BerriAI/litellm · error · HTTPException

Bad Request - messages must be provided if 'model' is provid

Error message

Bad Request - messages must be provided if 'model' is provided

What it means

Error "Bad Request - messages must be provided if 'model' is provided" thrown in BerriAI/litellm.

Source

Thrown at litellm/proxy/spend_tracking/spend_management_endpoints.py:2096

            }]
            "usage": {
                "prompt_tokens": 9,
                "completion_tokens": 12,
                "total_tokens": 21
            }
        }
    }'
    ```
    """
    try:
        from litellm import completion_cost
        from litellm.cost_calculator import CostPerToken
        from litellm.proxy.proxy_server import llm_router

        _cost = None
        if request.model is not None:
            if request.messages is None:
                raise HTTPException(
                    status_code=400,
                    detail="Bad Request - messages must be provided if 'model' is provided",
                )

            # check if model in llm_router
            _model_in_llm_router = None
            cost_per_token: CostPerToken | None = None
            if llm_router is not None:
                if llm_router.model_group_alias is not None and request.model in llm_router.model_group_alias:
                    # lookup alias in llm_router
                    _model_group_name: Final = llm_router.model_group_alias[request.model]
                    for model in llm_router.model_list:
                        if model.get("model_name") == _model_group_name:
                            _model_in_llm_router = model

                else:
                    # no model_group aliases set -> try finding model in llm_router
                    # find model in llm_router

View on GitHub (pinned to 77b7c6c40c)

Solutions

1. Include a messages array when providing a model for cost calculation, or provide completion_response instead.

When it happens

Trigger: Thrown at litellm/proxy/spend_tracking/spend_management_endpoints.py:2096 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of BerriAI/litellm@77b7c6c40c (2026-08-18). Data as JSON: /api/errors/884bf124c54d3fc3. Report an issue: GitHub.