Cerebras stock hits post-IPO low, down 20% for week on Nvidia report and lockup

Cerebras Systems closed Friday at $166.43, ending a week in which the stock slid nearly 20% to its lowest price since the chipmaker's May debut on the Nasdaq. The shares are now down by more than half from the pop that followed the IPO. The stock recovered slightly after the closing bell, rising almost 3% in extended trading.

The decline followed a Wednesday post on X from research firm SemiAnalysis stating that OpenAI will use Nvidia graphics processing units, rather than Cerebras hardware, to power the "Ultrafast" mode of its GPT-6.1 Sol model. The report struck at a core part of the Cerebras investment case: that it provides customers a viable alternative to Nvidia for running AI inference.

A second source of pressure was the expiration of post-IPO restrictions on insider shares. According to the company's prospectus, up to 19.4 million shares held by directors, officers, non-executive employees and non-employee holders unlocked on Wednesday, equal to 8% of total shares outstanding. Before that, up to 14.6 million shares had been unlocking for sale every two weeks since Aug. 19. CEO Andrew Feldman and CTO Sean Lie sold over $240 million of Class A shares between Aug. 20 and Sept. 25 under trading plans adopted shortly after the IPO, and other executives have also sold shares valued in the millions.

Cerebras builds dinner plate-sized ASICs — custom microchips designed for inference workloads — and leases them from inside its own data centers as a cloud service. In January, the company struck a deal worth more than $10 billion to supply OpenAI with 750 megawatts of computing power through 2028. Cerebras closed its first day of trading at a $95 billion market cap, just shy of the group of companies including Meta, Alibaba and SpaceX that finished their debuts above $100 billion. Its market cap now sits at just over $39 billion.

Friday's after-hours gain came after OpenAI CEO Sam Altman responded to what he called "speculation about our partnership with Cerebras" in a post on X. "Cerebras is a close partner, and we have a deep engagement pushing on the frontiers of speed," Altman wrote. The loss of a high-profile OpenAI workload to Nvidia comes as McKinsey projects inference will surpass training as the dominant workload in AI data centers by the end of the decade, and as additional shares are set to reach the market over time.