[BUG] MSIX Installation failure: AddPackage failed with HRESULT 0x80073CF9

Managed to work around the issue this second time more quickly by basically a) backing up existing state b) deleting the blocking CoWork service, c) then running the installer which then succeeds and d) restoring the application state afterwards. Claude assisted and wrote this summary of the procedure:

Claude Desktop Upgrade failure workaround (0x80073CF6)

Symptom: Upgrade/install fails with 0x80073CF6/0x80073CF9; log shows WARNING: CoworkVMService already exists and failed to remove conflicting service: Access is denied.
Root cause: Orphaned/DACL-locked CoworkVMService blocks MSIX windows.service registration (known bug — see Appendix). Recovery requires package removal, which wipes Cowork state unless backed up first.
Validated: 2026-07-04, full data recovery achieved.

---

Step 1 — BACKUP (never skip)

$stamp = Get-Date -Format 'yyyyMMdd-HHmmss'
$bk = "C:\Backups\ClaudeCowork-$stamp"
New-Item -ItemType Directory -Force $bk | Out-Null
Copy-Item "$env:USERPROFILE\Documents\Claude" "$bk\Documents-Claude" -Recurse -ErrorAction SilentlyContinue
Copy-Item "$env:LOCALAPPDATA\Packages\Claude_pzs8sxrjxfjjc" "$bk\Packages-Claude" -Recurse -ErrorAction SilentlyContinue
Write-Host "Backup at $bk"

✅ Check: Get-ChildItem "$bk\Packages-Claude" shows LocalState, LocalCache, Settings. LocalCache is large (multi-GB, contains Cowork VM disk) — that's expected.

What lives where:

• Documents\Claude\{Projects,Artifacts,Scheduled} — content + task SKILL.md files (survives reinstall anyway)
• Packages\Claude_pzs8sxrjxfjjc\ — project registrations, session history, memory, run history (deleted by uninstall)

Step 2 — Remove Claude packages (elevated PowerShell)

Get-AppxPackage -AllUsers *Claude* | Format-List Name, Version, Status, PackageUserInformation   # inspect first
Get-AppxPackage -AllUsers *Claude* | Remove-AppxPackage -AllUsers

✅ Check: Get-AppxPackage -AllUsers *Claude* returns nothing.
⚠️ If removal fails 0x80073CFA on a Status: Servicing package → see full guide Tier 3/4 (psexec / WinRE StateRepository surgery).

Step 3 — Delete orphaned CoworkVMService (elevated)

reg delete "HKLM\SYSTEM\CurrentControlSet\Services\CoworkVMService" /f

If Access Denied: psexec -s reg delete "HKLM\SYSTEM\CurrentControlSet\Services\CoworkVMService" /f

✅ Check: Get-Item "HKLM:\SYSTEM\CurrentControlSet\Services\CoworkVMService" -EA SilentlyContinue returns nothing.

Step 4 — Reboot, then install

Run Claude Setup.exe.
✅ Check: log ends === Claude Setup completed successfully ===; Get-AppxPackage *Claude* shows Status: Ok. Cowork showing in Start menu with proper icon etc.

• If app missing from Start menu: reboot again (stale shell cache/pending installer actions -- do not skip). Post 2nd reboot app should show in menu with proper icon etc.

Step 5 — Restore Cowork state

Close Claude fully first:

Get-Process | ? { $_.Name -match "Claude" -and $_.MainWindowHandle -ne 0 } | % { $_.CloseMainWindow() | Out-Null }
Start-Sleep 5
Stop-Service CoworkVMService -ErrorAction SilentlyContinue
Get-Process | ? { $_.Name -match "Claude|cowork" } | Stop-Process -Force   # stragglers only

Restore:

$pkg = "$env:LOCALAPPDATA\Packages\Claude_pzs8sxrjxfjjc"
$bk  = "C:\Backups\ClaudeCowork-<STAMP>\Packages-Claude"   # your backup path
Copy-Item $pkg "$pkg-fresh" -Recurse                        # rollback safety copy
Copy-Item "$bk\LocalState" $pkg -Recurse -Force
Copy-Item "$bk\Settings"   $pkg -Recurse -Force
Copy-Item "$bk\LocalCache" $pkg -Recurse -Force

✅ Check: Launch Claude → Cowork → Projects and Scheduled entries present.
⚠️ Known quirk: app may automatically restart shortly after initial start (crash?) on first use after restore. Post restart it should be fine.
🔙 Rollback: delete restored folders, copy back from $pkg-fresh.

Step 6 — Housekeeping

• Delete $pkg-fresh once confirmed stable.
• Keep the backup a week or two.
• Report to Anthropic with %TEMP%\ClaudeSetup.log — reference issues in Appendix below.

⚠️ Known quirk: You may run into this:

<img width="710" height="149" alt="Image" src="https://github.com/user-attachments/assets/31fff912-14e7-444e-bba2-48cf517060dd" />

If you do, follow the offered "reinstall" path after which this should be resolved too.

Appendix — Related GitHub Issues (anthropics/claude-code)

| Issue | Description | Status |
|---|---|---|
| #37898 | Cowork MSIX fails 0x80073CF6 after full uninstall | Closed (duplicate) |
| #48437 | AddPackage 0x80073CF6, CoworkVMService Access Denied | Closed (not planned) |
| #49540 | Cowork install fails 0x80073CF6, misdirected support response | Closed (not planned) |
| #49917 | AddPackage 0x80073CF6 after earlier install left package inconsistent | Open (reopened) |
| #53504 | Install fails 0x80073D28, permanent Servicing deadlock, registry key missing | Closed (duplicate) |
| #59471 | AddPackage 0x80073CF6 on retry, elevated and non-elevated | Closed (not planned) |
| #61392 | 0x80073D28 and 0x80073CF6, invalid PreserveApplicationData flag combo | Closed (not planned) |
| #67547 | 0x80073CF6, but root cause looks like MSIX download/Edge-installer crash, not CoworkVMService | Open |
| #74170 | This report (yours) — CoworkVMService Access Denied, 0x80073CF9, second recurrence | Open |

Today I was offered an upgrade in Claude Desktop app. The installer has again failed with:

<img width="525" height="163" alt="Image" src="https://github.com/user-attachments/assets/d30e7fa8-8391-46da-97bd-0a4176f76f95" />

I'm expecting it's going to break the app again. ... Yep won't start now. Trying manual install...:

<img width="400" height="355" alt="Image" src="https://github.com/user-attachments/assets/bfaf2d6c-9066-4f9d-8b0d-d52b64212401" />

<img width="394" height="185" alt="Image" src="https://github.com/user-attachments/assets/d5b0f8e2-7e3c-49f7-81b6-328c016a53b3" />

Error log:

2026/07/07 10:01:37.632630 Log file: C:\Users\walterp\AppData\Local\Temp\ClaudeSetup.log
2026/07/07 10:01:37.633635 === Claude Setup b682d9f76a56cebb3327f0de7eda65a8399d4835 started ===
2026/07/07 10:01:37.634668 AllowAllTrustedApps not found (sideloading assumed enabled): The system cannot find the file specified.
2026/07/07 10:01:37.635193 Windows edition: Professional
2026/07/07 10:01:37.635711 WARNING: CoworkVMService already exists (potential conflict)
2026/07/07 10:01:37.635711 Windows version: 10.0.26200
2026/07/07 10:01:37.635711 Native arch: x64
2026/07/07 10:01:37.635711 Elevation type: Limited
2026/07/07 10:01:37.635711 Is elevated: false
2026/07/07 10:01:37.635711 Sideloading enabled: true
2026/07/07 10:01:37.635711 S Mode: false
2026/07/07 10:01:37.635711 Conflicting service: true
2026/07/07 10:01:37.635711 Running in non-elevated context
2026/07/07 10:01:37.635711 User can elevate — installing MSIX directly
2026/07/07 10:01:37.661498 Splash: 400x300, 8 frame(s), animated=true
2026/07/07 10:01:37.661498 System DPI: 96 (scale: 100%)
2026/07/07 10:01:37.727220 MSIX URL: https://api.anthropic.com/api/desktop/win32/x64/msix/latest/redirect
2026/07/07 10:01:37.727741 Downloading MSIX to C:\Users\walterp\AppData\Local\Temp\Claude-4031370224.msix
2026/07/07 10:01:37.742282 proxy: WinHttpGetProxyForUrl("https://api.anthropic.com/api/desktop/win32/x64/msix/latest/redirect"): winapi error #12167
2026/07/07 10:01:38.140399 proxy: WinHttpGetProxyForUrl("https://downloads.claude.ai/releases/win32/x64/1.18286.2/Claude-b682d9f76a56cebb3327f0de7eda65a8399d4835.msix"): winapi error #12167
2026/07/07 10:01:39.651447 Download progress: 10% (23560016 / 235535538 bytes)
2026/07/07 10:01:40.542486 Download progress: 20% (47120032 / 235535538 bytes)
2026/07/07 10:01:41.433573 Download progress: 30% (70680112 / 235535538 bytes)
2026/07/07 10:01:42.325332 Download progress: 40% (94239488 / 235535538 bytes)
2026/07/07 10:01:43.215867 Download progress: 50% (117783680 / 235535538 bytes)
2026/07/07 10:01:44.221187 Download progress: 60% (141327312 / 235535538 bytes)
2026/07/07 10:01:45.116568 Download progress: 70% (164886752 / 235535538 bytes)
2026/07/07 10:01:46.008403 Download progress: 80% (188446768 / 235535538 bytes)
2026/07/07 10:01:46.899827 Download progress: 90% (212007344 / 235535538 bytes)
2026/07/07 10:01:47.797047 Download progress: 100% (235535538 / 235535538 bytes)
2026/07/07 10:01:47.798090 Download complete: 235535538 bytes, SHA256: 48204aba2f44cf8c08b913eec12d2a7f6e335680129fdc0811f2e789c645dbff
2026/07/07 10:01:47.799131 Download complete
2026/07/07 10:01:47.807047 Self-elevating: C:\Users\walterp\Downloads\Claude Setup.exe --elevated --msix-path "C:\Users\walterp\AppData\Local\Temp\Claude-4031370224.msix" --log-path "C:\Users\walterp\AppData\Local\Temp\ClaudeSetup.log"
2026/07/07 10:01:51.492742 Waiting for elevated process to complete...
2026/07/07 10:01:51.509821 Log file: C:\Users\walterp\AppData\Local\Temp\ClaudeSetup.log
2026/07/07 10:01:51.510346 === Claude Setup b682d9f76a56cebb3327f0de7eda65a8399d4835 started ===
2026/07/07 10:01:51.511932 AllowAllTrustedApps not found (sideloading assumed enabled): The system cannot find the file specified.
2026/07/07 10:01:51.512446 Windows edition: Professional
2026/07/07 10:01:51.512969 WARNING: CoworkVMService already exists (potential conflict)
2026/07/07 10:01:51.513492 Windows version: 10.0.26200
2026/07/07 10:01:51.513492 Native arch: x64
2026/07/07 10:01:51.513492 Elevation type: Full
2026/07/07 10:01:51.513492 Is elevated: true
2026/07/07 10:01:51.513492 Sideloading enabled: true
2026/07/07 10:01:51.513492 S Mode: false
2026/07/07 10:01:51.513492 Conflicting service: true
2026/07/07 10:01:51.513492 Running in elevated context
2026/07/07 10:01:51.513492 Installing MSIX from C:\Users\walterp\AppData\Local\Temp\Claude-4031370224.msix (all-users: false)
2026/07/07 10:01:51.546208 Splash: 400x300, 8 frame(s), animated=true
2026/07/07 10:01:51.546726 System DPI: 96 (scale: 100%)
2026/07/07 10:01:51.624770 Verifying Authenticode signature on C:\Users\walterp\AppData\Local\Temp\Claude-4031370224.msix
2026/07/07 10:01:52.413615 WinVerifyTrust: MSIX signature is valid
2026/07/07 10:01:52.748130 Signature verified: MSIX signer matches bootstrapper
2026/07/07 10:01:52.749956 Extracted family name from MSIX manifest: Claude_pzs8sxrjxfjjc
2026/07/07 10:01:52.749956 Squirrel process prefix: c:\users\walterp\appdata\local\anthropicclaude\
2026/07/07 10:01:52.749956 Checking for running Squirrel Claude processes...
2026/07/07 10:01:52.768076 No Squirrel Claude processes found
2026/07/07 10:01:52.768076 Removing conflicting CoworkVMService...
2026/07/07 10:01:52.768076 WARNING: failed to remove conflicting service: could not open CoworkVMService: Access is denied.
2026/07/07 10:01:52.768076 Checking for existing Claude MSIX packages...
2026/07/07 10:01:52.787713 Removing: Claude_1.18286.0.0_x64__pzs8sxrjxfjjc
2026/07/07 10:01:52.792348 Windows rejected data-preserving removal for Claude_1.18286.0.0_x64__pzs8sxrjxfjjc (0x80073CFA, requires developer mode); relying on in-place update
2026/07/07 10:01:52.792348 Removing: Claude_1.18286.2.0_x64__pzs8sxrjxfjjc
2026/07/07 10:01:52.795438 Windows rejected data-preserving removal for Claude_1.18286.2.0_x64__pzs8sxrjxfjjc (0x80073CFA, requires developer mode); relying on in-place update
2026/07/07 10:01:52.813949 Removing (user): Claude_1.18286.0.0_x64__pzs8sxrjxfjjc
2026/07/07 10:01:52.817659 Windows rejected data-preserving removal for Claude_1.18286.0.0_x64__pzs8sxrjxfjjc (0x80073CFA, requires developer mode); relying on in-place update
2026/07/07 10:01:52.817659 Installing MSIX: C:\Users\walterp\AppData\Local\Temp\Claude-4031370224.msix
2026/07/07 10:01:52.817659 Standard install (not split-account), using AddPackage
2026/07/07 10:01:52.817659 Installing via AddPackage (current-user)...
2026/07/07 10:01:54.101339 MSIX installation failed: AddPackage failed: AddPackage failed with HRESULT 0x80073CF9
2026/07/07 10:01:54.101872 ERROR dialog (opening log): Installation failed: AddPackage failed: AddPackage failed with HRESULT 0x80073CF9

Please share this log with us.
2026/07/07 10:02:04.590353 Elevated process exited with code 1
2026/07/07 10:02:04.590353 Elevation failed: elevated installer exited with code 1
2026/07/07 10:02:04.590353 ERROR dialog (with log path): Administrator access is required to install Claude with full features. You can try again or install without Cowork.

Same failure mode as before. 😞 The installer cannot handle the upgrade on my machine properly.

@ByteJuggler I have fixed the issue with the methods here.
https://www.reddit.com/r/ClaudeAI/comments/1so7vb7/if_you_run_into_issues_installing_or_updating/

@ByteJuggler I have fixed the issue with the methods here. https://www.reddit.com/r/ClaudeAI/comments/1so7vb7/if_you_run_into_issues_installing_or_updating/

Thanks, appreciate it. I (had to) go through a similar deep dive originally to fix this but to note, currently if you're seeing specifically AddPackage failed: AddPackage failed with HRESULT 0x80073CF9 then my steps above resolve it with less complexity and more importantly, it ensures you don't lose state/data.

To explain, the original procedure I used more or less mirrors your link, probably because mine procedure, and by the looks of its process, was generated by Claude itself, and does manage to get you to a point of being able to install the application again. _However,_ it lost my Cowork project state. So, I strongly suspect the linked process will also still lose user state, because I see no mention of any backups being taken that addresses that problem.

My simplified process (above) is what I distilled the fix to when I ran into this issue. It addresses this by backing up the state first, then doing a minimal cleanup to allow the installer to succeed, then restoring the state afterwards. This works for the specific case of AddPackage failed: AddPackage failed with HRESULT 0x80073CF9 accompanied by WARNING: failed to remove conflicting service: could not open CoworkVMService: Access is denied. in the log.

Nevertheless, thanks for the link, it may be useful for others in the same boat. It is a very infuriating bug.

The latest build of Claude desktop still exhibits this bug, and again broke my installation. Log: https://gist.github.com/ByteJuggler/6e74daa2dc652f6b17ff42622bd60eea

The fix process documented earlier (again) resolved this.

Then let the AI completely uninstall everything related to Claude, and then try reinstalling it.

Thank you, this worked exactly to solve claude breaking after an update+restart, thank you, youve earned my follow ❤️

Hitting this same failure on Windows 10, which may narrow the cause.

Environment

• Claude Desktop 1.24012.9.0 (MSIX), family Claude_pzs8sxrjxfjjc
• Windows 10 Pro 19045 (22H2), x64, Italian locale
• No Hyper-V, no Docker Desktop
• Claude Code 2.1.181 (standalone CLI); app bundles 2.1.219

Two differences from the original report that might help:

1. Not Windows 11 specific — same failure on 10.0.19045 vs the reporter's 10.0.26200.
2. Not Hyper-V/Docker specific — neither is installed here, so the suggested repro condition isn't necessary.
3. Same-version case — my install was removing and reinstalling 1.24012.9.0 over itself, not upgrading across versions. Same result.

The common factor in both reports is the orphaned CoworkVMService, which fails to be removed even in the elevated pass:

WARNING: CoworkVMService already exists (potential conflict)
...
Running in elevated context
...
Removing conflicting CoworkVMService...
WARNING: failed to remove conflicting service: could not open CoworkVMService: Accesso negato.
Checking for existing Claude MSIX packages...
Removing: Claude_1.24012.9.0_x64__pzs8sxrjxfjjc
Windows rejected data-preserving removal for Claude_1.24012.9.0_x64__pzs8sxrjxfjjc (0x80073CFA, requires developer mode); relying on in-place update
Installing via AddPackage (current-user)...
MSIX installation failed: AddPackage failed: AddPackage failed with HRESULT 0x80073CF9

Followed by the same misleading dialog — "Administrator access is required" — despite Is elevated: true two lines earlier in the log.

Also worth noting what sent me here: the desktop app crashed when I opened the plan-change screen, which is what prompted the reinstall in the first place. That has now happened twice, and each reinstall destroyed my Claude Code session history. Filing that separately.