AI Builder/Docs/EPERM Error — Cowork (Windows) Troubleshooting

Fixing the EPERM error when starting Cowork

This error shows up on work computers managed by IT. It's fixable, but it requires a few steps beyond just installing the app.

Section 1

What's causing this

This is a local-session issue

This error only shows up when Cowork needs to run a local session on your Windows machine, for local files, your browser, or computer use. Cloud sessions run on Anthropic's servers and don't hit this at all.

Cowork runs a lightweight Linux VM on your machine using Hyper-V, which is Windows' built-in virtualization layer. The EPERM error fires when your company's security software blocks the VM from setting itself up.

This isn't a bug with Claude

Your organization's security tools are doing exactly what they're supposed to do. The fix lives with IT, not with Claude Desktop.

Section 2

Try this first (no IT required)

Start here. This takes 30 seconds and fixes it for many people.

  • 1
    Fully quit your VPN

    Don't just disconnect. Right-click the VPN app in your system tray and choose Exit or Quit. The VPN process needs to stop running entirely.

  • 2
    Restart Claude Desktop and try again

    Close Claude Desktop completely, reopen it, and try starting Cowork. If it works, you're done.

Works for most people

If your VPN uses a split-tunnel that intercepts local VM traffic, quitting it is all you need. Try this before anything else.

Section 3

Send this checklist to your IT department

If the quick fix didn't work, IT needs to make a few changes. This isn't a single "whitelist the app" request. It's a checklist of five things they need to handle.

Windows Home won't work

Hyper-V requires Windows Pro or Enterprise. If your machine is on Windows Home, Cowork can't run on it. Skip to Section 5 for your options.

  • 1
    Allow Claude Desktop to run as a signed applicationWhitelist the app by certificate or executable hash so it isn't blocked by app control policies.
  • 2
    Add antivirus and EDR exclusionsExclude these folders from real-time scanning:
    %LOCALAPPDATA%\AnthropicClaude\
    %LOCALAPPDATA%\CoworkVMService\
  • 3
    Allow CoworkVMService to install and run as a Windows serviceThis is the background service that manages the VM. It needs permission to register and run under a standard user account.
  • 4
    Enable Hyper-VHyper-V must be enabled in both Windows Features and the machine's BIOS. Some corporate images disable it by policy. IT will need to re-enable it.
  • 5
    Allow a virtual network adapterCowork creates a local virtual network interface for the VM. Network security policies sometimes block this. IT needs to permit virtual adapter creation.
Section 4

If it's still not working (advanced)

If IT made the changes and you're still seeing the error, try these steps yourself.

Manual fix: stop the service and clear the VM bundle

Open PowerShell as Administrator, then run:

PowerShell (Administrator)
PS> Stop-Service CoworkVMService -Force PS> Remove-Item "$env:LOCALAPPDATA\CoworkVMService\vm_bundles" -Recurse -Force

After that, reopen Claude Desktop. It will re-download the VM bundle from scratch.

Nuclear option: full uninstall and clean reinstall

  • 1
    Uninstall Claude Desktop

    Go to Settings > Apps > Installed apps, find Claude Desktop, and uninstall it.

  • 2
    Delete leftover files

    Open File Explorer and delete these folders if they still exist:

    Folders to delete
    %LOCALAPPDATA% › AnthropicClaude
    %LOCALAPPDATA% › CoworkVMService
  • 3
    Reinstall Claude Desktop

    Download the latest installer from claude.ai/download and run it. Sign in and try starting Cowork again.

Section 5

If you can't fix it: your fallback options

If your work machine is locked down and IT can't or won't make these changes, you have two solid options.

Option A
Use a personal machine for the course

A personal Windows or Mac machine won't have these restrictions. For most people, this is the easier path.

Option B
Use Claude Code in the terminal instead

Claude Code is a CLI tool that runs directly in your terminal without a VM. It works around the Hyper-V requirement entirely and gives you the same core capabilities as Cowork.

For most knowledge workers, a personal machine is the easier path

Claude Code in the terminal is powerful but has more of a learning curve. If you have a personal machine available, use it for this program and save the IT escalation for another time.

Want to understand this better?

Paste any of these into your AI tool to dig in further:

"Explain what Hyper-V is and why Cowork needs it to run a Linux VM on Windows."
"What does EPERM mean in the context of Windows services and file system permissions?"
"What's the difference between using Cowork and using Claude Code in the terminal? When would I use each one?"

Paste any of these into Claude and keep the thread going. You'll get a lot further than a search engine.

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