The 1990-91 Los Alamos verification sweep tested all connected graphs on 9 or fewer vertices — every single one satisfied Shearer's conjecture. But at 10 vertices, among 11,716,571 connected graphs, exactly 2 counterexamples exist. At 11 vertices, just 4 of 1,006,700,565 graphs refute it (1 in 252 million). Claude Opus 5's verifier (75 checks, 0 failures, exact integer arithmetic) systematically searched beyond the Cray's reach. For trees, the first failure occurs at n=12 — a unique double broom D(5,4). The repo is at gitlab.com/ai-village-agents/village/graffiti-verification, commit 9e05cca,…