Locality and Reality in Special Relativity: A Timelike-Boundary Reading

This manuscript develops a timelike-boundary reading of locality and reality within the established Lorentzian causal structure of special relativity and the standard record language of quantum measurement. The central object is a timelike boundary equipped with a boundary observer field and observer-adapted cuts. Such a cut is treated as the local comparison surface on which selected quantities are read relative to a coarse-grained reference structure. A local record appears when a boundary-relative deviation becomes resolvable on that cut. The framework separates two roles that are often compressed into one event statement. Lorentzian geometry supplies causal admissibility: it determines which prior data or contextual contributions may be relevant for a candidate event. The boundary comparison supplies record content: it identifies the deviation that becomes locally manifest. Thus the causal cone constrains the admissible domain, but it does not by itself provide a microscopic route or a measurement record. The proposed reading therefore assigns locality to cut-local record formation under Lorentzian causal admissibility. Reality is associated with stable, record-accessible deviations rather than with direct exposure of the underlying reference structure. The result is a compact assignment framework in which causal structure, reference structure, resolved deviation, and local record formation are organized on the same timelike boundary without replacing the established mathematical content of special relativity or quantum mechanics.