safe_move_file used shutil.move, which for a CROSS-filesystem move (downloads volume ->
library volume, common in Docker/NAS) copies the file to the FINAL path incrementally. A
media-server real-time watcher (Jellyfin) can catch that partial file mid-write and cache it
with null/incomplete metadata — tracks landing with no disc. Inconsistent because it only bites
cross-fs and races the scan tick; 're-add library' fixes it (rescan reads the now-complete file)
and the on-disk tags are fine — exactly the reported symptoms.
Fix: same-fs uses an atomic os.replace (also overwrites dst); cross-fs copies to a HIDDEN temp
sibling, fsyncs, then atomic os.replace into place (+ temp cleanup on failure). A watcher only
ever sees the COMPLETE file. EXDEV/EPERM/EACCES + the old string check route here, so detection
is strictly broader than before.
Tests: same-fs move, simulated EXDEV routes to the atomic path and leaves no partial temp, helper
completes+cleans, helper cleans temp + preserves source on failure. Existing replace-destination
test still green; 574 imports+relocate tests pass.
9d091207f6