OpenAI Launches the GPT-5.6 Series

Don't Worry About the Vase (Zvi) · rss · 2026-07-14

This is an in-depth review of OpenAI's new GPT-5.6 series: Sol, Terra, and Luna. The author suggests that while both Sol and Fable are highly capable, they serve different purposes: Fable acts as a "smarter partner/architect," whereas Sol is the "workhorse that gets things done." The article also summarizes official claims and community feedback: - **Pricing**: Sol is priced at $5/$30, Terra at $2.50/$15, and Luna at $1/$6; comparisons are drawn to Opus and Fable pricing. - **Coding/Agent capabilities**: OpenAI highlights benchmarks like Agents’ Last Exam, AA Agent Coding Index v1.1, and BrowseComp, claiming leadership across various tasks. - **Internal usage**: OpenAI notes that researchers use GPT-5.6 to accelerate debugging, training system optimization, experiment execution, and result analysis, with rapid growth in internal research-related coding inference and agentic token usage. - **Healthcare evaluation**: Officially, GPT-5.6 performs better at lower costs in medical scenarios, with some blind-tested doctors preferring its responses over those written by humans. - **Safety & Bio/Cyber Risks**: The article mentions OpenAI touched on safety guardrails but provided limited details. Overall, the author concludes that Sol excels at "actually getting things done," especially paired with coding/agentic workflows, while tasks requiring higher intelligence and stronger "planning" still lean towards Fable.

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