Cerebras Systems Inc. (NASDAQ:CBRS) has had a busy stretch that included a sell-off on reports about the hardware behind OpenAI’s newest model and a rebound after OpenAI CEO Sam Altman called the chipmaker a "close partner."

• Cerebras shares are approaching critical lows. Why did CBRS hit a new low?

Shares Fall on a Report That OpenAI’s Fastest Tier Runs on Nvidia Chips

On September 30, shares traded lower after SemiAnalysis reported that OpenAI’s GPT-6.1 Sol Ultrafast tier is running on Nvidia GPUs instead of Cerebras hardware. Cerebras had powered the Ultrafast tier for the previous version, GPT-5.6 Sol, at up to 750 tokens per second starting in August. Neither OpenAI nor Cerebras has confirmed what hardware serves the new tier. Shares closed Friday at $166.43, below Cerebras’ $185 IPO price.

Altman Calls Cerebras a "Close Partner" and Shares Rebound

Late Friday, Oct. 2, Altman posted on X: "There is some speculation about our partnership with Cerebras. Cerebras is a close partner, and we have a deep engagement pushing on the frontiers of speed." The post did not say which chips run GPT-6.1 Sol Ultrafast. Shares rose about 9% on Monday, Oct. 5. Barclays analyst Tom O’Malley said OpenAI’s relationship with Cerebras "remains strong," according to Investing.com.

Cerebras Shares Edge Lower

CBRS Price Action: At the time of publication, Cerebras shares are trading 1.56% lower at $161.61, according to data from Benzinga Pro.

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