Work locally
No account is required to model, save a project, or export a part. Browser projects and recovery history stay on the device.
The product
CAD that can explain its work
PartMode builds parametric parts and structured assemblies from sketches, features, parameters, configurations, and mates. The same editable document drives exact inspection, projected drawings, and ordinary CAD exchange files.
It is not a prompt-to-picture modeler. PartMode keeps the construction history, document revision, persistent entity identity, and exact OpenCascade B-rep in view, so a person or agent can show what changed and why the result is valid.
Bound the agent
A key authenticates an agent; it does not silently grant access to a CAD project. Browser authority is visible, scoped, and temporary.
Prove the result
Completion means settled revision and kernel evidence, valid exact solids, and the requested checked artifact—not only a shaded screenshot.
Capabilities
From first sketch to exchange file
Start from a blank sketch or an editable template, then keep working in a normal feature history. PartMode supports both direct human operation and typed agent procedures against the same document model.
- Dimensioned sketches and parametric features
- Parts, reusable definitions, and structured assemblies
- Parameters, equations, and named configurations
- Persistent references, dependencies, and where-used inspection
- Exact mass, topology, health, and measurement evidence
- Projected drawings from the settled active configuration
- STEP import and exact STEP exchange
- Project, STL, AMF, 3MF, SVG, DXF, and PDF output
Agents
Useful authority, not invisible authority
PartMode's hosted MCP endpoint lets a compatible agent discover live capabilities, inspect exact document state, preview bounded changes, commit against one known revision, and export evidence-bound artifacts.
The normal path keeps the project in an open browser tab and asks the person to approve a session with explicit permissions, duration, and commit budget. Server-headless CAD is a separate, deliberate per-key grant; committed headless documents are stored under the account until account deletion.
Concurrent edits, unsupported operations, ambiguous results, and stale revisions fail closed. The agent must inspect again instead of guessing or blindly repeating a mutation.
Evidence
The model is the source of truth
A visible surface is feedback, not final proof. PartMode records a settled document revision, applied kernel revision, exact body validity, persistent topology, measurements, mass properties, and artifact checks when they apply.
Drawings come from exact OpenCascade hidden-line removal. Saved projects preserve the editable document. STEP exchanges exact bodies and assembly structure; mesh formats remain mesh artifacts and are checked as such.
Current boundary: PartMode is not engineering simulation, certified analysis, automated design approval, CAM, or a complete replacement for every enterprise CAD and drawing-release workflow. Imported STEP retains exact geometry but does not reconstruct vendor-native feature history, mates, or PMI.
Source
Free and open source
PartMode is free and open source under the GNU Affero General Public License v3.0. Read, run, audit, and improve the public source repository; the repository also carries the notices for separately licensed geometry and rendering dependencies.
Its geometry foundation is OpenCascade compiled to WebAssembly, with replicad and three.js. Local modeling works without sending project geometry to the account service. The explicit headless-agent path is the documented exception.
Maker
Made by Sphinx
PartMode is made by Sphinx. Sphinx's interests include software, manufacturing, and how practical knowledge becomes repeatable work.
The aim is straightforward: capable mechanical CAD that a person can understand, an agent can operate within clear limits, and either can verify from the same exact model.