hive-blender

A host-neutral IAddon for the Blender MCP add-on's base command catalog and loopback socket. The built-in export_scene supports GLB and FBX only; STL requires a separately authorized execute_code operation and an installed Blender STL exporter. No native 3MF export is claimed.

Running

Install and enable the reference Blender MCP addon.py in a GUI Blender instance, on the same host as hive-blender. Set BLENDERMCP_NO_UPDATE_CHECK=1 in Blender's environment before launching to disable the add-on's network update check. The direct socket path never imports its Python MCP server; hive-blender makes no telemetry, update, Premium or cloud provider calls. Do not enable optional provider integrations in the baseline. Blender is not installed in the current test environment; tests use an in-process fake add-on server, not verified against a real Blender. Restrict access to the loopback listener: the reference add-on has no socket authentication and other local processes can send it commands directly.

Configure the addon in hive-mcp's config.edn under :addons:

{:addons {"hive.blender"
          {:port 9876
           :code-gate {:max-bytes 200000
                       :deny-substrings ["import os" "subprocess" "requests" "urllib"
                                         "premium" "telemetry" "polyhaven" "sketchfab"
                                         "hyper3d" "tripo" "open("]
                       :require-confirm true}}}}

The addon refuses to mount without a valid :code-gate. Alternatively, a host can inject a hive-blender.port/CodeGate record under that key. The data policy requires a positive :max-bytes of at most 200000 UTF-8 bytes, a nonempty case-insensitive substring deny-list, and :require-confirm true; it cannot accept regular expressions or executable policy code. execute_code always requires :confirm true and gate approval. The gate is a policy hook, not a Python sandbox. On socket timeout the typed :blender/unknown-outcome means a mutation might already have run; never replay it automatically. Every call uses a fresh socket, closed after reply or error, one outstanding command per socket. Configure socket time/size bounds via socket-link; the destination is hardwired to IPv4 loopback, default port 9876.

The tool offers catalog, doctor, call and export_stl; optional provider handlers are not catalogued.

Blender → Bambu hand-off

Use two tool calls, with no dependency between the addons:

1. blender with {"command":"export_stl","params":{"path":"$HOME/models/cube.stl","objects":"selected"}} (replace $HOME with your absolute home path before calling the tool). Choose a new path under your home directory (not /tmp); objects may be selected, all, or an array of object names/name prefixes. By default the exporter scales Blender metres-as-units by 1000 into millimetres. Specify scale (positive, at most 1000) or target-mm (positive largest bounding-box dimension), never both. It executes through the mandatory CodeGate with confirmation, verifies the binary STL and returns a ModelArtifact with path, format, sha256, bytes, units, mm, bbox-mm and provenance.
2. bambu with {"command":"slice","model":{"path":"$HOME/models/cube.stl","format":"stl","sha256":"<returned sha256>","bytes":<returned bytes>},"preset":{"printer":"<printer>","process":"<process>","filament":"<filament>"}}. Supply the four shared keys from the artifact (the slicer re-fingerprints the file); choose your actual installed preset names. This does not print: upload/print still requires the independent PrintGate.

The Bambu ModelArtifact schema is an open Malli map; its slicer fingerprint check currently compares the full map against its own four-key projection, so pass only those four keys to slice, not the extra Blender metadata. An export timeout after dispatch is :blender/unknown-outcome: inspect the destination manually; never retry automatically. Scene and object references are values containing file identity and names, not bpy pointers. See native seams for deployment limits and unanswered questions.

Run clojure -M:test and dev/verify_portability.sh for the fake-server conformance and JVM/cljw/cljrs/cljs portable codec checks. The GPL bambu-printer-mcp bridge is used for interoperability facts only; redistributing or requiring it from an MIT addon needs a separate licensing decision.

License: MIT.