.act tool invocation fails – LMStudioUnknownMessageError on every model

[Dariton4000]

Problem

When a model tries to run a tool using .act, it does not work no matter what I try or which code I use.

Replication

Model

This issue occurs with any model tested:

• Qwen 3: 1.7B, 4B, 8B, 14B
• Mistral Small 3.2
• Qwen 2.5: 7B, 14B

Software

• LM-Studio version: 0.3.17 Build 7
• Operating System: Windows 11
• CUDA 12 llama.cpp (Windows)

Code

• Tested with my own code: https://github.com/Dariton4000/searchassistant
• Tested with official documentation code: https://lmstudio.ai/docs/python/agent/act

Both result in the same error.

Error

lmstudio.LMStudioUnknownMessageError: Chat response unexpected message contents: {'type': 'toolCallGenerationNameReceived', 'name': 'multiply'}

[ncoghlan]

Thanks for the report - this was a compatibility issue between the SDK and recent builds of the main LM Studio application.

1.3.2 has been published to PyPI with support for the additional messages (a future update will downgrade the unknown message handling from raising an immediate exception to emitting a runtime warning using the warnings module).