ATOMICMBAG/Duet-MCP

An MCP server (Model Context Protocol) that lets an AI assistant such as Claude operate a **Duet machine (RepRapFirmware)** over your LAN/WLAN: read status, manage files, look at camera pictures, home axes, start and supervise prints, and follow a filament change. The server is a safety layer between the AI and the machine, and it comes with a live **cockpit** so that you can watch what the machine and the AI are doing from another room.
> **Safety first.** Heaters and motors are dangerous. This is alpha software without any warranty. Never run it unattended and keep the emergency stop within reach. Read SAFETY.md before the first use, and see SAFETY_RULES.md for the rules the server enforces.
>
> **Unofficial community project**, not affiliated with Duet3D. License: MIT.
>
> **Status: alpha.** Verified on one machine only: **Duet 2 WiFi, RepRapFirmware 3.2.x**, standalone, Cartesian printer, with real prints (including a supervised filament change) and about 255 automated tests against a simulated Duet. Everything else is "expected to work, untested". Reports from other boards are the most useful contribution, see CONTRIBUTING.md.
_The author's setup: Cartesian printer in a wooden enclosure with a Duet 2 WiFi, a camera, and the notebook that runs Claude Code._
What it does
- **Read-only by default.** Control tools exist only with DUET_READ_ONLY=false.
- **The human approves, not the AI.** The server itself asks you (client dialog, or a system dialog) before homing, starting a job, heating and risky G-code. The AI cannot approve for you.
- **G-code guard:** axis limits taken from your config.g, maximum temperatures, homed check, macro allowlist, blocked commands.
- **Pre-flight check** of G-code files, with optional fixes in a patched copy (and an M600 filament change at a layer of your choice).
- **Supervisor:** pauses on heat-up timeout, temperature deviation, no progress, board restart or lost connection; warns when a pause with a hot nozzle lasts too long. Heaters left on are switched off by an idle watchdog.
- **Filament change** (M600) followed step by step: the machine's message is shown, the assistant answers it only after you approve (docs/FILAMENT_CHANGE.md).
- **Speed profile per layer** (for example 30 % on layer 1, 50 % on layer 2).
- **Cameras:** snapshots from HTTP cameras, RTSP or a local webcam (via ffmpeg), several views at once, each with a note and a brightness check. Every picture the assistant looks at is saved with a time, the camera and the layer, and linked in the audit log; optional periodic pictures give a timeline (docs/CAMERAS.md).
- **Cockpit** (optional, monitoring only, DUET_VIEWER_PORT): a page on your own PC that shows a banner for what needs you, machine and job, heaters and fans, endstops as virtual LEDs, the camera and zoomed cut-outs (filament, board LEDs), what was sent to the machine and what was decided, what was asked, and the notices. It has no buttons: every answer and approval stays in the chat.
- **Tamper-evident audit log:** every line carries the checksum of the previous one, and verify-audit.js finds inserted, edited or removed lines.
- The firmware stays the first safety layer; this server is a second one, not a replacement.
Screenshots
**Cockpit and chat.** Claude Code (desktop app) on the right, the cockpit in the preview pane on the left, during a supervised print: the assistant reports the state and shows the camera picture, the cockpit shows machine, heaters, endstops and the newest pictures. The chat is in German (the author's language); the assistant answers in the language you write.
**Zoomed views.** Cut-outs of the camera picture (the filament in front of its blue strip, the LEDs of the Duet 2 board) next to the values from the firmware, so that you can compare what the machine reports with what the camera shows. Nothing is analysed; you do the comparing.