The o-series of models are trained with reinforcement learning to think before they answer and perform complex reasoning. The o3-pro model uses more compute to think harder and provide consistently better answers. o3-pro is available in the Responses API only to enable support for multi-turn model interactions before responding to API requests, and other advanced API features in the future. Since o3-pro is designed to tackle tough problems, some requests may take several minutes to finish. To avoid timeouts, try using background mode.