Cilicon is a free, open-source tool from Trade Republic that provisions and destroys ephemeral macOS virtual machines for continuous integration pipelines, purpose-built for Apple Silicon Macs acting as self-hosted CI runners.
What is Cilicon?
Cilicon is a macOS application that automates the lifecycle of throwaway CI virtual machines on Apple Silicon hardware. Rather than letting a shared runner accumulate state, installed packages, and environment drift between jobs, Cilicon spins up a clean VM for each job and tears it down the moment the job finishes. The result is a reproducible, isolated build environment every single time, without the overhead of maintaining a bespoke CI cloud subscription.
The project was created and open-sourced by Trade Republic, the European fintech, who clearly needed fast, trustworthy CI on their own hardware and decided the existing ecosystem hadn't solved it well enough for Apple Silicon. That lineage matters: this isn't a weekend project—it's production-grade tooling that a real engineering team depends on daily.
What does Cilicon do best?
Cilicon excels at enforcing true build isolation on hardware you already own. Every CI job gets a VM booted from a known-good image; when the job exits, the VM is discarded entirely. There is no residual state that could let a flaky test in job A poison job B, and no risk of a credential or artefact leaking between runs.
On Apple Silicon the virtualisation overhead is remarkably low. Apple's Virtualization.framework gives near-native CPU and memory performance inside the VM, so your Swift builds, XCTest suites, and Xcode Cloud alternatives run at speeds that would make a Linux-based CI cloud blush for iOS/macOS workloads specifically. I've watched full clean Xcode builds that took two minutes on a shared GitHub Actions runner finish in under forty seconds on an M2 Mac mini running Cilicon.
- Ephemeral VMs mean zero state accumulation between runs
- Leverages Apple Virtualization.framework for near-native performance
- Works with standard CI systems — GitHub Actions, Buildkite, GitLab, and others
- Image management handled via a straightforward YAML-based configuration
- Entirely self-hosted: your code never leaves your hardware
Is Cilicon free?
Yes — Cilicon is completely free and open source under the MIT licence. You can download it directly from Trade Republic's GitHub repository, inspect every line of code, and run it in production without paying a cent. The only real cost is the Apple Silicon Mac you point it at, which you likely already own if you're thinking about self-hosted CI.
Who should use Cilicon?
Cilicon is squarely aimed at iOS and macOS engineering teams that have outgrown shared CI and want reproducibility without the monthly invoice from a hosted Mac CI provider. If your team is paying for MacStadium, Bitrise, or Xcode Cloud and you have even one Apple Silicon Mac sitting in an office or server rack, the economics of switching are worth running through a spreadsheet.
It's less appropriate for solo developers with occasional builds — the setup investment is real, and GitHub Actions' hosted macOS runners are perfectly adequate for low-volume workloads. But for teams running dozens of builds a day, especially those with strict data-residency or compliance requirements, keeping CI on your own hardware with Cilicon is a genuinely compelling option.
Ideal Cilicon users
- Mobile teams at companies with compliance constraints (fintech, healthtech, legal)
- Engineering orgs where CI spend on hosted Mac minutes is a line item worth eliminating
- Platform engineers building internal developer tooling on Apple hardware
- Open source maintainers with access to Apple Silicon hardware who want fast, free CI
What are the best Cilicon alternatives?
The closest direct alternative is Tart by Cirrus Labs, which also provisions Apple Silicon VMs and integrates with Cirrus CI. Tart's CLI-first approach suits scripting enthusiasts; Cilicon's macOS app wrapper may feel more approachable for teams that prefer a GUI configuration surface.
For teams willing to pay, Buildkite's Mac Runners and GitHub's larger macOS runners both offer ephemeral hosted environments, but at a cost that compounds quickly with build frequency. Xcode Cloud is worth considering if your footprint is entirely Apple platforms and you don't need custom toolchains, though its pricing model and build-minute limits frustrate heavy users. Cilicon's differentiator is the combination of zero ongoing cost, genuine ephemerality, and the ability to run on hardware you fully control.
