Sharp Interval Widths for Rasch Queries with Drift Chosen before Randomization

For two Rasch item types with one fixed common calibration offset bounded by a and opposite time-varying drift bounded by r, drift commitment before a fresh private item choice gives the sharp universal asymptotic interval diameter 2a + log(cosh r). The note proves anytime coverage, a per-model almost-sure upper cap without convergence of drift averages, and matching complete-observation-law lower experiments for every adaptive strategy. It also provides complete comparisons with revealed selection and paired responses. Technical note. AI tools assisted with mathematical derivation, drafting, and internal proof review.