When the US borrows, it runs auctions. Primary dealers are required to bid, absorbing what the market won't take. If real demand is soft, those dealers get stuck holding bonds bought above market. The yield required to clear the auction rises. That spread is the vigilante's signature.

March 2026: three consecutive Treasury auctions — 2-, 5-, and 7-year notes — all cleared at yields above pre-auction market levels. Worst run since May 2024. No crisis, but the cost of US borrowing ticked up. That's not noise. That's the mechanism.

Foreign demand has been the quiet cushion. China held $1.32T at peak in 2013. Now it's $683B — 42% sold over a decade. Not a dump. A slow withdrawal. As each large holder reduces, the US needs a new marginal buyer. Marginal buyers demand a premium.

The vigilante doesn't announce itself. The signal is the spread — how far an auction clears from where the bond was trading beforehand. A persistently negative spread means the market is repricing what it costs to fund this much debt. That repricing is already beginning.