Performance Logging (Developer settings) logs a resource sample every 5s
in the foreground and background: CPU by area and thread, wakeups, GPU,
memory, disk, activity counters as rates (mpv property updates, player
time publishes, renders, saves, network, images, CloudKit events, log
entries, main run-loop wakeups), SwiftUI body evaluations of the player
views, and app/player/battery context. Each foreground/background
transition logs a summary of the period. MetricKit metrics and
diagnostics (CPU exceptions, hangs) are logged whenever logging is on.
Background diagnostics (iOS) log lifecycle, audio session and power
events with an app/player/render snapshot and a heartbeat that detects
suspension gaps and main-thread stalls. Logs are persisted per session
in Caches/Logs and the previous session is included in exports, so logs
survive the app being swiped away.
On tvOS SwiftData keeps the store in the app group's Library/Caches,
which the system may purge. The CKSyncEngine tokens live in UserDefaults
and survive, so the next launch opened an empty store and fetched only
records changed since the old tokens; subscriptions and bookmarks that
had not changed since never came back.
DataManager now records whether the store file existed when the
container opened, and the sync engine clears its persisted state once
per launch when it did not, so the first sync after a loss is a full
fetch. Also log the store path and a persistent-store failure that
previously fell back to in-memory storage silently.
