Leopold Aschenbrenner, the 23-year-old former OpenAI researcher who founded Situational Awareness hedge fund in 2024, was forced to sell his entire public stock portfolio in a single block trade on Thursday, with Ken Griffin's Citadel as the buyer. The fund, which had grown to as much as $45 billion and posted gains of 439 percent through June 2026, was shattered by July's AI selloff. Losses came from two directions: long positions in AI infrastructure stocks, most notably SK Hynix, fell sharply, while short positions in software companies including Adobe moved against the fund as software stocks rallied. The combination, amplified by significant leverage from prime brokers including Bank of America, Goldman Sachs and JPMorgan, triggered margin calls the fund could not meet without selling. Aschenbrenner wrote in a July 24 investor letter that lower AI valuations had created the most attractive entry points he had seen since the fund's launch, but the capital to take advantage of them was gone. The fund had also been trying to sell stakes in privately held companies including Anthropic, where his wife Avital Balwit serves as chief of staff to CEO Dario Amodei, to raise cash. Citadel's purchase of the public book was confirmed by CNBC Thursday morning.