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Claude Code Issues / #32481

[BUG] CoworkVMService crashes with 'Incorrect function' on Windows 11 Pro 25H2 Build 26200 (v1.1.5749)

Status Fixed / completed
Maintainer reply None cached
Activity 4 comments · opened Mar 9, 2026 · closed Apr 5, 2026

Bug Description

CoworkVMService immediately crashes with "Incorrect function" (service-specific error) on Windows 11 Pro 25H2 Build 26200. The VM bundle downloads successfully ("All files ready") but the service binary (cowork-svc.exe) fails to initialize.

Environment

  • OS: Windows 11 Pro 25H2 (Build 26200.7922)
  • Claude Desktop: v1.1.5749.0 (MSIX)
  • CPU: x64
  • WSL: 2.5.9.0, Kernel 6.6.87.2-1
  • HyperVisorPresent: True

Windows Features (all enabled)

  • VirtualMachinePlatform: Enabled
  • Microsoft-Hyper-V: Enabled
  • Microsoft-Hyper-V-All: Enabled
  • HypervisorPlatform: Enabled
  • Microsoft-Windows-Subsystem-Linux: Enabled

Services (all running)

  • vmcompute: Running
  • vmms: Running
  • hns: Running
  • CoworkVMService: Stopped (crashes on start)

User is in Hyper-V Administrators group: Yes

Error

Windows System Event Log (Event ID 7024):

The Claude service terminated with the following service-specific error: Incorrect function.

Also observed DCOM Event 10016:

The application-specific permission settings do not grant Local Activation permission 
for the COM Server application with CLSID {2593F8B9-4EAF-457C-B68A-50F6B8EA6B54} 
and APPID {15C20B67-12E7-4BB6-92BB-7AFF07997402} 
to the user AMER\HP ZBOOK SID (S-1-5-21-205957447-2577333058-211944522-1002)

Steps to Reproduce

  1. Install Claude Desktop v1.1.5749 on Windows 11 Pro Build 26200
  2. Enable Hyper-V, VirtualMachinePlatform, HypervisorPlatform
  3. Open Claude Desktop → Cowork
  4. Bundle downloads successfully ("All files ready in vm_bundles\claudevm.bundle")
  5. CoworkVMService starts and immediately crashes with "Incorrect function"

cowork_vm_node.log (relevant section)

[info] rootfs.vhdx.zst checksum validated
[info] [downloadVM] Saved compressed rootfs.vhdx to cache
[info] vmlinuz.zst checksum validated
[info] [downloadVM] Saved compressed vmlinuz to cache
[info] initrd.zst checksum validated
[info] [downloadVM] Saved compressed initrd to cache
[info] All files ready in C:\Users\HP ZBOOK\AppData\Roaming\Claude\vm_bundles\claudevm.bundle
[info] [VM] Loading vmClient (TypeScript) module...
[info] [VM] Module loaded successfully

The Node.js vmClient module loads but never proceeds — the service pipe/socket never responds because cowork-svc.exe has already crashed.

What I've Tried (none resolved the crash)

  1. DCOM permission fix: Added user SID and app container SID to LaunchPermission for APPID {15C20B67-12E7-4BB6-92BB-7AFF07997402} — DCOM 10016 may be resolved but service still crashes
  2. Enabled HypervisorPlatform Windows feature + reboot
  3. Added user to Hyper-V Administrators group + reboot
  4. Deleted vm_bundles and claude-code-vm folders for clean rebuild
  5. Restarted HNS + vmcompute services, flushed DNS
  6. Windows Defender exclusions for Claude WindowsApps and AppData paths
  7. Copied cowork-svc.exe out of WindowsApps to bypass MSIX sandbox — still crashes
  8. Fixed EXDEV cross-device rename errors (TEMP was on D:, AppData on C:) — bundle now downloads successfully
  9. Freed disk space (C: was at 162MB, now 29GB free)

Additional Notes

  • The TEMP/TMP env vars were originally pointing to D:\Caches\Temp while AppData is on C:, causing EXDEV errors during download. Fixed by changing TEMP to C:\Users\...\AppData\Local\Temp.
  • The MSIX sandbox complicates debugging — cowork-svc.exe cannot be launched directly ("Access is denied") and sc.exe config also returns "Access denied" for this MSIX-registered service.
  • The service crashes before any HCS/network operations — "Incorrect function" appears to be during early initialization (possibly signature verification or path resolution).

Related Issues

  • #30179 (DCOM 10016 blocks CoworkVMService)
  • #27652 (HcnCreateNetwork fails on Build 26200)
  • #27801 (VM service not running, persists after reboot)
  • #30584 (EXDEV cross-device link on MSIX)

@MarshallOfSound — would appreciate any guidance. Happy to provide additional logs or run diagnostic commands.

View original on GitHub ↗

4 Comments

LozadAPP · 6 months ago

Same build here — Windows 11 Pro 25H2 Build 26200. Had the exact same "Incorrect function" / signature verification crash.

I see you already tried a lot of things. Here's what ended up working for me:

For the signature verification / "Incorrect function" error:

Make sure your Windows is fully updated. I installed KB5086672 (takes you to build 26200.8117) and also activated my Windows license. After doing both, the service started without any workarounds — no need to copy cowork-svc.exe anywhere.

You can check your current build with winver. If you're still on 26200.7922, that update might make the difference.

After this fix, my service log went from the crash to:

[Server] Signature verification initialized [Server] Client signature verified Service ready. Listening on \\.\pipe\cowork-vm-service

About the EXDEV error you also fixed:

I had that one too. In my case it wasn't just about TEMP being on D:\. The real cause was that in Settings > System > Storage > Where new content is saved, apps were set to save on D:\. This makes Windows create symlinks inside AppData\Local\Packages\Claude_pzs8sxrjxfjjc\ pointing to D:\WpSystem\..., so any rename inside that path is cross-device.

You can check with:

Get-ChildItem "$env:LOCALAPPDATA\Packages\Claude_pzs8sxrjxfjjc" | Format-Table Name, Attributes, Target

If you see symlinks to D:\ → change app storage to C:\, then clean reinstall:

Remove-Item "$env:APPDATA\Claude" -Recurse -Force
Remove-Item "$env:LOCALAPPDATA\Claude" -Recurse -Force
Remove-Item "C:\ProgramData\Claude" -Recurse -Force
Remove-Item "$env:LOCALAPPDATA\Packages\Claude_pzs8sxrjxfjjc" -Recurse -Force
Remove-Item "D:\WpSystem\*\AppData\Local\Packages\Claude_pzs8sxrjxfjjc" -Recurse -Force

After all this, Cowork installed and runs fine. Hope it helps since we have the same build.

Tip: If you have Claude Code (CLI or VS Code), you can ask it to help you diagnose. That's actually how I found the symlinks to D:\ — Claude Code can run PowerShell commands and check your system for you. Ask it something like "check if my Claude Desktop MSIX package has symlinks pointing to another drive" and it'll find residual files you might miss during cleanup.

AmerSarhan · 6 months ago

Update: RESOLVED!

Huge thanks to @perdido-hat for the fix — your comment was spot on.

The root cause was that my Windows "Where new content is saved" setting had apps saving to D:, which caused Windows to create symlinks inside AppData\Local\Packages\Claude_pzs8sxrjxfjjc\ pointing to D:\WpSystem\.... This cross-drive symlink setup broke both the VM bundle download (EXDEV rename errors) and the service initialization ("Incorrect function").

What fixed it:

  1. Changed Settings → System → Storage → Where new content is saved → Apps to C:
  2. Clean uninstall — removed all Claude data from both C: and D: (including D:\WpSystem\...\Claude_pzs8sxrjxfjjc)
  3. Rebooted
  4. Fresh reinstall from claude.ai/download
  5. Cowork started on first try

For anyone hitting the same issue, check for symlinks with:

Get-ChildItem "$env:LOCALAPPDATA\Packages\Claude_pzs8sxrjxfjjc" | Format-Table Name, Attributes, Target

If you see ReparsePoint entries pointing to another drive, that's your problem.

Thanks again @perdido-hat — saved me after hours of debugging!

LozadAPP · 6 months ago

Glad it worked! Same thing happened to me — spent hours checking Hyper-V, WSL2, registry, everything... and it turned out to be a storage setting. Sometimes the fix is simpler than we think 😄

---
📌 Full diagnostic tool and step-by-step guide: https://github.com/LozadAPP/claude-cowork-windows-fix

github-actions[bot] · 6 months ago

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