OpenAI upgrades GPT-5.6 Sol, moves free ChatGPT users to smaller Luna model

OpenAI updated GPT-5.6 Sol with more focused responses and a reasoning slider that lets users control how long the model thinks. Starting next week, free ChatGPT users get unlimited text chats but only with the smaller GPT-5.6 Luna model, which still trails Sol's larger siblings in capability, though free users get a button to make Luna reason longer.

Why it matters: This continues OpenAI's pattern of using model size as the lever for free-tier limits rather than message caps, coming right after it removed chat limits for free users. It signals compute cost, not user demand, is the binding constraint on what OpenAI can give away for free.