The dev server is public the moment it listens

You run npm run dev in a container. Vite says it's listening on 5173. It is also, already, at https://…-http-5173.…containers.hoody.com, with a certificate, on the public internet.

You paste that URL to the designer. She opens it on her phone. You change a margin; her screen updates through HMR the same way yours does. Stripe's test webhook points at the same hostname and lands in the handler you're writing.

No ngrok session, no tunnel that rotates its hostname every restart, no --host flag and firewall exception, no "works on my machine" because the machine is the URL. Any port from 1 to 65535 gets the same treatment; one container can serve as many as you start.

You didn't expose the port. The port was born exposed.