Open-source CAD tools in Rust, built around AI coding agents

A rover made of 3,323 editable steps, each one rebuilt without errors, was modelled entirely through the MCP server of SolidCraft, an open-source 3D CAD program. CAD, computer-aided design, is the software engineers use to draw parts on screen before they are machined or printed. The rover was built by an outside user, @0xlillith. It is one community example of what agent-driven modelling can produce with SolidCraft and its 2D sibling CADCraft, the two open-source projects discussed here.

SolidCraft works as a parametric modeller: a part is a numbered list of operations such as extrude, fillet or hole, and any step can be edited later without starting over. It runs on the desktop or in a browser, and exports to the neutral exchange formats STEP AP242 and IGES, along with 3MF, STL and OBJ. Its maintainers are candid about the gaps. Its checks reproduce analytic or FreeCAD-computed volume, area, centre of mass and bounding box on 75 of 76 public reference parts, but they state that this does not establish full equivalence with commercial software. Mesh modelling, simulation, CAM (toolpaths for machine tools) and 2D drawings are all deferred. CADCraft, for its part, opens DXF files from R12 to 2018 and DWG files through an open-source library, and saves them as R2000. Entities it does not yet understand are dropped on save. Its roadmap puts AutoCAD parity at about 29% overall and 55% for 2D drafting, while 3D modelling stands at 0%. Whether its files open correctly in AutoCAD itself is not yet confirmed.

The agents are written into the code. Both repositories contain a CLAUDE.md file, a set of instructions addressed to AI agents, telling them to work autonomously and to stop only when a decision belongs to the owner. Quality is enforced by automated gates: no panics in production code, and every crash fix must ship with a regression test. The projects also set rules on sources. SolidCraft may only observe the commercial Fusion software as a black box, and its agents are barred from reading GPL-licensed geometry code such as OpenCASCADE, FreeCAD and SolveSpace. CADCraft applies the same policy to AutoCAD, and its file formats must come from public specifications. The developers estimate the remaining work in agent time: about 82 agent hours to a useful SolidCraft alpha, and for CADCraft roughly 50 model hours, or 15 to 20 elapsed hours with three or four agents working in parallel. Neither project publishes how much of its code was written by AI.

The real obstacle is the geometry kernel, the engine that computes how shapes meet, cut and round off, and which has historically been the costliest layer to build. SolidCraft runs on an existing Apache-2.0 kernel called truck, with its own blend operations and validation layered on top. A companion project, solidcore, is a Rust port of NVIDIA's SMLib boundary-representation kernel, released by NVIDIA under the Apache-2.0 licence. Its author aims to match the original C++ to within 1e-9 relative error with identical topology, checking each unit side by side against the original, and says the port is early, with modules still being ported one at a time.

For engineers and small workshops, the consequence is a possible cheaper route to specialised design tools, but not yet a usable one. A permissively licensed kernel plus agent-driven development could, in principle, shorten the time to build a CAD program. Whether the result is dependable enough for manufacturing depends on what neither project claims yet: robust boolean operations on complex geometry, and verified round-trips with the commercial formats engineers exchange every day. The next milestones are the alphas both teams have scheduled, and the first outside test of whether a CADCraft drawing opens cleanly in AutoCAD. Until those land, the rover is the one concrete example reported so far.