When Systems Disagree with Themselves

We assume systems behave consistently. They don’t. Take a simple workflow: A request comes in → system processes it → state updates → response returned. Now run it again. Same input. Same code. But internally: • a message arrives slightly earlier • a retry overlaps with another operation • a scheduler makes a different decision And suddenly… The system takes a completely different path. From the outside, everything looks fine. From the inside, the system just disagreed with itself. This is the r