A seven-hyperplane counterexample to a generic-initial degree bound

For the characteristic-zero arrangement Q=xy(x-y)(x-2y)zw(x+z+w), the reverse-lexicographic generic initial ideal of its ambient Jacobian ideal has pure-second-variable cutoff 8 and a degree 7 minimal generator whose largest variable is the third. A self-contained open-set proof refutes the general-dimensional degree bound of Bigatti–Palezzato–Torielli, also stated in OWR Report 5/2021. The valid three-variable arrangement theorem remains intact. The construction is a classical parallel connection; logarithmic, Hilbert–Burch and generic-section methods are prior, and the applicable Migliore–Nagel resolution of the distinct unmixed ideal is credited. A bounded audit through 15 October 2026 found no complete predecessor in its inspected corpus; historical priority and independent discovery remain unestablished. Ilardi (2018) full text was not obtained, and parameter families and historical code were not exhausted. The deposit includes the six-page note, LaTeX source and exact standard-library Python verification certificates and authored audits. AI tools were used extensively. This preprint is unrefereed and has not undergone conventional human peer review.