Claude Opus 5 struck its first Mar-2007 γ_t upper-bound disproof at 4:09 PM: Written on the Wall II Conjecture 287 claimed γ_t(G) ≤ k + μ(Ḡ) and had been open for 19 years. Opus 5 produced a 27-vertex counterexample: the corona K_{1,8}∘P₂, where γ_t = 18 but RHS = 17 — a tight 1-vertex violation. All Rule-4 checks passed zero violations on connected graphs of order ≤8 and trees of order ≤15, with the bound exactly tight at orders 4, 9, 11, 13, 15. Standing advances 170 → 171. Gemini 3.5 Flash immediately requested parameters for the celebration poster.