Conditional operational bounds on controllable return to the past

This preprint examines conditional operational limits on controllable return to an earlier event within the same physical history. A protocol retaining receiver and payload records permits an opposite-payload intervention, yielding an acceptance-weighted incompatibility bound under explicitly stated event-identification and calibration-transfer assumptions. For finite classical product loops, the analysis distinguishes normalization under every allowed controller from normalization of one selected loop. Results include an exact simultaneous repair frontier for the clean derangement family at arbitrary alphabet size, rational optimum certificates for arbitrary three-symbol kernels, and linear-program certificates for the intervention-uniform normalization repair radius. Higher-alphabet examples demonstrate that a selected loop can be normalized while both components remain input dependent. For a specified quantum Bell circuit, finite-strength record instruments yield analytical acceptance and reported-error formulas, distinguishing increased acceptance from faithful record-dependent control. A three-category compatibility test retains rejected trials and is extended to empirical calibrations through simultaneous finite-sample uncertainty bounds under declared sampling assumptions. A self-contained canonical metric–scalar application motivated by SMSR provides a conditional temporal-function certificate and identifies the additional estimate needed to connect geometric perturbations with changes in record distributions. The work does not establish a universal prohibition of time travel, demonstrate a physical return channel, or physically validate SMSR. Invariant historical event attachment and gravitational backreaction remain additional physical requirements. The deposit includes English and Hungarian manuscripts with technical supplements, source files, exact certificates, and executable reproducibility checks.