Investors should be on high alert for more AI-stock weakness after DeepSeek disrupted markets and sent shares tumbling.

Operator, a new computer-using tool from OpenAI, is brittle and occasionally erratic, but it points to a future of powerful A.I. agents.

OpenAI CEO Sam Altman is a billionaire, thanks to his investments in technology companies like Reddit, Stripe, Airbnb, and more. Here's how Altman made his money.