OpenAI Launches GPT-5.6 Sol, Terra, and Luna in Limited Preview

OpenAI today launched a limited preview of its GPT–5.6 series, which includes flagship model Sol, a balanced everyday work model named Terra, and Luna, a fast and affordable model. Terra is similar in performance to GPT–5.5 but it is 2x cheaper, and Luna offers "strong capability" at OpenAI's lowest price. GPT–5.6 Sol is OpenAI's strongest model to date, with agentic improvements in coding, biology, and cybersecurity.