Partsmith

Partsmith — the printability gate for generative CAD. AI can generate a 3D model in seconds, but can you print it? Partsmith's Caliper engine measures every generated part (overhang, wall thickness, real-world fit) in build123d and ships it only if it passes — or rejects it with the exact number. The check that has to sit between "generate" and "print." Describe a part; Claude Code agents write the build123d; Caliper gates it on measured geometry, and a broken design is auto-repaired red→green until every check passes. Three agents raced the same spec into three support-free designs, and Caliper ranked the leanest that passes: 131 mm³, 80× leaner than a naive solid block, all seven checks green. The checks are the optimization target — generative CAD stops being a dice-roll and becomes an engineering loop. Honest scope: these are geometric printability + fit checks (the proven first pillar), not physical-function proof; structural/flow verification (FEA/CFD) is the roadmap. The repo runs green, and the gate demonstrably rejects bad parts (a too-thin wall, a too-tight slot, an oversize body — each caught with the measured number). Built clean-room during the hackathon.