/cad

name: cad
description: Create, modify, inspect, and validate parametric CAD parts and assemblies authored as cadgen model scripts. Use for natural-language CAD specs, reference images, 2D technical drawings, STEP/STP generation or direct inspection, Python CAD source, source-level joints, selector references, geometry facts, measurements, mating deltas, snapshots, and STL/3MF/native GLB outputs from CAD geometry. Also covers project structure for multi-part CAD work - src/ for model scripts and shared code, format folders (STEP/, DXF/, STL/) for raw outputs, naming, and commit policy for projects with several @step/@dxf model scripts and imported source files; use it when starting a CAD project with more than a couple of models, when asked how to organize CAD code and artifacts, or when growing a flat folder of models into a project.

CAD generation, inspection, and validation

Provenance: maintained in [earthtojake/text-to-cad](https://github.com/earthtojake/text-to-cad). Use the installed local skill files as the runtime source of truth; the repository link is only for provenance and release review.

Setup

This skill's commands are thin entrypoints over the `cadgen` distribution, which carries the Python build runtime and the JavaScript it executes. Install it once:

python -m pip install -r requirements.txt

Rendering additionally needs a browser, which pip cannot supply:

python -m playwright install chromium

Purpose

Create or modify parametric CAD models from natural-language requirements, build validated STEP/STP (or mesh) outputs, inspect geometry references, and return checked outputs. STEP is the default output of CAD geometry and the one the inspection tools read; STL, 3MF, and native GLB are mesh outputs a model declares beside it — or instead of it, when the part is print-only. For assemblies, prefer `cadgen.assembly.AssemblyHelper` with source-level build123d joints, named mating datums, and native labels when the parts have functional assembly relationships.

There are two ways into the STEP workflow: build from a build123d model script (the default when designing from scratch or modifying a generated model), or import an existing STEP/STP file directly (when no script exists or the user explicitly targets the STEP file). Both are inspected, snapshotted and exported the same way.

Use this skill when

Use this skill when the user asks for CAD files, STEP/STP files, build123d source, selector refs such as `#o1.2.f1`, mechanical parts, assemblies, enclosures, brackets, fixtures, holes, counterbores, countersinks, slots, pockets, bosses, standoffs, ribs, fillets, chamfers, shells, source-level joints, mating, or measurements. Also use it when the user supplies reference images or 2D technical drawings of a part to reproduce or take design intent from.

Also use it when the user asks for STL, 3MF, or native GLB output from CAD geometry; load `supported-exports.md` for details. For 2D DXF drawings, use the `$dxf` skill; when a DXF projects from a 3D part, this skill owns the part and `$dxf` owns the drawing.

Do not use this skill for render-only concept art, CAM toolpaths, engineering certification, FEA conclusions, architectural BIM, or freehand illustration unless the user also needs CAD geometry.

Default assumptions

Use these defaults unless the user specifies otherwise. These are first-pass modeling defaults, not manufacturability, tolerance, or certification claims:

• Units: millimeters.
• Origin: per the part-type defaults in `references/positioning.md`; center of the main part or assembly when nothing better applies.
• Base plane: XY.
• Up/extrusion axis: positive Z.
• Output geometry: closed, positive-volume solids unless the user requests surfaces or construction geometry.
• STEP structure: one valid solid, a compound of solids, or a labeled assembly compound.
• Assembly structure: fixed root part, part-local frames, named mating datums, `AssemblyHelper` relationships backed by build123d joints where applicable, explicit generated placements, and verbose native labels.
• Small plastic enclosure wall: 2.0-3.0 mm when unspecified.
• Cosmetic fillet: 1.0-3.0 mm when safe for local geometry.
• M3/M4/M5 normal clearance holes: 3.4/4.5/5.5 mm unless another standard is requested.

Ask one focused clarification question only when missing information makes the model impossible, fit-critical, safety-critical, or compliance-bound. Otherwise proceed with explicit assumptions.

Tools and paths

The command surface (the `cadgen` console script, installed with the package):

python <model>.py            # its __main__ calls the model, which builds it
cadgen step build IN OUT     # re-emit an existing STEP as a new one, with kinematics
cadgen stl build ...         # one door per mesh format; `3mf` and `glb` are the others
cadgen step inspect ...      # refs, measure, align, frame, diff
cadgen step snapshot ...     # PNG visual review packets, for STEP
cadgen stl snapshot ...      # the same, for a mesh file; `3mf` and `glb` again
cadgen store why <model>.py  # why the model is stale or current, clause by clause
cadgen daemon status         # the warm workers and the jobs they are running

**Scripts are RUN; commands take DOCUMENTS.** `python model.py` is the one source door — it writes every output the model declares and (only when the model declares kinematics, animation, or mesh exports) its sidecar. Every command above takes a `.step`/`.stl`/`.dxf` FILE, and one handed a `.py` says so. A door asks one question of a document: does the store have a tree for this file's bytes? If so it reads it; if not it compiles one from the bytes as a job in the pool — generated or imported alike. **A door never refuses a document and never runs a script.** Whether a document is behind its script is the model's business (`cadgen store why`), not the door's.

Use the active project Python interpreter; treat `python` in examples as a