DBT Bureau
Pune, 28 June 2026
OpenAI is beginning a limited preview of the GPT-5.6 series: Sol, its flagship model; Terra, a balanced model for everyday work; and Luna, a fast and affordable model. Terra has competitive performance to GPT-5.5 while being 2x cheaper, and Luna brings strong capability at the lowest cost.
GPT-5.6 Sol launches with OpenAI’s most robust safety stack to date, featuring strengthened protections for higher-risk activity, sensitive cyber requests, and repeated misuse. OpenAI also spent multiple weeks identifying weaknesses, pressure-testing its system, and hardening it against real-world attacks.
OpenAI believes in broad access and plans to make GPT-5.6 Sol, Terra, and Luna generally available in the coming weeks. As part of its ongoing engagement with the U.S. government, the company previewed its plans and the models’ capabilities ahead of the launch. At the government’s request, OpenAI is starting with a limited preview for a small group of trusted partners whose participation has been shared with the government, before releasing the models more broadly.
GPT-5.6 Sol introduces improved reasoning capabilities, a new max reasoning effort mode, and ultra mode, which uses subagents to accelerate complex tasks. The model also achieves state-of-the-art performance on Terminal-Bench 2.1 for coding workflows.
OpenAI said GPT-5.6 uses a layered safety approach that combines model-level safeguards, real-time misuse detection, account-level monitoring, and continuous testing to strengthen protection against evolving threats.
During the preview, GPT-5.6 models are available through the API and Codex for select partners. Pricing starts at $5/$30 (input/output) per 1 million tokens for Sol, $2.50/$15 for Terra, and $1/$6 for Luna. OpenAI also announced more predictable prompt caching and plans to launch GPT-5.6 Sol on Cerebras in July with speeds of up to 750 tokens per second.
