I build Edda (https://edda-lang.org), an experimental open-source programming language with built-in formal verification. The compiler, standard library and website are written in Edda itself — source at edda-lang (https://github.com/edda-lang).
Everything here is built AI-first - agents write all of the code.
Also here: nanorun (https://github.com/eyesupplysky/nanorun) (async runtime in Rust), nanopt (https://github.com/eyesupplysky/nanopt) (spectral path tracer in C++20), nanoad (https://github.com/eyesupplysky/nanoad) (reverse-mode autograd and a tiny GPT in pure NumPy), hello-ring-0 (https://github.com/eyesupplysky/hello-ring-0) (x86-64 kernel in assembly).