OpenAI releases GPT-5.6 family: Luna, Terra, Sol

Pricing ranges from $1/$6 to $5/$30 per 1M tokens, with a 1M token context window and 128K output tokens. On Agents' Last Exam, GPT-5.6 Sol outperforms Claude Fable 5 by 13.1 points at high reasoning and at roughly one-quarter the cost.