Cybersecurity shares rose 10% to 15% while semiconductor stocks fell about 5% on Sept. 14, as calls by Anthropic and OpenAI to slow AI development raised concerns about demand for computing infrastructure. The rally extended across software, with a median gain of 4.5% among companies tracked by Tomasz Tunguz. Of the 87 stocks in his index, 80 advanced and 12 gained at least 10%.

Nvidia fell 2.8% and Oracle declined 4.3%. Earlier, SoftBank closed down 11% in Japan, and its US depositary receipts dropped 12.5% before the US market opened. CoreWeave fell 9% in premarket trading, while Nasdaq futures lost 1.6%. The infrastructure selloff reflected concerns that slower development of advanced models could reduce demand for GPUs, memory, networking and data centers.

Anthropic CEO Dario Amodei urged slower capability improvements over the weekend so safety work could keep up, winning support from OpenAI CEO Sam Altman and Elon Musk. Anthropic and OpenAI committed to giving independent evaluators access comparable to employees to assess their systems. Amodei said the proposal did not mean halting training or technical progress. Asked on CBS whether Anthropic would stop releasing more advanced models, he said: “It doesn't mean that. What it means is that we need to make sure that every generation of models that we release is properly tested.”