Cerebras Systems is trading down 5.15% at $173.85 amid supply and customer concerns. - September 30 lockup release made approximately 19.4 million shares sale-eligible; officer Form 144 notices cover about $84.3 million in stock, indicating planned, not necessarily completed, sales. - Investors also weigh an unverified report that OpenAI’s newest fast model uses Nvidia GPUs rather than Cerebras hardware. - No fresh company announcement directly explains October 1; coverage links pressure to September 30 developments; indexes fell modestly.