[Bug]: Agent preview tabs never close and all keep playing background audio #20890

Before submitting

• I searched existing issues and did not find a duplicate.
• I included enough detail to reproduce or investigate the problem.

Area

apps/desktop

Steps to reproduce

1. Open a project whose page plays background audio when it loads, such as a browser game with looping music.
2. Ask the agent to make a change and check it in the app. The agent opens the page in the preview side panel, and the audio starts playing.
3. Do this a few more times, in the same thread or in other threads of the same project. Each check opens a new preview tab.
4. Settle those threads.

Expected behavior

Any one of these:

• Preview tabs opened by an agent close, or are at least suspended or muted, once the thread is settled or the panel is dismissed.
• Preview tabs running in the background don't play audio unless the user turns it on.
• A global setting mutes audio in all preview tabs.

Actual behavior

The preview tabs never close, not even after the thread is settled. Each tab keeps its own copy of the background audio playing, so the same sound plays from many tabs at once. After a while there can be dozens of tabs playing over each other. There's no single place to find and silence them; the only fix is closing them one by one or restarting T3 Code.

Impact

Minor bug or occasional failure

Version or commit

0.0.45 (6c8fed3)

Environment

T3 Code (Claude Code harness), macOS (Darwin 25.6.0)

Logs or stack traces

None. Nothing errors; the tabs just stay open and keep playing.

Screenshots, recordings, or supporting files

No response

Workaround

For now, close the preview tabs by hand, or restart the app. It may not be possible to tell reliably when a preview tab is no longer needed. So a simple fix would be a setting like "Mute preview tabs by default": every preview tab starts muted, and you unmute one when you want to hear it. It would also help to mute tabs that aren't visible, close a thread's tabs when it's settled, and add a "Mute all" or "Close all preview tabs" action.