Cerebras Systems shares surged as much as 8% on Monday, rebounding from an all-time low close on Friday, after OpenAI CEO Sam Altman publicly backed the AI chipmaker on social media.
Altman posted on X late Friday evening that "Cerebras is a close partner, and we have a deep engagement pushing on the frontiers of speed." The statement landed just after Friday's close, when Cerebras shares had finished at $166.43 — their lowest close since the company's May IPO, down nearly 20% for the week.
Cerebras (CBRS) traded around $179.29 in early Monday trading, up 7.7%, and rose as much as 8.1% at its peak. Even with the bounce, the stock remains just below its $185 IPO price.
The relief rally followed a brutal five-session stretch in which the shares fell 15%. The trigger was a report from semiconductor research firm SemiAnalysis claiming that OpenAI's "Ultrafast" mode for its latest GPT-6.1 Sol model is powered by Nvidia GPUs at low batch sizes — not by Cerebras hardware.
Investors read that as a sign that OpenAI, by far Cerebras' biggest customer, might be shifting high-speed inference workloads toward Nvidia. Cerebras' core pitch is unusually large AI chips that run models at extreme speeds, so the report struck directly at its growth story.
Altman's post did not address the SemiAnalysis report in detail, nor did it confirm the status of the 750-megawatt deployment agreement the two companies signed in January. Under that deal, valued at $10 billion, Cerebras is to supply ChatGPT with 750 megawatts of computing power through 2028. OpenAI is Cerebras' largest customer by revenue backlog.
That concentration is exactly what worries Wall Street. Barron's has previously flagged the stock's high valuation and its dependence on OpenAI as the key risks. Cerebras opened trading at $350 following its May IPO, but early enthusiasm faded as earnings failed to impress.
The selloff drew at least one contrarian. Paul Meeks, head of technology research at Freedom Capital Markets, upgraded Cerebras to Buy from Hold on Friday, arguing the decline had gone too far. "The key for this stock is can they add the necessary capacity on time and on budget," he wrote, adding that his team is watching for execution risk to be "squeezed out."
JR Research kept a Hold rating, acknowledging that the inference opportunity is large enough that Cerebras should not be written off, but pointing to customer concentration and substantial execution risk as the overhangs.
What comes next is straightforward to track: whether Cerebras can deliver new capacity on schedule, and whether OpenAI's Ultrafast workloads eventually run on Cerebras chips. Altman's one-liner steadied the stock for a day. Ending the slide since the IPO will take hardware, not words.