[BUG] Cowork sub-agents fail with virtiofs sandbox error on native Windows despite sandbox disabled`

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?

Environment:

• Claude Code: 2.1.34
• OS: Windows 11 Pro (native, not WSL/Docker)
• Platform: win32

Problem:
Running claude --cowork fails with:

sandbox-helper: host share not mounted at /mnt/.virtiofs-root/shared: not a mount point
CLI output was not valid JSON. This may indicate an error during startup.

What I've tried:

• Set "sandbox": { "enabled": false } in ~/.claude/settings.json — error persists
• Regular claude sessions work fine — only --cowork sub-agents trigger this
• Restarted terminal and killed all Node processes
• Updated Claude Code to latest version

Expected behavior:
Cowork sub-agents should respect sandbox.enabled: false and not attempt virtiofs initialization on native Windows, where sandboxing is unsupported.

Settings file:

{
  "sandbox": {
    "enabled": false
  },
  "permissions": {
    "allow": [...]
  }
}

What Should Happen?

claude --cowork sub-agents should respect sandbox.enabled: false in settings and not attempt virtiofs initialization on native Windows

Error Messages/Logs

sandbox-helper: host share not mounted at /mnt/.virtiofs-root/shared: not a mount point CLI output was not valid JSON. This may indicate an error during startup.

Steps to Reproduce

1. Install Claude Code on native Windows 11 (not WSL) 2. Add "sandbox": { "enabled": false } to ~/.claude/settings.json 3. Run claude --cowork 4. Sub-agents fail with virtiofs mount error

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.34 (Claude Code)

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

WSL (Windows Subsystem for Linux)

Additional Information

Settings file (~/.claude/settings.json): {"sandbox": {"enabled": false}, "permissions": {"allow": [...]}}. Regular claude sessions work fine. Only --cowork sub-agents trigger this error. Native Windows 11, no WSL or Docker involved.