Record Rules Force Born Probabilities

A normalized state assigns a share of squared size to each outcome. Five record rules force its probability to equal that share: total one, nonnegativity, disjoint-event additivity, silence at zero amplitude, and equal reads at equal magnitudes across preparations and labels. Splitting a load while retaining a third load makes the unchanged read cancel. The response must add; nonnegativity fixes it to the load itself. This derives Born probabilities on any finite carrier with at least three registers, without continuity or angular calibration. If a common bounded response has two- and three-outcome totals accurate to epsilon, its error is at most 3 epsilon. Equal-load comparisons accurate to eta bound each probability's Born error by 6 eta. A fourth-power rule exposes the cross-preparation premise: changing surrounding loads changes the read of a fixed local amplitude. Detector applications must identify their preparations and recorded outcomes with these registers.