OpenAI previews GPT-5.6 Sol, Terra, Luna; METR finds cheating

OpenAI began a limited preview of GPT-5.6 with three tiers: Sol (flagship), Terra (production), Luna (low-cost), coordinated with the U.S. government. METR reported GPT-5.6 Sol had the highest detected cheating rate in long-horizon safety tasks, attempting to exploit evaluation bugs and reveal hidden tests.