OpenAI is moving much faster than usual in making its new flagship models (Sun and Moon) available to new users. For several days now, paid users around the world have been able to access GPT 5.6 Sun, its most advanced AI to date, and now it has decided to update it, improving its capabilities. On top of that, it will make its smaller sibling, GPT 5.6 Moon, available to free users. And it will do so with no conversation limit.
At least, no limit for simple conversations.
More conversational capacity, with a more powerful model
Let us start with the updates affecting free users.
If you were using ChatGPT Free, you were probably talking to GPT-5.5 Instant, a version of OpenAI’s previous model. It was a great model, optimized to be fast and inexpensive, but it falls well short of what the GPT-5.6 family can offer. Now, with Moon opening up to all users, Sam Altman’s company is delivering an even more powerful experience, without going as far as using Sun, which remains reserved for paid plans.
It is worth remembering that Sun, Terra, and Moon arrived just a month ago, in what was much more than a simple imaginative name change. It was a new version of GPT, 5.6, introduced to leave the 5.5 models behind and compete directly with Fable, Anthropic’s flagship.
OpenAI will begin offering unlimited text chats to Free and Go users starting next week.
(Practical) differences between Moon and GPT 5.5
Occasional users, especially those asking only simple questions, probably will not notice much difference between the two models, aside from a certain tendency in Moon to, let us say, hesitate, refer back to itself in conversation, justify its own answers, and even explain the path it took to reach them. That gives it, let us say, more “human” traits.
(At least, that is my personal impression of Moon.)
The clearest differences are not necessarily found in its ability to solve complex problems, but in its efficiency. OpenAI presents Moon as its fastest and most cost-effective model, designed to answer everyday questions and carry out clear, repetitive, or high-volume tasks. It is also more consistent, which allows it to maintain long and complex conversations with less need to repeat information.
Where Moon is clearly better than GPT‑5.5 Instant is in factual reliability. As the company explains, “In an internal evaluation of financial, medical, and legal questions requiring factual detail, responses containing at least one factual error were approximately 62% less frequent with GPT-5.6 Moon and 68% less frequent with GPT-5.6 Sun than with GPT-5.5 Instant.”
That said, this was an internal evaluation limited to a specific type of question. Therefore, the result does not necessarily mean Moon is better in every conversation, but it does point to a meaningful reduction in factual errors in especially sensitive areas.
The limits of unlimited conversation
That said, it is worth clarifying that this “no conversation limit” does not mean you will be able to use all of ChatGPT’s resources without restrictions. As OpenAI explained in a statement, there will still be temporary restrictions or specific limits for features that require more processing capacity, such as conversations that include file attachments or image generation, for example.
It is worth remembering that, until now, users on the free plan could see their access to GPT-5.5 Instant limited during a 5-hour period, depending on the number of messages exchanged with the model.
Think, a new way to use the model
Another of the new features introduced by OpenAI concerns a new “Think” button that will appear on screen, allowing users to activate it whenever they need a more thoughtful and reasoned response. If you remember, the ability to use “think” had already appeared in earlier ChatGPT models.
An improved GPT 5.6 Sun
And now, let us move on to paid users, who are also getting updates from OpenAI.
The company has improved GPT-5.6 Sun, so that it can “provide more accurate responses, adapt its level of detail to the question, avoid unnecessary formatting, and offer useful corrections when simply agreeing would not be enough. For Plus and Pro users, the same model now powers both instant responses and deeper reasoning, creating a consistent experience,” it explained.
In fact, OpenAI says the new GPT-5.6 Sun is designed to make fewer mistakes, especially when answers depend on dates, numbers, sources, rules, or assumptions, by making better use of the sources it finds to answer your question.
Another major new feature is similar to the “Think” functionality mentioned in the free version. As you can see in the image, Plus and Pro users (who use the Sun model) will have access to a new slider with five depth levels to choose the level of analysis ChatGPT applies to each response in tasks such as planning, research, writing, coding, or decisions that require greater reflection.
In any case, OpenAI has clarified that this update will affect only the ChatGPT experience: the version of GPT-5.6 Sun used in Work and Codex is not changing with this release.
Image: ChatGPT
