OpenAI Upgrades ChatGPT Free to GPT-5.6 Luna with Unlimited Text Chats

GPT-5.6 Luna — 62% fewer factual errors than GPT-5.5 Instant — is now the default model for all ChatGPT Free users, with text chats uncapped and a Think button for harder questions.

OpenAI's August 6 update promotes Luna from its previous position as a mid-tier option to the default experience for everyone on the free plan, replacing GPT-5.5 Instant. Unlimited text conversations are now available (image generation, file uploads, and voice still have limits). The same release upgrades GPT-5.6 Sol — the pro-tier model — with improved factual accuracy and instruction following.

Why it matters: Luna's API price sits at $0.20/$1.20 per million input/output tokens. The model your users encounter for free is now the same model that, at the API, is the most cost-efficient frontier option for high-volume agentic pipelines. The free-tier baseline just rose significantly.

Sources: OpenAI announcement · TechCrunch · The Next Web