CADSketch

Sketch-first CAD. Draw a rough shape and it snaps to clean, constrained, dimensioned geometry, then extrudes to a 3D part you can add to, cut into, assemble, and export.

Where	How
iPhone and iPad	App Store
Any browser	cadsketch.ai/app
Codex and ChatGPT desktop	the plugin, below

It is one codebase: a Flutter app with a C++ geometry kernel (native via FFI, WebAssembly on the web). The plugin embeds the same web build.

Use it inside Codex or ChatGPT

The plugin puts the editor in the app's sidebar, opens .cadsketch and .dxf files from your workspace in it, and lets the agent work in the same sketch you are looking at: read the canvas, move vertices, add holes, set driving dimensions and constraints, undo, take a screenshot, and export STL.

Needs Node.js 18 or later and a recent Codex (tested with 0.157).

codex plugin marketplace add punkfab/cadsketch
codex plugin add cadsketch@cadsketch

To update an existing install, refresh Codex's copy of this repository, then install again (the same two steps do not fetch a newer version by themselves):

codex plugin marketplace upgrade
codex plugin add cadsketch@cadsketch

Restart the desktop app, then click CADSketch in the sidebar, or ask:

Create bracket.cadsketch for a 60 × 30 mm L-bracket, 5 mm thick, with three M4 holes, and open it.

Then, with it open: "make it 95 mm wide and add a hole 8 mm in from each corner."

How it works, the tools, and the file format are in mcp/README.md. It is built on the open MCP Apps standard plus OpenAI's plugin extensions, so the same server also works as a connector in Claude and other MCP hosts.

What it does

• Freehand to geometry. Strokes are recognised as lines, arcs and circles, endpoints weld, and horizontal, vertical, parallel and perpendicular constraints are inferred.
• Live constraint solving. Tap a length and type a value; the sketch re-solves. Drag a point and the rest follows its constraints.
• 3D. A closed profile extrudes to a solid. Sketch on a face to add material or cut into the part.
• Assemblies. Several parts, mate connectors on faces, fasten mates, and parameters shared across parts.
• Import and export. DXF, STL and OBJ in; STL out. A featuretree IR goes both ways: out, it re-authors the part as an editable FreeCAD tree; in, a feature tree (one recovered from a STEP file, say) opens as a body with its holes and face features, and anything CADSketch can't show is named rather than dropped. tool/ir_roundtrip_volumes.py checks the round trip against featuretree's own build123d backend.

GUIDE.md is the user guide.

Repository layout

native/        C++ geometry kernel behind a flat C ABI (line/circle fitting, the
               Levenberg-Marquardt constraint solver)
lib/
  sketch/      the sketch model, recognition, constraints, solids, import
  ui/          the 2D canvas, 3D views, parts tree
  export/      STL, mesh, featuretree IR
  import/      featuretree IR
  ffi/         kernel bindings: dart:ffi natively, js_interop to WASM on the web
  mcp/         the bridge and editing commands used when embedded in an AI host
mcp/           the MCP server and the widget an AI host renders
plugin/        the Codex / ChatGPT plugin (built output committed) and the
               directory submission
landing/       cadsketch.ai
ios/ web/      platform shells
test/          the Dart test suite

Design rule: stable heavy math goes in the C++ kernel; tune-by-feel logic stays in Dart, where hot reload makes tuning instant.

Develop

./build_native.sh          # the kernel, for desktop runs and tests
flutter test               # the Dart suite
flutter run -d linux       # desktop harness
./build_wasm.sh && flutter build web --release --base-href /app/   # the web build

cd mcp && npm install && npm test    # the MCP server and plugin

Deployment (TestFlight, the website, the MCP server) is described in DEPLOY.md and mcp/README.md.

License

No license is granted. The source is published so you can read it and install the plugin; all rights are reserved.

CADSketch is a punkfab project.