ChatGPT Expands GPT-5.6 Luna Access and Adds a Reasoning Slider
In August 2026 OpenAI made GPT-5.6 Sol the single Chat experience for Plus and Pro, with a reasoning slider on web, mobile, and desktop, and moved Free and Go to GPT-5.6 Luna with unlimited text chats and a Think button. Since October 7, GPT-6 Sol and Luna are rolling out in their place.
OpenAI is expanding access to its GPT-5.6 family in ChatGPT while making the model choice feel less like a model switch. In an official announcement, OpenAI says the updated GPT-5.6 Sol now powers both Instant responses and deeper reasoning for Plus and Pro users, while GPT-5.6 Luna became the default for Free and Go users. (OpenAI; OpenAI on X) These GPT-5.6 models have since been succeeded in Chat: since October 7, 2026, ChatGPT's Chat tab is powered by GPT-6 Sol for Plus, Pro, Business, and Enterprise and GPT-6 Luna for Free and Go. See GPT-6 Sol and Luna. (OpenAI)
The practical change was a new control layer: paid users can move a slider to choose how much thought ChatGPT puts into each response, and free users got a Think button for questions that need more reasoning. (OpenAI)
What Changed by Plan
| Plan | Model and control | Timing and caveats |
|---|---|---|
| Free and Go | GPT-5.6 Luna became the default Chat model; a Think button adds more reasoning | Luna default the week of August 6, then unlimited text chats and Think; Think on the web listed August 14; abuse guardrails apply |
| Plus and Pro | Updated GPT-5.6 Sol powers Instant and deeper reasoning; a reasoning slider is available | From August 6 in ChatGPT on web, mobile, and desktop |
| Work and Codex | No change to the GPT-5.6 Sol version used there | Explicitly outside this ChatGPT release |
OpenAI rolled the update out in stages. Plus and Pro users got the updated Sol and slider starting August 6, GPT-5.6 Luna became the default for Free and Go users that week, and unlimited text chats plus Think followed the next week. OpenAI's release notes list Think for Free and Go on the web on August 14, 2026. (OpenAI; ChatGPT release notes)
The Reasoning Slider Replaces a Sharper Choice
The slider is meant to make effort a decision you can take per response. Keep it low for a quick answer, or move it higher for planning, research, writing, coding, or a decision where a more complete answer is worth the extra time. OpenAI describes this as one consistent experience rather than moving between models with different tones or behaviors. (OpenAI)
That distinction matters for everyday work. A user can keep a conversation in the same ChatGPT surface and spend more reasoning only when the task warrants it, instead of manually choosing a separate model and then re-establishing context. The control is available on web, mobile, and desktop for Plus and Pro users. (OpenAI)
What Free and Go Users Got
Free and Go users moved to GPT-5.6 Luna as the default model for ChatGPT conversations in August 2026, and to GPT-6 Luna from October 8. OpenAI's August post added unlimited text chats with Luna, subject to abuse guardrails, plus a Think button that gives Luna more time to work through harder questions. (OpenAI; OpenAI on X)
The word unlimited applies to text chats. OpenAI explicitly says limits still apply to file uploads, images, and other tools, so the broader ChatGPT product is not becoming unlimited in every dimension. (OpenAI)
The Think button is the free-tier counterpart to the paid slider: instead of continuously choosing an effort level, a user can ask Luna to spend more time on a difficult question. OpenAI says this is intended for questions that need deeper reasoning, not as a separate model the user has to configure. (OpenAI on X)
What Did Not Change
This release is specific to everyday ChatGPT conversations. OpenAI says the updated GPT-5.6 Sol is available only in the Chat experience and that the GPT-5.6 Sol version powering Work and Codex is not changing as part of the release. (OpenAI)
That boundary is useful when comparing the update with the earlier GPT-5.6 launch. The model family already spans ChatGPT, Work, Codex, and the API; this announcement changes the consumer Chat experience and its controls, not every surface where GPT-5.6 appears. OpenAI's original family announcement remains the durable reference for the wider model lineup and API availability. (OpenAI GPT-5.6 announcement)
What to Try First
These suggestions still apply to the reasoning control on GPT-6 Sol and Luna. If you are on Plus or Pro, use the slider on one real task that changes character as it gets harder: a planning memo, a multi-file coding explanation, or a research question with several constraints. Compare a quick setting with a higher-effort setting on the same prompt, and watch both answer quality and waiting time.
If you are on Free or Go, test Luna on ordinary text work first, then use Think only when the question benefits from a more deliberate pass. Treat the unlimited text-chat promise separately from uploads, images, and tool usage, because those surfaces retain their own limits. (OpenAI)
Bottom Line
In August 2026 OpenAI widened GPT-5.6 access in ChatGPT and turned reasoning effort into a user-facing control. Plus and Pro users got updated Sol with a web, mobile, and desktop slider; Free and Go users got Luna as the default, unlimited text chats, and a Think button. The change applied to everyday ChatGPT Chat, not Work or Codex. Since October 7, 2026, GPT-6 Sol and Luna are rolling out as the Chat models. (OpenAI; OpenAI)
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Corrections and Updates
- October 9, 2026: This page described the Free and Go rollout as happening "this week" and "next week"; it completed in August 2026, and since October 7 GPT-6 Sol (paid tiers) and GPT-6 Luna (Free and Go) are rolling out as ChatGPT's Chat models.
Sources
- OpenAI, “Improving GPT-5.6 Sol in ChatGPT -- and expanding access to GPT-5.6 Luna for free users” (August 6, 2026): https://openai.com/index/improving-gpt-5-6-sol-in-chatgpt/
- OpenAI on X, “We’re making better intelligence easier to access in ChatGPT for everyone” (August 6, 2026): https://x.com/OpenAI/status/2085434712429052386
- OpenAI on X, “Free and Go users can now use the Think button” (August 6, 2026): https://x.com/OpenAI/status/2085434717051240642
- OpenAI, “GPT-5.6: Frontier intelligence that scales with your ambition” (July 9, 2026): https://openai.com/index/gpt-5-6/
- OpenAI Help Center, ChatGPT release notes (August 6 and August 14, 2026 entries): https://help.openai.com/en/articles/6825453-chatgpt-release-notes
- OpenAI, “GPT-6 and Intelligent UI for everyone” (October 7, 2026): https://openai.com/index/gpt-6-for-everyone/
Frequently Asked Questions
What changed in ChatGPT with GPT-5.6?
On August 6, 2026, OpenAI updated GPT-5.6 Sol in ChatGPT for Plus and Pro users, added a reasoning-effort slider, and expanded Free and Go access to GPT-5.6 Luna with unlimited text chats and a Think button. GPT-6 Sol and GPT-6 Luna began replacing them in Chat on October 7.
Who gets the ChatGPT reasoning slider?
Plus and Pro users can use the new reasoning slider in ChatGPT on web, mobile, and desktop. The slider controls how much thought ChatGPT puts into an answer, from quick everyday responses to more deliberate work.
Do Free and Go users get unlimited GPT-5.6 Luna chats?
Yes, from August 2026. GPT-5.6 Luna became the Free and Go default the week of August 6, with unlimited text chats and Think following; Think reached the web on August 14. Abuse guardrails apply, and file uploads, images, and tools stay limited. GPT-6 Luna now powers Free and Go Chat.
Does this change GPT-5.6 Sol in Work or Codex?
No. OpenAI says the GPT-5.6 Sol version that powers Work and Codex is not changing in this release. The updated Sol covered here was optimized for everyday ChatGPT conversations in the Chat experience.