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Claude Code Issues / #73484

[BUG] Cowork tab missing after July 1-2 update on Windows 11 Pro — yukonSilver marked as unsupported (regression)

Open 💬 3 comments Opened Jul 2, 2026 by pc130412-cpu

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?

Preflight Checklist

  • [x] I have searched existing issues (related: #25136, #27316, #47327, #48407, #48540)
  • [x] This is a single bug report
  • [x] I am using the latest version of the Claude desktop app

What's Wrong?

The Cowork tab is completely missing from Claude Desktop after the update around July 1–2, 2026. Only the Chat tab is visible. No error message is shown — the tab simply does not appear.

The log shows the known yukonSilver platform detection issue:

2026-07-02 23:55:53 [info] [cleanupVMBundleIfUnsupported] yukonSilver not supported (status=unsupported), checking for stale bundle...

This appears to be the same platform-detection bug reported in #25136 / #47327 / #48540, now reproducing on the latest July 2026 build.

Environment

| Item | Value |
|---|---|
| OS | Windows 11 Pro (x64) — clean reinstall of Windows performed |
| Claude Desktop version | [앱 버전 입력, e.g. 1.xxxx.0] |
| CPU | [CPU 모델 입력, e.g. Intel Core i7-13700 / AMD Ryzen 7 7800X] |
| Plan | Pro (paid) |
| Virtualization (BIOS) | Enabled — Task Manager shows "Virtualization: Enabled" |
| Hyper-V | Enabled |
| Virtual Machine Platform | Enabled |
| CoworkVMService | Present; sc start CoworkVMService and start= auto applied |
| VPN / Docker | Not running during testing |

Steps to Reproduce

  1. Claude Desktop auto-updated around July 1–2, 2026 on Windows 11 Pro x64
  2. Launch the app
  3. Cowork tab is absent from navigation; no error message
  4. Log shows yukonSilver not supported (status=unsupported) on every launch

Troubleshooting Already Attempted (issue persists after all of these)

  • Started CoworkVMService and set startup type to Automatic
  • Verified virtualization enabled in BIOS (Task Manager confirms "Enabled")
  • Enabled Hyper-V, Virtual Machine Platform, Windows Hypervisor Platform; rebooted
  • Full uninstall → deleted %APPDATA%\Claude and %LOCALAPPDATA% residuals → reinstalled latest MSIX as Administrator
  • Performed a complete clean reinstall of Windows 11 Pro — issue still reproduces immediately on a fresh OS
  • Tested with VPN disabled

Expected Behavior

The Cowork tab should appear and function on Windows 11 Pro x64 with all virtualization features enabled. yukonSilver should not be classified as unsupported on this configuration.

Notes

  • Reproducing on a freshly installed OS rules out any system configuration or leftover-state cause; this appears to be an app-side (or server-side flag) detection bug.
  • Timing strongly suggests a regression introduced in the update deployed around July 1–2, 2026.

What Should Happen?

Preflight Checklist

  • [x] I have searched existing issues (related: #25136, #27316, #47327, #48407, #48540)
  • [x] This is a single bug report
  • [x] I am using the latest version of the Claude desktop app

What's Wrong?

The Cowork tab is completely missing from Claude Desktop after the update around July 1–2, 2026. Only the Chat tab is visible. No error message is shown — the tab simply does not appear.

The log shows the known yukonSilver platform detection issue:

2026-07-02 23:55:53 [info] [cleanupVMBundleIfUnsupported] yukonSilver not supported (status=unsupported), checking for stale bundle...

This appears to be the same platform-detection bug reported in #25136 / #47327 / #48540, now reproducing on the latest July 2026 build.

Environment

| Item | Value |
|---|---|
| OS | Windows 11 Pro (x64) — clean reinstall of Windows performed |
| Claude Desktop version | [앱 버전 입력, e.g. 1.xxxx.0] |
| CPU | [CPU 모델 입력, e.g. Intel Core i7-13700 / AMD Ryzen 7 7800X] |
| Plan | Pro (paid) |
| Virtualization (BIOS) | Enabled — Task Manager shows "Virtualization: Enabled" |
| Hyper-V | Enabled |
| Virtual Machine Platform | Enabled |
| CoworkVMService | Present; sc start CoworkVMService and start= auto applied |
| VPN / Docker | Not running during testing |

Steps to Reproduce

  1. Claude Desktop auto-updated around July 1–2, 2026 on Windows 11 Pro x64
  2. Launch the app
  3. Cowork tab is absent from navigation; no error message
  4. Log shows yukonSilver not supported (status=unsupported) on every launch

Troubleshooting Already Attempted (issue persists after all of these)

  • Started CoworkVMService and set startup type to Automatic
  • Verified virtualization enabled in BIOS (Task Manager confirms "Enabled")
  • Enabled Hyper-V, Virtual Machine Platform, Windows Hypervisor Platform; rebooted
  • Full uninstall → deleted %APPDATA%\Claude and %LOCALAPPDATA% residuals → reinstalled latest MSIX as Administrator
  • Performed a complete clean reinstall of Windows 11 Pro — issue still reproduces immediately on a fresh OS
  • Tested with VPN disabled

Expected Behavior

The Cowork tab should appear and function on Windows 11 Pro x64 with all virtualization features enabled. yukonSilver should not be classified as unsupported on this configuration.

Notes

  • Reproducing on a freshly installed OS rules out any system configuration or leftover-state cause; this appears to be an app-side (or server-side flag) detection bug.
  • Timing strongly suggests a regression introduced in the update deployed around July 1–2, 2026.

Error Messages/Logs

Steps to Reproduce

Preflight Checklist

  • [x] I have searched existing issues (related: #25136, #27316, #47327, #48407, #48540)
  • [x] This is a single bug report
  • [x] I am using the latest version of the Claude desktop app

What's Wrong?

The Cowork tab is completely missing from Claude Desktop after the update around July 1–2, 2026. Only the Chat tab is visible. No error message is shown — the tab simply does not appear.

The log shows the known yukonSilver platform detection issue:

2026-07-02 23:55:53 [info] [cleanupVMBundleIfUnsupported] yukonSilver not supported (status=unsupported), checking for stale bundle...

This appears to be the same platform-detection bug reported in #25136 / #47327 / #48540, now reproducing on the latest July 2026 build.

Environment

| Item | Value |
|---|---|
| OS | Windows 11 Pro (x64) — clean reinstall of Windows performed |
| Claude Desktop version | [앱 버전 입력, e.g. 1.xxxx.0] |
| CPU | [CPU 모델 입력, e.g. Intel Core i7-13700 / AMD Ryzen 7 7800X] |
| Plan | Pro (paid) |
| Virtualization (BIOS) | Enabled — Task Manager shows "Virtualization: Enabled" |
| Hyper-V | Enabled |
| Virtual Machine Platform | Enabled |
| CoworkVMService | Present; sc start CoworkVMService and start= auto applied |
| VPN / Docker | Not running during testing |

Steps to Reproduce

  1. Claude Desktop auto-updated around July 1–2, 2026 on Windows 11 Pro x64
  2. Launch the app
  3. Cowork tab is absent from navigation; no error message
  4. Log shows yukonSilver not supported (status=unsupported) on every launch

Troubleshooting Already Attempted (issue persists after all of these)

  • Started CoworkVMService and set startup type to Automatic
  • Verified virtualization enabled in BIOS (Task Manager confirms "Enabled")
  • Enabled Hyper-V, Virtual Machine Platform, Windows Hypervisor Platform; rebooted
  • Full uninstall → deleted %APPDATA%\Claude and %LOCALAPPDATA% residuals → reinstalled latest MSIX as Administrator
  • Performed a complete clean reinstall of Windows 11 Pro — issue still reproduces immediately on a fresh OS
  • Tested with VPN disabled

Expected Behavior

The Cowork tab should appear and function on Windows 11 Pro x64 with all virtualization features enabled. yukonSilver should not be classified as unsupported on this configuration.

Notes

  • Reproducing on a freshly installed OS rules out any system configuration or leftover-state cause; this appears to be an app-side (or server-side flag) detection bug.
  • Timing strongly suggests a regression introduced in the update deployed around July 1–2, 2026.

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

버전 1.17377.2 (e0ea9e)

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_

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