Beyond Balanced Benchmarks: Calibration, Uncertainty, and Deployment-Aware Evaluation of Prompt-Injection Detectors under Source Shift

This study examines prompt-injection detectors under source shift using calibration, frozen thresholds, and uncertainty-based deferral. It shows that better calibration does not always improve detection decisions. The results also reveal that deferral can still leave considerable attack leakage. Overall, the work provides a practical deployment-oriented evaluation using PromptShield and NotInject.