[BUG] Cowork "Add folder" silently fails on Windows MSIX install — wrong vmStorageDir path

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?

Adding a folder to a Cowork session silently fails with "Session VM process not available." The folder picker opens, a folder is selected, but it is never added to the session. No error is shown beyond the initial banner message.

What Should Happen?

The selected folder should be mounted into the Cowork VM and appear in the session.

Error Messages/Logs

Error Messages/Logs
From main.log:
[info] LocalAgentModeSessions.addFolderToSession: sessionId=local_f2407164-58e1-47f6-bfcc-9edda515e9e1, path=(picker)
[info] [VM] getVMStorageSubpath: vmStorageDir=C:\Users\Matt\AppData\Roaming\Claude\claude-code-vm, subpath=c/Users/Matt/AppData/Local/Packages/Claude_pzs8sxrjxfjjc/LocalCache/Roaming/Claude/claude-code-vm
The log ends here — no error, no mount attempt, no further output. The vmStorageDir path (C:\Users\Matt\AppData\Roaming\Claude\claude-code-vm) does not exist on MSIX installs. The correct base path is C:\Users\Matt\AppData\Local\Packages\Claude_pzs8sxrjxfjjc\LocalCache\Roaming\Claude\. Manually creating the missing directory tree did not resolve the issue.
Note: The VM itself starts and runs successfully — cowork-service.log and coworkd logs both confirm full boot, network connectivity, Plan9 share mounting, and API reachability.

Steps to Reproduce

Install Claude Desktop via MSIX on Windows 10 Pro
Open Cowork
Click to add a folder to the session
Select any folder in the picker
Observe: folder is never added, "Session VM process not available" error appears

Claude Model

None

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

1.2278.0.0

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Other

Additional Information

CoworkVMService is running and set to Automatic
Hyper-V, VirtualMachinePlatform, and HypervisorPlatform are all Enabled
VM bundle exists at C:\Users\Matt\AppData\Local\Packages\Claude_pzs8sxrjxfjjc\LocalCache\Roaming\Claude\vm_bundles\claudevm.bundle
The failure appears to be that getVMStorageSubpath uses a non-virtualized %APPDATA% path instead of the MSIX-virtualized one, and then silently swallows the resulting error with no log output