How can an app observe TV (master) volume changes on webOS TV Lite 8.3.0

Web App Development
1

My app shows a volume indicator and needs to stay in sync when the user changes
the TV volume with the remote or Bluetooth headphone buttons.

Device: webOS TV Lite, release 8.3.0 (Core OS Rockhopper 8.3.0-915, firmware
built 2025-08, manufacturing version 03.33.46).

What I found on this platform:

  • The documented Audio API (luna://com.webos.audio) only offers volumeUp,
    volumeDown and setMuted — control methods, but no way to read or observe
    the current level.
  • getVolume does respond (undocumented), but a "subscribe":true call, while
    accepted ("subscribed":true), never delivers change events — and the service
    unloads after a short idle period, taking the subscription with it
    (“com.webos.audio is not running”).
  • luna://com.webos.service.audio/master/getVolume (documented in webOS OSE as
    change-notifying) returns “Message status unknown” here.
  • Settings Service getSystemSettings has no volume-related key to subscribe to.
  • Volume keys are handled by the system and never reach the app’s input events.

Paired external controllers (LG Connect / SSAP clients) clearly do receive
volume-change notifications via ssap://audio/getVolume. Is there a supported
equivalent for an app running on the TV itself — on webOS TV Lite specifically,
or on webOS TV in general? Or is polling getVolume the intended approach?

If no such API exists today, please consider this a feature request: a
subscribable volume/mute status for apps (e.g. a subscribe-capable getVolume
or a Settings Service key).