A worker thread leases a group and takes its ranges in article order through one carried window; the coordinator keeps one cursor a group (group_leases, migration 6500) and hands out the next range, the rules and nothing about where the chunks are: the range stream serves a stored range's chunks from the corpus file and a live one's from the spool. The window's snapshot (bincode: the frontier, the open files, releases and albums, the upload numbers, the batch-counter table) goes to the coordinator every EDGE_SNAPSHOT_MINUTES and when the group is given back, and the next holder restores it; a takeover after LEASE_TTL_SECONDS plans the ranges from the snapshot's article again. The prefetcher runs ahead of held groups' cursors and skips chunks the corpus has. LEASE_MIN_PRIORITY..LEASE_MAX_PRIORITY bound what is leased. edge-node holds groups by default; --ranges keeps the old per-range path. Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>