[BUG] Cowork VM never starts after update chain from 1.2773.0 onwards despite bundle intact and module loading successfully

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] Searched existing issues (related: #48407, #49748, #50401, #50495, #50895, #47327)
• [x] Single bug report
• [x] Using latest version of Claude Desktop

What's Wrong?

Cowork worked reliably on my machine from 24 Feb 2026 through 16 Apr 2026.
The last successful VM start was logged on 16 Apr 2026 at 09:35:19.
Since then, every app launch produces only [VM] Loading vmClient module entries
but never a [VM:start] Beginning startup. The Cowork tab is absent from the UI.

This is NOT the classic "yukonSilver unsupported" bug — my bundle is on the
newer hash 5680b11bcdab215cccf07e0c0bd1bd9213b0c25d (VM 1.2.234+), not the
old fb30784.... The VM module loads fine; something downstream refuses to
trigger the VM start or render the tab.

Expected Behaviour

Cowork tab should be visible and VM should start on demand as it did until 16 Apr.

Environment

• OS: Windows 11 Pro x64
• App versions observed as broken: 1.2773.0, 1.3109.0, 1.3561.0
• Last working app version: 1.2773.0.0 (single successful spawn on 16 Apr at 09:35)
• VM Bundle version: 5680b11bcdab215cccf07e0c0bd1bd9213b0c25d (correct, matches

all warm fetches up to 1.3561.0)

• Subscription: Pro (paid)
• Virtualization: Hyper-V, Virtual Machine Platform, Windows Hypervisor Platform

all enabled and working (proven by successful Cowork usage for 7 weeks)

Key log evidence

Last successful VM start:
2026-04-16 09:35:00 [info] [VM:start] Beginning startup
2026-04-16 09:35:00 [info] [VM:start] Bundle version: 5680b11bcdab215cccf07e0c0bd1bd9213b0c25d
2026-04-16 09:35:19 [info] [VM:start] Startup complete, total time: 19316ms

Every launch since then only produces:
2026-04-16 16:29:56 [info] [VM] Loading vmClient module...
2026-04-16 16:29:56 [info] [VM] Module loaded successfully
2026-04-17 08:16:00 [info] [VM] Loading vmClient module...
2026-04-17 08:16:00 [info] [VM] Module loaded successfully
(etc. through 2026-04-21 09:44:51, same pattern, no VM start ever triggered)

Warm bundle hash fetches succeed for every new version (1.3109.0, 1.3561.0),
confirming the bundle is valid. The break is in the UI-to-VM trigger path, not
in bundle distribution or VM capability.

What I already tried

• Restart app: issue persists
• Restart machine: issue persists
• Verified Cowork is still listed in web settings
• Verified CoworkVMService is running

Steps to Reproduce

1. Install Claude Desktop 1.2773.0 or newer on Windows 11 Pro x64
2. Confirm bundle version is 5680b11bcdab215cccf07e0c0bd1bd9213b0c25d
3. Launch Claude Desktop
4. Observe: only Chat and Code tabs visible in mode selector
5. Check %APPDATA%\Claude\logs\cowork_vm_node.log — shows only module load,

no [VM:start] Beginning startup ever fires

What Should Happen?

The Cowork tab should be visible in the mode selector alongside Chat and Code, and the Cowork VM should start on demand when the tab is selected, as it did reliably on my machine from 24 Feb 2026 through 16 Apr 2026.

Specifically:

1. Launching Claude Desktop should trigger a [VM:start] Beginning startup entry in cowork_vm_node.log (not just [VM] Loading vmClient module).
2. The Cowork tab should render in the UI navigation.
3. Existing Cowork sessions (like my admiring-laughing-johnson session resumed under ID a51f94c0-7637-47e3-8f2a-a9ec0a97b5bc) should remain accessible.

All prerequisites on my system are met and verified working: Hyper-V, Virtual Machine Platform, and Windows Hypervisor Platform are enabled, CoworkVMService is running, the VM bundle is at the correct current hash (5680b11bcdab215cccf07e0c0bd1bd9213b0c25d), and warm bundle fetches succeed for every new app version. The break is clearly in the UI-to-VM trigger path, not in bundle distribution or VM capability.

Error Messages/Logs

2026-04-16 16:29:56 [info] [VM] Loading vmClient module...
2026-04-16 16:29:56 [info] [VM] Module loaded successfully
2026-04-17 08:16:00 [info] [VM] Loading vmClient module...
2026-04-17 08:16:00 [info] [VM] Module loaded successfully
(etc. through 2026-04-21 09:44:51, same pattern, no VM start ever triggered)

Steps to Reproduce

Steps to Reproduce

1. Install Claude Desktop 1.2773.0 or newer on Windows 11 Pro x64
2. Confirm bundle version is 5680b11bcdab215cccf07e0c0bd1bd9213b0c25d
3. Launch Claude Desktop
4. Observe: only Chat and Code tabs visible in mode selector
5. Check %APPDATA%\Claude\logs\cowork_vm_node.log — shows only module load,

no [VM:start] Beginning startup ever fires

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2026-04-21 08:21:12 [info] [warm] Fetching VM hash for version 1.3561.0

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

_No response_