Circuit breaker

A circuit breaker opens after a run of failures so calls fail fast instead of piling up timeouts, then half-opens to test a single request before fully closing. It complements retries: a retry handles a transient blip, a breaker handles a sustained outage.

For a decision pipeline it is the mechanism behind the fail-open or fail-closed posture, because the open state is where the fallback path runs. Pair it with a bounded total time so the transition to the fallback is predictable.