The Trace Outlives the Record - Archive-free branch recovery on a growing Penrose frontier

Can a growing pattern discard its buried construction history while retaining a readable consequence of an earlier choice? We examine this question in local-rule Penrose growth using a pruned active boundary ring (termed the active skin), counterfactual branch comparisons, and internal-space compatibility regions. Across three specified histories, a retained-skin engine matches a full-history reference across 21,185 frontier candidate checks over 310 steps, and fresh-process cold restarts match a further 12,078 checks over 130 continuation steps. In a confirmatory closure study of 22 selected forks (88 branch continuations), 49 continuations from 20 forks reach a valid postprune readout state at step 44, while 39 are censored by horizon or frontier arrest. In all 49 scored continuations, the surviving boundary geometry recovers the recorded choice. A separate, standard-library-only numerical reader reproduces the reference compatibility constraints purely from the surviving skin geometry — without access to deleted interior tiles or retained vertex lift labels — given a common pre-fork coordinate frame, a four-layer convention, and the two historical candidate regions. In the five closure forks where paired branches both prune their original choice-tiles and remain active at a common comparison step, all five retain nonzero median decoration differences on shared spatial coverage (median fraction 0.1605). Supporting studies across a 24-world catalogue characterize how open frontier opportunities settle: 5,434 of 6,606 observed settlements (82.3%) are decided by a single necessary-and-sufficient neighbouring addition within the tested intervention set, completed keystone corners exhibit a strong inward perpendicular-space alignment toward the window centroid (+0.749), and bounded forced-only saturation leaves 3,931 of 9,985 recurring-class occurrences (39.4%) unresolved across 83 of 91 malleable fingerprint classes, cleanly separating burst-resolved ties from persistent open forks in internal compatibility space. Together, these results establish finite-horizon, anchored recovery of an erased local choice from the surviving present structure of an advancing aperiodic frontier. Contact: [email protected]