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Design@donghyeok99Staff

SolidCraft: open-source parametric CAD your agent can drive

Someone had Claude Code model their house's staircase without touching the CAD tools

An agent sketches, extrudes and shells a box over MCP; height goes from 24 to 32 mm and the timeline rebuilds as the box grows
An agent sketches, extrudes and shells a box over MCP; height goes from 24 to 32 mm and the timeline rebuilds as the box grows
Who
Tangency Labs' open-source parametric CAD in Rust, for people who model by hand and people who hand it to an agent. MIT or Apache-2.0.
When
The repository opened on 7 October 2026; the latest release is v0.26.0, from 29 October 2026.
Where
Windows, macOS and Linux desktop, or the browser. Over MCP: Claude Code, Codex, Cursor, Gemini, Claude Desktop and more, on your machine.

What was hard

Ask an agent for a part and what you usually get back is a single mesh. Want it a little taller? You ask again from scratch, and there's no history to open and see how it was built.

What it does about it

SolidCraft puts an MCP server inside a CAD app people already use by hand. The agent's calls become the same engine commands as the toolbar buttons and land one by one on the feature timeline; leave the app open and you watch the model take shape in its window. What you get is an editable design, so changing a single parameter recomputes every feature after it.

The README demo: a Raspberry Pi 4 case, rebuilt when its height changes
A half-turn staircase modelled by Claude Code over MCP
A half-turn staircase modelled by Claude Code over MCP

What people made with it

Redditu/mj_09012026-10-27

A half-turn staircase for their house, described to Claude Code in plain words. Change the height or riser count and it all rebuilds; the structural check is in Python.

The whole model was built by Claude Code through SolidCraft’s MCP connector. I described what I wanted in plain language, Claude created the sketches and features
Redditu/dude1995aa2026-10-24

Telecaster guitar bodies from PDFs they had, then bindings and a kill switch added by desktop ChatGPT. The first run left out the wire holes between the pickup pockets, they note.

Took seconds to have desktop ChatGPT add bindings, add a kill switch just for fun.
GitHub@0xlillith2026-10-13

SELENE, a rover built only through SolidCraft's MCP commands: 1,395 bodies and 3,324 history entries, released as an editable native file plus STEP and 3MF.

The rover has six driven wheels, visible suspension and dampers, an articulated sampling arm, a camera and lighting turret, deployable solar panels, a steerable dish

How it runs inside

  1. 1

    Claude Code → solidcraft-cli mcp

    tools/call batch {commands: [...]}One JSON-RPC line over stdio; the server checks the arguments and runs the tool inside the agent's folders only.crates/mcp/src/server.rs
  2. 2

    solidcraft-cli mcp → Headless engine session

    engine.execute {command, params}Each tool becomes an engine command: set_parameter runs parameters.change, export runs file.export.crates/mcp/src/tools.rs
  3. 3

    solidcraft-cli mcp → Headless engine session

    edit.checkpoint → edit.restore_checkpointA batch takes a checkpoint first; if any step fails, the design and undo history go back to where they were.crates/mcp/src/tools.rs
  4. 4

    solidcraft-cli mcp → SolidCraft app (control port)

    engine.batch over the 127.0.0.1 control portWith the app open and nothing built yet, it bridges there, sends that launch's token and runs a batch in one frame.crates/mcp/src/backend.rs
  5. 5

    Headless engine session → PNG screenshot · STEP file

    ui.render → PNG, file.export → STEPHeadless, it renders the model on the GPU (or CPU) and returns a PNG; export writes STEP, 3MF, STL and more.crates/mcp/src/backend.rs

What goes in, what comes out

examples/bracket.json (a command script)bracket.step
A Pi 4 case at 24 mm highSet to 32 mm, rebuilt down to the standoffs and the engraving
A STEP assemblyA close-up PNG with covers removed and a section cut

Is it for you

Good for

  • Trying out cases or brackets for 3D printing with an agent such as Claude Code or Codex
  • Getting an editable design with real dimensions back instead of a single mesh
  • Watching an agent model in the app window and stepping in midway
  • Using a feature-timeline CAD that is free and open source

Not for

  • Still early and suited to simple parts: 75 of 76 public reference parts match their volume, area and centre of mass; the other is a tracked bug.
  • The Windows downloads aren't signed yet, so SmartScreen needs More info, then Run anyway.
  • The agent can only save in set folders, like the open design's; add others with --allow-path.
  • Calls bridged to the app don't get parameter checking yet.

Reviewed by Devalley’s editor before publishing. How the column is made

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