GPT-5.6 Sol gets reasoning slider; Luna becomes default for free ChatGPT users
OpenAI
OpenAI updated GPT-5.6 Sol with a new reasoning-effort slider for Plus/Pro users on web, mobile, and desktop, and began rolling out GPT-5.6 Luna as the default model for Free and Go tier users with unlimited text chats. OpenAI reported factual-error rates roughly 62-68% lower than GPT-5.5 Instant on financial, medical, and legal test prompts.
Why it matters
Pushes a smaller, cheaper model to the free tier while giving paid users finer control over latency vs. reasoning depth, continuing OpenAI's shift toward tiered model routing instead of a single flagship.
Importance: 3/5
Notable product change affecting all ChatGPT tiers: unlimited free chats plus a new reasoning control for paid users.