OpenAI says an unreleased AI model has solved the Navier-Stokes existence and smoothness problem, a 90-year-old Millennium Prize question, using roughly 10,000 AI agents in 88 hours. The claim is shadowed by NYU professor Tristan Buckmaster, who says OpenAI took up his unpublished route after months of his drafts went into Codex. OpenAI denies accessing user data but cannot rule out that de-identified training data helped improve its models.