[BUG] Cowork Windows — VirtioFS mount of secondary partition (E:\) appears empty; regression after KB5089549 (Windows 11 Home)

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?

Cowork on Windows 11 Home mounts a folder from a secondary NTFS partition (E:\mercurio) but the directory appears completely empty inside the sandbox. The filesystem is mounted correctly — df -h inside the sandbox shows the correct size (7.7 GB used of 9.6 GB total) and the mount point exists — but ls and all file tools return no content.

Environment:

• OS: Windows 11 Home
• Drive: E:\ is a secondary partition on the same physical SSD (PNY CS900 250GB, Disk 0, Partition 1, NTFS, Fixed)
• C:\ is the system partition on the same disk
• Cowork folder selected: E:\mercurio (7.7 GB of data)
• CoworkVMService: Running, StartType Automatic
• HypervisorPlatform: Enabled
• VirtualMachinePlatform: Enabled
• Hyper-V: Not available on Windows Home

This is a regression. The folder was accessible via Cowork before May 27, 2026. On that date, Windows Update KB5089549 was automatically installed. After that date, E:\mercurio appears empty in Cowork.

Workarounds attempted (all failed):

1. Reconnecting the folder in Cowork
2. Creating a symbolic link `C:\Users\rcc88\mercCowork on Windows 11 Home mounts a folder from a secondary NTFS partition (E:\mercurio) but the directory appears completely empty inside the sandbox. df -h shows the correct size (7.7 GB used of 9.6 GB total) and the mount point exists, but ls and all file tools return no content.
4. Environment:
5. - OS: Windows 11 Home
6. - Drive: E:\ is a secondary partition on the same physical SSD (PNY CS900 250GB, Disk 0, Partition 1, NTFS, Fixed)
7. - C:\ is the system partition on the same disk
8. - Cowork folder: E:\mercurio (7.7 GB of data)
9. - CoworkVMService: Running, StartType Automatic
10. - HypervisorPlatform: Enabled, VirtualMachinePlatform: Enabled
11. - Hyper-V: Not available on Windows Home
13. This is a regression. Folder was accessible via Cowork before May 27, 2026. Windows Update KB5089549 installed on 27/05/2026. After that, E:\mercurio appears empty in Cowork.
15. Workarounds attempted (all failed):
16. 1. Reconnecting folder in Cowork
17. 2. Symbolic link C:\Users\rcc88\mercurio -> E:\mercurio - Cowork resolves symlink to real target before mounting
18. 3. Microsoft official KB5089549 registry fix (EspPaddingPercent=0) and reboot
19. 4. Enabling HypervisorPlatform (was Disabled) and reboot
21. Diagnostic output:
22. - df: /mnt/.virtiofs-root/shared/e/mercurio 9.6G 7.7G 1.9G 81%
23. - ls returns nothing (only . and .. entries)
24. - Get-HotFix KB5089549 InstalledOn: 27/05/2026urio -> E:\mercurio — Cowork resolves the symlink to its real target E:\` before mounting, so the folder still appears empty
25. Applying Microsoft's official KB5089549 registry fix and rebooting
26. Enabling HypervisorPlatform (was Disabled) and rebootingDiagnostic output:``# df shows the mount exists with correct size:/mnt/.virtiofs-root/shared/e/mercurio 9.6G 7.7G 1.9G 81%# But ls returns nothing:s /sessions/.../mnt/mercurio/ # (no output)# Directory entry only shows . and ..total 8drwx------ 2 ... 4096 May 30 02:02 .drwxr-xr-x 7 ... 4096 May 30 10:39 ..``

What Should Happen?

Cowork should be able to read and list files inside a folder selected from any secondary NTFS partition (e.g., E:\), not just from C:\. The VirtioFS mount shows the correct disk usage, which means the partition is reachable — the directory listing should reflect the actual files on disk.
Cowork should be able to read and list files inside a folder selected from any secondary NTFS partition (e.g., E:\), not just from C:\. The VirtioFS mount shows the correct disk usage, which means the partition is reachable - the directory listing should reflect the actual files on disk.
Selecting E:\mercurio in Cowork and asking Claude to list files should return the actual directory contents, not an empty listing.

Error Messages/Logs

Steps to Reproduce

1. Have Windows 11 Home with a secondary NTFS partition on a different drive letter (e.g., E:\) on the same physical disk as C:\
2. Have KB5089549 installed (installed automatically by Windows Update around May 12–27, 2026)
3. Open Claude Desktop → Cowork tab
4. Select any folder on E:\ as the workspace
5. Ask Claude to list the files in the folder
6. Observed: Empty directory listing. ls in bash returns nothing. df -h shows the correct mount size.
7. Expected: Full directory listing of the files in the folder

Additional verification:1. Have Windows 11 Home with a secondary NTFS partition on a different drive letter (e.g., E:\) on the same physical disk as C:\

1. Have KB5089549 installed (installed automatically around May 27, 2026)
2. 3. Open Claude Desktop > Cowork tab
3. 4. Select any folder on E:\ as the workspace
4. 5. Ask Claude to list the files in the folder
5. 6. Observed: Empty directory listing. ls in bash returns nothing. df -h shows correct mount size.
6. 7. Expected: Full directory listing

Verification commands:
Get-Volume -DriveLetter E | Select-Object DriveType, FileSystem
Result: DriveType Fixed, FileSystem NTFS

Get-Partition -DriveLetter E | Select-Object DiskNumber, IsBoot, IsSystem
Result: DiskNumber 0, IsBoot False, IsSystem False

Get-HotFix -Id KB5089549 | Select-Object InstalledOn
Result: 27/05/2026

# Confirms secondary partition exists and is healthy
Get-Volume -DriveLetter E | Select-Object DriveType, FileSystem, Size
# DriveType: Fixed, FileSystem: NTFS

Get-Partition -DriveLetter E | Select-Object DiskNumber, PartitionNumber, IsSystem, IsBoot
# DiskNumber: 0, PartitionNumber: 1, IsSystem: False, IsBoot: False

Get-HotFix -Id KB5089549 | Select-Object InstalledOn
# InstalledOn: 27/05/2026

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.156 (Claude Code) / Claude Desktop 1.9659.2

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

_No response_