next.config.js rewrites() bakes its destination into the build
(routes-manifest.json), capturing FASTAPI_URL at build time. Because one
frontend image is promoted staging->prod, the baked backend host forced
every environment to name the backend service identically; staging names
it 'backend_stg', so the browser's /api/* calls proxied to the baked
'http://backend' and failed with getaddrinfo ENOTFOUND backend. (SSR was
unaffected because lib/api.ts reads FASTAPI_URL at runtime.)
Replace the rewrites with route handlers that read FASTAPI_URL per
request:
- app/api/[...path]/route.ts — transparent proxy for all methods, streams
the response, strips hop-by-hop headers, and returns 502 on upstream
failure instead of crashing.
- app/sitemap.xml/route.ts — proxies the backend sitemap (robots.ts points
crawlers here).
The same promoted image now adapts to whatever the backend is called in
each environment. Verified: production build succeeds with /api/[...path]
and /sitemap.xml as dynamic routes and an empty rewrites manifest.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
