OpenAI's GPT-5.6 Sol is now public. The company released its new flagship model to general users today, launching alongside two smaller siblings, Terra and Luna, after the U.S. Department of Commerce kept a preview restricted to about 20 trusted partners for two weeks.
The naming strategy is new for OpenAI. This is the first time the company gives names to its models instead of simply using numbers. Sol, Terra, and Luna mark capability tiers that can move on their own cadence. Sol is the flagship, Terra the everyday model OpenAI says matches GPT-5.5 at half the price, and Luna the cheaper option.
Pricing runs $5 and $30 per million input and output tokens for Sol, dropping to $1 and $6 for Luna. (Tokens, for those not in the know, are the smallest unit of information a model can handle. And companies typically price their models on a per token basis for API services) Two new knobs ship with it: a max reasoning effort that lets Sol think longer, and an ultra mode that farms work out to subagents.
For context, Anthropic charges $10/$50 for Claude Fable 5, Google charges $2/$12 for Gemini 3.1 Pro, xAI charges $15/$75 for Grok 4.5.
On the Chinese side: DeepSeek charges $1.74/$3.48 for V4 Pro, and Xiaomi charges just $1/$5 for MiMo v2.5 Pro—placing Sol between the premium U.S. frontier models and China's low-cost challengers.
What the benchmarks showOn Terminal-Bench 2.1—a test of command-line workflows that reward planning, tool use, and iteration, scored as the share of tasks a model completes—Sol in its ultra configuration hit 91.9%, with standard Sol at 88.8%.
OpenAI leaned hardest on cyber. On ExploitBench, which measures how well a model finds and weaponizes software vulnerabilities, Sol matched the restricted Mythos Preview while spending roughly a third of the tokens. OpenAI says Sol still doesn't cross the "Cyber Critical" line in its own risk framework.
Early access was loud. Theo, a well-known developer, AI youtuber and CEO of the AI platform T3 Chat, called Sol "world leading in computer use" and said it fixed the complaints he had with GPT-5.5.
Apparently I'm allowed to talk about GPT-5.6 now?
It's a damn good model. Not quite as "smart" as Fable, but it is incredibly capable. Fixed all the problems I had with GPT-5.5.
It is incredibly determined. Will run for a day without even using a /goal. It understands subagents…
Dan Shipper, whose team at Every tested it for a month, offered the cleaner line: "GPT-5.6 is like a Porsche, Fable is like a warp drive." His read is that Sol is the daily driver and Fable the thing you reach for to cross the galaxy.
GPT-5.6 is like a Porsche, Fable is like a warp drive.
Fable is a different beast. If you need to get…
Researcher Daichi Konno, who got in early, said Sol clearly beats GPT-5.5 and lands near Fable 5, with Anthropic still ahead in writing tasks. His sharper note: Sol's safeguards didn't trip on life-science questions, which he thinks could make it a default for biology work.
GPT-5.6-Solを一通り触りましたが、GPT-5.5より明らかに性能が高く、Claude Fable 5と優劣つけがたい印象です！
1. 文章執筆はFableに軍配が上がる2. 生命科学系の話題に対してもセーフガードが発動しない
