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

Priced per 1M input/output tokens at $1/$6 (Luna), $2.50/$15 (Terra), and $5/$30 (Sol), with 1M token context and 128k output. On Agents' Last Exam, Sol scored 53.6, beating Claude Fable 5 by 13.1 points at ~1/4 the cost. However, Sol trailed Fable 5 on SWE-Bench Pro (64.6% vs 80%), and OpenAI had previously flagged issues with that benchmark.