The safest loan in the world just started costing too much

I move money.

Every Friday, payroll clears and a wire goes out. I never think about how the cash gets from my bank to yours by morning. It just arrives.

There's a hidden market that makes that happen. Banks and money funds lend each other cash overnight, backed by Treasury bonds. It's the safest loan there is. You hand over a government bond, you get cash, and you pay it back tomorrow.

The rate on that loan is called SOFR. For years it sat quiet, a few pennies under the Fed's target. I never gave it a thought.

But last fall it started jumping. At the end of each quarter, the cost to borrow cash against Treasuries spiked above the Fed's own ceiling. On the last day of 2025, it hit 3.87%. The Fed's ceiling was 3.75%.

That gap sounds tiny. In this market it isn't. It means the safest corner of finance ran short of cash. The lenders who normally rush to park money wanted more to hand it over.

When the safest loan in the world costs more than the Fed says it should, something is short of cash.

So the Fed stepped in. It had pulled cash out of the system for three years. In December it stopped… and started buying Treasury bills again to put cash back.

I have no idea when this matters for stocks. It might not, for a long time. Plumbing can knock for months before anything breaks.

But when that safe rate breaks above the Fed's ceiling, I want to know why. When the Fed reverses three years of tightening to keep the system running, I want to know who's short of cash.

That's the story this week. It runs under the headlines, under the CPI prints and the bank earnings. So we followed the cash.

This starts with a cushion — one that took years to build and only months to burn through.

For a stretch after the pandemic, money funds had more cash than they could use. They parked the extra at the Fed overnight. At the peak, that pile topped $2 trillion.

It worked like a shock absorber. When the Treasury sold a wave of bonds, or taxes came due, the cash came out of this pile first. Bank reserves barely felt it.

The Fed's own market desk says part of the recent stress is ordinary. Banks dress up their books at the end of each quarter, which nudges rates for a day or two. That's fair. The jumps have been brief.

But the direction is one-way. The pile is gone now. The absorber that kept the system calm isn't there for the next shock.

And here's where it spreads. In December, the Fed did something it hadn't done in three years. It started buying Treasuries again.

For three years it had let bonds roll off, shrinking its holdings. That's called quantitative tightening. On December 1 it stopped. Eleven days later it began buying Treasury bills — about $40 billion a month to start.

Its balance sheet, near $6.7 trillion, is growing again.

The Fed is careful about the name. This is not QE, it says. QE is meant to push down long-term rates and juice the economy. This is only to keep enough cash in the system. There's something to that distinction.

But it did the same thing in October 2019, under the same name, for the same reason. Whatever you call it, the Fed is a steady buyer of government debt again.

Meanwhile, the Treasury is borrowing at a pace that's hard to picture.

The national debt runs near $39 trillion. Of that, about $6.7 trillion is short-term Treasury bills — IOUs that have to be paid off and reissued within a year.

So the government is flooding the market with bills at the exact moment the Fed has started buying them.

Follow the loop. Washington issues the bills. Money funds and the Fed buy them. And the cash to buy them is the same cash that's getting scarce in the overnight market.

One arm of Washington borrows short. Another buys it back. And the cushion that used to make this painless is empty.

Three more things worth keeping track of…

Silver.  It went vertical, then fell by nearly half. Silver hit a record near $121 an ounce in late January, its first all-time high in 45 years, then lost close to half its value by summer. Under the swing sits a fifth straight year where the world used more silver than it dug up. The paper market dwarfs the metal in the warehouses. Cover that thin can turn a rally into a squeeze fast.

British debt.  Britain is paying the most to borrow in nearly three decades. The 30-year gilt yield pushed past 5.8% this spring, its highest since 1998, and it hasn't come back far. A new prime minister, Andy Burnham, is set to take over on July 20 with the bond market already tense. When a government's long-term borrowing costs sit at a 27-year high, the budget math turns ugly.

Power bills.  Electricity is getting expensive in a hurry. On PJM, the largest US grid, wholesale power ran about 76% higher early this year than a year before. The grid's own monitor put the blame on data centers. Power feeds straight into inflation, and into how angry voters feel. It's the computing boom showing up on the utility bill.

We'll see.

You keep cash somewhere safe. A checking account, maybe. Or a money-market fund.

A money-market fund feels like cash. You put in a dollar, you get back a dollar, plus a little interest. The price never moves. That's the whole promise. A dollar in, a dollar out.

There is now about $7.95 trillion sitting in these funds. A record. More than ever before. Families, companies, retirees — all parking cash in something that feels as safe as a bank account.

But it isn't a bank account. There's no government guarantee behind that steady dollar. The fund just owns short-term IOUs and promises you a dollar back.

Most of the time, the promise holds. Once, it didn't.

In September 2008, the oldest money-market fund in the country held a pile of Lehman Brothers debt. Lehman went bankrupt on a Monday. The next day, the fund's dollar was worth 97 cents. They called it "breaking the buck."

Word got out. In a single day, investors pulled more than $140 billion out of money funds. Within days, the whole industry saw hundreds of billions leave. A run — on the safest thing people thought they owned.

It got so bad the Treasury stepped in and guaranteed the funds, the way it guarantees bank deposits. That was the only thing that stopped it.

A dollar in, a dollar out… until the day it isn't.

Nothing says today's funds are about to break. They're better regulated now, and most hold government paper. Most will be fine.

But $7.95 trillion is a lot of money resting on a promise that has been broken before. And the last time it broke, it broke over a weekend.

Safe is a story we tell ourselves about cash. Sometimes the story is wrong.

We'll see.