o3

これは何か

o3 is a reasoning model OpenAI released in April 2025, part of the o series. Unlike models that answer directly, it performs an internal chain of reasoning before producing its output, then derives the answer from that reasoning. The series is trained with reinforcement learning so the model learns to spend more reasoning steps when they buy a more reliable answer. o3 accepts text and image input and serves as the main version for mathematics, coding and scientific reasoning tasks.