one move: preserve an invariant
Report more than accuracy: compute precision, recall, F1, and confusion counts for a binary classifier. In the Hybrid Ranker system, implement this level as a deterministic contract before composing it with the next service.
def classification_report(y_true, y_pred, positive=1):
return {'accuracy': ..., 'precision': ..., 'recall': ..., 'f1': ..., 'confusion': ...}