[BUG] Updater misdetects sideloaded MSIX as a Store install and hangs the app on every launch

### Preflight Checklist

- [x] I have searched [existing issues](https://github.com/anthropics/claude-code/issues?q=is%3Aissue%20state%3Aopen%20label%3Abug) and this hasn't been reported yet
- [x] This is a single bug report (please file separate reports for different bugs)
- [x] I am using the latest version of Claude Code

### What's Wrong?

On Windows, Claude Desktop installed from claude.com/download (sideloaded MSIX, SignatureKind: Developer) is detected by the updater as a Microsoft Store install:

[updater] MSIX detected: windowsStore=true, appPathMatch=true, source=windowsStore,
exe=C:\Program Files\WindowsApps\Claude_1.46388.1.0_x64__pzs8sxrjxfjjc\app\Claude.exe

appPathMatch appears to infer the source from the WindowsApps path, which every registered MSIX uses regardless of origin. SignatureKind would distinguish the two and does not appear in the log. The app is not present in the Microsoft Store library.

Roughly 33 seconds after each launch the updater fires and begins a download. Within 17–29 seconds the app becomes unusable:

[updater] Found an update, downloading
Main webview is unresponsive, will kill and reload
Network Service process gone (reason=killed, exitCode=1) outside app quit
— main-process networking is broken until relaunch

The network service is not respawned, so the app is alive but cannot make any network request. The device bridge then fails handshakes indefinitely with exponential backoff (reconnect #1–#12, out to 30s). The renderer the watchdog kills is not the process at fault.

Correlation: four Found an update, downloading events in the log, each followed within 17–29s by a hang. No hang occurs without one. Not GPU-related (no GPU process gone), not memory (~24 GB free of 32 GB throughout), not virtualization (no vmcompute warnings).

Aggravating factor: [updater] Using GrowthBook check_interval_ticks=1 (default 4) — checks run 4× more often than default, so this triggers on essentially every launch.

### What Should Happen?

Expected: a sideloaded MSIX should be detected by signature, not install path. A failed or unsupported update download should not kill the network service, and the loss of the network service should not leave the app running-but-dead.

### Error Messages/Logs

```shell

```

### Steps to Reproduce

n/a

### Claude Model

None

### Is this a regression?

Yes, this worked in a previous version

### Last Working Version

_No response_

### Claude Code Version

Windows, Claude Desktop 1.46388.1 (MSIX, sideloaded from claude.com), CCD 2.1.260, Node 24.18.1, 32 GB RAM.

### Platform

Other

### Operating System

Windows

### Terminal/Shell

Other

### Additional Information

_No response_

No source files, tests, or reproducible steps are identified. Start by tracing the Windows updater's MSIX detection and download-trigger path, comparing SignatureKind with the logged appPathMatch result. Done means a sideloaded MSIX is not treated as a Store install and update or network-service failures do not leave the app unusable.

Rédigé par le modèle d'indexation à partir du texte de l'issue.