GPT-6.1 Terra
CLOSEDAPI id gpt-6.1-terra, released 2026-10-26 as 'a fast, efficient model that combines detailed visual reasoning and precise computer use alongside clearer, more natural writing' and the successor to GPT-5.6 Terra. It costs $1/$5 per Mtok with cached input at $0.05 and 30-minute cache writes at $1.25, which OpenAI says is 50% below GPT-5.6 Terra and GPT-6.1 Sol. It has a 1.05M context with 922K max input. The launch post gives Agents' Last Exam, MMMU-Pro, OSWorld 2.1 and Terminal-Bench Science 0.1 only as charts and relative claims (e.g. Agents' Last Exam +15 pp over GPT-5.6 Terra at medium effort; Terminal-Bench Science within five points of Opus 5.5 at max), so none of those are filed. OpenAI treats it as Critical in cybersecurity under its Preparedness Framework and applies the GPT-6 Astra safeguards stack.