Jane Street, the secretive Wall Street trading giant, absorbed a $15 billion hit in a single month after an AI-focused hedge fund run by a former OpenAI researcher suffered margin calls and dumped its stock portfolio in a fire sale.
The firm's executives acknowledged the damage in an internal note to employees on Friday, calling July a "bad month", a striking understatement for a loss that wiped out months of gains and forced the firm to pull back from risk across multiple strategies. Reuters obtained and reviewed the note, which the New York Post first reported.
At the center of the wreck sits Situational Awareness, an AI-focused hedge fund managed by Leopold Aschenbrenner, a former OpenAI researcher sometimes called the "Nostradamus of AI." The fund had posted strong returns in the first half of the year, swelling Jane Street's stake. Then the AI trade reversed hard in July, and the fund's concentrated bets turned into liabilities overnight.
When AI-exposed stocks cratered in July, Situational Awareness faced margin calls it could not absorb. The fund offloaded the bulk of its stock portfolio in a fire sale to Citadel, the firm controlled by billionaire Ken Griffin. The terms of that sale, how much stock changed hands and at what discount, remain undisclosed.
Jane Street's internal note framed the damage in measured terms, telling employees the firm's stake in Situational Awareness was left "about flat on the year" after the drawdown but was "still up over the entire period we have been invested." That language suggests the first-half gains cushioned the blow, but did not come close to offsetting the broader damage across Jane Street's book.
The note spelled out just how brutal the month was for AI-linked positions:
"We largely lost on the same portfolio of trades that had strong outperformance in the second quarter. AI-exposed stocks were down a lot during July, several of the largest memory and semiconductor stocks were down around 50%."
A 50-percent decline in major memory and semiconductor names in a single month is not a routine pullback. It is the kind of collapse that punishes leveraged bets and concentrated positions, exactly the profile Situational Awareness appears to have carried.
The firm told employees it had already begun cutting exposure. Jane Street said it had "closed a significant portion of our risk in the specific areas we lost on in July, and have also reduced risk taking in other strategies." Going forward, the firm promised to be "more selective" about risk.
That pivot matters. Jane Street is not a small shop gambling with house money. Two people familiar with the matter told Reuters the $15 billion figure reflected the firm's combined losses from its Situational Awareness stake and other tech stock positions battered by the same selloff. A single source pegged Jane Street's year-to-date trading revenue at more than $40 billion, meaning July's loss consumed more than a third of the firm's total haul for the year.
Jane Street could not be immediately reached for comment beyond the internal note.
The losses were not limited to AI names. Jane Street also held long positions in non-AI stocks in Asia, many of which had outperformed earlier in the year. Those positions declined in July as well, compounding the damage from a month that hit the firm from multiple directions at once.
The episode lands at a moment when AI remains the dominant force in global markets and in geopolitics. President Trump arrived in Beijing this summer for talks with President Xi Jinping that were expected to cover trade and artificial intelligence, with Nvidia CEO Jensen Huang and Tesla CEO Elon Musk among the executives traveling aboard Air Force One. Leaders from BlackRock, Goldman Sachs, Meta, Qualcomm, Micron, and other major firms joined the delegation, a sign that AI-linked commerce sits at the center of American economic strategy.
But strategy built on a sector that can shed half its value in a month carries obvious risks. Jane Street's $15 billion loss did not come from a fraud or a regulatory crackdown. It came from a straightforward bet that AI stocks would keep climbing, a bet shared, in various forms, by pension funds, sovereign wealth funds, and retail investors across the country.
Aschenbrenner earned the "Nostradamus" label by making bold predictions about artificial intelligence after leaving OpenAI. His hedge fund rode those convictions to strong first-half returns. The market rewarded the thesis until it didn't, and when the reversal came, the fund's concentrated positions left no room to maneuver. Margin calls followed. Then the fire sale to Citadel.
Several questions remain unanswered. What is the current status of Situational Awareness as an operating fund? How large was Jane Street's original stake? What specific stocks drove the losses? Jane Street's internal note offered employees reassurance but not transparency, and the firm has said nothing publicly.
When the smartest traders on Wall Street lose $15 billion in 31 days on a single thesis, ordinary investors watching their 401(k) statements should take the hint: nobody can see the future, not even the man they call Nostradamus.