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GPT-6 Astra vs Sol vs Luna: Which Model Do You Get
Key Takeaway: Astra is the most powerful model, Sol is the everyday model on paid plans, and Luna is the low-cost model on Free and Go. Which one you actually see depends on your plan, your app version and how far the rollout has reached your account.
The three names in plain words
OpenAI released the GPT-6 family in stages. Astra came first. Sol and Luna arrived on September 22, 2026, in ChatGPT Work and Codex, according to 9to5Mac's report of OpenAI's announcement. The Chat tab got GPT-6 on October 7. I could not find an exact Astra date on the OpenAI pages I opened, so I leave it out.
| Name | What it is | Where you meet it |
|---|---|---|
| GPT-6 Astra | OpenAI's most powerful model | "GPT-6 Pro" in Chat on higher plans, and in Work and Codex |
| GPT-6 Sol | The everyday model for complex work | The GPT-6 option in Chat on paid plans. In the menu it is labeled GPT-6, not Sol |
| GPT-6 Luna | The most cost-efficient model | The default for Free and Go, with the detail below |
OpenAI's own model guide says Luna is the most efficient and Astra is the most powerful, and suggests defaulting to Astra only if you do not need to think about cost or waiting time.
Which model your plan gets
This table is based on OpenAI's help article "GPT-6 and other models in ChatGPT," which I read on October 17, 2026. It was marked as updated a week earlier.
| Plan | Chat tab | Higher thinking levels | Astra |
|---|---|---|---|
| Free and Go | Luna (see the disagreement below) | "Think" option, which uses Luna | Not in Chat |
| Plus | GPT-6 (Sol), Instant through High | Extra High not included | Work and Codex only |
| Pro ($100 and $200) | GPT-6 (Sol), Instant through Extra High | Included, plus Pro effort | GPT-6 Pro in Chat, plus Work and Codex |
| Business and Enterprise | GPT-6 (Sol) | Included, and admins can control model access | GPT-6 Pro, depending on workspace permissions |
Two more details from the same page. GPT-6 replaces the old "Latest" entry in the model menu, and GPT-5.6 Sol stays as a separate choice for people who want it. And GPT-6.1 Sol is only in Work and Codex, not in Chat.
Is GPT-6 free? Where OpenAI's pages disagree
Here is the part most guides skip. As reported by Notebookcheck and others, OpenAI's October 7 launch post, its ChatGPT release notes and its system card all say Free and Go users get GPT-6 Luna in Chat from October 8. But the help article on models, which I read on October 17, still says Free and Go users receive GPT-5.6 Luna and that it is "becoming the default." It also says Think on Free and Go uses GPT-5.6 Luna.
I could not find a correction from OpenAI. So the honest answer is that Free and Go users get Luna, and the exact version name is not settled in OpenAI's own pages. I did not open the launch post or the release notes myself, so that side of the disagreement comes from reports about them.
What the Free plan does allow
- Everyday text chats: OpenAI says Free and Go users have unlimited everyday text chats, subject to abuse-prevention safeguards.
- Everything else is limited: file uploads, image generation, voice, data analysis and other tools have separate limits.
- Harder questions: use Think. It uses Luna, not Sol.
So "ChatGPT free unlimited access" is partly true: the plain text chat is unlimited, but the extras are not.
Why you may not see GPT-6 yet
- The rollout is phased. OpenAI says GPT-6 is rolling out to eligible paid accounts, so it may not be in your menu yet.
- Look for the right name. Search the menu for GPT-6. It is not labeled Sol.
- Update your app. OpenAI says older desktop apps for Mac and Windows do not support Intelligent UI, and recommends using ChatGPT on the web.
- Managed workspaces. On Business and Enterprise, admins control which models people can use.
If you want ideas for what to try once it shows up, my guide to 10 prompts for ChatGPT's Intelligent UI covers it. OpenAI says Intelligent UI has no separate usage quota, and it does not work with the Pro effort setting.
Astra is not unlimited, even on Pro
OpenAI states that a Pro subscription does not include unlimited GPT-6 Pro use. On Pro $100, GPT-6 Pro and GPT-5.6 Sol Pro share one weekly allowance, so switching between them does not give you more messages. On Pro $200, when you reach the GPT-6 Pro weekly limit, ChatGPT switches to GPT-5.6 Thinking at Medium. Work and Codex have their own separate allowances, so a limit in one place does not use up the other.
Which one should a blogger use?
This is my reading, not OpenAI's advice. For outlines, headline ideas and rewriting your own drafts, the free Luna experience is usually enough. Sol on a paid plan helps with longer research and structured work. Astra is rarely needed for blog work, and it is the most limited. Whatever model you use, a stronger model does not remove the need to check facts. My fact-check checklist for AI drafts applies to every model on this page. And if you also use Google's free tier, see my guide to the Gemini free Flash-Lite change for the comparison.
A 2-minute check of your own account
- Open the model menu in ChatGPT on the web and write down what you see, such as GPT-6, GPT-5.6 Sol or Think.
- Open the Thinking slider if you have it and note the highest level offered.
- Check your plan name in your account settings.
- Open OpenAI's "GPT-6 and other models in ChatGPT" help article and note the "Updated" date at the top.
- Compare your menu with the plan table above, and note any difference.
What we do not know yet
- The exact Free and Go model name. GPT-6 Luna or GPT-5.6 Luna depends on which OpenAI page you trust.
- When your account gets GPT-6. OpenAI gives no schedule beyond "rolling out."
- Exact message counts. OpenAI describes limits by plan but does not publish one simple number for Plus.
Final thoughts
The names sound confusing, but the pattern is simple: Luna for the cheapest plans, Sol for everyday paid use, Astra for the heaviest work on the top plans. Check your own menu, ignore any guide that sounds too sure about the Free plan, and come back to the help page when its date changes.
Pro Tip: Keep a note of the date you checked your model menu. When a friend says "I have GPT-6 and you don't," you will know whether it is a plan difference or just the rollout.
Sources and limits: this article is based on OpenAI's help article "GPT-6 and other models in ChatGPT," which I read on October 17, 2026 and which was marked as updated a week earlier, and OpenAI's model selection guide. Details about OpenAI's October 7 launch post, release notes and system card come from reports by Notebookcheck and others, and details about the September 22 Sol and Luna release come from 9to5Mac. I did not open the launch post or the release notes directly. OpenAI's pages disagree on the Free and Go model name, so that row may change. This is general information, not a guarantee about what your account will show.
