Natural language to 3D print file. Describe a part in plain English, get a downloadable STL/3MF in seconds.

CAD Cursor is a full-stack web app that bridges conversational AI and parametric 3D modeling. Users type what they want — "make a pipe flange with bolt holes" — and Claude generates JSCAD code that's compiled, validated, and rendered in a live 3D viewport. The result can be exported directly to STL or 3MF for slicing and 3D printing.

User prompt
    │
    ▼
┌─────────────────────┐
│   ChatPanel (React)  │──── conversation history + current code
│                      │
└────────┬────────────┘
         │  POST /api/generate
         ▼
┌─────────────────────┐
│   API Route (Next)   │──── server-side only, API key never touches client
│   lib/claude.ts      │──── system prompt + optional code context
│                      │
└────────┬────────────┘
         │  JSCAD code string
         ▼
┌─────────────────────┐
│   Sandbox Validator  │──── new Function() wrapper, not eval()
│   lib/jscad-runner   │──── validates return is geom3
│                      │
│   ┌── FAIL ──────┐  │     Up to 3 retries with error feedback
│   │ Retry with   │  │     sent back to Claude
│   │ error context │◄─┘
│   └──────────────┘
│
│   ── SUCCESS ──
         │
         ▼
┌─────────────────────┐
│   jscad-to-three.ts  │──── Geom3 → Three.js BufferGeometry
│                      │──── fan-triangulation + flat-shaded normals
└────────┬────────────┘
         │
         ▼
┌─────────────────────┐
│   React Three Fiber  │──── OrbitControls, three-point lighting
│   ViewportCanvas     │──── wireframe toggle, grid, axis lines
│                      │
│   Export → STL / 3MF │──── browser download with smart filename
└─────────────────────┘

• Conversational generation — full conversation history is threaded to Claude, so "make it taller" and "add a hole through the center" work naturally
• Context-aware editing — current model code is injected into the system prompt so Claude edits rather than regenerates
• Self-correcting retry loop — if generated code fails sandbox validation, the error is fed back to Claude for up to 3 automatic retries
• Sandboxed execution — JSCAD code runs in a new Function() wrapper with only 11 whitelisted primitives passed as arguments

• Real-time rendering via React Three Fiber with OrbitControls (rotate, zoom, pan)
• Three-point lighting for polished model presentation
• Wireframe toggle to inspect geometry structure
• Adjustable grid with +/- controls (10-100 units)
• Reset view button to snap back to default camera position
• XYZ axis indicator lines (red/green/blue)

• STL export (binary) — universal format for all slicers
• 3MF export (binary) — modern format preferred by Bambu Studio, PrusaSlicer
• Smart filenames derived from the user's prompt (e.g., pipe-flange-with-bolt-holes.stl)
• Format toggle in the HUD — switch between STL and 3MF with one click

• Glass-morphism chat island — floating panel on the right, resizable (320-600px), with show/hide toggle
• Quick prompt chips — 6 pre-tested example prompts for instant onboarding
• Typing indicator with animated dots during generation
• Loading overlay with cycling status messages ("Interpreting prompt..." → "Generating geometry..." → "Compiling model...")
• Clean error states — every failure path shows a user-friendly message, never raw errors or stack traces
• Model info HUD — face count, watertight status indicator

• God Mode (Cmd+Shift+G / Ctrl+Shift+G) — hidden shortcut that instantly loads a pre-validated mechanical bearing housing model, bypassing Claude entirely. Invisible to the audience; exists solely as a safety net for live demos.

• Node.js 18+
• An Anthropic API key

# Clone the repo
git clone https://github.com/your-username/cursorcad.git
cd cursorcad

# Install dependencies
npm install

# Configure environment
cp .env.example .env.local
# Edit .env.local and add your Anthropic API key:
# ANTHROPIC_API_KEY=sk-ant-...

# Start development server
npm run dev

Open http://localhost:3000 in your browser.

cursorcad/
├── app/
│   ├── api/generate/
│   │   └── route.ts            # POST endpoint — Claude API (server-side only)
│   ├── page.tsx                # Root layout: viewport + chat island + god mode
│   ├── layout.tsx              # HTML shell, fonts, metadata
│   └── globals.css             # Tailwind import + base styles
│
├── components/
│   ├── chat/
│   │   ├── ChatPanel.tsx       # Message list, retry loop, conversation history
│   │   ├── InputBar.tsx        # Auto-expanding textarea, Enter to send
│   │   ├── MessageBubble.tsx   # User (violet) / assistant (gray) bubbles
│   │   ├── QuickPromptChips.tsx # 6 example prompt buttons
│   │   └── TypingIndicator.tsx # Animated dots
│   └── viewport/
│       ├── Viewport.tsx        # Dynamic import wrapper (ssr: false)
│       ├── ViewportCanvas.tsx  # R3F canvas, lighting, grid, controls
│       ├── GeometryMesh.tsx    # Mesh renderer (solid + wireframe)
│       ├── ViewportHUD.tsx     # Model info, export button, toggles
│       └── LoadingOverlay.tsx  # Cycling status messages
│
├── lib/
│   ├── claude.ts               # Anthropic SDK wrapper, system prompt injection
│   ├── jscad-runner.ts         # Sandbox executor (new Function + 11 primitives)
│   ├── jscad-to-three.ts       # Geom3 → Three.js BufferGeometry converter
│   ├── stl-export.ts           # Binary STL export + browser download
│   ├── 3mf-export.ts           # Binary 3MF export + browser download
│   └── types.ts                # ConversationMessage interface
│
├── prompts/
│   └── system.ts               # Full system prompt with constraints + examples
│
├── types/
│   └── jscad.d.ts              # TypeScript declarations for JSCAD serializers
│
└── .env.example                # ANTHROPIC_API_KEY=

The app enforces a strict separation:

• Server-side — Claude API calls happen exclusively in app/api/generate/route.ts. The API key never reaches the client.
• Client-side — JSCAD code execution, geometry conversion, Three.js rendering, and file export all happen in the browser. JSCAD modules are never imported in server components.

Generated code is executed via new Function(), not eval(). The 11 allowed primitives are passed as function arguments — the generated code has no access to import, require, window, or document:

cuboid  sphere  cylinder  torus
union  subtract  intersect
translate  rotate  scale  mirror

The sandbox validates that the return value is a valid geom3 object before passing it to the renderer.

The app maintains two parallel message tracks:

1. UI messages (useState) — what the user sees ("Model generated — check the viewport")
2. Claude messages (useRef) — what Claude sees (the actual JSCAD code as assistant turns)

This separation means Claude always has the real code context for follow-up edits, while the user sees clean status messages. The conversationRef is a ref (not state) to avoid unnecessary re-renders.

When Claude generates code that fails sandbox validation:

1. The error message and failed code are packaged into a retry prompt
2. This retry prompt is sent as a temporary message (not persisted to conversation history)
3. Claude generates a corrected version
4. This repeats up to 3 times
5. Only the final successful code (or failure message) is persisted to the conversation

JSCAD Geom3 → @jscad/stl-serializer (binary) → Blob → URL.createObjectURL → <a> download
                                                  ↕
              @jscad/3mf-serializer (binary) → Blob → URL.createObjectURL → <a> download

Filenames are derived from the user's last prompt, slugified (lowercased, special chars replaced with hyphens, capped at 40 characters).

These are the only operations available to generated code:

The app handles a missing key gracefully — the API route returns a clean 500 error ("Server is not configured — missing API key") and the chat shows the error without exposing internals.

Every failure path produces a clean, user-facing message:

npm run build   # Compiles and optimizes
npm run start   # Serves on port 3000

Set ANTHROPIC_API_KEY in your hosting provider's environment variables. The app has no other external dependencies — no database, no Redis, no file storage.

• Node.js 18+ runtime
• Single environment variable (ANTHROPIC_API_KEY)
• No persistent storage needed
• All computation happens in the user's browser (JSCAD, Three.js) or via Anthropic's API

Private project.