[BUG] Cowork tab missing on Windows 10 Enterprise — yukonSilverGems platform detection regression in v1.2581.0

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?

Description

The Cowork tab has disappeared from Claude Desktop after updating to v1.2581.0 on Windows 10 Enterprise. Cowork was working correctly on v1.1062.0 the previous day (April 14, 2026).

Root Cause Identified

The cowork_vm_node.log shows the following on every app launch:

yukonSilver not supported (status=unsupported), checking for stale bundle...
deleteVMBundle: Deleting reinstall files from ...\vm_bundles\claudevm.bundle

Investigation of index-C_v2hJCF.js in the app resources confirms v1.2581.0 introduced a new yukonSilverGems platform check:

isSupported: "supported" === G2(e,"yukonSilverGems").status

This check incorrectly marks Windows 10 Enterprise as unsupported and deletes the VM bundle on every launch, preventing the Cowork tab from appearing. Restoring the VM bundle from backup does not help — it gets deleted again on the next launch.

What Should Happen

The Cowork tab should appear alongside Chat in Claude Desktop, as it did in v1.1062.0 on the same machine. The VM bundle should not be deleted on startup. Claude Desktop should correctly identify Windows 10 Enterprise Build 19045 with Hyper-V enabled as a supported platform for Cowork.

Steps to Reproduce

1. Have Windows 10 Enterprise Build 19045 (x64) with Hyper-V enabled
2. Install Claude Desktop v1.2581.0 (direct installer, not Store version)
3. Launch Claude Desktop
4. Observe: only "Chat" tab is visible — no Cowork tab
5. Check %APPDATA%\Claude\logs\cowork_vm_node.log
6. Observe: "yukonSilver not supported (status=unsupported)" on every launch, followed by VM bundle deletion

Note: Same machine ran Cowork successfully on v1.1062.0 the previous day. CoworkVMService is present and running. Restoring the VM bundle from backup does not help — deleted again on next launch.

System Information

• OS: Windows 10 Enterprise, Build 19045 (x64)
• Claude Desktop version: 1.2581.0
• Last working version: 1.1062.0 (April 14, 2026)
• Hyper-V: Enabled
• Virtual Machine Platform: Enabled
• CoworkVMService: Present and running
• Account: Enterprise plan

Logs

2026-04-15 06:47:09 [info] [cleanupVMBundleIfUnsupported] yukonSilver not supported (status=unsupported), checking for stale bundle...
2026-04-15 07:45:55 [info] [cleanupVMBundleIfUnsupported] yukonSilver not supported (status=unsupported), checking for stale bundle...
2026-04-15 07:45:55 [info] [deleteVMBundle] Deleting reinstall files from C:\Users\robertmartin\AppData\Roaming\Claude\vm_bundles\claudevm.bundle
2026-04-15 07:45:55 [info] [deleteVMBundle] Reinstall files deleted (sessiondata.img and rootfs.img.zst preserved)

Code reference in index-C_v2hJCF.js:

isSupported: "supported" === G2(e,"yukonSilverGems").status
T5 function returns: {loading: false, status: "unsupported"} via G2(e,"yukonSilver")

Additional Notes

• Confirmed regression — same machine, same OS, worked in v1.1062.0
• Rollback to v1.1062.0 not publicly available
• Enterprise customer impact: Cowork sessions and scheduled tasks inaccessible

What Should Happen?

The Cowork tab should appear alongside Chat in Claude Desktop, as it did in v1.1062.0 on the same machine. The VM bundle should not be deleted on startup. Claude Desktop should correctly identify Windows 10 Enterprise Build 19045 with Hyper-V enabled as a supported platform for Cowork.

Error Messages/Logs

2026-04-15 06:47:09 [info] [cleanupVMBundleIfUnsupported] yukonSilver not supported (status=unsupported), checking for stale bundle...
2026-04-15 07:45:55 [info] [cleanupVMBundleIfUnsupported] yukonSilver not supported (status=unsupported), checking for stale bundle...
2026-04-15 07:45:55 [info] [deleteVMBundle] Deleting reinstall files from C:\Users\robertmartin\AppData\Roaming\Claude\vm_bundles\claudevm.bundle
2026-04-15 07:45:55 [info] [deleteVMBundle] Reinstall files deleted (sessiondata.img and rootfs.img.zst preserved)

Source: %APPDATA%\Claude\logs\cowork_vm_node.log

Code reference in index-C_v2hJCF.js:
isSupported: "supported" === G2(e,"yukonSilverGems").status
T5 function returns: {loading: false, status: "unsupported"} via G2(e,"yukonSilver")

Steps to Reproduce

1. Have Windows 10 Enterprise Build 19045 (x64) with Hyper-V enabled
2. Install Claude Desktop v1.2581.0 using the direct installer (not Store version)
3. Launch Claude Desktop and log in
4. Observe: only "Chat" tab is visible — no Cowork tab
5. Check %APPDATA%\Claude\logs\cowork_vm_node.log
6. Observe: "yukonSilver not supported (status=unsupported)" on every launch, followed by VM bundle deletion

Note: Same machine ran Cowork successfully on v1.1062.0 the previous day (April 14, 2026). CoworkVMService is present and running. Restoring the VM bundle from backup does not help — it gets deleted again on the next launch.

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

1.1062.0 (April 14, 2026 — last known working version)

Claude Code Version

Claude Desktop 1.2581.0 (Windows)

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

• OS: Windows 10 Enterprise Build 19045 (x64)
• Hyper-V: Enabled
• Virtual Machine Platform: Enabled
• CoworkVMService: Present and running
• Account type: Enterprise plan
• This is a confirmed regression — Cowork worked on this exact machine/OS on v1.1062.0
• Rollback to v1.1062.0 is not publicly available
• The yukonSilverGems check was introduced in v1.2581.0 and incorrectly flags Windows 10 Enterprise as unsupported
• Anthropic support confirmed this is a bug and directed filing here