Just to make sure I understand the scenario correctly: Is your frontend trying to connect to your backend from the client-side of the frontend or the server-side of the frontend?
You should be able to do client-side calls to the backend today since your browser is authenticated to both the frontend and backend codespaces, but server-side calls from the frontend container to the backend container in a different codespace won’t work out of the box. We are working on allowing you to open up the ports as “public ports” instead of “private ports”, which would remove the auth on the url. That would enable this scenario for server-to-server calls across multiple codespaces. Until that is available, you could try a couple other options:
- Run both services in the same codespace
- Use a different proxying solution for the backend service to expose it on a public url, such as ngrok