harnesscad

harnesscad is a text-to-CAD agent harness built on one rule the README states as soundness, not completeness: it will never ship a wrong part, and it says no when a plan is infeasible, when its backends disagree, or when it cannot measure the result. It verifies the operation stream before any CAD kernel runs, so an infeasible plan becomes a named diagnostic instead of a meaningless solid. The README example is a 20 by 10 by 5 plate with a radius 8 fillet and a thickness 9 shell, where preflight checks flag the fillet radius and the shell thickness before the kernel is called.

The harness cross-checks built geometry across independent kernels and measures the result exactly, so a wrong part is caught by disagreement or by measurement rather than trusted because one kernel returned a number. It ships a kernel-free geometry backend for basic work and drives OCCT and other kernels through the same operation stream for production boundary representation.

A computer-use system in io/cua and agents/cua drives CAD in real graphical interfaces. The README rests it on two facts: CAD toolbars are pixel stable, so template matching on icon bitmaps grounds most actions without a vision model, and scriptable CAD exposes the rest. A Parts-Driven Development section frames requirements as parts with measurable acceptance, so a passing spec test is not the only proof the spec is right.