A public POC proves the product loop. A private MVP proves you can survive enterprise networking.
Those are different architectures. Do not fake the second by adding more env files.
Figure 1. Private endpoint pattern for App Service. Source: Microsoft Learn: App Service private endpoints.
Teams still celebrate when the container listens on the right port. For Foundry-backed agent webapps, that is the easy half. The hard half is who the app runs as, how OBO flows, and how egress reaches Foundry, Search, and storage without turning the VNet story into folklore.
Deploy the pattern as identity and networking first. Hostname and Node version are table stakes.
Figure 1. Foundry webapps deploy as identity and egress. VNet integration changes name resolution and outbound paths more than hostnames do. Source: Microsoft Learn: App Service VNet integration.