OpenAI said on 6 August that GPT-5.6 Luna will become the default model for ChatGPT's Free and Go tiers, and that both will get unlimited text chats. The company recently passed 1 billion weekly users. Neither change was live at announcement.
The schedule
Plus and Pro subscribers got the updated GPT-5.6 Sol and a thinking slider immediately. The model swap for free accounts lands during the week; unlimited text chats and a new "Think" button arrive the week after, and OpenAI notes the offer is subject to abuse guardrails. Nothing about the cap has changed for anyone yet.
What "unlimited" covers
Text only. Separate limits stay on files, images, voice and image generation — the four request types that cost OpenAI the most to serve. A free account can now type forever and still hit a wall the moment it uploads a PDF.
The numbers are self-graded
OpenAI reports factual errors 62% less common with Luna and 68% less common with Sol. Both are measured against GPT-5.5 Instant — the model free users are leaving — on OpenAI's own evaluations. Neither is a comparison against Sol, against a rival, or against an external benchmark.
A re-tiering, not an upgrade
Luna is OpenAI's smallest and cheapest model. The Think button extends how long Luna reasons; it does not route the query to a stronger model. The free tier gains volume and loses ceiling, while Sol and adjustable reasoning depth stay paid. The message cap was the thing users complained about. The model ceiling is the thing that now separates the tiers.