OpenAI released GPT-6.1 Terra on 26 October, an upgrade to its mid-tier Terra model that takes over from GPT-5.6 Terra. It is rolling out to Plus, Pro, Enterprise and Edu users in ChatGPT Work and Codex, and in the API as gpt-6.1-terra. Terra was passed over last month, when OpenAI released the GPT-6 models Sol and Luna.
Standard API prices are half what GPT-5.6 Terra cost. On OpenAI's internal benchmark of prompts designed to provoke errors, the error rate at low reasoning effort fell from 53.6% to 16.7%, and at maximum effort it dropped 18 points to 4.3%, close to the level of GPT-6 Astra and GPT-6.1 Sol; the low-effort gain is nearly 37 points. OpenAI also says it clearly beats the older Terra on Agents' Last Exam, a test of agents working in office software.
Chart posted with OpenAI's announcement comparing GPT-6.1 Terra with other models on Agents' Last Exam
OpenAI · Image: OpenAI Developer Community
The pitch is speed and cost. OpenAI says Terra matches Astra at a tenth of the price per token and finishes tasks more than three times faster on average than Astra and Sol, and that usage allowances in ChatGPT Work and Codex stretch further with it. From cheapest to most capable, the families run Luna, Terra, Sol and Astra.
About GPT-6.1 Terra
GPT-6.1 Terra is OpenAI's medium-sized model, meant to balance intelligence and affordability. OpenAI has four main model classes, from lowest price and capability to highest: Luna, Terra, Sol and Astra. It takes the place of GPT-5.6 Terra.
It was visible before OpenAI announced it. On 20 October a Microsoft pull request surfaced in which 18 evaluation configurations had been renamed from GPT-5.6 Terra to the new name, which TestingCatalog read as a sign that testing was close. The model also fills a gap left in September, when OpenAI released the GPT-6 models Sol and Luna and left Terra on the GPT-5.6 generation.
Oct 2026
Released
It is aimed at visual reasoning, precise computer use and clearer writing: drafting proposals, reading technical drawings, filling in forms and editing video. OpenAI describes it as a model that reads what is on screen, acts across apps and writes naturally. It steers everyday work to Terra and in-depth research or complex coding to Sol or Astra. 9to5Mac sees it as a way to do more work for longer at lower cost. The announcement uses the full name throughout, bar one heading that drops the ".1".
Sources · 2