Live · MIT · npm 3.11.0

Parametric CAD that runs in a browser.
Real B-rep. No install.

cycleCAD is the modelling core of the Suite. Thirteen sketch tools. Twelve constraint types. Real B-rep booleans on OpenCascade.js. Assemblies with seven joint types. AI Copilot that writes the geometry for you.

Launch cycleCAD → See the features

SolidWorks is $4,495. Fusion is $545/year. Onshape is $1,500/year.

They all require an install, an account, a license server, and a lot of luck your machine is fast enough. You pay annually. You pay per seat. You pay whether you use it or not.

$$
SolidWorks
~$4,495/yr
$$
Fusion 360
~$545/yr
$$
Onshape
~$1,500/yr
$$
CATIA
$10k+/yr
$$
Creo
~$2,400/yr
cycleCAD is free. Open source. In the browser.
The Design Workspace

Five modules. One browser tab.

cycleCAD is the modelling stage of the Suite. It goes from empty sketch to parametric assembly to exported STEP — without leaving the browser, without installing a driver, without a license server.

01

Sketch Engine

Thirteen sketch tools, twelve constraint types, iterative relaxation solver. Grid snap, auto-inferred constraints, degree-of-freedom analysis.

02

Solid Modeller

Sixteen operations: extrude, revolve, sweep, loft, fillet, chamfer, shell, pattern, hole, thread, mirror, draft, scale, combine, split, boolean.

03

Assembly Workspace

Seven joint types with mate constraints. Explode, collapse, interference check, contact sets, motion study. Import Inventor .iam and .ipj.

04

AI Copilot

Natural-language → geometry. Eight template families cover common parts; LLM planner handles everything else. Multi-step plans up to twenty steps.

05

Agent API

Fifty-five commands across ten namespaces. JSON-RPC surface scriptable from the browser console, MCP server, REST API, or CLI.

Sketch Engine

Twelve constraints. Real solver.

A proper iterative constraint solver — not a trick, not a cheat. Auto-infers constraints as you sketch, does degree-of-freedom analysis, and tells you when a sketch is fully defined.

Coincident

Point · Geometric

Lock a point to another point, line, arc, or circle. The default constraint, applied on pick.

Horizontal

Line · Geometric

Force a line to align with the X axis. Applies across a chain of lines if selected together.

Vertical

Line · Geometric

Force a line to align with the Y axis. Complementary to horizontal, both can coexist in a sketch.

Parallel

Line · Geometric

Keep two lines at the same angle without fixing that angle. The solver preserves it through edits.

Perpendicular

Line · Geometric

Lock two lines at exactly 90°. Works with tilted sketches — the right angle is preserved.

Tangent

Line · Arc · Circle

Touch a line or curve to an arc or circle at exactly one point. Auto-inferred on drag near a curve.

Equal

Line · Arc

Two lines the same length, two arcs the same radius. Creates links the solver maintains.

Fixed

Point · Ground

Pin a point to its current position. Fully defining a sketch usually starts with one fixed point.

Concentric

Arc · Circle

Lock two arcs or circles to share a centre. Classic for bolt-hole patterns and coaxial bores.

Symmetric

Point · Line

Mirror two points across a reference line. Edit one side, the other follows.

42

Distance

Point · Line · Dim

Fix a numeric distance between two entities. The dimension is parametric and editable.

Angle

Line · Dim

Fix a numeric angle between two lines. Solver re-orients both to satisfy the constraint network.

B-rep Kernel

Real B-rep. Real booleans.

Under the hood cycleCAD runs OpenCascade.js — the same CAD kernel the pros use. Your extrudes, fillets, and booleans produce real topology, not mesh approximations.

Round-trip to STEP preserves the feature tree. Round-trip to IGES preserves NURBS. Round-trip to GLB gives you a tessellated mesh suitable for the web — all from the same parametric source.

  • Real topology: faces, edges, vertices, loops
  • Real booleans: union, cut, intersect — no mesh approximation
  • Real fillets and chamfers — edge-based, preserves parametric intent
  • STEP ↔ IGES ↔ GLB round-trip via converter server
  • Incremental rebuild on parameter change
cycleCAD feature tree — live from the browser 
// cycleCAD Agent API · window.cycleCAD.execute
// Mounting plate with four-hole pattern

const plate = await cycleCAD.execute({
  method: 'sketch.rect',
  params: { width: 100, height: 60 }
});

await cycleCAD.execute({
  method: 'ops.extrude',
  params: { depth: 5 }
});

const holes = await cycleCAD.execute({
  method: 'ops.pattern',
  params: { count: 4, spacingX: 80 }
});

await cycleCAD.execute({
  method: 'export.step',
  params: { filename: 'plate.step' }
});

// → B-rep solid · 4 holes · STEP-ready
AI Copilot

Type a prompt. Get geometry.

Describe what you want in plain English. The Copilot parses your intent, picks the right template or asks an LLM to plan it, and executes the plan step-by-step in the scene. Every geometry operation uses the real kernel.

Common parts use offline templates — no API key needed. Novel geometry routes to a large language model that returns a plan the Copilot validates and runs.

  • Eight template families: Pi cases, nuts, washers, flanges, threaded rod, gears, pulleys, bearings + housings
  • Plus T-slot extrusions, U-brackets, L-brackets, plates, boxes
  • Multi-step plans up to twenty operations with rollback
  • Works offline with templates — no API key required for common parts
  • Gemini 2.0 Flash · Groq Llama 3.3 70B · Claude Sonnet 4.6
  • Self-correcting: watches for errors and auto-recovers
Agent API

cycleCAD is for agents, too.

A JSON-RPC surface covering every geometry, query, and export operation. Fifty-five commands across ten namespaces. Scripted from the browser console, the MCP server, the REST API, or the command line via npx cyclecad.

🤖

Agent

Any LLM or script
🔌

cycleCAD API

JSON-RPC · 55 commands
📐

3D Scene

B-rep · Three.js · live
Call window.cycleCAD.execute({ method, params }). Self-describing schema via getSchema().
● sketch.* ● ops.* ● assembly.* ● view.* ● query.* ● validate.* ● export.* ● import.* ● render.* ● file.*
Roadmap

Phased. Honest about where we are.

The core is shipped and running in production. Engineering analysis is the active sprint. Real-time collaboration and a plugin marketplace are on deck.

Done

Phase 0 · Core

  • Browser-native UI
  • 45 modules
  • 138 MB STEP import
  • AI Copilot core
  • Agent API · 55 commands
  • MCP server · REST API · CLI
In progress

Phase 1 · Engineering Analyst

  • Bolted-joint analysis ✓
  • Gear (AGMA bending + pitting)
  • Shaft (Goodman / Soderberg)
  • Bearings (L10 life)
  • Welds (throat stress)

Ship models. Not licence-server tickets.

Open cycleCAD in the browser. Start a sketch. Extrude, fillet, assemble. Export STEP. No install. No account. MIT-licensed, forever.

Launch cycleCAD → View on GitHub View on npm
cycleCAD is MIT-licensed. Part of the cycleCAD Suite.