OpenAI has introduced GPT-5.6, a new family of large language models led by its flagship Sol model, alongside Terra and Luna variants built for different performance and cost requirements. However, the company is limiting the initial rollout to a small group of trusted U.S.-based partners after a request from the U.S. government.
The GPT-5.6 series introduces a new naming system, with Sol representing the highest capability tier, Terra offering GPT-5.5-level performance at half the cost, and Luna targeting lower-cost, faster AI applications. OpenAI said the models will become generally available through ChatGPT, Codex, and its API in the coming weeks.
GPT-5.6 Sol also introduces a new maximum reasoning mode that gives the model more time to solve complex tasks. OpenAI is also launching an Ultra mode that uses subagents to tackle sophisticated workflows beyond the capabilities of a single AI agent.
The company said GPT-5.6 Sol delivers its strongest performance yet in coding, biology, and cybersecurity while introducing its “most robust safety stack to date.”
Smarter models arrive
According to OpenAI, GPT-5.6 Sol achieved a new state of the art on TerminalBench 2.1, a benchmark for command-line coding workflows. In biology, the company said the model outperformed GPT-5.5 on GeneBench v1 while using fewer output tokens.
OpenAI also highlighted gains in cybersecurity. On ExploitBench, GPT-5.6 Sol matched the performance of Anthropic’s Mythos Preview while using roughly one-third of the output tokens. On ExploitGym, developed by researchers at UC Berkeley with OpenAI and other frontier AI labs, all three GPT-5.6 models showed improved cyber capabilities as reasoning increased.
Despite those gains, OpenAI said GPT-5.6 Sol does not cross the Cyber Critical threshold under its Preparedness Framework.
“GPT-5.6 Sol is better at helping people find and fix vulnerabilities than reliably carrying out end-to-end attacks,” the company said.
The company also introduced a layered safety system that combines model-level protections, real-time misuse detection, account-level monitoring, differentiated access, and extensive automated and human red-teaming. OpenAI said it dedicated more than 700,000 A100-equivalent GPU hours to automated red-teaming to uncover jailbreak techniques before release.
Phased rollout begins
Unlike previous launches, GPT-5.6 will initially be available only to a select group of trusted partners.
“As part of our ongoing engagement with the U.S. government, we previewed our plans and the models’ capabilities ahead of today’s launch,” OpenAI said.
“At their request, we are starting with a limited preview for a small group of trusted partners whose participation has been shared with the government, before releasing more broadly.”
OpenAI said it does not want government previews to become standard practice.
“We don’t believe this kind of government access process should become the long-term default,” the company said, adding that it is taking the temporary step while working with the administration on a repeatable framework for future frontier AI releases.
CEO Sam Altman echoed that view on X, saying the government requested a limited preview instead of the broader launch OpenAI had planned. He added that the company hopes to make GPT-5.6 widely available as quickly as possible while developing a transparent process for future releases.
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With over a decade-long career in journalism, Neetika Walter has worked with The Economic Times, ANI, and Hindustan Times, covering politics, business, technology, and the clean energy sector. Passionate about contemporary culture, books, poetry, and storytelling, she brings depth and insight to her writing. When she isn’t chasing stories, she’s likely lost in a book or enjoying the company of her dogs.