hive-blender

An agent can inspect a Blender scene, capture its viewport, and run guarded Blender commands through hive's loopback tool.

What it looks like

This is a live Blender 5.2 Flatpak run, not a mock render. Follow the calls and exports.

View	Call that produced it
	Confirmed execute_code calls built six rings of hexagonal slabs; get_viewport_screenshot captured the result.
	Confirmed execute_code added amber material and a basalt ground; get_viewport_screenshot captured the result.
	Confirmed execute_code added seven rings and a central hexagon; get_viewport_screenshot captured the result.
	Confirmed execute_code placed the camera and light; get_viewport_screenshot captured the viewport.

Try it

Install and enable the reference Blender MCP addon.py in a GUI Blender instance on the same host. Set BLENDERMCP_NO_UPDATE_CHECK=1 in Blender's environment before starting it. Its loopback listener uses port 9876 by default. Put this entry under :addons in hive-mcp's config.edn:

{: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}}}}

Inspect the scene with the blender tool:

{"command":"call","id":"get_scene_info","params":{}}

For code execution, use "id":"execute_code", put Python in "params":{"code":"..."}, and add "confirm":true. CodeGate approval is required; this is not a Python sandbox.

Measured

In the live Blender 5.2 run, get_scene_info returned 102 objects. A CodeGate-confirmed execute_code exported 91 selected slabs with bpy.ops.wm.stl_export(..., export_selected_objects=True, apply_modifiers=True, global_scale=10.0). The resulting STL is about 130 mm across. Without that source export scale, Blender units exported at about 13 mm. The scaled STL was then sliced through hive-bambu: 15.1 s wall time, 3.14 MB .gcode.3mf, 9822 s (2 h 44 min) estimated print time, 19.4 m filament. These are measurements of this run, not general performance claims.

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. Automated tests use an in-process fake add-on server; the showcase above records a separate live Blender 5.2 run. 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.