[BUG] Desktop app 1.24012.9 (Windows/MS Store): in-app per-message Read Aloud play button does nothing after update

Environment

• Claude desktop app 1.24012.9 (Microsoft Store install), Windows 11 Pro 10.0.26300
• Update was staged by the Store on 2026-08-01 ~19:11 and took effect when the app restarted on 2026-08-03 ~10:30 (SAST)

Symptom

The per-message Read Aloud / play control in the app (footer of each assistant reply) stopped producing any audio the moment the updated version took effect. Pressing play/pause does nothing audible on any message, in any session, including old replies that previously played fine.

What we ruled out (extensive local diagnosis)

• System audio is healthy: WAV system sounds and console beeps play; other apps play audio.
• Windows default output device (both Console and Multimedia roles) verified and corrected — no change to the in-app button.
• Full app restart after the update (twice) — no change.
• No newer Store version available at time of filing.

Expected

Pressing the play control on any assistant message reads that message aloud, as it did for weeks up to and including the morning of 2026-08-03 on the pre-update version.

Notes

• Possibly related to #72123 (Read Out Loud degradation), but this presents as a complete no-op rather than degradation.
• The user relies on this feature for accessibility (prefers listening over reading long replies).

🤖 Filed with Claude Code on the user's behalf.