Part 2 of the AI CAD Bench.
This round covered the other two part families: formed sheet metal and an aluminium extrusion.
And it got boring: two kernels, two agents that never saw each other's work, and the exact same 94,544.257 mm³.
Same setup as part 1. A fresh Opus 5.5 agent rebuilds a part from an engineering drawing in FreeCAD 1.1.4 and in SolidCraft 0.27.1, from one shared reading of the sheet, with the same rules, graded against the original geometry.
Sheet-metal bracket (NIST PMI test case 3, graded against NIST's own model):
FreeCAD: 99.65% overlap, volume −0.04%
SolidCraft: 99.67% overlap, volume −0.07%
Both were missing the same 658 mm³, which is the "NIST" engraving that the rules said to leave out.
SolidCraft needed 3 script runs to FreeCAD's 1. Two of those were the agent's own bugs. The third is the fun one: the agent made each slot as a box with a cylinder touching each end, and SolidCraft won't cut where curved faces only graze the body. FreeCAD took it without complaint. A human would never build a slot that way. The agent switched to SolidCraft's slot command, and it worked first time. One rerun.
SolidCraft's strictness also helped. It refused a malformed sketch loop with a named error, right at the sketch. FreeCAD might have quietly turned the same wire into a solid that looked right and measured wrong.
Heat sink, with nine unevenly spaced fins and twelve holes: identical to three decimal places. Both had 53 faces and fins 1.75 / 1.51 mm wide, 34 s vs 32 s, zero refusals. Both agents also hit on the same workaround on their own: draw one fin, place nine copies by coordinate, fuse once, cut once.
All four parts: three ties and one clear FreeCAD win, on the drafted, lofted moulded bracket (99.5% vs 97.1%).
So on most parts that get modelled from a drawing, the kernel doesn't decide it. Where it does is tangent booleans and tight fillet chains on drafted faces. I'm curious which of those agents learn to route around first.
Caveats: single runs, one model, no sheet-metal workbench on either side, and the heat sink was graded against the reading rather than a model.