Report says OpenAI moved Ultrafast workload to Nvidia; Cerebras down about 19.5% that week

A report attributed to CNBC said Cerebras lost a key OpenAI workload to Nvidia, tied to the Ultrafast mode of one OpenAI model. The stock fell 19.5% between September 25 and October 2, 2026, with its sharpest session on September 30, when it dropped 8.9%. Reported insider sales and the lock-up expiry landed the same week, so the drop is not from the report alone.

• Stock down 19.5% from September 25 to October 2, 2026
• Report says an OpenAI Ultrafast workload moved to Nvidia
• OpenAI's share of Cerebras revenue makes the relationship central
• S&P 500 slipped 0.2% over the same period