Claude Desktop fails to launch silently on Windows 11 25H2 — vmcompute.dll sandbox access denied

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?

Claude Desktop fails to launch silently on Windows 11 25H2 — vmcompute.dll sandbox access denied
Summary
Claude Desktop installs successfully but fails to launch with "Claude Desktop failed to launch" error. No crash appears in Windows Event Viewer. Root cause identified in cowork-service.log: MSIX sandbox cannot access vmcompute.dll despite the file existing in System32 and vmcompute service running.
System Information
OS: Windows 11 Home Single Language, Version 25H2
Build: 26200.8246
Architecture: x64
RAM: 15.8 GB
Disk free: ~16 GB
Claude version installed: 1.1617.0 (via winget) / also tested 1.2581.0.0
Steps to Reproduce
Install Claude Desktop via winget: winget install Anthropic.Claude
Installation reports success: "MSIX installation succeeded" / "Claude Setup completed successfully"
Launch Claude Desktop from Start menu
App immediately shows: "Claude Desktop failed to launch. Please check for updates and try again."
Troubleshooting Already Completed
✅ Enabled VirtualMachinePlatform: Enable-WindowsOptionalFeature -Online -FeatureName VirtualMachinePlatform
✅ vmcompute service status: Running
✅ vmcompute.dll exists: C:\Windows\System32\vmcompute.dll (832,976 bytes, updated 14/04/2026)
✅ Removed AppX package and reinstalled clean via winget
✅ Removed CoworkVMService from registry
✅ Restarted vmcompute service
✅ Multiple system reboots
❌ No Claude-related errors in Windows Event Viewer Application log
❌ No crash dump generated
Key Error from cowork-service.log

[HCS] Warning: Failed to load vmcompute.dll: The specified module could not be found.
[Cleanup] Warning: failed to enumerate HCN networks: HcnEnumerateNetworks failed with HRESULT 0x800706d9
[VM] Stale VM scan failed, continuing without cleanup: HCS not initialized
Warning: failed to open service for recovery config: Access is denied.

Log Location
C:\ProgramData\Claude\Logs\cowork-service.log
Analysis
The vmcompute.dll file exists in System32 and the vmcompute Windows service is running. However, the Claude MSIX package (running in sandbox) cannot load vmcompute.dll. This suggests the MSIX sandbox permissions do not include access to the Hyper-V Compute Service DLLs required by CoworkVMService.
Expected Behavior
Claude Desktop launches successfully and CoworkVMService initializes vmcompute.dll.
Actual Behavior
Silent launch failure. No crash log generated by the main app. CoworkVMService logs the vmcompute.dll load failure but continues running.
Additional Context
Confirmed with Anthropic support that this is an MSIX package compatibility issue, not a user configuration problem.
Web version (claude.ai) works correctly.
ClaudeSetup.log reports installation success but also shows: WARNING: CoworkVMService already exists (potential conflict)

What Should Happen?

Claude Desktop should launch successfully and display the main interface, allowing the user to chat and access Cowork features.

Error Messages/Logs

Steps to Reproduce

Claude Desktop should launch successfully and display the main interface, allowing the user to chat and access Cowork features.

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

1.1617.0 (Claude Desktop)

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_