It's also embeddable as a library, which means being able to make web-based object customisers: client-side, script-driven tools that don't require CAD knowledge for the user. Like the Thingiverse customiser but on steroids. It's a fascinating project.

And I think it's not the statefulness that is the significant thing about CadQuery and Build123D. It's the access to a bRep kernel, so you can do operations with faces and vertices, you can reflect (analyse, measure) the model, etc.

Being able to do operations on a generated face or edge means not needing to know (or recalculate) the location of that face in 3D space; it saves you so much in the way of maths.

If you have very simple (or very mathematical!) models, OpenSCAD can help. But once things get complex you just have file after file of variable definitions.

Functional flows on vertexes, edges and faces created by previous operations is much closer to a code equivalent of GUI CAD.

OpenSCAD integrated manifold into its codebase though you would need to use a development build to actually use it since the last release is in 2021. I heard manifold is significantly faster than CGAL.

Please correct me if I’m wrong, but it doesn’t appear stateful to me. The context managers mostly make the organization of objects be reflected in the organization of the code.

They’re stateful in the sense that some bits are part of a larger assembly, but I think that’s inherent in the domain. The features of the object have to relate to each other so it knows how to stitch the object together (eg which side of a face is external and which is internal).

Build123d has stateless algebra mode. And you could replace math with simple construction elements and simply ask intersection points.