Use when a task needs a new or modified YouTube Music API call, response parser validation, authenticated endpoint investigation, or fixture capture; explore endpoints with `swift run api-explorer` before changing production code.
Use when you need a fresh packaged `.app` bundle, a fast build-package-relaunch loop, or a packaged runtime repro for Kaset instead of a compile-only verification.
Use when playback, auth recovery, queue sync, or hidden WebView state diverges from native Swift state and you need to debug the DRM playback WebView, bridge events, or cookie/auth behavior.