OpenAI Updates GPT-5.6 Sol and Expands Luna Access to Free Users
New updates introduce user-controlled reasoning depth and expand high-capability models to the free tier.
OpenAI has updated its GPT-5.6 Sol model for Plus and Pro users and expanded access to GPT-5.6 Luna for free users. These changes aim to increase factual reliability and give users more direct control over the model's reasoning process.
For Plus and Pro subscribers, the updated GPT-5.6 Sol now features tighter formatting and more focused responses. The most significant addition is a "thought" slider, which allows users to manually adjust the amount of internal processing the model applies to a given prompt. Meanwhile, users on the Free and Go tiers will transition to GPT-5.6 Luna as their default model this week. This rollout includes unlimited text chats, with a "Think" button for complex reasoning tasks scheduled to arrive next week.
Performance Gains
According to OpenAI, these updates significantly reduce hallucinations in high-stakes domains. Internal evaluations revealed that factual errors were 68% less common with GPT-5.6 Sol and 62% less common with GPT-5.6 Luna when compared to GPT-5.5 Instant. These improvements were specifically measured across financial, medical, and legal prompts, where precision is critical.
It is important to note that these updates are limited in scope. The updated GPT-5.6 Sol is exclusive to the ChatGPT Chat experience; the versions of the model powering Work and Codex remain unchanged.
Shifting the Inference Balance
The introduction of the thought slider and Think button represents a strategic shift toward user-controlled inference compute. By allowing users to trade latency for quality, OpenAI is moving away from a one-size-fits-all response model. This allows the system to remain fast for simple queries while providing deep reasoning for complex problems only when requested.
Furthermore, providing unlimited text chats and advanced reasoning capabilities to free users lowers the barrier to entry for the company's most sophisticated models. This move appears designed to maintain market share as LLM chat interfaces become commoditized and competition intensifies.
Expanding Opportunity
OpenAI stated that "Access shapes opportunity, and this update gives more people the ability to keep asking, develop an idea, and get help when they need it."
Industry observers will now be watching to see how the "Think" button performs in the wild for free users and whether the increased compute costs of unlimited text chats lead to further tier adjustments. For now, the focus remains on balancing the speed of "Instant" models with the depth of "Thinking" models within a unified interface.