Windows11 Sound settings don't remember per-app volume after reboot

Because the master volume persists while every per-app slider returns to 100%, the issue is in the app audio-session state, not the speaker volume itself. First confirm the same output device is selected before and after restart; Windows stores app controls against an application and audio endpoint. In Settings, open System, Sound, Volume mixer, use Reset once, then set two easy-to-test apps to different levels and restart. If both still reset, restart Windows Audio and Windows Audio Endpoint Builder, install Windows updates, and update the audio driver through Device Manager or the PC manufacturer’s supported package. Then test with a clean boot to exclude an audio utility or startup program rewriting the mixer. If only one app resets, repair or update that app instead. If all apps still reset on the current Windows build, reproduce in a new local profile and submit Feedback Hub diagnostics.