A wildly risky AI-infrastructure bet made huge gains, then collapsed almost overnight — bad for the fund's investors, but a discount win for Ken Griffin's Citadel.

• Leopold Aschenbrenner, a 24-year-old former OpenAI researcher, built a hedge fund betting heavily on AI infrastructure stocks like Nebius, Micron, SanDisk, and CoreWeave.
• The fund posted a 439% return in six months, ballooning from $225 million to $45 billion as big money piled in.
• He used up to 4x borrowed money, so when his stocks dropped 35% in a month — and his short bet Adobe rose — the losses multiplied and lenders forced a fire sale.
• The fund crashed to about $10 billion, though Aschenbrenner is still personally worth a few hundred million.
• Citadel's Ken Griffin bought the entire book of positions at a discount, stopping a wider market sell-off while profiting himself.

Outlook: The fund survives at a fraction of its peak, and expect this young manager to resurface with more caution and closer scrutiny next time.