A frontend-agnostic crate for moving a Qobuz account's favorites and
playlists into another account, additively (contract
qbz-nix-docs/specs/2026-09-02-account-migration-contract.md §9):
- snapshot: capture the signed-in account (five favorite kinds with
favorited_at, owned playlists with track ids in order, followed
playlists) into users/<uid>/account_migration/snapshot-*.json; the same
capture is the target's live state at migration time.
- plan: the pure delta against the target and the ledger. Same-name
playlists holding nothing foreign are the same playlist and get the
missing tracks appended; anything foreign means a different playlist and
a " (migrated)" copy. Favorites are written oldest first so the target's
own stamps keep the chronology.
- apply: one favorite per call with pacing and bounded retries, 50-track
chunks, subscriptions re-followed; every success lands in the ledger
before the next write, so a run resumes and a second run adds nothing.
- local: copy the old profile directory row by row (library folders and
scanned tracks on the fast path, playlist folders, settings keyed by
qobuz_playlist_id remapped through the ledger, pinned items, orders,
preferences, blacklist; media servers, scrobblers and listening history
behind options). Never the favorites cache, the subscription clock, the
session or the purchases.
The writes are the ones the app already issues when a user hearts or
creates a playlist; nothing touches subscriptions, purchases or account
data.
cc
