Overview
- OpenAI announced the changes on Thursday, Aug. 6, and began rolling them out the same day with wider Free/Go availability following across the week.
- Free and Go users will get GPT‑5.6 Luna as the default model and will receive unlimited text chats next week with a new Think button to request higher‑reasoning answers.
- Plus and Pro subscribers already have access to a ChatGPT‑tuned GPT‑5.6 Sol and a reasoning slider that lets them choose how much compute and time the model spends on a reply.
- OpenAI said internal evaluations show Sol produces about 68% fewer responses containing at least one factual error and Luna about 62% fewer compared with GPT‑5.5 Instant, though full reproducible benchmarks were not released.
- The Sol update applies only to consumer ChatGPT chat and does not change the Sol versions used by Codex or ChatGPT Work, and OpenAI says safety and abuse guardrails and non‑text limits (files, images, voice, image generation) remain in place.