Localizing Game State Divergence

Purpose

Find when a gameplay defect happens, in tick order, before anyone argues about where in the code it lives. A semantic game defect — score credited twice, a cooldown that never expires, a resource that refills across a save — throws nothing. There is no stack trace, so backward tracing from an error has no starting point. The starting point has to be constructed: a per-event trace plus a predicate that is true of every healthy state, scanned for the first index where the predicate fails.

The output is a tick index and two states, not a diagnosis and not a patch.

When to Use