One William Street Capital Management, L.P.

One William Street Capital Management, a credit-focused hedge fund, filed a Q1 2026 13F that is unusual for its concentration: of roughly $1.18 billion in reported positions, a single holding -- the iShares iBoxx High Yield Corporate Bond ETF (HYG) -- accounts for about $1.059 billion, or 89.85% of the book. The remainder is a thin tail of liquid instruments: the Invesco Senior Loan ETF (BKLN) at 4.72%, SPY at 1.79%, and the iShares Russell 2000 ETF (IWM) at 0.89%, alongside small credit-and-real-estate names like TPG RE Finance (TRTX), Cousins Properties (CUZ), Rocket Companies (RKT), and Apollo Commercial Real Estate Finance (ARI). The quarter's defining move was the HYG position itself, which grew by roughly $360 million and drove reported assets up from about $745 million to $1.18 billion. New positions in BKLN ($55.6M), SPY ($21.1M), and the Vanguard Intermediate-Term Corporate Bond ETF (VCIT, $5.9M) reinforced the credit-and-index tilt, while the fund exited the Invesco S&P 500 Equal Weight ETF (RSP, about $28.7M). The picture is the liquid, ETF-heavy sleeve of a credit manager -- a 13F that captures fixed-income beta exposure far more than single-name equity conviction.