Current circuit state
Failure count (window or consecutive, depending on config)
Consecutive success count (used in HALF_OPEN)
Timestamp of last failure, or null
Timestamp of last success, or null
Timestamp when circuit was opened, or null
Timestamp when circuit entered HALF_OPEN, or null
Total requests ever attempted
Total failures ever recorded
Total successes ever recorded
Total requests rejected while OPEN
Current in-flight probe requests in HALF_OPEN
Current state snapshot — safe to serialize.