Moving a custom domain to a new service breaks OAuth unless env follows

When a custom domain is moved from one hosting service to another (for example during a platform cutover on Railway), every integration whose OAuth redirect URI uses that domain now runs on the new service. If the new service was set up with only a minimal environment, OAuth start routes fail with "missing configuration" even though the old service is still fully configured. Users only see this when they try to connect. Before or right after moving a domain, compare the environment variable names on the old and new services. Pay special attention to the integration credentials whose redirect URIs use that domain. Limits: comparing names shows missing keys, not wrong values. The external app registration's redirect URI and any bot messaging endpoint still need their own check.

Applies when: a user-facing integration starts failing with missing-config errors right after a domain or service cutover. Keywords: custom domain cutover OAuth redirect env vars missing Railway Microsoft Teams service migration