[BUG] Cowork API connection issue + Coworke Tab disappears on restart

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?

Co work API not connecting and the whole tab will disappear upon restart

What Should Happen?

Co work should function

Error Messages/Logs

# [BUG] Cowork tab disappears after restart — YukonSilver marked unsupported on Windows 11 Pro x64

## Preflight Checklist

- [x] I have searched existing issues and this hasn't been reported yet
- [x] This is a single bug report
- [x] I am using the latest version of Claude Desktop

## What's Wrong?

Cowork tab appears on fresh install/launch but disappears after restarting the Claude Desktop app. Logs show the VM boots successfully, connects to the network, and installs the SDK — but then fails the API reachability check. A separate cleanup routine then marks YukonSilver as "unsupported," deletes the VM bundle, and hides the Cowork tab entirely.

When the Cowork tab is visible, it shows: **"Failed to start Claude's workspace — Can't reach the Claude API from Claude's workspace."**

## Environment

- **Claude Desktop Version:** 1.1.2685
- **Platform:** Windows 11 Pro (upgraded from Home during troubleshooting), x64
- **Windows Build:** 10.0.26200
- **CPU/RAM:** Not specified
- **Network:** Wi-Fi (Killer Wi-Fi 6E AX1675i 160MHz)
- **Hyper-V:** Enabled (full, after Pro upgrade)
- **Subscription:** Pro

## Network Adapters

| Adapter | Status |
|---------|--------|
| vEthernet (cowork-vm-nat) — Hyper-V Virtual Ethernet Adapter #2 | Up |
| vEthernet (Default Switch) — Hyper-V Virtual Ethernet Adapter | Up |
| Wi-Fi — Killer Wi-Fi 6E AX1675i 160MHz | Up |
| Ethernet — Realtek PCIe GbE Family Controller | Disconnected |
| Bluetooth Network Connection | Disconnected |

## Key Observations

1. **IPv6 only:** `ping api.anthropic.com` resolves to IPv6 (`2607:6bc0::10`) and succeeds. `ping -4 api.anthropic.com` fails — no IPv4 (A record) available from this network. The Cowork VM likely only has IPv4 connectivity through NAT, which would explain the API unreachability.

2. **No NAT configured:** `Get-NetNat` returns empty. The cowork-vm-nat switch exists but has no NAT routing configured by the app.

3. **YukonSilver cleanup kills Cowork:** After the API reachability check fails, a cleanup routine marks YukonSilver as unsupported, deletes the VM bundle, and removes the Cowork tab from the UI.

4. **App Control for Business:** `systeminfo` shows "App Control for Business policy: Enforced" even though this is a personal, non-domain-joined PC with no group policies applied (`gpresult /r` shows N/A). This initially blocked installation with "App installation is blocked by IT policy" error.

5. **DeviceGuard:** `DeviceGuardCodeIntegrityPolicyEnforcementStatus: EnforcementMode` with HypervisorEnforcedCodeIntegrity running.

## Relevant Log Entries

### VM boots successfully but API is unreachable:

2026-02-12 00:50:31 [info] [VM:start] Configuring Windows VM service...
2026-02-12 00:50:31 [info] [VM:start] Windows VM service configured
2026-02-12 00:50:36 [info] [VM] Network status: NOT_CONNECTED
2026-02-12 00:50:36 [info] [VM] Network status: CONNECTED
2026-02-12 00:50:38 [info] [VM:start] Startup complete, total time: 7681ms
2026-02-12 00:50:41 [info] [VM] API reachability: PROBABLY_UNREACHABLE
2026-02-12 00:51:05 [info] [VM] API reachability: UNREACHABLE
2026-02-12 00:51:05 [warn] [VM:network] API is unreachable


### Cleanup deletes VM bundle and hides Cowork tab:

2026-02-12 01:01:00 [info] [cleanupVMBundleIfUnsupported] yukonSilver not supported (status=unsupported), checking for stale bundle...
2026-02-12 01:01:00 [info] [deleteVMBundle] Deleting reinstall files from C:\Users\trevo\AppData\Roaming\Claude\vm_bundles\claudevm.bundle
2026-02-12 01:01:00 [info] [deleteVMBundle] Reinstall files deleted (sessiondata.img preserved)


### YukonSilver explicitly marked unsupported:

2026-02-12 01:01:50 [info] [warm] Skipping VM warm download - YukonSilver not supported (Not supported on win32 yet)


### CSP errors (recurring every ~20 minutes):

2026-02-12 00:23:18 [error] Connecting to 'https://a-api.anthropic.com/v1/m' violates the following Content Security Policy directive: "connect-src 'self' https://api.segment.io https://*.segment.io https://*.segment.com https://a-cdn.anthropic.com https://*.google.com https://*.facebook.com https://*.facebook.net https://*.doubleclick.net". The action has been blocked.


## Steps to Reproduce

1. Install Claude Desktop 1.1.2685 on Windows 11 Pro x64 with Hyper-V enabled
2. Open app — Cowork tab appears
3. Cowork shows "Failed to start Claude's workspace — Can't reach the Claude API"
4. Close and reopen Claude Desktop
5. Cowork tab is gone — VM bundle has been deleted

## Expected Behavior

Cowork tab should persist across app restarts and the VM should be able to reach the Claude API.

## Troubleshooting Already Attempted

- Upgraded from Windows 11 Home to Pro
- Enabled full Hyper-V
- Disabled Windows Defender Firewall
- Manually configured NAT (New-VMSwitch, New-NetIPAddress, New-NetNat)
- Clean reinstall of Claude Desktop (uninstall + delete %APPDATA%\Claude)
- Verified host can reach api.anthropic.com (IPv6 only — IPv4 fails)

Steps to Reproduce

Download latest version of Claude (I upgraded to windows pro)
Co work tries to connect to API and gives an error stating to restart or reconnect WIFI
Restart the app
Co work tab disappears

Claude Model

None

Is this a regression?

No, this never worked

Last Working Version

_No response_

Claude Code Version

Co work

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

_No response_