The heaviest weight on the market was Nvidia, whose chips are powering much of the move into AI. It sank 3.5%.

Rishi Jaluria of RBC Capital Management, a subsidiary of the Royal Bank of Canada, has a $45 price target on Palantir's stock. So the stock still needs to tumble about 70% more to reach his price target. That's a long way to fall for a proven AI leader, but is that a legitimate price target?

U.S. stock indexes ended mixed after Nvidia, Palantir and other superstar stocks pared most of their steep losses from the morning.