Digital information can be copied, so payment systems need consensus, trusted ledgers, or another authoritative mechanism to prevent one balance from satisfying conflicting transactions. A merchant that acts before sufficient settlement finality may accept a payment that later loses.
Agent transactions can increase exposure because purchases are automated and frequent. Providers should define confirmation thresholds, bounded credit, escrow, replay protection, duplicate detection, and what happens when a transaction fails after service begins.
ELI5
Double spending means trying to pay two recipients with the same digital funds before the system decides which payment is real. A payment message alone is not always enough to prove the value has finally moved.
For example, a service that delivers costly work immediately may later learn that its payment lost to a conflicting transaction. Waiting for settlement or using trusted escrow reduces that risk but can add delay or fees.
