Termination-selected spin crossovers in inverse-spectral Ising chains

Microscopic termination can affect a macroscopic spin correlation even when the leading spectral density is unchanged. We study this effect in derivative-seeded inverse-spectral Ising analogues of open multispin chains with positive, periodically repeated couplings. When two tied maximal squared inputs are split by O(L-1), termination selects a discrete low-energy measure. Reconstructing the canonically weighted measure produces a spatial field-bond imbalance of order L-1, which survives over an O(L) spin string in three order-one crossover functions. In a strict interior window, we derive the absolutely normalized continuum correlation in the ground state and when the scaled inverse temperature approaches a positive constant. The representation combines a regularized determinant with a separately controlled ordinary trace. The Ising L-1/4 prefactor is unchanged, and at zero splitting the ground-state branch with one maximal input omitted gives the known free/free strip correlator. Direct finite-chain determinants agree with independent continuum calculations for two backgrounds and spatial intervals, including threshold and subgap modes. The largest relative difference is 0.319% at L = 256. This deposit contains the R8 manuscript PDF. The source archive and numerical reproduction files referenced in its Data availability statement are held separately.