Review correctness under concurrent execution — atomic shared-state mutations, idempotency where required, and race-free interleavings; deeper than single-flow async I/O. Flags read-modify-write across await with no atomicity, check-then-act without a constraint/lock, non-idempotent handlers on at-least-once channels, shared mutable module state, and mis-scoped locks. Use when multiple requests/workers/processes touch shared state or when debugging intermittent load-dependent corruption. Produces an evidence-based, explainable report.
