For a crystal-clear understanding of the system’s structure, start here.
This project reimagines UNIX Sixth Edition
Rewritten in Zig with modern clarity and minimalism on the RISC-V architecture.
If you want to understand how a system works, you must write one — under the POSIX.
A quiet name for a quiet system.
In the spirit of UNIX, the specification is simple.
Everything else emerges from these foundations.
You deserve Lisp. And I, Zig.
- An experimental Lisp extension
- The core implementation of UNIX Sixth Edition
Claudia Design Spec — v6-inspired OS in Zig on RISC-V
Zig is the only requirement.
You can build and run Claudia with the Zig compiler version 0.14.1, available at ziglang.org.
Claudia depends on no operating system, no runtime, and no external libraries. It builds a system — from first principles, not from dependencies.
You may run it on QEMU, or on real hardware. That's an implementation detail.
You can build and run Claudia with a single command:
zig build run
This will:
- Build the kernel and userland
- Launch the system in QEMU
UNIX Sixth Edition was small enough to be understood.
Lions' Commentary proved that a system can be read like a book.
Claudia inherits that spirit:
- POSIX is the contract, not the system.
- The kernel is written in Zig, exposing syscalls as they are.
- The userland shell is minimal — Lisp is the modern extension.
A system is structure. Everything else is noise.
Claudia refuses to grow beyond what can be read.
How to Read Claudia: Claudia Reading Guide — Speaks Only in Code
Claudia is built in the shadow of giants — with gratitude to Ken Thompson and Dennis Ritchie, whose creation of UNIX continues to shape everything we build.
Copyright KEI SAWAMURA 2025.
Claudia is licensed under the MIT License. Copying, sharing, and modifying is encouraged and appreciated.