Cerebras Stock Decline: Nvidia Report and Share Unlocks

Cerebras stock fell nearly 20% in the week ending October 2, 2026, reaching its lowest price since the company’s May IPO. Two pressures converged: a report that Nvidia would handle a particular OpenAI inference workload, and the expiration of restrictions on some insider shares. The first raised questions about workload allocation; the second made more shares eligible for sale. Neither, by itself, establishes that Cerebras has lost its broader OpenAI relationship or that every unlocked share was sold. CNBC reported the weekly decline and the two pressures.

One reported workload, not an ended partnership

Research firm SemiAnalysis reported on September 30 that OpenAI would use Nvidia GPUs, rather than Cerebras hardware, for the “Ultrafast” mode of GPT-6.1 Sol. That is a specific reported deployment choice, not evidence that OpenAI has moved all inference away from Cerebras. CNBC described Cerebras as a provider of custom inference chips that leases computing capacity from its own data centers as a cloud service. The report concerned the named GPT-6.1 Sol mode.

The distinction matters because Cerebras’ OpenAI relationship is larger than that one workload. The company said in January that its agreement with OpenAI was worth more than $10 billion and covered 750 megawatts of computing power through 2028. After speculation about the relationship, OpenAI CEO Sam Altman called Cerebras a close partner and described a deep engagement focused on speed. The January agreement and Altman’s response were reported by CNBC.

The stock closed Friday at $166.43, and CNBC put Cerebras’ market capitalization at just over $39 billion, compared with $95 billion at the close of its first trading day. The reaction suggests investors are attentive to whether major inference workloads go to Cerebras or Nvidia, even as the public evidence describes an allocation decision for one mode rather than the end of a partnership. Those closing figures and market-cap comparisons.

Lockup expiration added potential supply

A separate near-term pressure came from the IPO lockup. Up to 19.4 million shares held by directors, officers, employees and other holders became unlocked on Wednesday, equal to about 8% of total shares outstanding. Earlier, up to 14.6 million shares had become eligible for sale every two weeks starting August 19. Unlocking shares makes them eligible to be sold; it does not mean every share was sold. CNBC reported the share figures and schedule.

CEO Andrew Feldman and CTO Sean Lie sold more than $240 million of Class A shares between August 20 and September 25 under trading plans adopted shortly after the IPO. Those sales took place before the latest unlock date, so they should not be conflated with sales of all 19.4 million newly eligible shares. The reported sales covered that earlier period.

For Cerebras, the market is weighing two different things: which hardware OpenAI uses for a particular inference mode, and how much stock newly eligible holders may choose to sell. Altman’s reassurance addresses the partnership question, but it does not specify how workloads will be allocated across the companies’ hardware.