Billionaire investor Mark Cuban says AI stocks and the broader market are in a bubble, which is bad news for anyone piling into AI trades expecting a smooth ride up.

• Cuban calls today's market a "bubble," though different from the 2000 dot-com crash — he says stocks now trade like meme stocks, swinging wildly on small news instead of real company value.
• Tech giants building AI data centers are borrowing more money than they're making, and rising interest rates could make that debt harder to pay off.
• He warns the U.S. could slide into a broader debt bubble, since the government and big tech companies are both borrowing heavily at the same time, and the country is already paying huge sums just in interest each year.
• He doesn't think AI itself is "smart" — it can't reason about consequences or ethics, so he sees AI more as a productivity boost than a replacement for human judgment, which cushions (but doesn't remove) the economic risk.
• He's personally playing defense by holding more cash and spreading money across different countries rather than going all-in on AI stocks.

Outlook: Cuban expects a shakeout is coming for over-leveraged AI companies, but says it's unclear which firms (maybe Nvidia, maybe others) end up the long-term winners once the bubble deflates.