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

[pc130412-cpu]

Preflight Checklist

• I have searched existing issues and this hasn't been reported yet
• This is a single bug report (please file separate reports for different bugs)
• I am using the latest version of Claude Code

What's Wrong?

Preflight Checklist

• I have searched existing issues (related: [BUG] Cowork tab not showing on Windows 11 Pro x64 — "yukonSilver" marked as unsupported + CoworkVMService cannot be removed #25136, [BUG] Cowork shows "Virtualization is not enabled" on Windows 10 Pro despite Hyper-V fully enabled #27316, [BUG] Cowork tab disabled — yukonSilver "unsupported" on Windows 11 Pro x64 (ongoing since March 2026) #47327, [BUG] Cowork tab missing in desktop app v1.2581.0 on Windows 11 #48407, [BUG] Cowork tab missing on Windows 10 Enterprise — yukonSilverGems platform detection regression in v1.2581.0 #48540)
• This is a single bug report
• 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

• I have searched existing issues (related: [BUG] Cowork tab not showing on Windows 11 Pro x64 — "yukonSilver" marked as unsupported + CoworkVMService cannot be removed #25136, [BUG] Cowork shows "Virtualization is not enabled" on Windows 10 Pro despite Hyper-V fully enabled #27316, [BUG] Cowork tab disabled — yukonSilver "unsupported" on Windows 11 Pro x64 (ongoing since March 2026) #47327, [BUG] Cowork tab missing in desktop app v1.2581.0 on Windows 11 #48407, [BUG] Cowork tab missing on Windows 10 Enterprise — yukonSilverGems platform detection regression in v1.2581.0 #48540)
• This is a single bug report
• 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

• I have searched existing issues (related: [BUG] Cowork tab not showing on Windows 11 Pro x64 — "yukonSilver" marked as unsupported + CoworkVMService cannot be removed #25136, [BUG] Cowork shows "Virtualization is not enabled" on Windows 10 Pro despite Hyper-V fully enabled #27316, [BUG] Cowork tab disabled — yukonSilver "unsupported" on Windows 11 Pro x64 (ongoing since March 2026) #47327, [BUG] Cowork tab missing in desktop app v1.2581.0 on Windows 11 #48407, [BUG] Cowork tab missing on Windows 10 Enterprise — yukonSilverGems platform detection regression in v1.2581.0 #48540)
• This is a single bug report
• 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

[jemmtaty-droid]

Confirmo que también estoy afectado por esta regresión.
Entorno:

OS: Microsoft Windows 11 Professional, versión 25H2 (compilación de SO 26200.8737)
Tipo de sistema: x64
Plataforma de máquina virtual: activada
Solo veo las pestañas Chat y Code — Cowork está completamente ausente
No aparece ningún mensaje de error

Diagnóstico:

La carpeta %APPDATA%\Claude\logs no existe en absoluto, lo que sugiere que Cowork nunca intenta inicializarse en mi máquina — el problema ocurre antes de cualquier intento de arranque del servicio.

Pasos ya intentados sin éxito:

Reinicio de la app
Reinicio del equipo
Verificación de que tengo la última versión instalada

[pc130412-cpu]

1. 앱 재시작 2. 기기 재시작. 3. 최신버전 재확인 모든 것을 진행하여도 동일한 현상으로 COWORK가 탭에서 나타나지 않습니다. 가지고 있는 PC 3대에서 동일한 증상이 발생되는 현상이 확인되며, 지금 계정이 뭔가 문제가 있는거 아닌지 확인이 필요합니다. 2026년 7월 12일 (일) 오전 3:46, jemmtaty-droid ***@***.***>님이 작성:

…

*jemmtaty-droid* left a comment (anthropics/claude-code#73484) <#73484 (comment)> Confirmo que también estoy afectado por esta regresión. Entorno: OS: Microsoft Windows 11 Professional, versión 25H2 (compilación de SO 26200.8737) Tipo de sistema: x64 Plataforma de máquina virtual: activada Solo veo las pestañas Chat y Code — Cowork está completamente ausente No aparece ningún mensaje de error Diagnóstico: La carpeta %APPDATA%\Claude\logs no existe en absoluto, lo que sugiere que Cowork nunca intenta inicializarse en mi máquina — el problema ocurre antes de cualquier intento de arranque del servicio. Pasos ya intentados sin éxito: Reinicio de la app Reinicio del equipo Verificación de que tengo la última versión instalada — Reply to this email directly, view it on GitHub <#73484?email_source=notifications&email_token=CHKRWUKEDF7SXLLSOIX2ZF35EKDO7A5CNFSNUABFM5UWIORPF5TWS5BNNB2WEL2JONZXKZKDN5WW2ZLOOQXTIOJUHAZTIMJZGM32M4TFMFZW63VGMF2XI2DPOKSWK5TFNZ2KYZTPN52GK4S7MNWGSY3L#issuecomment-4948341937>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/CHKRWUPNRE32Z5BBHFZYRI35EKDO7AVCNFSNUABFKJSXA33TNF2G64TZHM4TGNZSGUZTINZVHNEXG43VMU5TINZZGU3TINBWGYZKC5QC> . Triage notifications, keep track of coding agent tasks and review pull requests on the go with GitHub Mobile for iOS <https://github.com/notifications/mobile/ios/CHKRWUK6LZVHSIMGUKI5JLL5EKDO7A5CNFSNUABFM5UWIORPF5TWS5BNNB2WEL2JONZXKZKDN5WW2ZLOOQXTIOJUHAZTIMJZGM32M4TFMFZW63VGMF2XI2DPOKSWK5TFNZ2KUZTPN52GK4S7NFXXG> and Android <https://github.com/notifications/mobile/android/CHKRWUJOXOI7XOSFJLDQGND5EKDO7A5CNFSNUABFM5UWIORPF5TWS5BNNB2WEL2JONZXKZKDN5WW2ZLOOQXTIOJUHAZTIMJZGM32M4TFMFZW63VGMF2XI2DPOKSWK5TFNZ2K4ZTPN52GK4S7MFXGI4TPNFSA>. Download it today! You are receiving this because you authored the thread.Message ID: ***@***.***>

[4mb6gjsh7n-afk]

Environment

• Device: Lenovo ThinkPad T480 (Intel, x64)
• OS: Windows 11 Pro x64, Build 26200.8875 (25H2)
• Virtualization: Hyper-V enabled, VT-x enabled in BIOS
• Install type: traditional (%APPDATA%\Claude), not MSIX/Store
• Claude Desktop version: 1.15962.0.0

What's wrong

The Cowork tab does not work on a fully capable system. The VM never
attempts to boot. Windows 11 Pro with Hyper-V active and hardware
virtualization enabled, yet the app's internal platform detection
classifies yukonSilver as unsupported.

Note: I am already on Windows 11 25H2 (Build 26200.8875), so the
"upgrade to 25H2 / Build 26200" workaround circulating online does
NOT resolve this. The bug reproduces on the current build.

Log evidence

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

[cleanupVMBundleIfUnsupported] yukonSilver not supported (status=unsupported), checking for stale bundle...

The line repeats on every launch. The VM is never started.

Expected behavior

yukonSilver should be recognized as supported on Windows 11 Pro x64
(Build 26200) with all virtualization features enabled, the VM bundle
should download, and Cowork should initialize.

Notes

Appears to be the same platform-detection regression tracked in
#73484 and related issues, still reproducing on the current build.

[kengo-inoue-sp02]

Same issue here.

• OS: Windows 11 Pro, version 25H2 (Build 26200.8875)
• Claude Pro subscription active
• Claude Desktop: latest version
• Hyper-V: Enabled
• vmms service: Running
• CoworkVMService: Running

Despite everything above being fully functional, the Cowork tab does not appear at all in the app navigation (only Chat and Code show up).

cowork_vm_node.log repeatedly shows:
yukonSilver not supported (status=unsupported), checking for stale bundle...

I contacted Anthropic support on July 13 and was escalated to a human agent, but have received no response after 4+ days. Any update on a fix would be greatly appreciated, since this is happening on a fully up-to-date Windows 11 Pro system with everything correctly configured.

[Gecs20nurrg]

Environment

Device: ASUS ExpertBook P5405CSA
OS: Windows 11 Pro x64, Build 26200.8875 (25H2)
Virtualization: enabled and confirmed working (Virtual Machine Platform, Hyper-V services, hypervisor all active)
Install type: genuine MSIX install (confirmed via PowerShell)
Claude Desktop version: 1.22209.3.0

What's wrong
Cowork doesn't work despite everything on my system being correctly set up. Sometimes the Cowork tab shows an error saying it "requires the modern installer" (even though I have confirmed a genuine MSIX install), and other times the Cowork tab disappears from the app entirely.

Verified via PowerShell (all confirmed working)

Claude is a genuine MSIX install
Virtual Machine Platform: Enabled
Required background services (vmcompute, hns): Running
Hypervisor: set to launch automatically
CoworkVMService: Running

Log evidence
This line repeats every time I try to open Cowork:
[cleanupVMBundleIfUnsupported] yukonSilver not supported (status=unsupported), checking for stale bundle...
[Bundle:status] rootfs.vhdx missing

Expected behavior
Since everything required is confirmed working, Cowork should recognize my system as supported and start normally.

Notes
This appears to be the same bug tracked in this thread, still happening on a fully up-to-date, correctly configured system. Chat works normally.

[bcherny]

Closing as a duplicate of #47327 — please follow and 👍 that issue instead so we can track it in one place. If you think this was closed in error, comment here and we'll reopen.

🤖 Generated with Claude Code