SameShock: Auditing Adaptive Stress Tests at Matched Intervention Exposure

An adaptive stress test can increase a controller's failure rate by changing when a fixed disturbance occurs. A valid comparison must distinguish harmful state-dependent timing from changes in the distribution of intervention times and in how often an intervention reaches an active system. We formulate this comparison through the joint law of scheduled time and pre-intervention activity, and develop a finite-sample audit for a frozen library of causal stressors. Untouched nominal trajectories estimate every candidate's intervention law by integrating its stopping probabilities; separate intervention rollouts estimate failure risk. A small linear program selects an episode-level mixture that certifies both a prescribed total-variation tolerance and a lower bound on excess failure probability after mixture selection. On 80 FrozenLake controllers, matching time alone permits an exact risk-maximizing tester to increase active exposure by 8.95 percentage points. Controlled audits separate savings from path sharing, modest gains from stopping integration, and gains from a sharper reference bound. On ten proximal policy optimization controllers in a continuous-state CartPole test, SameShock exposes a mean 2.40 percentage-point failure increase at a 1% joint-law tolerance, using a strict matched transition budget. At a lower impulse strength, independent-shock failure falls to 57.15% and the audited failure increment remains 2.28 percentage points.