A rollout reaches 80%, but one customer remains on the old path. The exception enters a spreadsheet as “temporary.” Six months later, nobody knows who approved it, which metric justified it, or whether removing the old path would break a contract. The flag is no longer reducing launch risk. It is financing two products indefinitely. A useful exception is a time-bounded decision with evidence. Use a ledger whose minimum record is: exception : legacy-export-path owner : plat...