OpenAI announces o3 and o4-mini reasoning models for ChatGPT (updated)

UPDATE: Apr. 16, 2025, 2:18 p.m. EDT Now that the OpenAI livestream has ended, this article has been updated with the latest information about the o3 and o4-mini launch. As expected, during a livestream event today, the ChatGPT maker released the newest versions of its reasoning models. OpenAI launched o1, its first reasoning or chain-of-thought model, last summer and skipped over o2 to announce its progress on o3 in late December. While o3 has not been publicly available until today, OpenAI already has a lightweight version, o3-mini, on the market. In the livestream, the OpenAI team (sans CEO Sam Altman) described some of the models' capabilities and demoed how users can use o3 and o4-mini.