OpenAI makes GPT-5.6 Luna default model, removes text chat limits for free users

OpenAI on Thursday announced that GPT-5.6 Luna will become the default model for Free and Go tier ChatGPT users, and that those users will gain unlimited text-based conversations — removing one of the chatbot's longest-standing friction points for its non-paying audience.

The company, which says ChatGPT now reaches 1 billion people each week, is rolling out Luna as the free default this week, with unlimited text chats and a new "Think" button arriving the week of August 10.techcrunch+1

What's Changing

Luna is the smallest and fastest model in the GPT-5.6 family that launched in general availability on July 9. According to OpenAI's internal evaluation, responses containing at least one factual error were 62% less common with Luna than with GPT-5.5 Instant, the model it replaces as the free default.axios+2

The unlimited access applies only to text chats; limits remain on file uploads, images, voice, and image generation. OpenAI says the offering is subject to abuse guardrails.unite+1

For Plus and Pro subscribers, OpenAI is shipping an updated GPT-5.6 Sol tuned for everyday conversation. The company said this version "delivers more focused answers, adapts its level of detail to the question, avoids unnecessary formatting, and offers a helpful correction when simply agreeing wouldn't be useful." OpenAI reports factual errors are 68% less common with the updated Sol compared to GPT-5.5 Instant. Paid users also gain a thinking slider that adjusts how much reasoning effort the model applies to a response.techcrunch+2

Competitive Context

The move comes amid mounting pressure from cheaper Chinese open-weight models that have forced frontier labs to justify their pricing, as Axios noted. OpenAI cut Luna's API price by 80% on July 30 — just three weeks after launch — a pace far faster than previous price reductions.openai+1

Safety Concerns

CNET flagged potential risks of unlimited access for vulnerable users, noting ongoing lawsuits alleging that excessive chatbot engagement has exacerbated mental health issues among young people. OpenAI says it has added guardrails so that models "avoid romantic roleplay, age-restricted challenges, and presenting itself as a substitute for real-world relationships" for users under 18.cnet