[BUG] Cowork on Windows: Network diagnostics uses macOS paths, VM connection timeout, missing sessiondata.vhdx

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 fails to start on Windows 11 25H2 (Build 26200) with multiple cascading issues:

1. Missing sessiondata.vhdx: After fresh VM bundle download, sessiondata.vhdx is never created. The VM fails with HCS operation failed: HRESULT 0x80070002 ("file not found") because it expects sessiondata.vhdx at Lun 2.

1. After manually creating sessiondata.vhdx: VM boots and reports "VM already connected", but Claude Code process inside the VM crashes immediately (exits in ~399ms) with sandbox-helper: failed to unmount host share (tried both virtiofs and Plan9): invalid argument.

1. Network diagnostics runs macOS commands on Windows: After VM connection timeout (60s), the diagnostic code attempts to spawn macOS-only binaries (/usr/bin/pgrep, /sbin/ifconfig, /usr/sbin/scutil, /usr/sbin/kextstat, /usr/bin/log) — all fail with ENOENT. Network diagnostics is completely non-functional on Windows.

What Should Happen?

• sessiondata.vhdx should be auto-created during VM bundle setup
• sandbox-helper should handle Windows mount types correctly (not assume virtiofs/Plan9)
• Network diagnostics should use Windows-native commands (ipconfig, netsh, Get-NetAdapter, etc.) instead of macOS binaries

Error Messages/Logs

=== cowork_vm_node.log — Sandbox error ===
[Spawn:create] id=19cd0c91 name=dreamy-upbeat-pascal cmd=/usr/local/bin/claude
[Process:19cd0c91] Created, total active=1
[Process:19cd0c91] Buffering stdin (spawn not yet confirmed): 50681 bytes
[Spawn:vm] id=19cd0c91 OAuth token approved with MITM proxy
[Process:19cd0c91] Spawn confirmed, flushing 2 buffered stdin chunks
[CoworkVMProcess:19cd0c91] kill called with signal: SIGTERM
[Process:19cd0c91] Exited, code=0, signal=null, duration=399ms, oom=false
[CoworkVMProcess:19cd0c91] kill failed: RPC error -1: process already exited

=== cowork_vm_node.log — macOS diagnostics on Windows ===
[networkDiagnostics] === vmnet/bridge interfaces ===
[networkDiagnostics] Failed to run /sbin/ifconfig: spawn /sbin/ifconfig ENOENT
[networkDiagnostics] Failed to run /usr/bin/pgrep: spawn /usr/bin/pgrep ENOENT
[networkDiagnostics] Failed to run /usr/sbin/scutil: spawn /usr/sbin/scutil ENOENT
[networkDiagnostics] Failed to run /usr/sbin/kextstat: spawn /usr/sbin/kextstat ENOENT
[networkDiagnostics] Failed to run /usr/bin/log: spawn /usr/bin/log ENOENT

=== HCS error (before manual sessiondata.vhdx fix) ===
HCS operation failed: failed to start VM
HRESULT 0x80070002: "Das System kann die angegebene Datei nicht finden."
Attachment "C:\Users\...\Claude\vm_bundles\claudevm.bundle\sessiondata.vhdx (Lun 2)" was not found

Steps to Reproduce

1. Install Claude Desktop 1.1.2685.0 on Windows 11 25H2 (Build 26200.0, x64)
2. Switch to Cowork tab
3. VM bundle downloads successfully (~9.4 GB rootfs.vhdx + kernel + initrd)
4. First error: VM fails to start — sessiondata.vhdx missing (HRESULT 0x80070002)
5. Manually create sessiondata.vhdx via diskpart (1 GB dynamic)
6. Second error: VM boots, but sandbox-helper fails with failed to unmount host share (tried both virtiofs and Plan9): invalid argument
7. Claude Code process exits in ~399ms, UI shows "CLI output was not valid JSON"
8. Third error: After 60s timeout, network diagnostics runs macOS commands — all fail with ENOENT
9. UI shows "Dein Computer stellt keine Netzwerkverbindung zu Claudes Workspace bereit"

Claude Model

None

Is this a regression?

No, this never worked

Last Working Version

_No response_

Claude Code Version

Claude Desktop 1.1.2685.0 (Cowork - not Claude Code CLI)

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

Environment:

• Windows 11 Pro 25H2 (Build 26200.0)
• Claude Desktop Version: 1.1.2685.0 (MSIX: Claude_1.1.2685.0_x64__pzs8sxrjxfjjc)
• Architecture: x64
• Hyper-V: Hypervisor detected and active
• Firewall: Claude rules present (Inbound + Outbound Allow)
• Disk space: 1.3 TB free
• VPN/Proxy: None active

VM bundle contents after download (sessiondata.vhdx is MISSING):

initrd               175,549,529 bytes
rootfs.vhdx        9,437,184,000 bytes
smol-bin.vhdx         37,748,736 bytes
vmlinuz               14,965,128 bytes

This appears to be three separate bugs that compound: (1) missing file creation, (2) incorrect sandbox mount handling on Windows, (3) macOS-only diagnostic code paths.