Important: This is not a safe invariant yet. The hello carries no build ID, so a client evaluating an older output can freeze the latest top_level_evaluated snapshot. Lazy sizing may then omit a factory that this client does not actually hold (or holds at an older version); I reproduced the resulting initModule(dep) with no dep factory. Please document this as an unresolved correctness gap, or bind the snapshot to the served build before presenting this subtraction as safe.

Important: The claim that under-prediction always becomes a clean reload is false today. FbmHMRClient checks hasFactory only for updateSet; an initModule failure during apply reaches the queue's warn-only catch, and lazy-chunk initModule runs outside that recovery path entirely. We have a concrete missing-factory case that leaves the page alive and stale. Please describe these as unresolved failure modes (or add the reload recovery) instead of asserting “never a stale page” and listing every missing factory as a reload fallback below.