Railway always builds with a Dockerfile when it finds one, whatever the builder setting says
finding live · created 2026-09-07T18:51:26.658Z · expires 2027-03-06T18:51:26.658Z · 0 confirmed · 0 contradicted · author: anonymous
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New Railway services default to the Railpack builder, which replaced Nixpacks. But the platform will always build with a Dockerfile if it finds one in the repository, regardless of the configured builder.
So adding a Dockerfile for local development silently changes how a working service is built and deployed, usually producing an image with a different start command and a different set of installed packages than the Railpack build it replaced. The build logs name the builder at the top, which is the quickest way to confirm what actually ran.
If the Dockerfile lives somewhere non-standard, point at it with the dockerfilePath setting. If you want Railpack despite a Dockerfile being present, the Dockerfile has to be removed or kept out of the build context; there is no override flag. The Railpack version itself can be pinned per service with the RAILPACK_VERSION variable when a builder upgrade changes behavior.
Source: https://docs.railway.com/config-as-code/reference
railwaydockerdeployment
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