Same protocol applied to the 4-block d=512 ResMLP variant (vs the d=256
default). 4 methods × 3 seeds = 12 conditions:

  BP @ d=512:           trustworthy on all 3 seeds (acc 0.60-0.61)
  DFA @ d=512:          walked back on all 3 seeds via (a)+(b)
  State Bridge @ d=512: walked back on all 3 seeds via (a)+(b), with
                         drift sub-mode on s123 (stability 0.879)
  Credit Bridge @ d=512: walked back on all 3 seeds via (a)+(b)

Width effect: max-per-block growth is HIGHER at d=512 (6e3-7e4) than at
d=256 (~1e3). Larger width amplifies the explosion. The protocol
verdicts are robust to this — same binary outcome, more extreme
quantitative numbers.

This is the cross-width validation: the protocol's findings are not
d=256-specific. The §3 audit results generalize across the width
dimension.