Key Notes
- OpenAI is making GPT-5.6 Luna the default ChatGPT model for Free and Go users this week, replacing GPT-5.5 Instant.
- Starting next week, Free and Go users will get unlimited text chats and a new Think button for harder questions, subject to abuse guardrails.
- OpenAI also updated GPT-5.6 Sol for Plus and Pro users to provide more focused answers and fewer factual errors.
OpenAI is making GPT-5.6 Luna the default model for ChatGPT’s Free and Go users and will remove limits on ordinary text conversations starting next week, a major expansion of access to its newest model family.
The company announced the changes on August 6 alongside an update to GPT-5.6 Sol for paying users. GPT-5.6 Luna will replace GPT-5.5 Instant as the default model for Free and Go accounts this week. Beginning next week, those users will also receive unlimited text chats and a new Think button that gives Luna more time to reason through difficult questions.
We’re making better intelligence easier to access in ChatGPT for everyone:
– GPT-5.6 Sol now powers both Instant and deep reasoning for Plus & Pro users, delivering more factual, focused responses.
– Free & Go users get unlimited text chats with GPT-5.6 Luna starting tomorrow. pic.twitter.com/JXhmj5GLTH
— OpenAI (@OpenAI) August 6, 2026
The change does not make every ChatGPT feature unlimited. OpenAI says limits will remain for file uploads, image generation and analysis, and other tools. Unlimited text conversations will also remain subject to abuse guardrails intended to prevent automated or otherwise excessive misuse.
The move substantially changes the free version of ChatGPT. Usage caps have historically forced free users to fall back to less capable models or wait for limits to reset. Once the new system is fully rolled out, ordinary text messages will no longer be counted against a fixed chat allowance.
GPT-5.6 Luna Replaces GPT-5.5 Instant
Luna is the fastest and lowest-cost member of the GPT-5.6 family, which also includes Terra and the flagship Sol model. OpenAI describes the three names as durable capability tiers rather than temporary model labels, allowing each tier to improve on its own schedule.
The wider large language model market has increasingly shifted toward smaller models that can deliver much of the quality of frontier systems at lower inference cost. OpenAI says Luna nearly matches GPT-5.5’s peak performance on several professional evaluations while operating at a substantially lower cost.
For free ChatGPT users, the more important change is how Luna is being deployed. Instead of making users choose between a fast model and a separate reasoning model, OpenAI is giving Luna two modes of interaction. Normal questions receive fast responses, while the Think button gives the same model additional reasoning time when a task requires more work.
That design makes deeper reasoning an explicit user choice rather than something reserved entirely for paid plans. It also brings the free product closer to the broader idea of an AI assistant that can move between quick everyday questions and more demanding planning, research, and analysis without forcing the user to switch products.
OpenAI says the rollout starts with Luna becoming the default for Free and Go users this week. Unlimited text chats and Think access are scheduled for the following week, so users may not see all three changes at the same time.
GPT-5.6 Sol Gets a ChatGPT-Specific Update
OpenAI is also updating GPT-5.6 Sol for Plus and Pro subscribers. The revised version is designed to answer more directly, use less unnecessary formatting, adapt its level of detail to the question, and rely more accurately on sources when answers depend on dates, numbers, rules, or other factual details.
In an internal evaluation covering financial, medical, and legal questions that required factual precision, OpenAI says responses containing at least one factual error were about 68% less common with the updated GPT-5.6 Sol than with GPT-5.5 Instant. GPT-5.6 Luna showed a 62% reduction in the same evaluation.
Plus and Pro users will also receive a new reasoning slider that controls how much effort ChatGPT puts into an answer. OpenAI says the same Sol model now powers both quick responses and deeper reasoning in the standard Chat experience, creating a more consistent interaction instead of moving between distinct models.
The update applies specifically to ChatGPT’s regular chat interface. OpenAI says the GPT-5.6 Sol version used in ChatGPT Work and Codex is not changing as part of this release.
The distinction follows OpenAI’s broader expansion of generative AI interfaces around the same model family. In July, the company launched GPT-Live, which separated real-time voice interaction from the larger reasoning model handling more difficult questions behind the scenes.
OpenAI Is Expanding the Free Tier as ChatGPT Reaches Massive Scale
OpenAI says around one billion people now use ChatGPT each week. Making unlimited text conversations available on the free tier means the company is choosing to absorb substantially more inference demand while reserving tighter limits for compute-heavy features such as files, images, and other tools.
The economics are helped by GPT-5.6 Luna’s lower serving cost. OpenAI recently cut Luna’s API price sharply and has described the model as its fastest and most affordable GPT-5.6 option. That efficiency gives the company more room to expand consumer access without offering unlimited use of its most expensive frontier model.
The free tier still remains clearly separated from paid subscriptions. Plus and Pro users receive the stronger GPT-5.6 Sol model and more control over reasoning effort, while Pro includes access to higher-end configurations for difficult work.
But the gap is narrowing for ordinary chat. A free user will soon be able to have unlimited text conversations with a current-generation model and manually invoke deeper reasoning when needed, without tracking how many messages remain.
For OpenAI, the change turns GPT-5.6 Luna from the cheapest member of its newest model family into the default front door to ChatGPT. For users, the practical effect is simpler: routine text conversations become unlimited, and harder questions get a dedicated Think button instead of requiring a paid upgrade or a separate model selection.
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