OpenAI makes GPT-5.6 Luna the free ChatGPT default with unlimited text chats

11:00 AM PT · August 11, 2026

OpenAI is expanding what free ChatGPT users get access to, making GPT-5.6 Luna, the fastest and lowest cost model in the GPT-5.6 family, the default for both Free and Go tier accounts. Alongside the switch, those users are gaining unlimited text based chats with no rate limit on message volume, plus a new ‘Think’ button that gives Luna more time to reason through harder questions on a per message basis without routing the request to a larger model like Sol or Terra. OpenAI says the unlimited access applies specifically to text conversations, with existing limits still in place for file uploads, image generation, and other tool use, and the offering remains subject to abuse guardrails to prevent misuse. For paying Plus and Pro subscribers, the company is separately retuning GPT-5.6 Sol in ChatGPT to be more reliable with facts and to give more focused answers in everyday conversation, alongside a new slider that lets users control how much reasoning effort the model applies to a given response. OpenAI frames the changes as part of a broader push to make its most capable free tier experience more usable at a moment when ChatGPT says it serves more than a billion people every week.