OpenAI has launched limited access to its GPT-5.6 Sol, Terra, and Luna models through API and Codex for a select group of trusted partners. The company initiated the preview at the request of U.S. authorities.
OpenAI plans to make GPT-5.6 Sol, Terra, and Luna widely available in the coming weeks. Before the launch, OpenAI presented the models’ plans and capabilities to the U.S. government. At the request of U.S. authorities, the initial phase is a limited preview, and information about partners has been shared with the government. OpenAI noted that this arrangement is not intended as a long-term norm.
Within the company, Sol is considered the flagship of the lineup, Terra is described as a “workhorse” model for everyday tasks, and Luna is a fast and cost-effective option. According to OpenAI, Terra offers performance comparable to GPT-5.5 at half the cost. Luna is described as the most affordable model in the lineup.
OpenAI also stated that GPT-5.6 Sol is the company’s most powerful model to date. The series includes a max reasoning mode, allowing Sol more time for in-depth task processing, and an ultra mode, which uses sub-agents to accelerate complex work.
According to OpenAI, Sol set a new record in Terminal-Bench 2.1 for command-line tasks, outperformed GPT-5.5 on GeneBench v1 with fewer tokens, and was competitive with Mythos Preview on ExploitBench, using about one-third of the output tokens.
In ExploitGym tests, the company claims all three models improved results in cyber tasks as the depth of reasoning increased.
OpenAI stated that GPT-5.6 Sol, Terra, and Luna have the strongest security stack in the lineup. According to the company, GPT-5.6 Sol does not cross the Cyber Critical threshold within the Preparedness Framework. In tests with Chromium and Firefox, the model identified bugs and exploitation primitives but could not autonomously create a fully functional exploit under verified conditions.
To test security, OpenAI utilized more than 700,000 GPU-hours equivalent to A100 for automated red teaming, aimed at finding universal jailbreaks. During the preview phase, multi-level measures are in place, including model-level restrictions, real-time checks, account-level signals, monitoring, and enforcement measures. The company warned that some requests may be blocked or take longer to process due to additional verification.
OpenAI also explained the new naming scheme: the number indicates the model generation, while Sol, Terra, and Luna represent capability levels. The price per 1 million tokens is $5 for input and $30 for output for Sol, $2.50 and $15 for Terra, and $1 and $6 for Luna.
In July, OpenAI plans to launch GPT-5.6 Sol on Cerebras at speeds of up to 750 tokens per second. Access at this stage will also be limited to select clients as the company expands its capacity.
Earlier in June, OpenAI confidentially filed an S-1 form with the U.S. Securities and Exchange Commission for a potential initial public offering.
