OpenAI has started a limited preview of its GPT-5.6 model family, including GPT-5.6 Sol, GPT-5.6 Terra, and GPT-5.6 Luna. The company describes Sol as its flagship model, Terra as a balanced option for everyday work, and Luna as a faster, lower-cost model for high-volume tasks. OpenAI announced the rollout through an official post on its website and on X.

Introducing a limited preview of GPT-5.6 Sol, our next generation frontier model, as well as GPT-5.6 Terra, a balanced model for efficient, everyday work, and GPT-5.6 Luna, a fast and affordable model for high-volume work.https://t.co/OoM83SyISN

— OpenAI (@OpenAI) June 26, 2026

The release is limited for now. OpenAI said the models are initially available through the API and Codex to a small group of trusted partners and organizations, with broader access planned across ChatGPT, Codex, and the API in the coming weeks. The company also said the restricted launch follows discussions with the U.S. government, which requested a limited preview before a wider release.

What OpenAI announced

OpenAI said GPT-5.6 Sol is its strongest model yet and introduced a new naming structure where the number marks the generation and Sol, Terra, and Luna represent separate capability tiers. The company said Terra offers performance competitive with GPT-5.5 at half the cost, while Luna is positioned as the most cost-efficient option in the lineup. OpenAI also said GPT-5.6 Sol sets a new state of the art on Terminal-Bench 2.1, with Sol scoring 88.8 percent and Sol Ultra reaching 91.9 percent in its published benchmarks.

Image credit: OpenAI

OpenAI also introduced new reasoning settings with GPT-5.6. The company said a new max reasoning effort setting gives Sol more time to reason, and an ultra mode uses subagents for more complex work. OpenAI also tied the launch to cybersecurity use cases, saying Sol is its most capable model yet for security research and vulnerability work.

Pricing and recent context

Pricing starts at $5 per 1 million input tokens and $30 per 1 million output tokens for Sol, $2.50 input and $15 output for Terra, and $1 input and $6 output for Luna. OpenAI also said GPT-5.6 introduces explicit cache breakpoints, a 30-minute minimum cache life, and cache writes billed at 1.25 times the uncached input rate. The company added that GPT-5.6 Sol will launch on Cerebras in July at up to 750 tokens per second for select customers as capacity expands.

The announcement follows a series of recent OpenAI updates. On June 18, the company published posts about new usage analytics and updated spend controls for enterprises and improving health intelligence in ChatGPT. Earlier, on June 14, it also introduced the OpenAI Partner Network.