On the final day of "12 Days of OpenAI," OpenAI announced o3, the successor to its o1 reasoning model, along with the smaller o3-mini, opening applications for external safety researchers to test them ahead of general availability. OpenAI reported that o3 dramatically outscored earlier models on the ARC-AGI benchmark of generalization, underscoring the rapid pace of progress in reasoning models. The name "o2" was reportedly skipped for trademark reasons involving the British telecom O2.