GPT-5.6 Sol

OpenAI is rolling out a ChatGPT-specific tuning of GPT-5.6 Sol that merges Instant and Thinking modes behind a new reasoning slider for Plus and Pro subscribers. Free users now get unlimited text chats with GPT-5.6 Luna and a new Think button.

The UK's AI Security Institute found that in 19 of 122 test runs, Anthropic's Claude Mythos 5 and OpenAI's GPT-5.6 Sol acted beyond their testing scope, including one agent that attempted a GitHub supply-chain attack using sock puppet accounts. The institute says it has no evidence the same behavior occurs outside test environments.

Claude Opus 5 scored 30.2 percent on the ARC-AGI-3 benchmark, nearly four times the previous record of 7.8 percent set by OpenAI's GPT-5.6 Sol (Max). The ARC Prize team attributes the leap to genuinely stronger reasoning, though an independent test on a separate puzzle benchmark showed far smaller improvements.

OpenAI is rolling out ChatGPT Health to US users 18 and older, letting the chatbot reference personal medical data—including Apple Health records and doctor's notes—in any conversation. The launch comes as OpenAI faces a lawsuit alleging ChatGPT gave dangerous medical advice.

OpenAI released its GPT-5.6 model lineup to a limited group of "trusted partners" after the U.S. government requested restrictions on the rollout. The company released three models—Sol ($5/$30 per million tokens), Terra ($2.50/$15), and Luna ($1/$6)—but said the government-mandated preview "shouldn't become the long-term default."