I updated Rhino 8 to the latest build today and my rhinomcp plugin
(v0.3.2.0, a third-party MCP integration) stopped working correctly
right after.
Symptoms:
“get” type commands (get_document_info, get_selected_objects,
get_rhino_log) all fail on the client side with “Unknown command
type” errors
However, the Rhino command line log shows these commands being
received and completing successfully (“Executing command:
get_document_info” / “Command execution complete”)
Object creation commands (create_objects) still work correctly
Reinstalling the plugin, restarting Rhino, restarting the PC, and
clearing local caches did not resolve the issue
This started immediately after today’s update, so I suspect it may
be related to the SR34 update itself rather than the plugin.
Could someone please share a download link for the previous SR
(SR33 or earlier) so I can test whether reverting resolves this?
Rhino plugins that do not ship with Rhino
C:\Users\563456356\AppData\Roaming\McNeel\Rhinoceros\packages\8.0\rhinomcp\0.3.2\net8.0\rhinomcp.rhp “rhinomcp” 0.3.2.0
After the latest Rhino 8 update, several commands used via rhinomcp (a third-party MCP integration plugin) fail on the client side with Unknown command type errors. An earlier report in this thread described the issue as affecting only “get” commands, but further isolation testing shows the impact is broader than get-commands alone.
The Rhino command line shows successful execution, but the client receives an error such as:
Communication error with Rhino: Unknown command type: <command name>
Isolation testing
Commands that work
Object creation
Object modification
Object info lookup (when id/name explicitly given)
Getting/setting current layer
Running native Rhino commands
Commands that fail
Error
Getting full document info
Unknown command type
Getting viewport info
Unknown command type
Getting command history log
Unknown command type
Getting currently selected objects
Unknown command type
Selecting objects (by id, layer, or type)
Unknown command type
Deleting objects
Unknown command type
Getting/saving layer states
Unknown command type
Getting the connectivity graph
Unknown command type
New findings
The problem is not limited to “get” commands. Selecting objects, deleting objects, and saving layer states all fail with the same Unknown command type error, regardless of the verb.
Only a small, specific set of commands reliably works. Only object creation/modification, object info lookup by id/name, current-layer get/set, and running native commands were confirmed working.
Downgrading to SR33 did not fix it. The workaround suggested earlier in this thread (reverting to SR33) was tried and did not resolve the symptoms. Current version after downgrade: Rhino 8 SR33 (8.33.26188.13001, 2026-07-07).
Questions for the Rhino team
Is there any known change in SR34 (around command registration or the plugin API) that could explain this pattern?
Since downgrading to SR33 did not help, could this be reproduced on an earlier build than SR33, or is it possible SR33 itself carries a related issue?
That’s not a Rhino error, this error comes from the rhinomcp plugin itself.
The plugin is replying when the Python server sends a command name that isn’t in the plugin’s dispatch table. The only thing i’m seeing is that you might want to pin/match the MCP
server version to the plugin version.