DrUSD — the payment leg

A fiat-referenced token: reserve-backed, redeemable one-for-one at will.

Invariants

Full backing, at all times. reserve >= totalSupply is asserted after every operation that touches either. This is the executable form of the minimum-value rule: reserve assets must at all times equal or exceed the total value of outstanding redemption claims. A design declaring less than full backing is provably outside the architecture grammar.

function _assertBacked() private view {
    if (reserve < totalSupply) revert BackingViolation(reserve, totalSupply);
}

Redemption at par, on demand. No queue, ever, on this leg — the rule is redemption at par no later than T+2. A queue here would require a regulator extension, and there is a theorem showing the optimum's queue is compliant only because it is scoped to the fund token.

Reserves are not the protocol's capital. Reserve assets cannot be lent, advanced, or used as venue liquidity. There is deliberately no function that moves reserve anywhere except to a redeeming holder.

Tests