When Is a Veto Worth Its Cost? Proposer Precision, Gate Selectivity, and Requalification under Distribution Shift

Downstream gates can reject, defer, or override proposals, but every veto can also suppress a useful action. We study requalification under distribution shift: a proposer recommends reactivating a previously rejected alternative and a downstream gate either authorizes the switch or keeps the incumbent. We operationalize the classical cost-sensitive/net-benefit break-even form using independently measured blocking rates and blocked-outcome severities, and compare learned gating with a switch-rate-matched random blocker. Across three controlled domains, calibration-only operating points predict holdout sign and magnitude better than a naive fixed-0.5 rule in the informative domains, while fresh audits show within-domain drift. A targeted severity learner fails: its low-precision benefit is mostly refusal rate, while an equal-rate oracle reveals unrealized selectivity. Degrading that oracle yields a representation target of Spearman $\rho \approx 0.68$, versus $\rho \approx 0.10$–$0.14$ for the learned signal. Fresh feature-tier and small-budget audits further show that better ranking and probability calibration do not necessarily improve frozen-threshold regret. A frozen external stress test on real handwritten-digit observations under constructed corruption shows the audit's own refusal condition: the break-even is weakly identified there, yet matched-rate selectivity remains detectable in three corruption levels. The contribution is an empirical operating audit that separates ranking, calibration, threshold portability, and selective action value.