ModernCI and Blacksmith
Blacksmith is a faster runner for GitHub Actions: you change runs-on to a Blacksmith label, and your workflows run on its machines with a colocated cache. ModernCI is a different layer: a self-hosted CI server and merge queue that decides what runs, cancels stale work, merges green pull requests and sends failures back to agents. If your workflows are fine and only slow, Blacksmith is the smaller change. If the queue of pull requests waiting to be tested and merged is the problem, that's what ModernCI addresses.
Marks: live is in release 0.4.28 on main; planned is decided, not built. Blacksmith facts are from blacksmith.sh/pricing and the Blacksmith quickstart, read 2026-10-13.
What Blacksmith is (from its public pages)
- Adoption: install the Blacksmith GitHub app for an organization (personal repositories aren't supported), then change
runs-on, for exampleruns-on: blacksmith-2vcpu-ubuntu-2404. - Cache: official GitHub and popular third-party cache actions use Blacksmith's colocated cache, which it describes as "4x faster", with 25 GB of free storage per repository per week.
- Price: Ubuntu x64 $0.004/min, Ubuntu ARM $0.0025/min, Windows x64 $0.008/min and macOS M4 $0.08/min, with 3,000 free minutes a month. Docker layer caching and sticky disks are $0.50/GB a month.
- Scope: GitHub Actions only. Its pages describe no other CI system and no self-hosting.
When Blacksmith is the better fit
- You want faster GitHub Actions runs today with a one-line change per job.
- You use Windows or macOS runners. ModernCI has no Windows support.
- You don't want to run anything yourself.
- Your pain is runner speed or cache speed, not queueing, re-runs or merging.
When to consider ModernCI
- Agent pull requests pile up waiting to be tested and merged. ModernCI's merge queue merges the deepest green prefix of a batch and bisects a failing one. live
- Runs a newer push made pointless keep burning minutes. ModernCI cancels them per check, and across pull requests whose heads contain each other. live
- Failures should go back to the coding agent that wrote the change, over MCP, with the reproduce command and diff. live
- You need to self-host, or run with no outside service. live
Using both
Blacksmith runs GitHub Actions jobs, and ModernCI runs its own checks on its own backends, so today they don't combine directly. With external checks planned, ModernCI's merge queue could use your Actions workflows, running on Blacksmith, as the result for the commit it tests.
Evidence
- Clean and incremental Rust build times, and cost per merged change, on matched runner sizes: measurement in progress. The method, the Blacksmith runner label and the pricing assumptions are on benchmarks.
Limitations of ModernCI here
- In 0.4.28 one pull request's checks run one after another. Parallel checks are planned.
- No public download yet and no hosted service, whereas Blacksmith is hosted.
- No Windows backend.
See also: GitHub Actions, Namespace, facts.