Improving GPT‑5.6 Sol in ChatGPT—and expanding access to GPT-5.6 Luna for free users

ChatGPT now ships an improved GPT-5.6 Sol with better accuracy and consistency, while OpenAI expands access so free users can use GPT-5.6 Luna and get unlimited everyday chats with that model.

On the product side, the change splits everyday use from higher-stakes work. GPT-5.6 Sol is the upgraded ChatGPT option aimed at more reliable answers. GPT-5.6 Luna is the free-tier model with unlimited everyday chats, so light use no longer depends on paid capacity for routine conversation.

For engineers and builders, accuracy and consistency on Sol matter when ChatGPT is part of a workflow—drafting specs, checking reasoning, or iterating on code—because fewer drifty or contradictory replies reduce rework. Unlimited everyday chats with Luna lower the friction of using ChatGPT for quick questions, brainstorming, and informal checks without burning through a free quota.

The move keeps OpenAI’s free and paid ChatGPT tiers more clearly separated by model: Sol for improved quality, Luna for open-ended daily access. That is a practical response to free-user demand and to competition that already offers generous free chat, while still reserving the stronger Sol experience for users who need higher reliability.

Watch whether free users stay on Luna for routine work and only step up when they need Sol’s accuracy and consistency, and whether Sol’s reliability gains show up in real multi-step tasks rather than only in short single-turn answers.