open-poly
Browser-based open source CAD tool with a constraint solver and MCP access for agents.
What it does and how it connects
Open Poly is an open source CAD tool that runs entirely in the browser and keeps work on the user's own machine. Modeling uses the OpenCASCADE kernel through replicad compiled to WebAssembly, rendered with three.js, with parametric sketch constraints from planegcs. Documents autosave to the browser's IndexedDB and can optionally sync with Google Drive; after the first visit it works offline.
It ships a built-in MCP server so a local agent can drive it while the user watches geometry build live in the browser. Claude Code is wired in already; other clients point at the same command. Every action routes through undo, and the agent talks to the browser tab over 127.0.0.1 only, so the bridge is inert on the hosted build at openpoly.dev.
Try it at openpoly.dev with no sign-up, no upload and nothing to install. The public deployment collects basic anonymous page analytics only. The README notes third-party license terms, including the LGPL constraint solver and the OCCT kernel, in its NOTICE file.
Alternatives
Compare side by side- parcad
Parametric CAD written as code with its own exact kernel and MCP surface, rather than a browser CAD app with an MCP bridge.
- cad-ai
A web-based CAD assistant pitched as a Cursor-style copilot, built over the OpenAI and KittyCAD APIs, rather than a self-contained browser CAD tool.
- CADStudio
An AI-native parametric CAD environment for the web with an editable feature tree and CadQuery export, rather than an OpenCASCADE browser app.
- cadgang
A CAD viewer and markup tool whose markups and joints are readable by Claude Code over MCP, rather than a modeling app.
- vibe-cading
CadQuery-based 3D model generators written for humans and LLM agents, rather than a browser CAD app.
Sources
Not verified
- Pricing (no price stated; the app is free to use at openpoly.dev)
- Real user voices (the repository's recent issues are maintainer pull requests)
- Related Error Index entries (no entry verified for this tool)
- A named individual builder beyond the repository owner handle eitan27
Last verified November 6, 2026. Listings are informational. The evidence score measures public, verifiable evidence and is not an endorsement or a compatibility claim.