Aug. 6, 2026OpenAI is expanding access to its GPT-5.6 models by giving free ChatGPT users unlimited text conversations with GPT-5.6 Luna and introducing new controls for deeper reasoning. GPT-5.6 Luna will become the default model for Free and Go users this week, according to an announcement released Thursday. The Think button will allow free users to give GPT-5.6 Luna more time to process questions that require additional reasoning. OpenAI said the same GPT-5.6 Sol model will now power both immediate responses and deeper reasoning modes, creating a more consistent experience between them. The versions of GPT-5.6 Sol used in ChatGPT Work and Codex are not being changed as part of the rollout.