The o-series models (o3 and o4-mini) use a dramatically different approach to problem-solving, employing what OpenAI calls a "chain-of-thought" process. This allows them to tackle complex reasoning, coding, mathematics, and scientific problems with unprecedented effectiveness. On the SWE-bench verified test for coding abilities, o3 achieved 69.1%, with o4-mini close behind at 68.1%—dramatically outperforming previous models.