Parametric CAD captures why a part is shaped the way it is, so a change to one dimension ripples through the whole model. These are the open-source tools doing it best — and where AI copilots are starting to help.
The open-source parametric CAD workbench — production-capable since the 1.0 release, with a real assembly workbench and a Python core.
Code-CAD in Python — the modern successor to CadQuery for parts defined as scripts, built on the OpenCASCADE kernel.
The programmer's solid modeller — fully declarative geometry, ideal for parametric libraries.
Not CAD, but unmatched for organic modelling, sculpting and the geometry-nodes pipeline.