lmstudio-ai / lmstudio-ai/docs
No local model is able to start a conversation in Bionic Omni Session.
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Description
Whenever a message is sent to a local backend, the request fails immediately with the following error message:
Engine protocol ngPredictTokens request returned 400: {"error":{"code":400,"message":"Failed to initialize samplers: failed to parse grammar","type":"invalid_request_error"}}
This occurs regardless of the selected local model (tested with both Qwen 3.5 9B and Nemotron Nano 3 4B.
To Reproduce:
Launch Bionic Omni Session with the local engine connected.
Load any local model (e.g., Qwen 3.5 9B or Nemotron Nano 3B).
Type any basic prompt in the chat box (e.g., "why any local ai model not working" or "anything ").
Submit the prompt. The engine immediately returns a 400 grammar parsing error.
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Reproduce the failure in Bionic Omni Session with the local engine connected, using a local model such as Qwen 3.5 9B or Nemotron Nano 3 4B and a basic prompt. Start from the reported ngPredictTokens 400 response and its failed to parse grammar message. Done means a local model can start a conversation without this error.
Written by the indexing model from the issue text.
Assessment
- Domain
- ai, backend-api-design
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Active
- Clarity
- Needs clarification
- Newbie friendliness
- 35/100