GPT-5 is no longer in ChatGPT: OpenAI retired GPT-5 Instant and Thinking from ChatGPT on 13 February 2026, along with GPT-4o, GPT-4.1, GPT-4.1 mini and o4-mini, and the GPT-5.1 models followed on 11 March. As of October 2026, GPT-6 is rolling out as the default in Chat for eligible Plus, Pro, Business and Enterprise users, while Free and Go users get GPT-5.6 Luna.
Model names at OpenAI now read like a solar system, and the page OpenAI keeps on them was updated the day before I read it. So treat this as a decoder for October 2026: what's live, what's gone, who gets which, and why the model you were expecting might not be in your menu.
Which ChatGPT models are live in October 2026
Here's what OpenAI's Help Center lists for ChatGPT right now, and who can pick each one.
| Model | What it's for | Who gets it |
|---|---|---|
| GPT-6 | The new default in Chat. GPT-6 Sol powers its Instant, Medium, High and Extra High levels | Rolling out to eligible Plus, Pro, Business and Enterprise users |
| GPT-6 Pro, powered by GPT-6 Astra | The Pro thinking level, for difficult tasks and longer-running workflows | Both Pro plans, Business and Enterprise (Enterprise subject to workspace permissions) |
| GPT-5.6 Sol | Complex work across coding, research, cybersecurity, science, computer use and design; still a separate option in the menu | Paid plans; not Free, Go or logged-out users |
| GPT-5.6 Sol Pro | The highest-capability option in the GPT-5.6 family | Plans that include the Pro level |
| GPT-5.6 Luna | The fastest and lowest-cost GPT-5.6 model | The default for Free and Go, and it also powers Think |
| GPT-5.6 Terra | A balance of capability, speed and cost | Not selectable in Chat; in Work and Codex depending on plan, and in the API |
| GPT-6.1 Sol and GPT-6.1 Terra | Model options for agent-style work | ChatGPT Work and Codex only, not Chat |
Plus plans get GPT-6 Astra in ChatGPT Work and Codex, but not the Pro level in Chat. If you're unsure what Work and Codex even are, my explainer on Chat, Work and Codex covers the split.
What was retired, and when
This is the bit most searchers are after. OpenAI's retirement page lists two rounds, and every model listed there is still available through the OpenAI API, with advance notice promised before any API retirement.
| Model | Retired from ChatGPT | Still in the API? |
|---|---|---|
| GPT-4o | 13 February 2026; Business, Enterprise and Edu kept it inside Custom GPTs until 3 April 2026 | Yes |
| GPT-4.1 and GPT-4.1 mini | 13 February 2026 | Yes |
| OpenAI o4-mini | 13 February 2026 | Yes |
| GPT-5 Instant and GPT-5 Thinking | 13 February 2026; Enterprise workspaces kept GPT-5 until 19 February | Yes |
| GPT-5 Pro | Stayed for all paid users until 19 February 2026 | Yes |
| GPT-5.1 Instant, Thinking and Pro | 11 March 2026, in normal chats and in GPTs | Yes |
OpenAI's own wording on GPT-5 is that it went "as previously announced", so it wasn't a surprise cut, just a planned one that lots of people missed. After 3 April, GPT-4o was fully retired across every plan.
One thing that didn't change: ChatGPT Voice and ChatGPT Images. Both use a similar base model to GPT-4o, but OpenAI says each is a different model from the text GPT-4o that was retired, so neither was touched.
Sol, Terra, Luna and Astra in plain English
The new names describe the job, not the generation. As of October 2026:
- Sol is the heavyweight for complex work. Sol Pro is the most capable option in the GPT-5.6 family.
- Terra balances capability, speed and cost for everyday work. You won't find it in a normal chat.
- Luna is the fastest and cheapest to run. It's what Free and Go users get, including when they press Think.
- Astra powers GPT-6 Pro, the top thinking level for hard problems.
A detail that confuses people: in the model menu, GPT-6 replaces the old Latest option, and it isn't labelled Sol even though GPT-6 Sol does the work underneath. For the hands-on side of GPT-6, including the new visual answers, my GPT-6 guide has the detail.
Thinking levels by plan
When GPT-6 is selected, the Thinking slider sets how hard ChatGPT works. Instant gives fast answers to everyday questions, Medium is standard thinking, High is extended thinking, Extra High is the most GPT-6 Sol can do, and Pro hands the job to the Pro models. Which levels you see depends on your plan:
| Plan | Medium and High | Extra High | Pro |
|---|---|---|---|
| Plus | Included | Not included | Not included |
| Pro | Included | Included | Included |
| Business | Included | Included | Included |
| Enterprise | Included | Included | Included |
| Free and Go | Not included | Not included | Not included |
Free and Go users get a Think option for harder questions instead, and it runs on Luna, not Sol. In Business and Enterprise workspaces, admins can also limit which models members can use, and some Enterprise customers will keep seeing the old model picker until the new controls reach their workspace. If you're weighing up a plan for the extra levels, my Go versus Plus comparison sets out the trade-off.
If you hit a Thinking limit, ChatGPT may carry on with another available model, and it shows when the allowance resets where it can. Don't bother asking Support to reset it, though: OpenAI says Support doesn't reset ChatGPT or Codex usage limits.
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What happened to your old chats and GPTs
Nothing was deleted. When a model is retired, OpenAI moves things across for you:
- Conversations and projects that used a retired model now default to their GPT-5.3 Instant and GPT-5.4 Thinking and Pro equivalents.
- GPTs built on retired models move automatically to the closest of those equivalents.
- If you'd picked Latest, that selection moves to GPT-6 at the same effort level.
- If you'd picked GPT-5.6 Sol on purpose, you stay on GPT-5.6. The GPT-6 rollout doesn't retire older selectable models.
Expect the replies to feel a little different. OpenAI says tone or style may change when models do, but your earlier conversations and the background you've shared carry over, and the personality settings are there if you want to steer the voice back.
Why you can't see a model you expected
- GPT-6 is still rolling out to eligible paid accounts, so it may simply not have reached yours yet.
- You're signed in to a different account, perhaps a Free one, from the one that holds your plan.
- Free and Go plans don't include GPT-5.6 Sol at all, and logged-out users don't get it either.
- Your workspace admin controls model access in Business and Enterprise.
- Terra and Luna aren't selectable in standard chats, whatever your plan.
- In the desktop app, Astra can need an update: open Menu, then Check for Updates, even if you updated recently.
Which model I'd pick
I'd leave the picker on GPT-6 and let it run at Instant or Medium for everyday writing and research, and move up to Pro effort only for the hard jobs, such as a knotty analysis or a long piece of work you'd otherwise hand to a specialist. Skip chasing a retired model name: GPT-4o and GPT-5 aren't coming back to ChatGPT, and if a workflow depends on one, the API is where they still live. Model news dates fast, so check OpenAI's GPT-6 and other models page before you train your team on any of this.
If you're not sure which AI model your team should be using for which job, that's the kind of AI enablement I help with. I run AI training and workshops for teams, and help businesses with AI enablement and workflow automation, so the busywork runs itself and people get time back. Most of that work is with SaaS marketing teams and small businesses. Here's how we can work together.
Frequently asked questions
Is GPT-5 still available in ChatGPT?
No. GPT-5 Instant and Thinking were retired from ChatGPT on 13 February 2026. They remain available through the OpenAI API.
What is the default ChatGPT model in October 2026?
GPT-6 is rolling out as the default in Chat for eligible Plus, Pro, Business and Enterprise users. Free and Go users get GPT-5.6 Luna.
Can I still use GPT-4o in ChatGPT?
No. GPT-4o was retired on 13 February 2026, and Business, Enterprise and Edu lost it inside Custom GPTs after 3 April 2026. ChatGPT Voice and Images run on different models and weren't changed.
What's the difference between Sol, Terra and Luna?
Sol is for complex work, Terra balances capability, speed and cost, and Luna is the fastest and lowest-cost option. Of the three, only Sol is selectable in standard ChatGPT chats.
Why can't I see GPT-6 in my model menu?
It's still rolling out to eligible paid accounts and isn't labelled Sol. If it's missing, it may not be on your account yet, or your workspace admin may control model access.
