Reported issues for build123d MCP

Pod holds 6 of 6 problems reported by people outside the maintainer team. Issues filed by the project's own owners, members and collaborators are excluded entirely — a maintainer's release checklist is not a warning to a prospective user.

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Most discussed

suggest_view_layout() pairs a centroid look_at with origin-anchored cameras, producing tilted elevations

Summary

suggest_view_layout() returns a look_at at the part centroid but pairs it with fixed camera positions anchored at the origin. For any part whose centroid is not at the origin, the camera-to-look_at axis is tilted, so the front and side views come out as slightly rotated projections rather than true orthographic elevations.

The plan view is unaffected, which is what makes this hard to notice.

Reproduction

A 60 x 40 x 10 mm plate sitting on z=0, so centroid `(0, 0, 5)

Read the thread · 2026-08-26 · closed · external user · 1 comment

resolve() reports a point on the entity, not its centre, for circles and cylinders

Summary

For any circular or cylindrical entity, resolve() reports a center that lies on the entity, displaced from the true centre by exactly the radius. It is correct for planar faces, which is what makes it easy to miss.

Reproduction

On a 60 x 40 x 10 mm plate with four dia-4.5 through holes at (+/-22, +/-12):

Read the thread · 2026-08-26 · closed · external user · 1 comment

DXF export writes centroid-relative coordinates, not model coordinates

Summary

render_view(format="dxf") writes coordinates that are relative to the part centroid, not to the model origin. The shape is exact; the origin is displaced. Importing the DXF into CAD expecting model coordinates puts every feature off by the centroid, and the error grows with how asymmetric the part is.

Reproduction

Test part: a 180 x 100 x 12 mm plate with two dia-20 bosses, a bolt circle, a counterbore, a countersink, a blind hole and a tap-drill bore -- deliberately asymm

Read the thread · 2026-08-26 · closed · external user · 1 comment

Windows + MCP host: subprocess.Popen blocks inside the worker, so render_view/health_check always hit the 150s timeout (BUILD123D_IN_PROCESS=1 works)

Summary

On Windows 11, when the server is launched by an MCP host (Claude Code, stdio), subprocess.Popen blocks indefinitely inside the worker process. The worker itself starts fine and pure-geometry tools work, but every tool that shells out to a helper subprocess — render_view, and therefore health_check — burns the full _RENDER_TIMEOUT (150s) and kills the session.

BUILD123D_IN_PROCESS=1 is a complete workaround: identical calls then succeed in ~15s.

This looks related to

Read the thread · 2026-08-26 · open · external user · 1 comment

import_cad_file: add 3MF support (build123d's Mesher already reads it, and yields solids not shells)

import_cad_file accepts only .step / .stp / .stl. 3MF is not supported, even though build123d ships Mesher, which reads it.

3MF is the native format of the consumer 3D-printing ecosystem -- it is what Bambu Studio, PrusaSlicer, MakerWorld and Printables hand you, and it is frequently the only format a downloaded model is distributed in. In a session adapting a downloaded rack-mount model, the 3MF was the only file containing the actual bracket; the accompanying STLs were just the fa

Read the thread · 2026-07-25 · closed · external user · 1 comment

Windows + Codex MCP host: execute fails with "Worker process failed to start within timeout", while WorkerSession works in PowerShell

Summary

I am testing build123d-mcp on a Windows workstation through the Codex MCP host.

The server starts and simple tools work:

• version returns 0.3.28
• reset returns Session reset.

However, any call to execute() fails, even a trivial print-only script.

Environment

• OS: Windows
• Python: 3.12.10
• build123d-mcp: 0.3.28
• MCP host: Codex desktop / Codex MCP
• Launch mode tested:
  1. uv tool run --python 3.12 build123d-mcp --exec-timeout 30
  2. local launcher with `

Read the thread · 2026-06-01 · closed · external user · 5 comments

Most recent

The remaining reports are on the project's issue tracker.