After infrastructure changes on 2026-04-03, the web service became completely unavailable. Users were either redirected to localhost:3000/pl or received a 500 Internal Server Error.
Root cause: Next.js 14 standalone was running behind Cloudflare Tunnel without Nginx as an intermediate proxy. Next.js internally builds request URLs using its own fetchHostname:port (127.0.0.1:3000) instead of the public Host header, causing next-intl middleware to generate redirects and rewrites targeting https...