The 8s watch-history poll ran refresh() on the main actor, which read and
JSON-decoded the unioned watch log THREE times (playedPaths, resumePositions,
episodeProgress each re-read) and called MediaPaths.toRemote() per event — and
every toRemote rebuilt ProcessInfo.environment (~22µs each, the whole env dict
is reconstructed on every access) plus a homeDirectory lookup. A live sample
caught the main thread 100% in this path; the app sat at 78–113% CPU.
- Cache MediaPaths.remoteRoot / mappings (process-constant) → kills the
per-call env-dictionary rebuild storm.
- WatchHistory.derivedState(): read+decode the log ONCE, feed all three
derived computations → 3× fewer reads/decodes per refresh.
- WatchHistoryController.refreshAsync(): the background poll now parses off the
main thread on a utility task and only assigns the small results on main.
Settled CPU drops from ~78% sustained to ~0% idle.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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