US AI Stocks Tumble as Semiconductor Index Drops 6% on Capex Concerns

US AI-related stocks suffered a sharp selloff on October 22, with the Philadelphia Semiconductor Index falling more than 6% intraday. Nvidia, AMD, and Meta were among the major decliners as investors grew more concerned about whether huge AI capital expenditures would deliver returns, while rising oil prices added to risk-off sentiment.

Chipmakers led the decline. Nvidia slid more than 4%, AMD fell about 8%, and semiconductor equipment makers Lam Research and KLA dropped over 10% and 9% respectively. Storage, optical communications, and AI infrastructure stocks also came under pressure: Micron fell 4.6%, SanDisk dropped nearly 7%, while Credo, Coherent, and Lumentum each fell around 10%. AI cloud provider CoreWeave lost nearly 9%, and Dell, Super Micro, and Oracle also declined.

Meta fell more than 7% at one point. Although the company beat third-quarter revenue and profit estimates, it raised its 2026 capital expenditure guidance to $135-145 billion and disclosed future spending commitments of up to $825 billion, fueling concerns about the scale, funding needs, and payback period of AI investment. Its five-year credit default swap spread hit a record high.

The selloff reflects a broader reassessment of the costs and returns of AI investment. Lam Research's cautious outlook due to supply constraints added to worries about revenue timing. Meanwhile, an attack in Saudi Arabia pushed Brent crude above $110 per barrel, heightening inflation concerns and driving funds toward safe-haven bonds. The episode signals that the AI trade is entering a phase where investors are focusing more on earnings delivery, capital efficiency, and financing sustainability.