GPT-5.6 is OpenAI's newest model family in three tiers: Sol — the flagship for reasoning, coding and agents — plus a balanced everyday Terra and a fast, low-cost Luna.

“GPT-5.6 Sol, along with Terra and Luna, will launch publicly this Thursday. We're expanding preview access globally now,” OpenAI said. The models first reached a small group of partners in a late-June preview under U.S. government review — Thursday marks their first public release.