01:44 PM EDT, 08/13/2026 (MT Newswires) -- Cerebras Systems ( CBRS ) said Thursday it is powering Ultrafast mode, a new service tier in OpenAI's application programming interface for GPT-5.6 Sol.

Ultrafast runs GPT-5.6 Sol at up to 750 output tokens per second and up to 14 times faster than Standard processing, the company said.

GPT-5.6 Sol Ultrafast answered the full 2500-question set for Humanity's Last Exam, a benchmark including graduate-level chemistry, economics and literature, in just over 11 hours, achieving comparable accuracy nearly seven times faster than Claude Fable 5, the company added.

Shares of Cerebras Systems ( CBRS ) were down nearly 14% in Thursday trading.

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