# 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.

Back to [build123d MCP](/mcp/build123d-mcp).

## 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](https://github.com/pzfreo/build123d-mcp/issues/457) · 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):

| selector | `resolve()` reports | true centre | error |
|---|---|---|---|
| hole wall face (cylinder) | `(24.25, 12, 5)` | `(22, 12, 5)` | `2.25` = r |
| hole rim edge

[Read the thread](https://github.com/pzfreo/build123d-mcp/issues/456) · 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](https://github.com/pzfreo/build123d-mcp/issues/455) · 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](https://github.com/pzfreo/build123d-mcp/issues/452) · 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](https://github.com/pzfreo/build123d-mcp/issues/422) · 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](https://github.com/pzfreo/build123d-mcp/issues/143) · 2026-06-01 · closed · external user · 5 comments

## Most recent

The remaining reports are on [the project's issue tracker](https://github.com/pzfreo/build123d-mcp/issues).