[BUG] Windows desktop app (MSIX) uninstalls itself and wipes all local data during silent auto-update when background sessions are running

Preflight Checklist

• [x] I have searched existing issues 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?

The Claude Desktop app on Windows (MSIX package Claude_pzs8sxrjxfjjc, v1.26832.0.0) force-closes and completely uninstalls itself while I'm working, whenever its silent auto-update/self-repair runs with background sessions active. On next launch Windows shows: "There's a problem with Claude. Reinstall the application from its original install location or contact the administrator." This happened ~6 times in one night (Aug 8-9, 2026 at 00:05, 00:18, 00:50, 01:31, 01:49, 02:15 local), and every cycle wipes all local data (chats, sessions, config, login).

Root cause visible in the Microsoft-Windows-AppXDeploymentServer/Operational event log:

1. The updater starts a deployment with ForceApplicationShutdownOption,ForceUpdateFromAnyVersion — this is what kills the app mid-work.
2. It tries Remove with PreserveApplicationData → Windows rejects it with 0x80073CFA ("PreserveApplicationData flag can only be used on a package deployed in development mode"), so app data is never preserved.
3. It falls back to a full Remove with RemoveForAllUsers → all container data (LocalCache) is destroyed.
4. The Add of the new .msix intermittently fails with 0x80070020 (file in use) and repair registration fails with 0x80073D02 (package in use) — background claude.exe processes from running sessions keep package files locked.
5. The package stays removed → app uninstalled, all local data lost.

Side effects: a WER AppHang for Claude.exe, repeated RegisterByPackageFullName ... RepairAppRegistrationOption failure loops, and orphaned chats that reappear in the session list but can't be resumed ("Remote control disconnected — the bridged Claude Code process stopped responding").

Note: updates on Jul 19 – Aug 6 (1.22209 → 1.24012 → 1.25927 → 1.26832) used a non-destructive flow (DeferRegistrationWhenPackageInUse) and succeeded without data loss. The destructive remove+add loop started Aug 8.

What Should Happen?

• The auto-updater should never fall back to a data-destroying full Remove when PreserveApplicationData is rejected by Windows.
• If the package is in use (running sessions/background agents), the update should be deferred or retried later — not force-close active work and leave the app uninstalled.
• User data (chats, sessions, config) should survive app updates/reinstalls instead of living only inside the MSIX container that the update path wipes.

Error Messages/Logs

From `Microsoft-Windows-AppXDeploymentServer/Operational`:

- [717] Windows cannot remove Claude_1.26832.0.0_x64__pzs8sxrjxfjjc because the PreserveApplicationData flag can only be used on a package that was deployed in development mode.
- [404] AppX Deployment operation failed for package with error 0x80073CFA.
- [603] Started deployment Remove operation ... Options PreserveApplicationData,RemoveForAllUsers
- [401] Deployment Add operation ... from: (Claude-623836466.msix) failed with error 0x80070020.
- [401] Deployment Register operation ... from: (AppxManifest.xml) failed with error 0x80073D02.

Windows error shown to the user on launch:
"There's a problem with Claude. Reinstall the application from its original install location or contact the administrator."

WER report: AppHang_Claude_1.26832.0 (Aug 9, 02:00 local).

Steps to Reproduce

1. Install Claude Desktop on Windows 10 Pro 22H2 (build 19045) — MSIX sideloaded package, Developer signature.
2. Start one or more long-running tasks/background agents so claude.exe processes stay alive (I had ~12 running).
3. Leave the app working and wait for the silent auto-update/self-repair to trigger (no user action, no visible "update pending" notice).
4. The app force-closes, the package is fully removed, and the re-install intermittently fails with 0x80070020 / 0x80073D02 because the running processes keep files locked.
5. Result: app uninstalled, all local data wiped. Reproduced ~6 times in one night.

Claude Model

Not sure / Multiple models

Is this a regression?

Yes, this worked in a previous version

Last Working Version

Desktop app 1.25927.0.0 (updated Aug 4 without data loss); destructive loop started Aug 8 on 1.26832.0.0

Claude Code Version

2.1.226 (Claude Code)

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

• Package: Claude_pzs8sxrjxfjjc, SignatureKind: Developer, installed under C:\Program Files\WindowsApps\.
• Disk and Windows package database are healthy (no NTFS/StateRepository errors) — ruled out as causes.
• Antivirus ruled out: Malwarebytes service stopped since Jul 25; Windows Defender has no detections for any Claude file.
• The updater downloads each .msix to %LOCALAPPDATA%\Temp\Claude-*.msix (~254 MB) before the remove+add cycle.