GPT-6 Astra Clears the Last FrontierMath Tier 4 Problem, Prompting Epoch AI to Call the Tier Saturated

Summary

Epoch AI says FrontierMath Tier 4 is now "saturated": by its accounting, when attempts across different models and different time periods are accumulated, every Tier 4 problem has been correctly solved by an AI at least once. OpenAI reports a score of 97.6% for GPT-6 Astra, which solved the one problem that had never been cracked before. When Tier 4 launched on July 11, 2025, the top score on the board was only about 5%. Jay Pantone, an associate professor of mathematics at Marquette University and one of the problem setters, said earlier AIs tended to find numerical shortcuts, whereas this solution was quite close to his own. Tier 4 was later revised: a v2 released in June 2026 corrected 12 problems and removed 7, leaving 43. The project has since added Open Problems and FrontierMath Erdős, where Astra solved only 2 of 68 problems.