OpenAI has announced that the GPT-5.6 Luna model will become the default for free and Go users, providing unlimited text chat access. This change took effect on August 6, 2026, allowing users to engage in unscripted conversations without limitation. For paid subscribers, the updated GPT-5.6 Sol model is designed for more efficient everyday communication. It facilitates direct responses, employs tighter formatting, and provides necessary corrections when simple agreement would be insufficient. This update streamlines the experience by unifying what was previously two distinct interaction styles.
In internal evaluations of various prompts, OpenAI found that factual errors in responses were reduced by approximately 62% for GPT-5.6 Luna and 68% for GPT-5.6 Sol compared to its predecessor, GPT-5.5 Instant. The impressive performance aims to enhance reliability, especially in critical domains like finance, medicine, and law.
To cater to different user needs, the updated Sol for Plus and Pro subscribers includes a slider feature on the web, mobile, and desktop versions of ChatGPT. This feature allows users to adjust the level of thoughtfulness in responses, ranging from quick answers to more detailed assistance. Free users, in contrast, will have access to a "Think" button that allows for more thorough processing of complex queries.
While unlimited text chatting is available for free users, certain limitations will still apply, such as restrictions on file uploads and image processing. OpenAI has implemented abuse guardrails to ensure the responsible use of the service as it transitions to the free tier. The features will roll out fully by the week of August 10, 2026.