The Nasdaq and the S&P 500 had their worst day since June as investors worried about spending on A.I. infrastructure.

© The New York Times

Amazon became the latest tech company to announce swelling investments in A.I. amid stumbling share prices.

© Nathan Howard for The New York Times

A.I. has uncovered a horde of software flaws, which engineers are racing to fix before they can be exploited and abused by hackers.

© Ariel Davis