Kimi K3.1 Pro puts open-source AI a month behind the best

Kimi K3.1 Pro scores 55.1 on the Artificial Analysis Intelligence Index, 2.5 points short of Claude Opus 5.5: open-source AI is now 31 days behind the best closed model, down from 104. It extends China’s run: a Chinese lab has had the best open model on every one of 765 days since September 2024.