Apple shares plunged over 9% after the iPhone maker issued a weaker-than-expected outlook, warning that AI-driven component shortages are straining global supply chains. The stock is on track for its worst one-day fall in more than six years, putting nearly $500 billion in market value at risk and lifting Nvidia's valuation lead.

Share price rally driven by strong product demand as well as decision to sit out AI spending race, amid wider tech sell-off

The jockeying between Apple and Nvidia reflects a debate about the future of AI that has preoccupied investors this summer.