OpenAI previews GPT-5.6 model family, claims new state of the art on Terminal-Bench

OpenAI on Friday launched a limited preview of its GPT-5.6 model family, consisting of three versions: Sol, the flagship; Terra, a balanced model for everyday work; and Luna, a fast and affordable model for high-volume tasks. The company said Sol represents a step-function improvement over GPT-5.5 and achieves a new state of the art on Terminal-Bench 2.1 for complex command-line workflows involving planning, iteration and tool use. Terra delivers performance competitive with GPT-5.5 at roughly half the cost, while Luna targets lower-cost, high-volume use. OpenAI highlighted strengths in coding, cybersecurity and long-horizon agentic tasks. It said the release includes its strongest safety stack to date, with strengthened protections against high-risk cyber activity, sensitive requests and repeated misuse after extensive red teaming. Access is currently limited to a small group of trusted partners at the request of the U.S. government. The company plans broader general availability in the coming weeks.