OpenAI launches GPT-5.6 family: Sol, Terra, Luna, pushing performance per dollar

GPT-5.6 系列模型发布：Sol、Terra、Luna

OpenAI released the GPT-5.6 family on July 9: flagship Sol, balanced Terra, and low-cost Luna. Sol scores 53.6 on Agents' Last Exam, beating Claude Fable 5 by 13.1 points at roughly one-quarter the estimated cost. A new `ultra` mode coordinates parallel agents to cut latency and lift scores on BrowseComp and Terminal-Bench 2.1. Sol also tops the Artificial Analysis Coding Agent Index at 80, using less than half the output tokens of Fable 5. Terra and Luna outperform Fable 5 at about one-sixteenth the cost. OpenAI ran extensive red-teaming and automated testing, and hardened safeguards with external partners during a preview period.

Why it matters: OpenAI's flagship model refresh with three variants, a direct benchmark win over Claude Fable 5 on long-horizon agent tasks, and a claimed 4x cost advantage. This is the most significant model launch of 2026 so far and will immediately reshape agent workflow decisions.