The rebuild runs before ingest dials (upstream ordering) and scales with the watermark backlog — hours on a large archive with a low watermark. It previously logged only on completion, making a long rebuild indistinguishable from a hang (the 2026-08-07 restart-pause diagnosis chase). Now: a start line with the loaded watermark and segment count, progress every 200 segments, and the live-entry gauge published as it grows. No semantic change.