An optimistic-concurrency expectation was not met.

Raised by the compare-and-swap surface - KeyValueStore.create, update(expectedRevision), delete(key, expectedRevision), purge(key, expectedRevision) - and by a JetStream publish whose eu.vstoyanov.natsy.jetstream.PublishExpectations did not hold.

A conflict is a normal outcome of a read-modify-write loop, not a fault: natsy does not log it, because the caller re-reads and retries. The server does not report the value that was actually there, so there is nothing to carry beyond the codes on NatsyServerException.