bambu_mcp

MCP server (Python, stdio) that lets Claude control Bambu Lab printers over the LAN (MQTT/TLS on 8883, FTPS on 990) and offloads long work (slice -> upload -> print -> watch) to a background job manager. Claude only polls (job_status) or long-polls (job_wait).

Setup

cd ~/projects/bambu_mcp
uv venv .venv && uv pip install --python .venv/bin/python mcp paho-mqtt pytest
.venv/bin/python -m pytest -q tests          # mock-based, never touches a printer
.venv/bin/python tests/stdio_smoke.py        # read-only + dry-run against the real printers

Printer credentials live OUTSIDE the repo in ~/.config/bambu_mcp/printers.json (mode 0600, {"a1mini": {"ip","serial","code","name"}, ...}). If the file is missing it is fetched once from streamer-officina:/home/tommaso/mmu_say/bambu.json over ssh (25 s hard timeout) and cached. Access codes and serials are never logged or returned (they are scrubbed from all output; the FTPS password is passed to curl through stdin, not argv).

Related MCP server: MCP 3D Printer Server

Tools

Read-only: list_printers, printer_status, ams_info, recent_events.

Jobs (return job_id immediately): print_3mf, slice_and_print, slice_model, watch_print; manage with job_status, job_wait(job_id, timeout_s<=240), job_list, job_cancel.

Control: pause, resume, stop (confirm), set_light, set_speed, send_gcode (confirm).

• tray is the AMS tray index ams_id*4 + slot_index (slot 3 of AMS 0 = 2).

• print_3mf needs a sliced .3mf containing Metadata/plate_N.gcode. It refuses unless the printer is IDLE/FINISH and every tray matches expect_filament / expect_color (RRGGBBAA or RRGGBB).

• With watch=true the job follows the print to FINISH (done), FAILED (failed) or IDLE-after-run (done, "stopped"). job_cancel stops the server-side job only, not the physical print.

• slice_and_print uses OrcaSlicer CLI (BAMBU_ORCA_BIN, default ~/projects/orca-pr12998/build/src/orca-slicer) with machine_flat.json, process_flat.json, filament_flat.json from profile_dir; outputs go to ~/.local/state/bambu_mcp/slices/<job_id>/.

Persistence

Job snapshots and print events (state changes, 10% progress milestones, errors, finish) are appended to ~/.local/state/bambu_mcp/events.jsonl. After a restart, old jobs are visible (job_list); in-flight ones are marked interrupted, and a background re-attach starts a new watch_print job for any printer that is still mid-print.

Safety rules

• stop and send_gcode need confirm=true; set it only after explicit user approval.

• dry_run=true per call, or BAMBU_MCP_DRY_RUN=1: builds and returns the payload, never publishes or uploads. print_3mf dry-run still reads printer state (read-only) and reports problems.

• BAMBU_MCP_READONLY=a1mini,p1s (or *): every control command and print start for those printers is refused (dry-run still allowed). The smoke test forces *.

• Unit tests use a fake MQTT client and a fake curl; no network.

Register in a Claude config (not done globally)

{
  "mcpServers": {
    "bambu": {
      "command": "/home/tommaso/projects/bambu_mcp/.venv/bin/python",
      "args": ["-m", "bambu_mcp"],
      "cwd": "/home/tommaso/projects/bambu_mcp"
    }
  }
}

Status of verification

Verified on hardware: read-only status of the A1 mini, FTPS/MQTT payload shapes are the ones proven manually. NOT verified on hardware through this server: real print start/upload, pause, resume, stop, light (work_light vs chamber_light node names), speed, gcode.

License

MIT, see LICENSE.