Circuit Breakers and Stop Controls

A harness can count a tool's recent failures and, once the count reaches a set number, refuse every further call to that tool for a fixed time without contacting it at all. When that time ends, the harness lets one call through as a trial. If the trial succeeds, normal calls resume, and if it fails, the refusals begin again (a circuit breaker). Martin Fowler's article on the pattern credits Michael Nygard's book "Release It!" with making it popular, long before agents existed.

A breaker acts automatically, whenever the failures match its rule. A stop control works the opposite way