[BUG] Cowork Windows - "Could not determine session storage dir" on Windows 10 Pro

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 10 Pro consistently fails with "Could not determine session storage dir" when attempting to start any task. The Cowork tab is visible and I can type tasks, but every task fails with this error.

Environment:

• Device: Lenovo ThinkPad X270
• Processor: Intel Core i5-7200U @ 2.50GHz
• RAM: 16GB
• Storage: 466GB SSD (Samsung 870 EVO)
• OS: Windows 10 Pro, Version 22H2 (upgraded from Home during troubleshooting)
• Claude Desktop: v1.1.3541.0 (installed from claude.ai/download)
• Network: Connecting via Mihomo Party proxy from mainland China

Other errors encountered during troubleshooting (now resolved):

• "Hyper-V is not installed on the host" → resolved by enabling Hyper-V
• "EBUSY: resource busy or locked, copyfile smol-bin.x64.vhdx" → resolved by manual file copy
• "The specified tag is already present" (HRESULT 0x800707de) → resolved by cleaning up VMs/containers via hcsdiag
• "RPC error -1: failed to ensure virtiofs mount: Plan9 mount failed: bad address"
• "VM service not running. The service failed to start." → CoworkVMService was Stopped, started manually
• "API Error: 500 Internal server error"

Extensive troubleshooting already completed:

1. Upgraded from Windows 10 Home to Pro to enable Hyper-V
2. Enabled Intel VT-x and VT-d in BIOS
3. Enabled Hyper-V, HypervisorPlatform, VirtualMachinePlatform, and Containers features
4. Confirmed vmms and vmcompute services are running (Automatic startup)
5. Started CoworkVMService manually
6. Added user to Hyper-V Administrators group
7. Manually created session directories in AppData\Roaming\Claude and AppData\Local\Claude
8. Set full NTFS permissions (icacls) on all Claude directories including the package folder
9. Manually copied smol-bin.x64.vhdx to vm_bundles\claudevm.bundle
10. Full uninstall and clean reinstall (deleted all AppData folders)
11. Reinstalled workspace multiple times from within the app
12. Ran Claude as Administrator

Despite all of the above, the "Could not determine session storage dir" error persists.

What Should Happen?

Cowork should start successfully and allow task execution. The session storage directory should be created and accessible automatically without manual intervention.

Error Messages/Logs

Steps to Reproduce

1. Install Claude Desktop v1.1.3541.0 on Windows 10 Pro (ThinkPad X270)
2. Enable Hyper-V and all required Windows features
3. Open Claude Desktop
4. Switch to the "Cowork" tab
5. Type any task (e.g., "organise the folder")
6. Error appears: "This task didn't load properly - Could not determine session storage dir"

Claude Model

Not sure / Multiple models

Is this a regression?

No, this never worked

Last Working Version

_No response_

Claude Code Version

Claude 1.1.3541 (1e65e4) 2026-02-18T19:23:37.000Z

Platform

Other

Operating System

Windows

Terminal/Shell

Windows Terminal

Additional Information

_No response_