OpenAI unveils GPT-5.6 Sol, Terra and Luna models — but only accessible to limited preview partners for now, per US Gov

OpenAI is introducing GPT-5.6, a next-generation model series featuring Sol, Terra, and Luna, two months after GPT-5.5. Currently in limited preview for approximately 20 trusted organizations and the U.S. government, these models target developer and enterprise workflows via multi-agent architecture and deep-reasoning. The flagship GPT-5.6 Sol, priced at $5.00 per million input and $30.00 per million output tokens, enhances performance for cybersecurity and long-horizon coding within ChatGPT and Codex updates.