From Treasuries to Basis Trades: Stablecoin Design Has Fractured

They were simple, legible, and boring by design. The original stablecoin model was custodial and cash-like: an issuer holds dollar reserves, you hold a claim, and arbitrage keeps the price at $1. If the token slips below $1, someone buys it cheap and redeems it for full value, nudging the price back up. Most of the market still works this way.

What changed is everything built on top.

The biggest evolution is also the most conservative. The largest new stablecoins are backed by short-term US Treasury bills – the same government debt that money market funds hold. Two camps have formed around what to do with the yield those bills throw off.

One camp keeps the yield. The other passes it through to holders. These yield-bearing stablecoins behave like tokenized money market funds. By mid-2026, they yield roughly 3.5–3.6%, tracking the prevailing short-term Treasury rate minus management fees.

Step away from cash, and the designs get stranger. A growing class of stablecoins holds its peg through financial engineering rather than a vault of dollars. The most common structure splits risk into two tranches. A senior tranche takes a lower, protected yield. A junior tranche absorbs the first losses in exchange for the bulk of the yield. If the underlying strategy stumbles, junior holders are hit before senior holders feel a thing. The model got its first real stress test in mid-2026, though on a yield token rather than a stablecoin. It held up. It is also young, thinly capitalized, and hasn’t yet been battle-tested during a real crisis.

Another engineered design backs the stablecoin with a market-neutral strategy called the basis trade: hold an asset and short futures against it. That swap captures where the category has gone. Synthetix’s sUSD successor will use this approach instead of volatile SNX collateral.

All this financial engineering has unintended consequences – it creates new ways to break. The clearest cautionary tale is the one now ending. Synthetix’s sUSD held its dollar peg through SNX collateral until a 2025 governance change cut the required collateral ratio from 750% to 200% and removed the incentive for holders to buy the coin back when it dipped. The peg slid to $0.68, then to around $0.21. The protocol is now winding it down near $0.25. Synthetix (SNX), with an Alpha Score of 73, is winding down its sUSD stablecoin after the peg collapsed.

Not every wobble is a failure. When Ethena’s USDe briefly fell to $0.65 on one major exchange during the October 2025 crash, it held near $1 on decentralized venues like Curve, and redemptions never stopped. That was a price dislocation, not a failure of the delta-neutral hedge backing the coin.

As the stablecoin market grows more crowded and increasingly varied, being able to tell the difference between a glitch and a collapse is now part of the job of holding one. The first question to ask: what is actually backing the token – Treasuries, arbitrage, or a financial engineering model that hasn’t seen a real crisis?