Open-source developer Mark Harmstone who is known for his work on developing a Btrfs file-system driver for Windows has spent the past few years working on a new hobby operating system. Moxnox is an HT-like, POSIX-compatible operating system.

Harmstone has been developing Moxnox for a while and today released version 1.0 that he's now eager to share with the world. This NT-like, POSIX-compatible operating system runs atop the Btrfs file-system, which shouldn't be too surprising given his history with Btrfs.

Moxnox 1.0 is capable of self-hosting, its system calls are modelled after Windows NT, capable of running software written for Unix-like systems, and amounts to around 130k lines of C++ code while targeting AMD64 and AArch64 hardware.

Moxnox targets x86_64-v3 while for now is easiest testing within QEMU due to the limited hardware/driver support.

Among the software ported to Moxnox include Bash and other common GNU utilities, the GCC compiler, CMake, Zstd, Git, and various libraries. With this v1.0 release there isn't yet any GUI support. While modeled around Windows NT syscalls, it's also not yet able to handle Windows EXE programs.

For those concerned whether this was AI-generated given 2026 trends, Harmstone says that none of the "substantive code" was written via AI and that AI was only used to help with some mechanical parts like porting and translating.

Those curious about Moxnox can learn more via the project's GitHub.