OpenAI GPT-5.6 Targets Anthropic's Claude Mythos 5

OpenAI has launched GPT-5.6, a three-tier model series comprising Sol, Terra, and Luna, designed to compete with Anthropic's Claude Mythos 5. The lineup introduces two new modes: a max setting for deeper reasoning and an ultra mode enabling parallel subagents. Sol scored 91.9% on TerminalBench-2.1 with ultra mode enabled, edging past Claude Mythos 5's 88%. Sol is priced at $5 per million input tokens and $30 per million output tokens, with Terra and Luna offering significant discounts. OpenAI is initially limiting access to trusted partners at the U.S. government's request, with general availability expected within weeks.