tl;dr: Kakehashi is an experimental userspace translation layer that runs macOS ARM64 Mach-O binaries natively on Linux aarch64 by mapping a freestanding libSystem and translating BSD syscalls—no JIT or instruction emulation. It currently works with CLI tools like 7zz, curl, and clang probes, running roughly 5× slower than native Linux on syscall-heavy workloads. The pitched use case is CI: even at 5× slowdown, running Darwin CLI tools on cheap Linux ARM runners can be cheaper than GitHub's macOS runners, which cost ~10–12× more per minute.