[Bug]: Railpack deployment fails in v4.1.2 with unknown flag: --builder

[Stacylia]

Error Message and Logs

Deployment fails during the Railpack Docker image build step, before the application build starts.

Environment:

• Coolify version: 4.1.2
• Docker version detected by Coolify: Docker 29.6.0 with BuildKit and Buildx
• Helper image: ghcr.io/coollabsio/coolify-helper:1.0.14
• Build pack: Railpack

The same project deployed successfully on the previous Coolify version. After upgrading to Coolify 4.1.2, the deployment started failing.

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Deployment failed: Command execution failed (exit code 125): docker exec x139l7fk9fnxh6er53g0za7y bash -c 'bash /artifacts/build.sh'
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Error: unknown flag: --builder
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Usage:  docker [OPTIONS] COMMAND [ARG...]
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Run 'docker --help' for more information
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Deployment failed. Removing the new version of your application.

Steps to Reproduce

1. Use Coolify version 4.1.2.
2. Deploy an application using the Railpack build pack.
3. Use a static frontend project that builds to Nginx, in this case an Astro project.
4. Make a small update in the project
5. Push the changes to the main branch.
6. Trigger a deployment in Coolify.
7. Coolify detects Docker, BuildKit, and Buildx successfully
8. The deployment starts normally and reaches the Railpack image build step:
9. The deployment then fails with:

Command execution failed (exit code 125): docker exec <helper-container> bash -c 'bash /artifacts/build.sh'
Error: unknown flag: --builder
Usage: docker [OPTIONS] COMMAND [ARG...]

Example Repository URL

No response

Coolify Version

v4.1.2

Are you using Coolify Cloud?

No (self-hosted)

Operating System and Version (self-hosted)

No response

Additional Information

No response

[shadowreviewer]

This issue might be a duplicate of existing issues. Please check:

• (Bug): Railpack deployment fails in v4.1.2 with unknown flag: --builder (#10769 · 100% similar)
• (Bug): git + docker-compose, changing build back from nix to docker compose can build in wrong place (#5896 · 87% similar)
• (Enhancement): Deploy from Github on release (#4972 · 83% similar)
• (Bug): Docker source builds fail on Coolify Cloud with “BuildKit is enabled but the buildx component is missing or broken” even though buildx is installed and working on the connected server (#9726 · 81% similar)
• (Bug): Build cache reused on GitHub-triggered auto-deploys even when cache is disabled (v4.0.0-beta.420.3, cloud, docker-compose) (#6133 · 81% similar)

Automated similarity check — not a definitive match. Close this if it's genuinely a duplicate, otherwise ignore.