Re-Phase Vol.4.1: Tolerant Compatibility and Feature Drift — Tolerant Fibers, Stable Recoverability, and Anchored Stability

This volume introduces tolerant compatibility in the Re-Phase framework. An exact admissible fiber is enlarged to a tolerant fiber: the set of candidates whose condition values remain within a prescribed tolerance. The central question is how much a recoverable feature may drift over this enlarged admissible set. Vol.4.1 separates nominal compatibility, tolerant admissibility, feature drift, target margin, and stable recoverability. A basic anchored stability estimate shows that if feature variation is bounded by condition variation over the tolerant region, then feature drift is controlled by tolerance. This note positions tolerance and feature drift within the Re-Phase grammar of compatibility, admissible fibers, and recoverability, without claiming to replace existing theories of error estimates, inverse problems, or robust optimization.