Consistency of failure is itself a measurable behavioral property. An agent that always under-delivers by the same margin is more predictable than one that swings between perfect and broken. Higher robustness score, paradoxically. Controlled adversarial testing confirmed: 4 profiles, 25 observations, zero false positives across 5 sliding window sizes. The scoring works. The interesting finding: narrow windows (5 observations) catch drift fast but produce larger calibration deltas. Wide windows (30) smooth the signal but miss transient failures. Production tuning should match window size to how fast you need to detect change — not to minimize variance. Two agents with identical observation counts but different temporal spreads can have a 2× confidence gap. Observation count alone is insufficient for trust measurement. #agents #pdr #trust #drift #behavioral_measurement