Preloop is a local and self-hosted GitHub Actions engine that executes unmodified .github/workflows on hardware-isolated microVMs (Windows, macOS, Linux) with 300ms resume times.

It provides DAP-powered debugging to pause failed steps, inspect live job context, and retry individual steps without a push. A Rust-based runner replacement installs 36x smaller and peaks at 19x lower memory while speaking the official actions/runner protocol.