From 6 August, free ChatGPT switches to GPT-5.6 Luna by default, with unlimited text chat. OpenAI does two things at once: retunes the model for paying users and lowers the threshold for free ones.
Fact
The facts: announced on 6 August. Plus and Pro get an updated GPT-5.6 Sol in the chat screen, with a slider that says how much the model should think, and with the same model behind both the fast and the deeper answer. Free users and the cheapest plan switch to GPT-5.6 Luna by default "this week", and get unlimited text conversations "from next week" plus a button for harder questions - with abuse safeguards kept in place. The limits on file uploads, images and other tools stay. By the company's internal evaluation, on questions from the financial, medical and legal fields, answers with at least one factual error are about 62% rarer for Luna and 68% for Sol compared to the previous fast model. It's explicitly noted that the model versions running in Codex aren't changed.
You'll see the 62-68% number retold as "68% more accurate". It isn't that. What's measured is how much rarer it is for an answer to have at least one error, against a specific previous model, on the company's own internal test. There's no named public exam, no outside checker. The direction is probably right. The magnitude is their word.
Unlimited applies to text. Files and photos stay rationed.
One excuse I hear regularly falls away - 'I don't have a subscription'. Have you hit a limit after four questions? Now you can actually get real work done, without paying. Running a training, or showing something to a client? The entry bar just dropped. The difference for us is small - nothing moves in Codex. Everyday work stays what it was.
Official primary sources
OpenAI - Improving GPT-5.6 Sol in ChatGPTOpenAI - GPT-5.6 August Updates (system card)The visual is generated code-art, no third-party images.