OpenAI launches GPT-5.6 with three model tiers: Sol, Terra, Luna

GPT-5.6 Sol scores similarly to Claude Fable 5 on GDPval-AA v2, while delivering top performance at nearly half the cost on FrontierCode 1.1 Extended. The family includes Sol for agentic work, Terra for everyday tasks, and Luna for high-volume speed, rolling out in ChatGPT, Codex, and the API.