Build .build/terebi beside the app. Parse a single local file or YouTube URL, --url, --, and help; reject invalid commands before GUI launch. Resolve the adjacent app through symlinks and launch through NSWorkspace, reusing its process/window and saved progress.
Launch the app without media before delivering URL events. Raw media argv suppress SwiftUI's initial singleton window. Own warm document and internet Apple events because SwiftUI's default external-event routing closes that window; retain initial Finder document delivery to create it.
Verified actual CLI 0/64/69 exit behavior, PATH/symlink discovery from another directory, cold local/YouTube playback, warm local/YouTube replacement in the same native window/process, resume, Finder-style cold launch, and make all check.
Persist authoritative per-video positions in UserDefaults. Save periodic checkpoints, pause, close, replacement, and quit; restore a validated position before autoplay. Canonical YouTube webpage URLs survive fresh stream extraction, and local symlinks share file progress.
Clear completed or out-of-duration bookmarks. Leave failed opens and live/non-seekable inputs out of persistence. Pending opens hide errors belonging to the previous source.
Verified separate-process restart, source replacement, failed-open recovery, completion, checkpoints, real YouTube short-link resume, live exclusion, and make all check.
Resolve public YouTube URLs through external yt-dlp and play selected streams in the existing native window.
Independent bounded network readers keep one authored timeline. Successful seeks clear FFmpeg's sticky aborted-read AVIO error; manifest seekability uses native format flags rather than a top-level I/O handle.
Verified real YouTube playback, seeking, frame stepping, compact mode, cancellation, and the complete native regression checks.
hl-valdemar