Fail closed on unreadable ingest manifest versions, key segment listings by name and sha, and reverify held files before returning duplicate or held-bearing ok responses. Lock ingest.json read-merge-write updates so concurrent additive uploads keep every manifest entry.\n\nAlso reserve the persistent ingest.json.lock sidecar created by the journal_io lock so transfer/export/discovery do not treat it as client content.\n\nCo-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>