The AI stock boom could crack well before companies stop pouring money into data centers, and that's a warning sign for investors.

• The AI trade is being compared to the dot-com bubble, and history says the top comes early.
• Back in 2000, the Nasdaq peaked in March, but the companies building fiber optic networks kept spending billions into 2001.
• The stock market fell a full year before that spending stopped, so waiting for CapEx to dry up is the wrong signal.
• The market turns when enough investors simply stop believing the story, not when the numbers change.
• The first company Wall Street rewards for cutting AI spending will give every other CEO cover to do the same.

Outlook: Watch for the first big spending cut to be cheered rather than punished — that could mark the moment the AI bubble starts to deflate.