[damianrosellen1]

On Netlify, canonicals, hreflang, og:url and the sitemap fell back to http://localhost:3000 on any deploy without NEXT_PUBLIC_SITE_URL, deploy previews always. siteUrl.ts reads Netlify's URL / DEPLOY_PRIME_URL at module load, but those only exist at build: the function runtime that serves ISR regenerations and route handlers doesn't have them. Found in a project built from the starter.

1. Inline the build-time origin (web/next.config.ts)
next.config.ts imports SITE_BASE_URL and sets NEXT_PUBLIC_SITE_URL: SITE_BASE_URL in env, so the value resolved at build is what every later render reads. An explicit NEXT_PUBLIC_SITE_URL still wins; a deploy host with nothing resolvable now fails at config load instead of later.

2. Production context takes URL (web/src/utils/siteUrl.ts)
netlifyOrigin() uses URL when isProduction || CONTEXT === "production". A staging site on the development dataset (SANITY_STUDIO_DEPLOYMENT_TARGET=development on the production context) serves its primary domain; DEPLOY_PRIME_URL there is the <branch>-- host. Doc comments in siteUrl.ts and isProductionDeployment updated to match.

Verified

• Resolver per context: production → URL; production + target development → URL; deploy preview / branch deploy → DEPLOY_PRIME_URL; runtime with only the inlined value → that value; Netlify with nothing → throws; local → http://localhost:3000.
• Local next build without any host variables succeeds; required-server-files.json carries NEXT_PUBLIC_SITE_URL: "http://localhost:3000".
• pnpm typecheck, pnpm lint, pnpm format (no diff).
• Deploy preview of this PR: canonical, hreflang, og:url and sitemap.xml use https://deploy-preview-245--…. So did preview fix: Presentation connects again from the Sanity Dashboard #243 before the fix: these pages are prerendered at build, where the old code already resolved.

Not verified: the runtime path the fix targets (an ISR regeneration or route handler on Netlify). It needs a revalidation on a deployed site.

Variant-Port: #246

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[Copilot]

🔵 Needs a closer look

The build-to-function handoff central to this fix remains unverified on a real Netlify deployment.

No open issues 🎉

What changed in this PR

This PR preserves the build-time site origin for later server renders, preventing Netlify metadata and sitemap URLs from falling back to localhost when runtime host variables are unavailable.

Changes:

• Inlines the resolved origin as NEXT_PUBLIC_SITE_URL through Next.js configuration.
• Uses Netlify’s primary domain in production context, including staging sites using the development dataset.
• Updates comments to explain origin resolution and deployment behavior.

File	Description
web/​src/​utils/​siteUrl.ts	Adjusts Netlify origin selection and documents build-time resolution.
web/​next.config.ts	Inlines the resolved site origin for application runtime use.
packages/​sanity-dataset-resolve/​src/​index.ts	Updates documentation for the Netlify canonical-origin exception.

_{Review effort: Balanced}

[damianrosellen1]

Runtime check: build env ≠ runtime env

Simulated the Netlify function runtime locally to check that the origin survives an ISR regeneration.

Setup, run for both the merge-base (4c26529d) and this branch (18e6f969):

1. next build with NETLIFY=true CONTEXT=deploy-preview URL=https://primary-site.example DEPLOY_PRIME_URL=https://deploy-preview-245--primary-site.example
2. next start with those four variables unset
3. Read canonical, og:url, hreflang of /docs and the first <loc> of sitemap.xml
4. Signed webhook POST /api/revalidate with {"_type":"page"} → {"revalidated":true,"tags":["pages","site-pages"]}
5. Fetch both again (the regenerated render)

Result

	4c26529d (main)	18e6f969 (this PR)
From the build	deploy-preview origin	deploy-preview origin
After revalidation: canonical	http://localhost:3000/docs ❌	https://deploy-preview-245--primary-site.example/docs ✅
og:url	localhost ❌	deploy-preview origin ✅
hreflang (en, de, x-default)	localhost ❌	deploy-preview origin ✅
sitemap <loc>	localhost ❌	deploy-preview origin ✅

On main the bug reproduces: without NETLIFY at runtime the resolver falls through to the local fallback, with no error. On this branch the inlined NEXT_PUBLIC_SITE_URL keeps the build-time origin. In both runs en/docs.html and the sitemap were rewritten after the build had finished, so the value on this branch comes from a runtime render, not from the build output.

Not covered: next start is not Netlify's function runtime or cache handler; only the missing build variables are reproduced. The new CONTEXT === "production" branch was not part of this run.