Atomic settlement

Atomic settlement means a multi-part transaction has exactly two possible outcomes: everything settles, or nothing does. In a token swap, the leg where you give up asset A and the leg where you receive asset B commit together. There is no window where one side has moved and the other has not, so neither party carries the risk of a half-finished trade.

Traditional finance handles this problem with intermediaries and delivery-versus-payment arrangements that coordinate the two legs across separate systems. A smart-contract ledger can do it structurally: both transfers are clauses of a single transaction, and the ledger's rules refuse to record one clause without the other. If any condition fails, such as insufficient output or an expired quote, the whole transaction is rejected and balances are untouched.

Canton's Daml contract model is built around this guarantee, which is one reason the network attracts settlement-focused institutional applications. On OneSwap, a swap against a pool settles atomically: the input deposit, the output withdrawal, and the fee accounting are one ledger transaction, so a failed swap costs nothing but the attempt.