mlflow/mlflow · error · MlflowException

When `task` is specified as `{inference_task}`, the signatur

Error message

When `task` is specified as `{inference_task}`, the signature would be set by MLflow. Please do not set the signature.

What it means

Error "When `task` is specified as `{inference_task}`, the signature would be set by MLflow. Please do not set the signature." thrown in mlflow/mlflow.

Source

Thrown at mlflow/transformers/llm_inference_utils.py:77

}

_LLM_INFERENCE_TASK_TO_DATA_FIELD = {
    _LLM_INFERENCE_TASK_CHAT: "messages",
    _LLM_INFERENCE_TASK_COMPLETIONS: "prompt",
}


def infer_signature_from_llm_inference_task(
    inference_task: str, signature: ModelSignature | None = None
) -> ModelSignature:
    """
    Infers the signature according to the MLflow inference task.
    Raises exception if a signature is given.
    """
    inferred_signature = _SIGNATURE_FOR_LLM_INFERENCE_TASK[inference_task]

    if signature is not None and signature != inferred_signature:
        raise MlflowException(
            f"When `task` is specified as `{inference_task}`, the signature would "
            "be set by MLflow. Please do not set the signature."
        )
    return inferred_signature


def convert_messages_to_prompt(messages: list[dict[str, Any]], tokenizer) -> str:
    """For the Chat inference task, apply chat template to messages to create prompt.

    Args:
        messages: List of message e.g. [{"role": user, "content": xxx}, ...]
        tokenizer: The tokenizer object used for inference.

    Returns:
        The prompt string contains the messages.
    """
    if not (isinstance(messages, list) and all(isinstance(msg, dict) for msg in messages)):
        raise MlflowException(

View on GitHub (pinned to 6a27f2decc)

When it happens

Trigger: Thrown at mlflow/transformers/llm_inference_utils.py:77 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of mlflow/mlflow@6a27f2decc (2026-08-29). Data as JSON: /api/errors/2b54cd52bf915d8b. Report an issue: GitHub.