What Happens If One Leg of an Atomic Swap Fails?

If one leg of an atomic swap fails (e.g. due to insufficient gas, an expired time lock, or a contract error), the entire transaction is reverted to its original state. The funds remain in their original wallets or are returned to the sender after the time lock expires.

This is the core guarantee of atomicity: no party is left with a partial or incomplete trade, eliminating counterparty default risk.