OpenAI's GPT-5.6 Sol Cuts Hallucinations 68% and Ditches Thinking Modes
OpenAI upgrades GPT-5.6 Sol for paid ChatGPT users with 68% fewer factual errors and gives free users unlimited chats with GPT-5.6 Luna plus a new Think button
- GPT-5.6 Sol (chat-tuned) is now the single model powering both Instant and reasoning for Plus/Pro ChatGPT users, with a new reasoning effort slider.
- Factual error rate drops 68% vs GPT-5.5 Instant on high-stakes finance, medicine, and legal prompts; 62% improvement for Luna.
- Free and Go users get GPT-5.6 Luna as default with unlimited text chats and a new Think button for harder questions.
- This chat-tuned Sol is separate from the July Sol used in Codex and ChatGPT Work — those are unchanged.
- OpenAI published first-ever dedicated U18 safety evaluations alongside this release, covering eating disorders, self-harm, and emotional reliance.
- API pricing: Sol at $5/$30, Terra at $2/$12, Luna at $0.20/$1.20 per million input/output tokens — full announcement here.
OpenAI has pushed a meaningful update to ChatGPT that quietly retires the old split between "Instant" and "Thinking" modes. For Plus and Pro users, a freshly tuned version of GPT-5.6 Sol now handles everything from quick replies to deep reasoning under one roof. For free users, GPT-5.6 Luna becomes the new default, and for the first time, text chats are unlimited. This is less a new model launch and more a deliberate push to make the frontier model feel like a single, coherent assistant rather than a patchwork of modes.
One model, one experience
The core problem this update solves is consistency. Previously, switching from a fast Instant response to a Thinking response in ChatGPT could feel like talking to a different model entirely. With this update, the same model now powers both Instant responses and deeper reasoning for Plus and Pro users, creating one consistent experience. The tone, style, and personality stay the same whether you ask a quick question or kick off a multi-step research task.
A new slider lets you choose how much thought ChatGPT puts into each response. Keep it low for quick factual lookups, nudge it up for planning, writing, or code review. This replaces the binary choice between Instant and Thinking, giving you a continuous dial instead of a hard switch.
Fewer hallucinations where it actually matters
The headline number is factual accuracy. In an internal evaluation of financial, medical, and legal prompts requiring factual detail, responses containing at least one factual error were about 62% less common with GPT-5.6 Luna and 68% less common with GPT-5.6 Sol than with GPT-5.5 Instant. OpenAI's