[BUG] MSIX package path resolution failure - "Open in Word" and "Show in Folder" completely broken in Cowork

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?

CRITICAL: This makes Cowork completely unusable for all Windows users.

When Claude Desktop Cowork creates files (Word documents, PDFs, etc.), clicking "Open in Word" or "Show in Folder" fails with error "The directory name isn't valid" or "Location is not available."

Files are successfully created inside the VM and exist in the MSIX container, but the UI passes truncated file paths to Windows that omit the container prefix, causing all file operations to fail.

This makes Cowork completely unusable - files are generated but cannot be accessed through the UI.

What Should Happen?

Open in Word" should open the document directly in Microsoft Word, and "Show in Folder" should open File Explorer to the file location. Users should be able to access their generated files without manual navigation through nested container folders.

Error Messages/Logs

Windows Error Dialog:
"The directory name isn't valid. (C:\...\Pre-existing_NAbs_AAV_Gene_The...)"

OR

"Location is not available
C:\Users\DarynShip(External)\AppData\Roaming\Claude\local-agent-mode-sessio...\outputs 
is unavailable. If the location is on this PC, make sure the device or drive is connected or the disc is inserted, and then try again."

Actual file location (verified via PowerShell):
C:\Users\DarynShip(External)\AppData\Local\Packages\Claude_pzs8sxrjxfjjc\LocalCache\Roaming\Claude\local-agent-mode-sessions\[session-id]\outputs\

cowork_vm_node.log shows successful file creation:
[2026-04-24 10:24:53] All files ready in C:\Users\DarynShip(External)\AppData\Roaming\Claude\vm_bundles\claudevm.bundle
[2026-04-24 10:25:13] [VM:start] Startup complete

Steps to Reproduce

1. Install Claude Desktop version 1.3883.0.0 from claude.ai/download on Windows 11 Enterprise
2. Enable Hyper-V and Virtual Machine Platform
3. Open Claude Desktop and switch to Cowork
4. Create any document task (e.g., "Create a Word document with my name on it")
5. Wait for file generation to complete (file appears in UI)
6. Click "Open in Word" button in the Cowork interface
7. Error appears: "The directory name isn't valid"

Alternatively, select the drop down and select "Show in Folder" - another error occurs.

Files can be manually accessed by navigating to:
C:\Users\%USERNAME%\AppData\Local\Packages\Claude_pzs8sxrjxfjjc\LocalCache\Roaming\Claude\local-agent-mode-sessions\

<img width="584" height="192" alt="Image" src="https://github.com/user-attachments/assets/65202f85-df84-44cf-a28d-7f41fd68ccc9" />
<img width="418" height="202" alt="Image" src="https://github.com/user-attachments/assets/d9fa7eaa-2095-433f-acc5-b71964263dfa" />

Claude Model

None

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

1.3883.0.0

Platform

Other

Operating System

Windows

Terminal/Shell

Other

Additional Information

Environment Details

• Windows 11 Enterprise (domain-joined)
• Microsoft Defender for Endpoint enabled
• Hyper-V enabled and functional
• CoworkVMService running (Status: Running)
• All users affected (50+ users in organization)

Technical Analysis

The MSIX package stores files at:
C:\Users\[User]\AppData\Local\Packages\Claude_pzs8sxrjxfjjc\LocalCache\Roaming\Claude\local-agent-mode-sessions\

But the UI passes paths to Windows missing the container prefix:
C:\Users\[User]\AppData\Roaming\Claude\local-agent-mode-sessions\

This path doesn't exist outside the MSIX container, causing Windows file operations to fail.

What We've Ruled Out

✅ Hyper-V is enabled and functional
✅ CoworkVMService is running
✅ Files ARE being created successfully (verified via PowerShell)
✅ Not a Defender/antivirus block (Event Viewer shows no blocks)
✅ Controlled Folder Access is OFF
✅ AppData is on C:\ (not redirected to network or D:\)
✅ No AppLocker policies interfering
✅ Multiple clean reinstalls attempted - same issue persists

Related Issues

Similar to #36298 (VM bundle path mismatch) and #37754 (AppData redirection failures)

Enterprise Impact

This is a showstopper bug for enterprise deployment. Cowork is the primary differentiator for Claude Desktop over the browser version, but it's completely unusable when users cannot access generated files.

Current workaround requires users to manually navigate nested container folders - not viable for production use.

Requested Resolution

Either:

1. Fix MSIX path resolution so file operations pass correct containerized paths to Windows
2. Provide a non-MSIX installer option that doesn't use container sandboxing
3. Document configuration to disable path sandboxing for enterprise deployments