Jane Street recorded a roughly $15 billion trading loss in July 2026, its worst month in a decade and first negative trading-revenue month since 2016, after a sharp sell-off in artificial-intelligence and chip stocks. The losses were linked in part to Situational Awareness, an AI-focused hedge fund run by former OpenAI researcher Leopold Aschenbrenner, which was forced to sell most of its public-equities portfolio to Citadel Securities. The Federal Reserve and Bank of England are asking global banks about their exposures to large trading firms, including how those exposures changed during the trading day, firms’ risk appetite and the operation of risk controls. The Financial Times reported the inquiries, which Reuters said it could not immediately verify. The episode has also drawn scrutiny from the U.S. Securities and Exchange Commission, which subpoenaed Wall Street banks including Goldman Sachs, JPMorgan, Citigroup and Bank of America over Situational Awareness’ trading activity, leverage, margin-call-triggering trades and communications with lenders. Despite the July setback, Jane Street had accumulated more than $40 billion in net trading revenue by mid-August 2026, exceeding its approximately $39.6 billion total for 2025. The developments add to existing concerns about banks’ counterparty and concentration risks from hedge funds and other non-bank financial institutions.