Canonical event

Colbrook publishes Kung–Traub conjecture proof and author-checked Lean formalization aided by ChatGPT

Matthew Colbrook submitted a 20 September 2026 preprint claiming a proof of the 1974 Kung–Traub optimal-order conjecture for memoryless root-finding, with a Lean formalization. Colbrook states ChatGPT 6 assisted Lean verification and ChatGPT 5.6/6 aided discussion, while the author reviewed and adopted the mathematical arguments. RTS discovered the September paper in November. The event date is its September submission, not its later discovery; the formalization has author-reported checks but no independently rerun build or completed peer review is asserted.