Chamfer
Text and image driven CAD agent that writes build123d Python, runs it on a real geometry kernel, and measures dimensions and holes against the request before showing the model, with an optional live Autodesk Fusion backend.
What it does and how it connects
Chamfer is a text and image driven CAD agent that writes build123d Python, runs it on a real geometry kernel, and measures dimensions and holes against the request before showing the model. That check is the whole point, per the README: geometry that was verified, not a model that merely claims to be right. Two CAD backends are picked per conversation: local build123d, or a live Autodesk Fusion session, which Chamfer discovers by itself with no port to configure. A free online try-out runs at chamferonline.com with free design credits included, and the user can add their own Anthropic, OpenAI or Google key.
The agent's plan is an auditable contract rather than criteria the agent can silently weaken: a 2026-07-12 hardening change made check identifiers stable after an issue showed a dimensioned multi-view drawing producing a model that "passed the verification gate" yet visibly failed it. Demos in the README include a finned motor bearing housing built in Fusion from one prompt and an espresso machine built from a product image. The agent runs under the pi agent harness with skills for build123d modeling, and supports different MCP servers and LLMs.
Alternatives
Compare side by side- MAC (Multi-Agent CAD)
Splits text-to-CAD across LangGraph agents with visual and geometric verification, rather than a single agent with an auditable plan contract.
- Text23D Mechanical
Turns chat prompts into CadQuery or FreeCAD models in a web workbench, rather than build123d or live Fusion with a verification gate.
- Forgent3D
Pairs coding agents with a desktop viewer to verify parametric models against real geometry, rather than an agent with a built-in verify gate.
- cad-agent (kerryshi)
Turns English into CadQuery through a frozen spec with spec-derived verification, rather than build123d with a plan contract.
- MecAgent
A commercial desktop copilot that acts inside an open SolidWorks session, rather than an open-source agent on build123d or Fusion.
Recurring errors it addresses
Error Index entries this tool is built to reduce or work around.
- Cloud-first file model makes local file control, rename/move/backup workflows feel alien and risky.Error Index
- General UI/UX is described as confusing and hostile for routine work.Error Index
- ChatGPT's Computer Use agent cannot drive Autodesk Fusion 360: selecting Always allow does not stick, a later window-state request fails with 'Computer Use was not approved to use fusion360', and the requested CAD design could not be created. Desktop logs recorded three allow-persist-always approvals with no persisted entry in the config.Error Index
- STEP carries geometry only and sketch DXF only 2D profiles, so moving a Fusion design to another parametric CAD tool loses its intent. The proposal is a JSON export of user parameters, the feature timeline, sketch constraints and component transforms, with the STEP kept as the reference to check the rebuild against by volume and bounding box.Error Index
Sources
Not verified
- Pricing: no prices are stated on the repo or site; the README says free design credits are included on chamferonline.com.
- The GitHub API classifies the repo license as NOASSERTION; the LICENSE file text is Apache License 2.0, so Apache-2.0 is used here.
- Real user voices: no real linked post read for this page; the repo's issues and pull requests are all maintainer-authored, and no independent user report was found.
Last verified November 6, 2026. Listings are informational. The evidence score measures public, verifiable evidence and is not an endorsement or a compatibility claim.