CNCjs MCP Server

MCP server bridging Claude Code to CNCjs for GRBL CNC control (FoxAlien XE Ultra).

Architecture

Claude Code ←stdio/MCP→ cncjs-mcp (Node.js) ←Socket.IO v1→ CNCjs :8000 ←USB Serial→ GRBL

Tools (30 total)

Read-Only (14)

list_serial_ports, get_connection_status, get_machine_state, get_machine_position, get_work_coordinate_offset, get_machine_settings, get_parser_state, get_loaded_gcode, get_job_progress, get_workflow_state, get_feeder_status, list_macros, list_machines, get_alarm_info

Control (11)

connect_to_port, disconnect_port, load_gcode, start_job, pause_job, resume_job, stop_job, home_machine, unlock_machine, set_feed_override, set_spindle_override

Direct Motion (3)

send_gcode, jog, run_macro

Critical Safety (2)

emergency_stop (soft reset 0x18), feed_hold

Windows PC Setup for CNCjs

1. Node.js (LTS recommended, v18+) — download from https://nodejs.org

2. CNCjs — install via npm after Node.js is set up:

   npm install -g cncjs

   Or download the desktop app installer from the CNCjs GitHub releases page.

3. USB/Serial driver for your FoxAlien XE Ultra — likely one of:

   • CH340 driver (most common on FoxAlien boards) — download from the manufacturer site

   • CP210x driver (if it uses a SiLabs chip)

   • Windows 10/11 may auto-install these, but if your board doesn't show up in Device Manager under "Ports (COM & LPT)", install the driver manually

Quick start after install:

cncjs

Then open http://localhost:8000 in your browser. Your FoxAlien will show up as a COM port (e.g., COM3). Select it, set baud rate to 115200, controller type Grbl, and connect.

Optional but recommended:

• Chrome/Edge — CNCjs web UI works best in Chromium browsers

• Python (sometimes needed for node-gyp native module builds during npm install)

MCP Server Setup

npm install
npm run build

Register with Claude Code:

claude mcp add cncjs-mcp node /path/to/cncjs-mcp/build/index.js

Environment Variables

• CNCJS_URL — CNCjs server URL (default: http://localhost:8000)

• CNCJS_TOKEN — Optional JWT token for CNCjs authentication