Parent

Sibling to #46 (Global MPRIS media controls — the Linux feature this mirrors), and part of the macOS platform-backend revisit groundwork (#24). Depends on nothing; feasibility is the open question, hence a spike.

Why file this now

The MPRIS media browser (#46) shipped behind a clean seam: the MprisBackend Protocol in daemon/deckd/mpris.py (row_ids(), read_state(row_id) -> MediaState | None, send_command(row_id, command)), with DbusMprisBackend (real D-Bus) and FakeMprisBackend (tests) as the two implementations. The whole browser — the mediabrowser widget, the chrome view, the per-row transport, the media_command dispatch — is written against that Protocol and knows nothing about D-Bus. A macOS "now playing" backend is, architecturally, just a third implementation of the same three methods. This ticket sizes whether that's actually feasible on modern macOS.

Research result

The off-Mac investigation is complete. See docs/research/issue-56-macos-nowplaying.md.

• MPNowPlayingInfoCenter and MPRemoteCommandCenter are publish/receive-side APIs, not system-wide read APIs. The correct target is private MediaRemote.framework.
• Direct unentitled MediaRemote reads are blocked since macOS 15.4. Transport commands remain available, but control without read access is insufficient.
• The currently viable route is shelling out to ungive/mediaremote-adapter or nowplaying-cli, whose shared /usr/bin/perl shim is reported working on Sequoia 15.7 and Tahoe 26.3.
• The existing MprisBackend seam and now-playing UI support one row or zero rows without client changes.
• AppleScript is a narrower per-app fallback for Music/Spotify, not a system-wide replacement.

Recommendation

Build behind the existing seam, keep the helper swappable and optional, and degrade cleanly if Apple closes the workaround. Do not make this undocumented path load-bearing.

Remaining Mac-only verification

Before creating an implementation ticket, verify on a live Mac and record the exact macOS version:

• nowplaying-cli get or the adapter equivalent returns the fields deckd renders.
• stream produces usable updates.
• Play/pause/next/previous work without a private entitlement.

The workaround is undocumented and may disappear, so this remains the sole open acceptance criterion.

Out of scope

• Actually shipping a merged MacNowPlayingBackend — that's a follow-up ticket after live verification.
• Windows now-playing (GlobalSystemMediaTransportControlsSessionManager / WinRT) — that's the natural sibling for Investigation: Windows platform backend (focus, injection, power sync) #32, filed separately if wanted.
• The passive playback-state tint on the chrome media icon (Chrome media icon: passive playback indicator #47) — orthogonal, Linux and macOS alike.