[BUG] Cowork "yukonSilver not supported" on Debian 12 (bookworm) — Linux beta, all VM prerequisites met

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?

What's Wrong?
Cowork's VM never initializes on Debian 12 (bookworm). cowork_vm_node.log shows yukonSilver not supported (status=unsupported), checking for stale bundle... on every launch attempt. The cowork-linux-helper process starts and opens its socket successfully, but the VM bundle download/boot is never attempted — the eligibility check appears to reject the platform before that point.
All documented Linux prerequisites are met:

qemu-system-x86 installed (1:7.2+dfsg-7+deb12u18+b2)
ovmf installed (2022.11-6+deb12u2)
virtiofsd present (bundled in qemu-system-common at /usr/lib/qemu/virtiofsd, functional — confirmed via sudo virtiofsd --version)
/dev/kvm present, user added to kvm group
25GB+ free disk, 8GB+ RAM available

Environment

OS: Debian GNU/Linux 12 (bookworm), kernel 6.1.0-49-amd64
Claude Desktop: 1.18286.2 (installed via official apt repo, not standalone .deb)
Install method: downloads.claude.ai/claude-desktop/apt/stable
Subscription: [your plan]

Relevant log excerpt (~/.config/Claude/logs/cowork_vm_node.log):
[info] [VM] Loading vmClient (TypeScript) module...
[info] [VM] Module loaded successfully
[info] [linux-vm] Spawning helper: /usr/lib/claude-desktop/resources/cowork-linux-helper
[info] [linux-vm-helper] [server] listening on /run/user/1000/claude-cowork-vm.sock
[info] [cleanupVMBundleIfUnsupported] yukonSilver not supported (status=unsupported), checking for stale bundle...

What Should Happen?

Expected Behavior
Cowork should recognize Debian 12 (bookworm) as a supported platform, since it's one of the two distros named in Anthropic's own install documentation, and download/boot the VM bundle normally.
Actual Behavior
The VM bundle is permanently rejected as unsupported; Cowork's UI shows a virtualization-related error despite all host-level prerequisites being met and verified.

Error Messages/Logs

[info] [VM] Loading vmClient (TypeScript) module...
[info] [VM] Module loaded successfully
[info] [linux-vm] Spawning helper: /usr/lib/claude-desktop/resources/cowork-linux-helper
[info] [linux-vm-helper] [server] listening on /run/user/1000/claude-cowork-vm.sock
[info] [cleanupVMBundleIfUnsupported] yukonSilver not supported (status=unsupported), checking for stale bundle...

Steps to Reproduce

Install Debian 12 (bookworm) and try it yourself.

Claude Model

Sonnet (default)

Is this a regression?

No, this never worked

Last Working Version

_No response_

Claude Code Version

1.18286.2 Claude Sonnet 5

Platform

Anthropic API

Operating System

Ubuntu/Debian Linux

Terminal/Shell

Xterm

Additional Information

Additional Notes
Anthropic's own install documentation explicitly names Debian as a supported Linux distro for Claude Desktop, including the dependency line this report follows:

"If you installed the .deb file directly on x64, run sudo apt install qemu-system-x86 ovmf virtiofsd"

Given that guidance, a stock Debian 12 (bookworm) install — the current Debian stable release for most of this development cycle — hitting a hard "unsupported" eligibility rejection suggests the yukonSilver platform allowlist hasn't been updated to match the officially documented install path, rather than this being a case where the platform is genuinely incompatible.