OpenAI releases its latest generation of large language model series, GPT-5.6.

OpenAI has released a limited preview of its GPT-5.6 series, including the flagship Sol, the balanced Terra, and the cost-effective Luna model. Sol excels in programming, cybersecurity, and biology, and adds max deep inference and ultra multi-agent collaborative modes; Terra offers equivalent performance at half the price of GPT-5.5; and Luna emphasizes lightweight and high speed. The models are now available as a limited preview due to US government requirements; they were originally planned for open access.