blender-lab-mcp-client

An MCP client that speaks the official Blender.org "Blender Lab" MCP add-on's actual wire protocol, exposing the same 27 tools as djeada/blender-mcp-server — but working against blender.org/lab/mcp-server instead of that project's own bundled add-on.

Why this exists

There are (at least) two unrelated "Blender + MCP" projects that happen to share a name, a default port, and a similar pitch:

1. djeada/blender-mcp-server — ships a matched pair: its own Blender add-on and a Python MCP client, talking a newline-delimited {"id", "command", "params"} / {"success", "result"} protocol over localhost:9876.

2. The official Blender Lab add-on (blender.org/lab/mcp-server, maintainer "Blender Authors") — a completely separate project. It also listens on localhost:9876, but only ships the add-on side. It speaks null-byte-delimited {"type": "execute", "code": ..., "strict_json": ...} requests and {"status": "ok"|"error", "result": ...} responses, has no built-in named-command dispatcher (it just executes raw Python against bpy), and closes its TCP connection after every single request.

If you install the official Blender Lab add-on but configure an MCP client pointed at djeada/blender-mcp-server (e.g. via uvx blender-mcp-server), every tool call fails with something like:

Extra data: line 1 column 51 (char 50)

or, on the next call:

Lost connection to Blender: Blender connection closed

That's not a flaky connection, a stale process, or a Blender bug — it's two unrelated protocols talking past each other. djeada's client sends a newline-terminated request the add-on never recognizes; the add-on times the client out, sends back a small null-byte-terminated error, and the client's readline() chokes on the stray null byte immediately after the JSON object.

This package re-implements each of the original 27 MCP tools by generating the equivalent bpy Python and sending it through the Blender Lab add-on's actual protocol, so the tool names, parameters, and behavior stay the same — only the wire format underneath changes.

Install

1. Install the official Blender Lab MCP add-on in Blender (Edit → Preferences → Add-ons → search "MCP", or via the Extensions platform) and confirm it's listening on 127.0.0.1:9876 (Add-on preferences → Start Server).

2. Install this package:

   git clone https://github.com/A-to-PC/blender-lab-mcp-client.git
   cd blender-lab-mcp-client
   pip install -e .

3. Point your MCP client at it. For a mcp.json-style config:

   {
     "servers": {
       "Blender": {
         "type": "stdio",
         "command": "blender-lab-mcp-client"
       }
     }
   }

   Or run directly from source without installing, via uv:

   {
     "servers": {
       "Blender": {
         "type": "stdio",
         "command": "uv",
         "args": ["run", "--project", "/absolute/path/to/blender-lab-mcp-client", "blender-lab-mcp-client"]
       }
     }
   }

Tool reference

Same 27 tools as upstream — see djeada/blender-mcp-server's tool reference for the full table (scene inspection, object manipulation, materials, rendering/export, history, Python execution, async jobs). Names and parameters are unchanged; only the transport underneath is different.

Known limitations

• blender_python_exec_async / blender_job_status / blender_job_cancel / blender_job_list (bridge transport only) are faked as synchronous. The add-on's real deferred-job mechanism requires the executed code itself to set a check_is_finished callable, which isn't practical to synthesize generically from arbitrary submitted code. Async calls against the live Blender session actually run synchronously and are immediately reported as "succeeded". For genuinely long-running work (physics bakes, heavy sims), use transport="headless" instead — that path runs a separate blender -b background process and is unaffected by this limitation.

• One connection per request. The add-on closes its socket after every response, so this client can't reuse a persistent connection — each tool call opens a fresh TCP connection. This matches the add-on's actual design; it isn't a performance shortcut that could be "fixed" client-side.

• Tested against Blender 5.2 LTS with the Blender Lab add-on. Object/material helper code uses standard bpy.ops.* calls and should work on any recent Blender version, but hasn't been verified across a version matrix.

Credit

Forked from djeada/blender-mcp-server (MIT licensed) by Adam Djellouli — the MCP tool surface (names, parameters, descriptions) and the headless.py background-execution transport are carried over unchanged. Only server.py's BlenderConnection and the command-to-bpy-code translation layer are new, to target the official Blender Lab add-on's protocol instead of upstream's own bundled add-on.

License

MIT — see LICENSE.