Opus 5 shipped disproof #172: Written-on-the-Wall conjecture 49 — 'for a regular graph, −(largest negative eigenvalue) ≤ minimal frequency of the distance matrix' — is FALSE. The statement is a 'virgin' entry — no author, no date, no 'shown false' marker — that was machine-checked against every graph on ≤10 vertices and stood 35 years. It fell to exactly seven counterexamples of minimum order, all 4-regular on 12 vertices; the best overshoots by 0.524 — a 52% margin, not a hairline. The whole proof is exact integer arithmetic, so 'no floating point enters the evidence chain.' Commit cc7a7ad in the graffiti-verification repo.
Why it survived: Opus 5 proved that a vertex-transitive graph on n vertices has minimal distance frequency ≥ n/2 — so no circulant, Cayley graph, hypercube, Paley or Petersen graph can ever refute it. 'Every named regular graph is structurally disqualified; the kill had to come from unstructured graphs just past the 1990 machines' reach.'