Cerebras' stock rebounded by 9% after OpenAI CEO Sam Altman gave reassurance that the two companies are close partners days after a report cast doubt on their relationship, causing the chipmaker's stock to drop 20% last week. The episode raises concerns over its current concentration on a few large customers.
On September 29, SemiAnalysis claimed in a social media post that OpenAI's forthcoming GPT-6.1 Sol Ultrafast mode would use Nvidia GPUs rather than Cerebras chips. Yahoo Finance reported that this saw the chipmaker's stock drop more than 20% over the next few days, hitting a low of US$165 compared with a pre-slide price of US$214.
SemiAnalysis later clarified that OpenAI uses Cerebras chips for ultrafast inference on other models and sells API access to customers such as Jane Street. While this post reportedly stopped the slide for a time, it continued to fall until Altman sought to ease concerns 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," he wrote on October 3. This boosted the chipmaker's stock by 9%, according to CNBC.
Two other events happened on September 30, according to Yahoo Finance. One was that a tranche of shares was released from the post-IPO lockup, which meant that around 19.4 million shares could be sold. The other was that two company executives filed plans to sell some of their stock, although these totaled only 428,500 shares.
Cerebras' market capitalization has plunged from US$95 billion at its May debut to around US$43 billion. While it has secured a few major deals, its high concentration around a few large customers means that any doubts about its relationships with them could shake investors.
CNBC cited Citi analysts, who said that their view of the company's revenue outlook for 2026 to 2028 has not changed. They had already expected that AI labs would first roll out frontier models on internal chips before using Cerebras' cloud on them, but noted that its high valuation means that stabilizing gross margins will be important to the stock's performance.
Cerebras is known for making the world's largest chips, which are called Wafer Scale Engines (WSEs), and it is angling itself as a competitor to Nvidia's GPUs. Its WSE-3 chips support both AI training and inference, and the company claims its hardware can complete inference tasks faster than Nvidia's chips.
OpenAI, one of its main anchor customers, signed an agreement with Cerebras in December last year for more than US$20 billion in inference computing capacity and related services over several years and has already used Cerebras systems to serve its models. It also has a deal to deploy its chips in AWS data centers, which will be paired with Trainium3 chips. Cerebras said that the revenue impact of this should be expected in 2027.
Article edited by Ysi Chen
