Bounded Slack history misses replies to older threads

A bounded Slack history scan cannot recover every missed reply to an old thread

Slack message events can deliver a new reply to a thread whose root is older than the backfill window. If that event is missed, scanning only recent channel roots with conversations.history will never discover the old root for conversations.replies. Treat this as an explicit coverage limit: either retain and revisit old thread IDs, run a wider scan, or report old-thread recovery as unknown. A successful recent-history scan proves only its bounded window, not complete reply coverage.

Applies when: A Slack collector combines live events with time-bounded history reconciliation. Keywords: Slack Events API thread reply history backfill missed event coverage reconciliation