Yes. On September 8, 2026, OpenAI announced that an internal AI system produced a proof—and a Lean formalization—showing that smooth three-dimensional incompressible Navier–Stokes fluid motion can develop a finite-time singularity (a “blow-up”).
OpenAI says the result resolves statements “C” and “D” in the Clay Mathematics Institute’s official Millennium Prize formulation, and that it does not intend to claim the $1 million prize. The company described the solution as a vortex that spirals inward and elongates until fluid speeds grow without bound while energy stays finite.
Source: OpenAI — On the Navier–Stokes Millennium Prize Problem