roboflow/supervision · error · ValueError

{role} class ids must be in [0, {num_classes - 1}], got {inv

Error message

{role} class ids must be in [0, {num_classes - 1}], got {invalid_values}.

What it means

Error "{role} class ids must be in [0, {num_classes - 1}], got {invalid_values}." thrown in roboflow/supervision.

Source

Thrown at src/supervision/metrics/detection.py:57

def _validated_class_ids(
    values: npt.NDArray[np.float32],
    num_classes: int,
    role: str,
) -> npt.NDArray[np.int64]:
    """Return class ids that are safe to use as confusion-matrix indexes."""
    if values.size == 0:
        return np.asarray(values, dtype=np.int64)

    finite = np.isfinite(values)
    integral = values == np.floor(values)
    if not np.all(finite & integral):
        raise ValueError(f"{role} class ids must be finite integers.")

    class_ids = values.astype(np.int64)
    invalid = (class_ids < 0) | (class_ids >= num_classes)
    if np.any(invalid):
        invalid_values = np.unique(class_ids[invalid]).tolist()
        raise ValueError(
            f"{role} class ids must be in [0, {num_classes - 1}], got {invalid_values}."
        )
    return class_ids


def detections_to_tensor(
    detections: Detections,
    with_confidence: bool = False,
    metric_target: MetricTarget = MetricTarget.BOXES,
) -> npt.NDArray[np.float32]:
    """
    Convert Supervision Detections to a numpy tensor for metric computation.

    Args:
        detections: Detections/Targets in the format of sv.Detections.
        with_confidence: Whether to include confidence as the last column.
        metric_target: The type of detection data to use.
            Supports `MetricTarget.BOXES` and

View on GitHub (pinned to 7f254d9784)

Solutions

1. Ensure every class id is within [0, num_classes - 1]; remap or filter out-of-range ids.
2. Check that your class list length matches the maximum class id used in predictions and targets.

When it happens

Trigger: Thrown at src/supervision/metrics/detection.py:57 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of roboflow/supervision@7f254d9784 (2026-08-15). Data as JSON: /api/errors/6e5bca7acf8c5872. Report an issue: GitHub.