Geop

open source · rust · runs in your browser

Parametric CAD on an exact NURBS kernel.

Sketch, extrude, fillet, assemble and export STEP: in the browser, from the command line, in VS Code, or through MCP from an AI agent. Every number is an interval, so no epsilon decides an answer, and parts are programs whose faces and edges keep their names on every rebuild.

▶ Try in your browser ★ Star on GitHub ↗

Nothing to install · files stay in your browser · MIT / Apache-2.0

  • 322 / 361public STEP corpus files import valid
  • 0.25 sfor a drag in a 2000-part assembly

built for the agentic era

An agent can drive geop directly — no GUI required.

A part is a plain JSON program: an ordered list of steps, each one operation with its arguments, referring to what earlier steps built only by name. An agent like Claude Code or Codex can write one step by step, compile it with the geop CLI, and see exactly what it built. Or register geop as an MCP server and it sketches, extrudes, fillets, inspects and exports through the same editor the web app runs: claude mcp add geop -- geop mcp for Claude Code, codex mcp add geop -- geop mcp for Codex.

agent — geop 

        

        

          

          
part.stl

        

      

      
      
The app: download, double-click, no terminal. Your computer warns once, as it is not yet signed: what to do.

      

        

          

            
            
            
            install the geop CLI
          


# macOS, Linux
$ curl -fsSL https://geop-cad.dev/install.sh | sh
# Windows (PowerShell)
> irm https://geop-cad.dev/install.ps1 | iex
# then
$ geop open                         # this folder's parts, in your browser
$ claude mcp add geop -- geop mcp   # for Claude Code
$ codex mcp add geop -- geop mcp    # for Codex
$ geop vscode                       # the VS Code extension

        

        
Checks every download's SHA-256 · no sudo

      

      

        Use with Claude Code (MCP) ↗
        VS Code extension ↗
      

    

  


  


  
  

    

      

        
the data model

        
A well-defined way of dealing with smooth 3D bodies.

      

      

        Geop's bodies are NURBS solids, top to bottom — it's SVG, but in 3D. The
        closest existing analogue is a STEP file, a powerful but famously opaque
        format. Geop gives you the same expressive power through curves, surfaces,
        and topological data structures you can actually read and extend.
      


      

        

          
          INTERVAL ARITHMETIC
          Every number is an interval and every comparison three-valued (definitely, could be). Searches subdivide to isolate and Newton to refine — Geop knows what it doesn't know, so it won't miss an intersection.
        

        

          
          NURBS CURVES & SURFACES
          The mathematical primitive underneath every smooth edge and face Geop draws.
        

        

          
          ROBUST BOOLEANS
          Union, intersect, and subtract on real geometry, without missing intersections.
        

        

          
          NON‑MANIFOLD TOPOLOGY
          Data structures that go beyond simple solids: 3-D sketches are wires, edges and vertices without faces.
        

        

          
          PARTS AS PROGRAMS
          An ordered list of steps that refer to what earlier steps built by stable names (extrude(box,end)), never by a kernel id — so a part rebuilds name for name.
        

      

    

  


  


  
  

    

      

        
what works today

        
The features an engineer reaches for when designing a real machine.

      

      

        

          
Sketching

          
2-D constraint sketches with slots, polygons, fillets, offsets, mirrors and patterns; redundant constraints proven and conflicts named. 3-D sketches as wires; exact helices.

        

        

          
Part features

          
Extrude, revolve, sweep and loft; ISO holes and threads; rolling-ball fillets with variable radius, chamfers; shell, rib, draft; patterns and mirrors; parameters as formulas.

        

        

          
Surfacing

          
Ruled, boundary, N-sided and Gordon surfaces; offset, thicken, knit, trim, extend; Catmull–Clark subdivision surfaces converted to valid NURBS solids.

        

        

          
Sheet metal

          
Base and edge flanges, hems, corners, cuts across bends; exact flat patterns as DXF.

        

        

          
Assemblies

          
Multi-file assemblies placed by mates; revolute, slider, cylindrical and fastened joints with limits; gear, rack and screw couplings; standard parts; wire harnesses.

        

        

          
Inspection & output

          
Measure, mass properties from the exact B-rep, interference, sections; BOMs; drawings as SVG and DXF; STEP AP214 import and export; URDF; STL.

        

      

      

        The full list, and what comes next, is in the
        roadmap.
        The book tours the crates and
        docs.geop-cad.dev is the API reference.
      

    

  


  
  

    

      
see it for yourself

      
Open an example and change a dimension. The model follows.

      

        ▶ Open the web app
        ★ Star on GitHub ↗
        Join the Discord ↗
      

    

  


  
  

    

      

        
Support the build

        

          Geop's mission is a genuinely competitive open-source CAD program, common
          infrastructure the way numpy is for scientific computing. Sponsors, business
          angels, early investors and founding engineers who want to help are welcome.
        

      

      

        Sponsor on Ko-fi ↗
        Get in touch →