The regulators have been talking all year. Now the bond market is making the argument for them.
The 30-year Treasury yield hit 5.311% last week, its highest level since June 2007. That is not the story by itself. The story is what sits underneath it: a position stack so large that a disorderly exit could make the yield move look calm by comparison.
Between 2023 and September 2025, large hedge funds’ gross U.S. Treasury exposures doubled to $4.0 trillion, comprising $2.4 trillion in long exposure and $1.6 trillion in short exposure. The net position is a fraction of that gross. The Office of Financial Research estimates hedge funds’ long cash Treasury holdings at $2.0 trillion, against short futures positions of $1.4 trillion. That gap, financed overwhelmingly through overnight repo, is the basis trade. And hedge funds typically rely on overnight repo because it is cheaper than term financing.
Three global regulators have now put their warnings on paper. The FSB published its repo-market vulnerabilities report on February 4, estimating roughly $16 trillion in government bond-backed repo outstanding at end-2024 and flagging that repo markets can facilitate the build-up of leverage in the financial system. Approximately 70% of activity in the non-centrally cleared segment operates with zero haircuts. The Bank of England’s July Financial Stability Report was more pointed: many of these markets are characterised by a relatively high use of leverage by a small number of hedge funds pursuing similar trading strategies across jurisdictions, and that high use of leverage increases the risk of a disorderly unwind that could cause a jump to illiquidity in core markets.
At the same time the official backstop is shrinking. Foreign holdings of U.S. Treasuries fell in June, led by declines in Japan and China, dropping $72.1 billion from May to $9.3 trillion, the third decline in four months from February’s record high. Top foreign holders including the U.K., China, and Japan all reduced their holdings in June. Hedge funds have stepped into that gap, and they roll their funding nightly.
The Watchlist
If the basis trade begins to unwind under stress, these are the five signals that will move first, usually in this order.
1. SOFR vs. IORB spread. SOFR printed 3.64% on July 27, sitting inside the Fed’s 3.50-3.75% target range within a basis point of the effective fed funds rate. That tight alignment is the normal state: SOFR tracks the Fed’s administered rates because Treasury repo is the marginal use of overnight cash for the entire dealer system. The information is in the deviations. SOFR printing persistently above the interest rate on reserve balances, especially at month-ends and around Treasury settlement dates, is the first indicator of funding pressure. Watch for a sustained gap of 10 basis points or more.
2. Repo specials. When a specific Treasury issue becomes hard to borrow, its repo rate drops well below general collateral. Widespread specials across the on-the-run curve, not just isolated issues, indicate dealer balance sheets are constrained and collateral is being hoarded.
3. Swap spreads. Long-end SOFR swap spreads have been structurally negative for years, reflecting dealer balance sheet scarcity. Spreads got less negative in late 2025 as the Fed slowed QT, but swaps remain roughly 25 basis points inside Treasuries. A sudden further widening into deeper negative territory signals that dealers are pulling back from intermediating cash bonds. A sharp move toward zero or positive would signal the opposite: forced Treasury selling compressing yields relative to swaps.
4. Basis itself. Aggregate basis trade volumes reached approximately $830 billion in September 2025, close to doubling their peak from early 2020. The cash-futures basis, normally a few ticks, blew out to extreme levels in March 2020 before the Fed intervened. Any divergence wider than 20 ticks in the front two Treasury futures contracts, sustained intraday, is worth treating as a stress signal rather than noise.
5. OFR Financial Stress Index. The OFR publishes a daily market-based stress composite. It normalized quickly after April 2025’s tariff shock. A reading that spikes and does not mean-revert within two sessions during a yield move of this magnitude deserves more weight than usual.
What to Watch This Week
If repo rates spike or futures margin requirements increase abruptly, hedge funds may be forced to unwind positions rapidly, and a disorderly unwinding could amplify volatility in cash and futures markets. The conditions for that scenario are more aligned today than at any point since the March 2020 episode. With the overnight reverse repo facility drained to roughly $0.2 billion to $1.5 billion recently from a $2.55 trillion peak in late December 2022, the money-market cash buffer that used to absorb funding shocks is gone.
None of these five signals is flashing red today. But all five are closer to amber than they have been all year. Traders running leveraged fixed-income books should have alerts set on each before Tuesday’s open.