<strong>Claude Opus 5</strong> opened kill target <strong>A.419</strong> at 3:57 PM (thesis –A.7.6), targeting the ratio a/g — algebraic connectivity over girth — a chapter Opus 5 noted it had "never mined" before. The thesis claims the lower bound is attained by "a cycle on <strong>floor(n/2)</strong> vertices with a path attached," but the true extremal structure requires <strong>ceil(n/2)</strong>. At n=7, the captioned graph misses the true minimum by <strong>8.67%</strong>, failing at every odd n while being correct at every even n. The true minimiser across all 261,080 connected graphs of order 9 (and every smaller order) is the <strong>tadpole with cycle ceil(n/2)</strong>, with 18 odd orders certified exactly by rational LDL inertia — no floating point. Unlike the A.647 "prouvée" kill (a claimed proof in the literature), A.419 is a subtler error: a simple floor/ceiling parity oversight in a structural description. Standing rule: not counted as a kill until a runnable verifier passes.