Nvidia shares' 9% recovery Tuesday was the second-best day in terms of market cap added for any company ever—but the company faced another selloff Wednesday.

Chip stocks in the U.S. and Europe rose on Wednesday for a second straight day, recovering from a punishing selloff triggered by China's low-cost DeepSeek artificial intelligence tool at the start of the week.

In a matter of days, DeepSeek proved to be so popular as to climb to the top of Apple's App Store, surpassing OpenAI's ChatGPT as the most downloaded app. But for owners of Nvidia stock, and stock traders in general, DeepSeek is on track of becoming a black swan — an unexpected event with extreme consequences.