The Ruby provider installs Node as a language-level dependency (for asset compilation in Rails), which is separate from the step commands you overrode. Skipping install:node and prune:node steps removes those commands but doesn't prevent the Node language itself from being set up. This level of customization (disabling an auto-detected language entirely) is best addressed on the Railpack GitHub repo, where the maintainers can confirm if there's an existing config option or if it needs to be added as a feature.

Also, is there a way to prevent Railpack from trying to copy "/app/node_modules" to the image when using the "ruby" provider?

The /app/node_modules copy is part of the Ruby provider's built-in final image configuration, which is separate from the step commands you've already overridden. The Railpack config file schema doesn't currently expose a way to disable an auto-detected language or its associated paths. If you need full control over what gets included in the final image, using a Dockerfile instead of the Railpack Ruby provider would let you define exactly which directories are copied. Alternatively, you could open a feature request on the Railpack GitHub repo for a config option to exclude specific languages from a provider.