User prompt → Agent edits models/*.py → Python skill regenerates artifacts → Viewer previews geometry

git clone https://github.com/earthtojake/text-to-cad.git
cd text-to-cad

python3.11 -m venv .venv
./.venv/bin/python -m pip install --upgrade pip
./.venv/bin/pip install -r requirements-cad.txt

cd viewer
npm install

npm run dev

text-to-cad/
├── models/                  # Your CAD source files live here
│   └── my_part/
│       ├── part.py          # build123d Python source
│       ├── part.step        # Generated STEP export
│       ├── part.stl         # Generated STL export
│       └── part.glb         # Generated GLB for viewer
├── skills/
│   ├── cad/
│   │   ├── SKILL.md         # CAD skill documentation
│   │   └── ...
│   └── urdf/
│       ├── SKILL.md         # URDF skill documentation
│       └── ...
├── viewer/                  # React/Vite local viewer
│   ├── package.json
│   └── src/
├── requirements-cad.txt     # Python dependencies
└── assets/

# models/bracket/bracket.py
from build123d import *

with BuildPart() as bracket:
    # Base plate
    with BuildSketch(Plane.XY):
        Rectangle(80, 60)
    extrude(amount=5)

    # Vertical wall
    with BuildSketch(Plane.XZ.offset(30)):
        Rectangle(80, 40)
    extrude(amount=5)

    # Fillets on all edges
    fillet(bracket.edges(), radius=2)

    # Mounting holes
    with BuildSketch(bracket.faces().filter_by(Axis.Z).sort_by(Axis.Z)[-1]):
        with Locations((-25, -15), (25, -15), (-25, 15), (25, 15)):
            Circle(3.5)
    extrude(amount=-5, mode=Mode.SUBTRACT)

# Export
export_step(bracket.part, "models/bracket/bracket.step")
export_stl(bracket.part, "models/bracket/bracket.stl")

./.venv/bin/python models/bracket/bracket.py

# models/hex_spacer/hex_spacer.py
from build123d import *

# Parameters — agent edits these values
OUTER_DIAMETER = 12.0   # mm, across-flats
HEIGHT = 10.0           # mm
HOLE_DIAMETER = 5.0     # mm (M5 clearance)
WALL_THICKNESS = 2.0    # mm

with BuildPart() as spacer:
    with BuildSketch(Plane.XY):
        RegularPolygon(radius=OUTER_DIAMETER / 2, side_count=6)
    extrude(amount=HEIGHT)

    with BuildSketch(Plane.XY):
        Circle(HOLE_DIAMETER / 2)
    extrude(amount=HEIGHT, mode=Mode.SUBTRACT)

    fillet(spacer.edges().filter_by(Axis.Z), radius=0.5)

export_step(spacer.part, "models/hex_spacer/hex_spacer.step")
export_stl(spacer.part, "models/hex_spacer/hex_spacer.stl")

# models/assembly/assembly.py
from build123d import *

# Base
with BuildPart() as base:
    with BuildSketch(Plane.XY):
        Rectangle(100, 80)
    extrude(amount=10)

# Post
with BuildPart() as post:
    with BuildSketch(Plane.XY):
        Circle(8)
    extrude(amount=50)

# Combine into assembly
assembly = Compound(
    children=[
        base.part,
        post.part.move(Location((0, 0, 10))),
    ]
)

export_step(assembly, "models/assembly/assembly.step")
export_stl(assembly, "models/assembly/assembly.stl")

from build123d import *

# STEP — full geometry, use for CAD interchange
export_step(part, "models/my_part/my_part.step")

# STL — mesh for 3D printing / simulation
export_stl(part, "models/my_part/my_part.stl")

# DXF — 2D drawing / laser cutting
section = part.section(Plane.XY)
export_dxf(section, "models/my_part/my_part.dxf")

# GLB — viewer-compatible 3D web format
export_gltf(part, "models/my_part/my_part.glb")

models/my_robot/
├── robot.py          # build123d geometry for each link
├── robot.urdf        # Generated URDF XML
└── meshes/
    ├── base.stl
    ├── arm.stl
    └── gripper.stl

<!-- models/my_robot/robot.urdf (generated) -->
<?xml version="1.0"?>
<robot name="my_robot">
  <link name="base_link">
    <visual>
      <geometry>
        <mesh filename="meshes/base.stl"/>
      </geometry>
    </visual>
  </link>
  <link name="arm_link">
    <visual>
      <geometry>
        <mesh filename="meshes/arm.stl"/>
      </geometry>
    </visual>
  </link>
  <joint name="base_to_arm" type="revolute">
    <parent link="base_link"/>
    <child link="arm_link"/>
    <origin xyz="0 0 0.1" rpy="0 0 0"/>
    <axis xyz="0 0 1"/>
    <limit lower="-1.57" upper="1.57" effort="10" velocity="1"/>
  </joint>
</robot>

cd viewer

# Start dev server
npm run dev          # → http://localhost:4178

# Build for static hosting
npm run build

# Preview production build
npm run preview

# Example agent follow-up using a reference
@cad[models/bracket/bracket.step#face:top] — add a countersunk hole at center

1. User: "Create a parametric L-bracket with 4 mounting holes, 5mm thick"

2. Agent: creates models/l_bracket/l_bracket.py using build123d

3. Agent runs: ./.venv/bin/python models/l_bracket/l_bracket.py
   → generates l_bracket.step, l_bracket.stl, l_bracket.glb

4. User: opens http://localhost:4178, inspects the model

5. User copies @cad[...] reference from viewer

6. User: "Make the wall taller — @cad[models/l_bracket/l_bracket.step#face:wall]"

7. Agent edits WALL_HEIGHT parameter in l_bracket.py, reruns script

8. User commits models/l_bracket/ (source + artifacts together)

with BuildPart() as panel:
    with BuildSketch(Plane.XY):
        Rectangle(100, 60)
    extrude(amount=3)

    # Horizontal slot
    with BuildSketch(Plane.XY):
        SlottedHole(length=30, radius=3, rotation=0, align=Align.CENTER)
    extrude(amount=-3, mode=Mode.SUBTRACT)

with BuildPart() as symmetric_part:
    with BuildSketch(Plane.XY):
        Rectangle(40, 20)
    extrude(amount=10)
    mirror(about=Plane.YZ)

with BuildPart() as box:
    Box(60, 40, 30)
    # Remove top face to shell into an open container
    shell(box.faces().sort_by(Axis.Z)[-1:], thickness=-2)

from build123d import *

with BuildPart() as my_part:
    Box(50, 50, 20)

# Check validity
assert my_part.part.is_valid, "Part geometry is invalid — check for bad operations"

export_step(my_part.part, "models/my_part/my_part.step")
print(f"Exported: volume={my_part.part.volume:.2f} mm³")