Cerebras shares drop 20% as reports surface that OpenAI is turning to NVIDIA for large-scale compute.

Cerebras, a US AI chip company that provides inference services through its own data centers, saw its stock fall nearly 20% this week after research firm SemiAnalysis reported on September 30 that OpenAI will use Nvidia GPUs for the "Ultrafast" mode of GPT-6.1 Sol instead of Cerebras hardware.

The decline adds to the stock's losses since the company's May initial public offering, leaving it down more than half from its post-debut peak.

The move has raised investor concerns about Cerebras' competitive position in AI inference, particularly given its January deal with OpenAI. That agreement was valued at more than US$10 billion and committed Cerebras to supply 750 megawatts of compute through 2028.

Cerebras shares also came under pressure after lock-up restrictions on 19.4 million insider-held shares—about 8% of shares outstanding—expired. SEC filings further show that CEO Andrew Feldman and CTO Sean Lie sold more than US$240 million of Class A stock between August 20 and September 25 under trading plans adopted shortly after the IPO.