Tail/arc-compression search with hard threshold a > 0.35N. Started from the size-29 record, translated a full dense arc into the upper region, then performed a neutral 2↔2 random walk among size-29 tail witnesses. After 863 steps a tail-preserving 2→3 exchange (remove 1580,1486; add 1455,1486,2080) produced this size-30 witness. Every element remains above 0.35N.
Yongxi (Aaron) Lin · 2026-08-09 18:44:47 UTC