = defineConfig({
  name: 'notificado',
  seo: {
    sitemap: {
      pageSize: 1000,
      sections: [
        { name: 'blog', match: '/blog/**' },
        { name: 'ciudades', match: ['/juzgados/**', '/ciudades/*'] },
      ],
    },
  },
});

/sitemap.xml becomes a <sitemapindex>; every listed page goes to /sitemaps/<name>-<n>.xml.

With no sections the output is byte-for-byte what it was: one urlset at /sitemap.xml, and past a cap (50,000 URLs, or 50 MB) the index with parts /sitemaps/1.xml, /sitemaps/2.xml, … (SITEMAP_PARTS_DIR). A part the index does not name is a 404, no-store. As of 2026-10.

Beyond site/, and <lastmod> (As of 22.10) — seo.sitemap in app.config.ts:

seo: { sitemap: { extra: ['/verificar', '/estado'], lastmod: 'git' } },

The scaffolded prerender.ts passes sitemap and root from loadSiteSettings(root); an app with its own prerender.ts adds sitemap: settings.sitemap, root to its siteSeo({ … }) call.

The parts of a split were /sitemap-N.xml once, which no running process could serve (Upgrading).