FreeCAD: https://freecad.org

Cadova - https://github.com/tomasf/Cadova

SolveSpace - https://github.com/solvespace/solvespace

This thread has turned into a great resource! build123d has been my favourite conceptually so far (it's just Python) but vcad looks very clean too. I like the abuse of + and - in both of these for booleans.

JSCAD (formerly OpenJSCAD) https://openjscad.xyz/

Awesome because you can build a model, expose the parameters, and allow web users to generate a model to fit their parameters.

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

Truck (Rust CAD Kernel) - https://github.com/ricosjp/truck

Brl-cad https://brlcad.org/

vcad was started in 2026 and has great ambitions: https://docs.vcad.io

I've been "vibe coding" with OpenSCAD with good results! OpenSCAD will automatically detect changes in the current open file and reload it, so I can use VS Code (with the OpenSCAD extension) to vibe code with Claude, and watch the changes appear on the OpenSCAD screen

KiCad - https://www.kicad.org/