Installing or updating Claude Desktop on Windows stops with:

text

AddPackage failed with HRESULT 0x80073CF9

30-second answer

Do not delete a service based on the error code alone. 0x80073CF9 only means

"install failed" and has several possible causes. Run Get-AppxLog first and read the log.

The workaround below applies only if the log shows a CoworkVMService conflict.

A different log means a different cause, and these steps will not help.

1. What the error means [Microsoft official]

Per Microsoft's documentation:

CodeNameMeaning
0x80073CF9ERROR_INSTALL_FAILEDPackage install failed. Contact the software vendor. Check the AppXDeployment-Server event log for details
0x80073CF6ERROR_INSTALL_REGISTRATION_FAILUREThe package can't be registered
0x80073CFAERROR_REMOVE_FAILEDPackage removal failed
0x80073D27ERROR_SERVICE_EXISTS_AS_NON_PACKAGED_SERVICEInstall failed because a version of the service exists outside the .msix package

0x80073CF9 on its own does not tell you the cause. You have to read the log.

2. Find the real error first — non-destructive [Microsoft official]

These commands only read. Run them in PowerShell.

powershell

Get-AppxLog

As a table:

powershell

Get-AppxLog | Out-GridView

You can also use Event Viewer. Run eventvwr.msc and open

**Applications and Services Logs → Microsoft → Windows → AppXDeployment-Server →

Microsoft-Windows-AppXDeploymentServer/Operational**.

3. Confirm this is your case [observed in the official issue]

The install log posted in Anthropic's public issue #74170 contained these lines:

text

Removing conflicting CoworkVMService...
WARNING: failed to remove conflicting service: ...

The user who worked around it described the matching symptom as:

text

WARNING: CoworkVMService already exists
failed to remove conflicting service: Access is denied

The same issue gives the install log location:

text

C:\Users\<user>\AppData\Local\Temp\ClaudeSetup.log

All three must match.

  1. The error is 0x80073CF9 or 0x80073CF6
  2. CoworkVMService appears in the log
  3. That line says already exists or Access is denied

4. If the log is different — stop here

If those three do not match, your cause is different. Do not run the steps below.

Deleting the service will not fix it and leaves you in a state that is hard to undo.

If Get-AppxLog shows a different code (0x80073CF4 disk space, 0x80073D01 policy block,

and so on), start from that entry in Microsoft's documentation instead.

5. Record the current state before changing anything

Capture what exists now. You will need it to undo.

powershell

Get-AppxPackage -AllUsers *Claude* | Format-List Name, Version, Status, PackageUserInformation
Get-Service CoworkVMService -ErrorAction SilentlyContinue | Format-List Name, Status, StartType
reg query "HKLM\SYSTEM\CurrentControlSet\Services\CoworkVMService"

Save the output to a file. It is the only record of what the original state was.

6. The workaround confirmed by users

⚠️ [Community-verified workaround]

This is not a procedure recommended by Microsoft or Anthropic.

A user in the public issue assembled it with AI assistance, applied it successfully twice,

and one other user confirmed it worked for them.

The issue is open with no official fix announced at the time of writing.

It removes packages and edits the registry, so treat it as a last resort.

6-1. Back up — do not skip

Removing the package deletes Cowork state. Copy it first.

powershell

$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

Check: Get-ChildItem "$bk\Packages-Claude" should show LocalState, LocalCache, Settings.

LocalCache is multi-GB — it holds the Cowork VM disk, which is expected.

What lives where:

  • Documents\Claude\ — content and task files. Survives a reinstall
  • Packages\Claude_pzs8sxrjxfjjc\ — project registrations, session history, memory. Deleted by removal

6-2. Remove the packages (elevated PowerShell)

powershell

Get-AppxPackage -AllUsers *Claude* | Remove-AppxPackage -AllUsers

Check: Get-AppxPackage -AllUsers *Claude* should return nothing.

If removal fails with 0x80073CFA on a package whose Status is Servicing, stop here

and read the public issue. Anything beyond this point touches deep system state.

6-3. Delete the orphaned service entry (elevated)

Confirm you completed step 5 first.

powershell

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

Check:

powershell

Get-Item "HKLM:\SYSTEM\CurrentControlSet\Services\CoworkVMService" -ErrorAction SilentlyContinue

Returning nothing means it is gone.

6-4. Reboot, then install

Reboot, then run Claude Setup.exe.

7. How to confirm it worked

powershell

Get-AppxPackage -AllUsers *Claude* | Format-List Name, Version, Status

Status: Ok with the new version means the install completed.

ClaudeSetup.log should no longer contain AddPackage failed.

Restoring your backed-up Packages-Claude brings back project registrations and session history.

8. What not to do

  • Deleting the service without reading the log — if the cause is different you only make it worse
  • Removing packages without a backup — Cowork state is gone
  • Deleting services other than CoworkVMService — only remove an exact name match
  • "Installation is broken, delete everything" — this error is not a PATH or permissions problem

9. Evidence

[Microsoft official] — error code meanings and the Get-AppxLog / AppXDeployment-Server

event log diagnostic procedure.

[Anthropic official issue] — that the Windows install failure occurs, the CoworkVMService

conflict log lines, and the install log location. Issues #74170 (labels platform:windows,

area:installation, area:cowork) and #80876 (interrupted auto-update leaves MSIX in

Servicing/Staged state).

[Community-verified] — the workaround in section 6. Not an official recommendation.

A user assembled it in the public issue; they confirmed it twice and one other user confirmed it.

What is officially confirmed stops at "this code means install failed, read the log."

"Delete CoworkVMService and it works" is a user-verified workaround, not an official fix.

10. Scope and review

  • Applies to: Windows · Claude Desktop (MSIX install)
  • Does not apply to: macOS · Linux · Claude Code CLI installed via npm
  • Status at time of writing: public issues #74170 and #80876 are both open, no official fix announced
  • Last reviewed: 2026-07-29