OpenAI’s September 8, 2026 announcement of an AI multi-agent proof for the Navier-Stokes existence and smoothness problem, complete with a publicly available Lean formalization, underpins the 94.5% market-implied probability against retraction by year-end. The claimed finite-time singularity construction via a spiraling vortex has withstood early checks, and OpenAI has not indicated any intent to withdraw the result despite credit disputes and mathematician scrutiny. Recent withdrawals of unrelated AI-generated preprints highlight the company’s willingness to correct errors quickly, yet the Navier-Stokes work’s machine-verified core and the Clay Institute’s deliberate review timeline reduce near-term reversal risk. Lingering mismatches between natural-language and Lean versions or new independent counterexamples could still force a reevaluation.