A verified state machine that loses state on a crash, or fires the same effect twice on a retry, is verified in theory and unreliable in production. polyrun closes that gap: one commit per step, effects emitted exactly once, and a composition gate that checks the check-then-effect sequence itself.
Correctness that survives a crash, not just a proof.
Every transition is durably recorded before its effect runs, so a crash mid-step never leaves the machine in an undefined state.
Retries replay the state, not the side effect; an email sent once stays sent once, even across a restart.
The gate verifies not just that the machine is correct, but that checking and acting are properly sequenced — closing a class of bug verification alone doesn't catch.