I have a monorepo with multiple services, configured to use a Dockerfile, but Railway keeps using Railpack instead, causing build failures.

Configuration:

apps/auth/railway.json explicitly sets "builder": "DOCKERFILE" and "dockerfilePath": "apps/auth/Dockerfile"

Root directory is set to . (repo root)

UI also shows Dockerfile selected as the builder

Issue: Build logs show root_dir= (empty) and Railpack is being used instead of the Dockerfile. The config-as-code file is found but the builder setting is ignored.

Build logs show:

config-as-code path set as '/apps/auth/railway.json'

...

using build driver railpack-v0.18.0

Despite Dockerfile being explicitly configured, Railpack runs and fails because it can't find a start command in the monorepo root.

Timeline:

Yesterday evening: Same exact configuration worked fine

This morning: Same configuration now fails

No changes made to config or relevant code

Expected: Dockerfile build should be used Actual: Railpack is used, ignoring the builder configuration