GPT-5.6 Sol, Terra, and Luna are here. See which one's best for you.

These days, new versions of AI chatbots don't just launch; they're unshackled and released to the public following government scrutiny. OpenAI's new GPT-5.6 models were – like Anthropic's Claude Mythos and Fable – apparently too powerful to just launch; but now, after some tinkering, they're available to you, dear customer.

In practice, it simply means that the new GPT-5.6 models are very powerful and smarter than before. In its introductory post, OpenAI shared a bunch of graphs showing just how much better GPT-5.6 is than the competition, whilst using fewer tokens and generally costing less.

OK, great. But GPT-5.6 is not just one model; it comes in three distinct flavors: Sol, Terra, and Luna. So what do different kinds of users get, what should they pay for, and which models should they (mostly) use? Let's dive in.

Free users get (almost) nothing

Sorry; if you're not a paying customer, you'll have to make do with OpenAI's previous flagship model, GPT-5.5. Any sort of access to GPT-5.6 models requires a subscription of some sort. Fortunately, GPT-5.5 is still quite capable at most tasks, but if you want the best of the best, you'll have to cough up the dough.

There's an exception to this: Free and Go users can access GPT-5.6 through ChatGPT Work. More on that below.

If you're a Plus or Business user, you can only get Sol (the most powerful model) at medium and higher effort settings. There's another, higher level of performance called Sol Pro, but that's only available for Pro and Enterprise users.

In terms of availability per one million tokens, the prices are: $5 input and $30 output for Sol. $2.5 input and $15 output for Terra, and $1 input and $6 output for Luna.

Sol, Terra, or Luna?

Why are there three models in the first place? Well, OpenAI always had a multi-tier model; for example, previously users were able to choose a "mini" version of the main model to get results done cheaper. Now, the model has been split into three tiers.

If you're a paying customer, you're free to use all three. But you know how it is in the world of LLMs: If you pick the smartest one, your usage limits will get hit faster (yes, there are always usage limits, even if you throw a ton of money at OpenAI).

In the simplest sense, GPT-5.6 Sol is the smartest model, Terra is in between (with roughly GPT-5.5 level of performance), and Luna is the cheapest, fastest, but also least capable of the bunch.

The breakdown is as follows: Terra is a "balanced" model for everyday work. That's the one you should be asking most of your questions. Don't underestimate it, though, as OpenAI claims it performs better than Anthropic's Fable 5 in some cases.

Luna is cost-efficient, and should be used for easy, non crucial everyday tasks; think recipes and movie recommendations. Again, OpenAI says it outperforms Anthropic's Opus 4.8 in some cases, so it's not a slouch, either.

Sol should be reserved for coding, deep research, planning, and cybersecurity: The most demanding tasks. Of course it comes at a (literal) cost: While OpenAI claims it spends less tokens than Anthropic's Fable 5, Sol will still hit usage limits a lot faster than the other variants.

Fun fact: If you ask GPT-5.5 about any of this, right now, it'll give you completely wrong answers. Hopefully OpenAI will fix this soon.

Wait, what's this ChatGPT Work thing, then?

Oh yeah, OpenAI also launched ChatGPT Work, which is a new agent in ChatGPT that can access and take actions on your apps and files, and work in the background until a task is finished. It's powered by Codex (OpenAI's software engineering agent) and GPT-5.6. Think about it as your buddy that will go through your emails and files, browse the web, fetch the relevant data, and create that presentation your boss wants before the day is done.

ChatGPT Work is rolling out to Pro, Enterprise and Edu users first on web and mobile; this will be expanded to Plus and Business users "over the next few days."

On the desktop, Work is available for everyone, including Free users.

Oh, and one more thing: The fact that ChatGPT Work has a built-in browser also means that OpenAI is sunsetting its standalone web browser, Atlas. Sorry.

How about GPT Live?

GPT Live is a new version of ChatGPT Voice and it will show up when you start talking to ChatGPT.

We've covered this in more depth here, but the bottom line is that GPT Live can listen and speak at the same time, allowing it to keep up a more realistic conversation.

Wrapping it all up

The new GPT-5.6 model is smart. It comes in three flavors: Luna, Terra, and Sol, with Sol being the most capable variant, Luna the most affordable one, and Terra somewhere in the middle. You can currently only get them on paid tiers, unless you're using ChatGPT Work on desktop. And ChatGPT Voice has also gotten smarter with GPT-Live underneath, a model that can listen and speak at the same time.