At the end of June, Lone Pine Capital’s flagship hedge fund was up 44% for the year. Three months later, almost all of it was gone after its bets on AI stocks turned.

The fund, called Cypress, finished September up just 0.6%, Bloomberg reported. Lone Pine manages about $19 billion. It had posted double-digit gains three years in a row.

The AI Bubble Is Affecting Biggest Wall Street Traders

Lone Pine Capital is historically considered one of Wall Street’s most successful and prominent hedge funds. However, its recent performance has experienced sharp ups and downs.

July did most of the damage. Cypress lost nearly 25% that month as AI and tech stocks sold off. Tensions involving Iran and a spike in oil prices made the rout worse.

The timing was brutal. Lone Pine bought five of its seven biggest US stock positions in the second quarter, according to figures cited by Hedgeweek. Together, they made up about 40% of its US portfolio.

The biggest was Nebius Group, a Dutch company that rents out AI computing power. Lone Pine held about $1.18 billion of it. The stock fell nearly a third in July.

Q3 share-price falls for Applied Materials, Nebius Group and Seagate, top Lone Pine hedge fund holdings

Applied Materials, which makes chipmaking machines, dropped 29%. ASML, AppLovin, Corning, and Home Depot also fell.

Cypress also bets on some stocks falling, a tactic called short selling. Those bets lost money too.

Lone Pine hedge fund year-to-date returns, end of June vs. end of September 2026

“Lone Pine gave it all back after being up 44% through the first half of the year. Gotta be real tough to explain this to the LPs,” stock trader Negligible Capital remarked.

Big Investors Are Split on the AI Trade

Lone Pine is not the only big name burned by AI. In July, AI bets nearly sank former OpenAI researcher Leopold Aschenbrenner’s hedge fund. He has since bought back into AI stocks.

Michael Burry, the investor made famous by “The Big Short,” is betting the other way. He holds put options on Nebius, contracts that pay off if the stock falls.

He explained the shift in a September 28 post.

“Fundamentally, I am moving timelines up,” Burry noted.

Lone Pine’s biggest AI bet is now one of Burry’s targets.

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