[BUG] Cowork shell sandbox fails on Windows ARM64 in Parallels — nested Hyper-V cannot execute VMs on Apple Silicon

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?

The Cowork workspace sandbox fails to start on Windows ARM64 running inside Parallels on Apple Silicon (M-series Mac). The root cause is not a configuration issue: Parallels on Apple Silicon uses Apple's Hypervisor framework, which cannot nest the ARM EL2 virtualization extensions required for Windows Hyper-V to actually execute guest VMs. This is a fundamental stack limitation that no amount of Windows-side configuration can resolve.

This is distinct from issues where users simply haven't enabled Hyper-V or nested virtualization. In this case, all prerequisites are correctly configured and confirmed working — VMs can be created but not started.

Environment

• Host: Apple Silicon Mac (ARM64)
• VM software: Parallels Desktop (nested virtualization enabled)
• Guest OS: Windows 11 ARM64, Build 26200
• Claude version: 1.9255.2.0 (MSIX, arm64)
• Install path: C:\Program Files\WindowsApps\Claude_1.9255.2.0_arm64__pzs8sxrjxfjjc\

What Should Happen?

Application should start without error. The error displayed:

<img width="690" height="165" alt="Image" src="https://github.com/user-attachments/assets/107f6485-ef1e-4810-be60-a51d2ae0391a" />

Or...

Application should detect the unsupported environment and refuse to run. The download page should be updated to state Windows 11 Arm64 in Parallels is not supported. Application requires nested Hyper-V support (x64) should be explicitly stated in requirements on the download page. The page currently has no requirements listed that I can see.

Error Messages/Logs

(from `cowork_vm_node.log`)
 

[VM:start] VM boot failed: HCS operation failed: failed to create compute system:
HcsWaitForOperationResult failed with HRESULT 0x80370102:
{
  "Error": -2143878910,
  "ErrorMessage": "The virtual machine could not be started because a required feature is not installed.",
  "ErrorEvents": [{
    "Message": "Cannot create system 'cowork-vm-2e4563b1' since Hyper-V is not installed on the host.",
    "Provider": "17103e3f-3c6e-4677-bb17-3b267eb5be57",
    "EventId": 11008
  }]
}
[VM:start] HCS error detected, available=true, missing=[], sentinel=HYPERVISOR_VIRT_DISABLED

 
## Confirmed working (not a misconfiguration)
 
All standard fixes were attempted and verified:
 
| Check | Result |
|---|---|
| Parallels nested virtualization | Enabled |
| `Microsoft-Hyper-V` and all sub-features | Enabled |
| `HypervisorPlatform` | Enabled |
| `Containers` and `Containers-HNS` | Enabled |
| `bcdedit hypervisorlaunchtype` | `Auto` |
| `vmms` service | Running |
| `vmcompute` service | Running |
| `HypervisorPresent` (WMI) | `True` |
| User in `Hyper-V Administrators` group | Yes |
| App manifest `runFullTrust` capability | Present |
 
**Critical confirmation — `New-VM` succeeds but `Start-VM` fails:**
 

PS> New-VM -Name "TestVM" -MemoryStartupBytes 512MB -NoVHD
# Succeeds — VM created in Off state
 
PS> Start-VM -Name TestVM
# FAILS:
# 'TestVM' failed to start.
# Failed to start the virtual machine 'TestVM' because one of the Hyper-V components is not running.

 
This confirms the sandbox failure is not an app-level bug — Windows Hyper-V itself cannot execute VMs in this environment. The Parallels → Apple Hypervisor framework → Windows ARM64 → Hyper-V nesting chain does not support actual VM execution.

Steps to Reproduce

1. Open the application.
2. Observe error.

Claude Model

Sonnet (default)

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

Claude 1.9255.2 (1dc8f7) 2026-05-27T01:57:20.000Z

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Windows Terminal

Additional Information

_No response_