OpenAI has made GPT-5.6 Luna the default model for free and go users. They want users on the lower plans to have access to their latest models.
They are also giving users on these plans unlimited text chats (with GPT-5.6 Luna) and a “Think” button so that users can turn on reasoning for more complex prompts.
Note that their “unlimited” text chats are “subject to abuse guardrails”. Meaning that if they think that you are using it too much, they will still cut you off. There will also still be limits for images, files uploads, tools, etc. Pretty much everything except text chats.
This is still a big increase over what the free and go plans offered before. If you are on either of those plans, you may want to take advantage of this. Who knows how long it will last. And GPT-5.6 Luna is a good model. Most people will be able to do just about everything with it (not complex coding/math/reasoning but most people don’t do those things yet…)
If you want to read more about it, here is their post - https://openai.com/index/improving-gpt-5-6-sol-in-chatgpt/