libfive - https://libfive.com
guile scheme, bindings in Rust and Python
personally exited to check it out for real constructive-solid modeling, as opposed to emulating that workflow over OpenCascade's (fickle but otherwise lovely) BREP modeling (ie. edges & faces) via build123d (which has been great but is increasingly vibe-coded :/)
discussed previously: https://news.ycombinator.com/item?id=12319406
a real constructive solid library (as opposed to emulation via modeling), with
Libfive has been superseded long ago by fidget (same author, Rust not C++).
https://www.mattkeeter.com/projects/fidget/
https://github.com/mkeeter/fidget