The high-performance AI model "Union Alpha," which was being released as a "stealth model" with its developer concealed on services such as "OpenRouter," has been identified as unbiased.ai's new model "Pareto 26.9."
Model ReleasesPricing & LimitsUnion Alphaunbiased.aiPareto 26.9
Mysterious AI "Union Alpha" Released on OpenRouter Identified as unbiased.ai's New Model "Pareto 26.9"
This article is a translation. Read the Japanese original
Union Alpha is a multimodal model released on OpenRouter on September 16, 2026. It is built for research, coding, and agent workflows, and features a context window (the length of information the model can process at once) of 260,000 2144 tokens. According to benchmark scores, it is said to demonstrate performance comparable to GPT-6 Astra and Claude Fable 5.1.
According to the model's X account, the decision to release it anonymously was made to monitor user reactions and reflect those findings in the official release scheduled for October 10, 2026.
However, immediately following its release, a surge in usage caused demand to reach scales of billions of tokens per minute, resulting in processing speeds falling below practical levels. Although processing capacity was tripled with the cooperation of AWS, it could not keep up with the demand, and the initially planned 1-week free trial ended after just one day.
Transitioning to paid access is currently underway, with pricing set at 2.50 dollars per 1 million input tokens, 7.50 dollars per 1 million output tokens, and 0.25 dollars for cache. Regarding this pricing, the model side explained it is "less than one-fourth the list price of Astra" (1 fraction).
Sources
- 謎の高性能AIモデル「Union Alpha」が公開される、GPT-6 AstraやClaude Fable 5.1と同等ベンチマークスコア （GIGAZINE、2026-09-18）