[BUG] Chat response completion notifications silent on Windows while Code and Cowork notifications fire correctly (same install)

Preflight Checklist

• I have searched existing issues and this hasn't been reported yet
• This is a single bug report (please file separate reports for different bugs)
• I am using the latest version of Claude Code

What's Wrong?

In the Claude desktop app on Windows 11, no Windows notification appears
when a Chat response finishes, even though the "Response completions"
toggle is ON. The failure is entirely silent: no toast, no sound, and no
entry accumulates in the Windows notification center. No error surfaces to
the user.

Key diagnostic element, which I have not seen reported elsewhere: on the
same machine and the same app install, Claude Code and Claude Cowork
notifications fire correctly. I reliably get Windows banners when a Code
session finishes. Only Chat response completions are silent.

Since Cowork runs through its own cowork-svc process and Code has its own
notification channel, the Chat completion trigger appears to be the only
path that is either not wired or not firing.

Everything below has been verified and ruled out:

• "Response completions" toggle is ON in app settings
• Claude is listed and enabled in Windows Settings > System > Notifications,
  with banners and sounds
• No Focus Assist or Do Not Disturb rule active
• A PowerShell toast test displays a banner correctly, so the OS
  notification pipeline works
• Full uninstall and clean reinstall performed
• Efficiency Mode removed from all Claude processes in Task Manager
• Background execution permission changed from "Power optimized" to "Always"
• "Run at startup" enabled
• Full machine restart after all of the above
• Tested repeatedly with long-running responses while focused on another
  application, to rule out foreground suppression

Additional observation: the Claude icon is no longer present in the Windows
system tray, and Claude does not appear under Personalization > Taskbar >
Other system tray icons. It used to be there before this started.

Related: #42041 (Windows, closed as Not planned and now locked) and #50480
(macOS, same symptom). Filing a new issue as instructed by the lock bot on
#42041.

A support ticket is open (ref 215475549252948). Support suggested a clean
reinstall, which cannot be the cause given that Code and Cowork notify from
this same install.

What Should Happen?

A Windows notification banner should appear when a Chat response finishes
while the app is unfocused, as it does for Code and Cowork sessions, and as
it did in earlier versions on this same machine.

Error Messages/Logs

Steps to Reproduce

1. Open the Claude desktop app on Windows 11.
2. Confirm "Response completions" is ON in Settings > Desktop app > General.
3. Send a long-running request (web search with synthesis, >60s).
4. Immediately switch focus to another application (e.g. Outlook).
5. Wait for the response to complete.

Expected: a Windows banner announces the completed response.
Actual: no banner, no sound, nothing in the notification center.

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

No response

Claude Code Version

1.32885.1.0 (Claude desktop app)

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Other

Additional Information

No response

No source files, tests, logs, or implementation entry points are identified. Reproduce on Windows 11 with Response completions enabled and compare the silent Chat path with the working Code and Cowork notification paths; done means a completion produces a Windows banner, sound, and notification-center entry while the app is unfocused.