OrcaSlicer MCP

An MCP server that gives Claude (or any MCP client) the full FDM pipeline: slice models headlessly with OrcaSlicer, manage presets, analyze G-code, and control your printer over the local network — Klipper, OctoPrint, Prusa, Duet, Elegoo, or Bambu.

Ask your assistant to "slice this STL with my draft profile and tell me the print time" or "check on the print and show me the camera" — and it can.

Tools

Tool	What it does
list_profiles	List machine/process/filament presets (system + user), with search
get_profile	Read a preset with its full inheritance chain resolved
update_profile	Edit a user preset (system presets are read-only)
gui_project_state	Read what's open in the OrcaSlicer GUI — file + chosen presets/settings
slice_model	STL/3MF/STEP → G-code via the OrcaSlicer CLI; presets default to the open GUI project; returns time/filament/temp stats
analyze_gcode	Parse Orca G-code: time, filament, layers, and the actual commanded temps (M109/M190)
printer_setup	What printer we can talk to and what's still needed — run this first
configure_printer	Point the server at a printer, verify it answers, save it
printer_status	Live normalized state (idle/heating/printing/paused/error), temps, layer progress
printer_snapshot	Webcam still — check first-layer adhesion remotely
printer_attributes	Model, firmware, mainboard id
printer_files	List files on the printer (where the firmware allows it)
upload_gcode	Upload G-code (does not start printing)
start_print	Start a print — checks the printer is idle first, then verifies the job actually started
print_control	Pause / resume / stop

Printer support

Slicing works for every printer OrcaSlicer supports. Printer control speaks these protocols:

Type	Printers	Needs	Verified
moonraker	Klipper — Voron, RatRig, Sovol, Creality K1, Neptune 4…	host, api_key (only if Moonraker requires one)	docs + mock tests
octoprint	Anything behind OctoPrint (most Marlin printers)	host, api_key (Settings → API)	docs + mock tests
prusalink	Prusa MK4 / MK3.9 / XL / MINI / CORE One	host, password (Settings → Network), user maker	docs + mock tests
duet	Duet 2/3 (RepRapFirmware)	host, password if set	docs + mock tests
elegoo	Elegoo Centauri Carbon	host	live hardware
bambu	Bambu Lab P1/X1/A1/H2, LAN mode — experimental	host, serial, access_code, [bambu] extra	docs only

You probably don't need to configure anything. If you already set up network printing in OrcaSlicer, the server reads the printer's address and protocol from your machine preset (print_host / host_type). Otherwise ask your assistant to run printer_setup — it scans, reports what it finds, and tells the assistant to ask you which printer you own rather than guessing.

Honest scope: only the Elegoo path has been exercised on real hardware by this project. The rest were built against each protocol's official docs and source (and fact-checked against them), with mock-transport tests asserting the parts that can bite — including that upload never starts a print (asserted for Moonraker, OctoPrint and PrusaLink, whose APIs have an auto-start flag to suppress; Duet, Elegoo and Bambu have no such flag — starting is a separate call by construction). Reports from real machines are welcome.

Adding a protocol is one small class in backends.py.

Setup

Requirements: Python 3.10+, OrcaSlicer (tested with 2.4.1), and — for printer control — a supported printer on your LAN.

git clone https://github.com/ShreddyKrueger75/orcaslicer-mcp
cd orcaslicer-mcp
uv venv --python 3.11 && uv pip install -e .
claude mcp add orcaslicer -- "$(pwd)/.venv/bin/python" "$(pwd)/server.py"

Configuration is optional — sensible defaults are detected per platform:

Env var	Default
ORCA_SLICER_BIN	the standard OrcaSlicer install path for your OS
ORCA_SLICER_DATA	OrcaSlicer's config dir (presets) for your OS
PRINTER_TYPE	read from your OrcaSlicer machine preset's host_type
PRINTER_HOST	the print_host saved in your OrcaSlicer machine preset
PRINTER_PORT, PRINTER_API_KEY, PRINTER_USER, PRINTER_PASSWORD, PRINTER_SERIAL, PRINTER_ACCESS_CODE	per-protocol; also readable from the preset or configure_printer
PRINTER_SNAPSHOT_URL	OctoPrint webcam URL (default http://<host>:8080/?action=snapshot)
ORCASLICER_MCP_CONFIG	~/.config/orcaslicer-mcp/printer.json (written 0600)
DEFAULT_BED_TYPE	Textured PEI Plate

Safety model

This server can heat hardware and start multi-day prints, so the dangerous paths are guarded:

• Plate type is always pinned. The Orca CLI silently defaults to Cool Plate (45 °C bed) — enough to detach a big part and wreck a hotend (ask us how we know). Every slice sets curr_bed_type explicitly, from the caller, the open GUI project, or DEFAULT_BED_TYPE.
• Stats report what the machine will do, not what the slicer intended: bed/nozzle temps are parsed from the M190/M109 commands in the G-code.
• start_print verifies. Some firmwares silently drop start commands sent while busy; the tool refuses to fire unless the printer is idle, then polls until the job demonstrably starts (or reports the error code if it doesn't).
• Upload never prints. Every backend suppresses its protocol's start-on-upload flag, with tests per protocol that has one.
• Filenames are data, never syntax. A name reaches firmware inside a G-code argument (Duet: M32 "name") and inside URLs; ; or " would let a crafted name append arbitrary G-code (M109 S300) or escape the upload directory. Names are validated before they leave the server.
• No guessing which printer. If several printers are configured and nothing says which you mean, the server asks instead of picking; an unknown host= is refused rather than driven with another printer's protocol and credentials.
• Bed type is whitelisted against OrcaSlicer's own BedType enum (all 7 plates, Supertack included). An unrecognized name would silently become Cool Plate; slice_model rejects invalid values instead.
• Plate-clear gate. Starting a new job while the previous one is COMPLETED/STOPPED (old part likely still on the plate) requires an explicit plate_cleared=True after the user confirms — otherwise the toolhead can crash into the finished part. Concurrent start_print calls are locked out.
• resume only resumes paused prints — never a stopped/errored job where the nozzle may be sitting in a failure.
• Preset edits can't become code. update_profile refuses the post_process key (it executes shell commands at slice time).
• Your GUI choices win. If a project is open in OrcaSlicer, unset slicing parameters come from it rather than from the model's guesses.
• start_print's description instructs clients to confirm with the user — it heats hardware.

Scope note: this is a local, single-user tool. File-path parameters (model_path, output_dir, gcode_path) operate on your filesystem with your permissions, like any local CLI.

How headless slicing works (the non-obvious part)

OrcaSlicer user presets are inheritance deltas (inherits: "<parent>", no type field) and the CLI rejects them as-is. The server resolves the full inheritance chain into flat JSON configs, tags them with type, and satisfies the CLI's compatibility check — which compares the process/filament compatible_printers list against the machine preset's inherits value — by pinning both to the machine's nearest system ancestor. Verified against the OrcaSlicer 2.4.1 source (src/OrcaSlicer.cpp, ~line 2560).

Known limits

• Centauri Carbon CC1 firmware cannot list/delete files or report disk space over SDCP (CC2 can). Uploads to a full or busy printer fail with HTTP 500 — manage storage on the touchscreen.
• OctoPrint and PrusaLink don't report layer counts over their APIs; Duet has no standard camera endpoint. Tools say so instead of failing obscurely.
• The plate-clear gate relies on the printer reporting a finished job. Duet (job.lastFileName) and OctoPrint (100% progress) are inferred; a cancelled OctoPrint job is indistinguishable from idle over its API, so that one case won't trip the gate.
• On Windows the saved config can't be locked to your user with chmod; it inherits the folder's ACL. Prefer PRINTER_* env vars if that matters.
• Cloud host types (PrusaConnect, CrealityPrint, Obico, SimplyPrint, 3DPrinterOS) aren't supported — point the server at the printer's own IP.
• Editing profiles while the OrcaSlicer GUI is open may be overwritten when the GUI exits.
• Slicing timeout is 600 s per call; the CLI reports no progress.

Credits

Elegoo control is pycentauri (Apache-2.0); optional Bambu control is bambulabs-api (MIT); other protocols are spoken directly over HTTP with httpx (BSD-3-Clause). Slicing is OrcaSlicer's own CLI. This project is MIT licensed.