OpenAI Previews GPT-5.6 With Three Tiers

OpenAI has begun a limited preview of GPT-5.6, its next-generation model series split into three tiers: Sol, Terra, and Luna. Sol is the flagship with gains in coding, biology, and cybersecurity. Terra matches GPT-5.5 performance at half the cost. Luna is the fast, low-cost option. Broader access is planned in coming weeks.