Cowork Linux Sandbox Startup Failure Fix

Symptoms

• Bash commands return: Workspace unavailable. The isolated Linux environment failed to start.
• Or repeatedly shows “Workspace still starting…” and eventually times out

Root Cause

Cowork’s Linux sandbox relies on CoworkVMService (a Windows service running as LocalSystem). This service looks for VM files under the Windows App Package isolated path, while the actual files are stored under the standard AppData location.

The VM service actively rejects directory junctions and symlinks with the error: path is a symlink or junction, refusing to open. This means NTFS hard links are the only viable workaround.

Required Files

Finding Your Package Suffix

Run this in PowerShell to find your Claude package folder name:

Get-ChildItem "$env:LOCALAPPDATA\Packages\" | Where-Object Name -like "Claude_*" | Select-Object Name

Fix Steps

Prerequisites

1. Close the Claude / Cowork desktop app
2. Right-click PowerShell → Run as Administrator

Commands

# Replace <username> with your Windows username and <package_suffix> with the value from above.

# 1. Create the target directory structure
New-Item -ItemType Directory -Path "C:\Users\<username>\AppData\Local\Packages\Claude_<package_suffix>\LocalCache\Roaming\Claude-3p\vm_bundles\claudevm.bundle" -Force

# 2. Create hard links for all VM files (zero additional disk usage)
$realPath = "C:\Users\<username>\AppData\Local\Claude-3p\vm_bundles\claudevm.bundle"
$linkPath = "C:\Users\<username>\AppData\Local\Packages\Claude_<package_suffix>\LocalCache\Roaming\Claude-3p\vm_bundles\claudevm.bundle"

$files = @("rootfs.vhdx", "vmlinuz", "initrd", "smol-bin.vhdx")
foreach ($file in $files) {
    New-Item -ItemType HardLink -Path "$linkPath\$file" -Target "$realPath\$file"
}

# 3. Verify hard links
Get-ChildItem $linkPath | Select-Object Name, Length, LinkType | Format-Table -AutoSize

Verification

Check that each file has LinkType set to HardLink:

Name              Length LinkType
----              ------ --------
initrd         177303315 HardLink
rootfs.vhdx   9453961216 HardLink
smol-bin.vhdx   37748736 HardLink
vmlinuz         14993800 HardLink

Restart the Claude desktop app. The sandbox should now start correctly.

Important Notes

1. Junctions / symlinks will NOT work — the VM service explicitly refuses them
2. Administrator rights required — hard link creation needs elevation
3. Package suffix changes on reinstall — if Claude gets updated or reinstalled, the Claude_<package_suffix> identifier may change, requiring a repeat of this procedure
4. Hard links share disk space — they point to the same on-disk data, taking no additional space