BerriAI/litellm · error · HTTPException

litellm_params.mode is required (e.g. pre_call, post_call)

Error message

litellm_params.mode is required (e.g. pre_call, post_call)

What it means

Raised in the generic-guardrail registration handler when litellm_params contains no 'mode' entry. The mode determines when the guardrail hook fires (pre_call, post_call, during_call, etc.); a registration without it cannot be scheduled into the hook pipeline, so the request is rejected with HTTP 400 at registration time.

Source

Thrown at litellm/proxy/guardrails/guardrail_endpoints.py:747

    if not api_base:
        raise HTTPException(
            status_code=400,
            detail="litellm_params.api_base is required for generic_guardrail_api",
        )
    parsed: Final = urlparse(api_base)
    if parsed.scheme not in ("http", "https"):
        raise HTTPException(
            status_code=400,
            detail="litellm_params.api_base must use http or https scheme",
        )
    if not parsed.hostname:
        raise HTTPException(
            status_code=400,
            detail="litellm_params.api_base must contain a valid hostname",
        )
    mode: Final = params.get("mode")
    if mode is None:
        raise HTTPException(
            status_code=400,
            detail="litellm_params.mode is required (e.g. pre_call, post_call)",
        )

    try:
        existing = await _guardrails_table(prisma_client).find_unique(where={"guardrail_name": request.guardrail_name})
        if existing is not None:
            raise HTTPException(
                status_code=400,
                detail=f"Guardrail with name {request.guardrail_name!r} already exists",
            )
    except HTTPException:
        raise
    except Exception as e:
        verbose_proxy_logger.exception("Error checking guardrail name uniqueness: %s", e)
        raise HTTPException(status_code=500, detail=str(e))

    now: Final = datetime.now(timezone.utc)

View on GitHub (pinned to 77b7c6c40c)

Solutions

1. Set litellm_params.mode (e.g. pre_call, post_call) on the guardrail.

Example fix

litellm_params:
  mode: pre_call

When it happens

Trigger: Thrown at litellm/proxy/guardrails/guardrail_endpoints.py:747 when the library encounters an invalid state.

Common situations: The guardrail config omitted the mode field.

AI-assisted analysis of BerriAI/litellm@77b7c6c40c (2026-08-18). Data as JSON: /api/errors/36a4162bfb9feb50. Report an issue: GitHub.