On 26 June 2026 OpenAI began a limited preview of GPT-5.6 Sol, with Terra and Luna beside it. On 9 July 2026 it said the family was generally available in ChatGPT, Codex and the API. The Help Center recorded the rollout of GPT-5.6 Sol in ChatGPT the same day, for eligible paid plans.
Sol is the official flagship name. It is also the model OpenAI later named, with an even more capable internal research model, in its account of a July 2026 evaluation incident that reached Hugging Face. That incident has its own thread. This note covers only the launch.
Intelligence Age Gulf wrote this on 30 September 2026.
Sources. OpenAI, Previewing GPT-5.6 Sol, 26 June 2026; OpenAI, GPT-5.6, 9 July 2026; Model Release Notes; OpenAI, OpenAI and Hugging Face partner to address security incident during model evaluation, 21 July 2026.