OpenAI Begins Limited Preview of GPT-5.6 Series with Sol, Terra, and Luna Models

OpenAI has begun a limited preview of its GPT-5.6 model family, which includes the Sol, Terra, and Luna variants, announced on its website. The preview is available to a small group of trusted partners before a broader rollout in the coming weeks.

GPT-5.6 Sol is described as the company’s most capable model, designed for advanced reasoning and cybersecurity tasks. It introduces a new max reasoning effort feature to allow deeper analysis and an ultra mode that coordinates subagents for complex tasks. Terra is positioned as a balanced model for general work, offering similar performance to GPT-5.5 at half the cost, while Luna provides faster responses at the lowest price tier.

All three variants include strengthened safeguards against misuse, with layered protections that combine model-level training, real time monitoring, and account-based review. OpenAI said it dedicated over 700,000 GPU hours to automated red teaming to identify universal jailbreaks and improve robustness against adversarial attacks.

Pricing for the models is set per one million tokens: Sol at $5 for input and $30 for output, Terra at $2.50 and $15, and Luna at $1 and $6. During the preview, access is available through the API and Codex, with plans to expand to ChatGPT users soon. OpenAI also plans to launch GPT-5.6 Sol on Cerebras hardware in July, allowing processing speeds of up to 750 tokens per second.