[BUG] Cowork session crashes immediately on macOS 26.3.1 — VM kernel panic "Attempted to kill the idle task!"

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 and this hasn't been reported yet
• [x] This is a single bug report
• [x] I am using the latest version of Claude Desktop

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Environment

• OS: macOS 26.3.1
• Claude Desktop version: latest (verified via Help → Check for Updates)
• Plan: Pro/Max (paid)
• VPN: none active

What's Wrong?

Cowork fails to execute any task. The session starts ("Starting session…") then silently disappears when switching tabs. The Cowork UI briefly shows "Finishing up… Cowork is taking a moment to cleanly exit. This may take up to a minute." before resetting.

Steps to Reproduce

1. Open Claude Desktop → Cowork tab
2. Workspace setup completes ("Setting up Claude's workspace…" spinner clears)
3. Enter any task and send
4. "Starting session…" spinner appears
5. Switch to another tab and return — the session is gone
6. Occasionally the "Finishing up…" exit dialog appears before reset

Expected Behavior

Task executes and returns a result.

Actual Behavior

VM crashes during session startup. The coworkd.log shows a Linux kernel panic inside the VM immediately after boot:

[KERNEL] [1.610319] Kernel panic - not syncing: Attempted to kill the idle task!
[KERNEL] [1.610653] SMP: stopping secondary CPUs
[KERNEL] [0.409183] Internal error: Oops - FPAC: 0000000072000000 [#1] SMP
[KERNEL] [0.409716] pstate: 610000c5 (nZCv daIF -PAN -UAO -TCO +DIT -SSBS BTYPE=--)
[KERNEL] [0.409739] pc : arch_cpu_idle+0x1c/0x38
[KERNEL] [0.409760] lr : default_idle_call+0x44/0x1b8
[KERNEL] Hardware name: Apple Inc. Apple Virtualization Generic Platform, BIOS 2094.80.5.0.0 01/16/2026

The guest Ubuntu 22.04 kernel (6.8.0-106-generic) panics at arch_cpu_idle on both CPU 0 and CPU 1 during the idle loop, before coworkd can initialize.

Workarounds Attempted (none resolved the issue)

• Full app restart and Mac reboot
• Deleted ~/Library/Application Support/Claude/vm_bundles
• Deleted ~/Library/Application Support/Claude/claude-code-vm
• Deleted ~/Library/Application Support/Claude/Cache and Code Cache
• Full wipe: deleted entire ~/Library/Application Support/Claude/, ~/Library/Caches/Claude/, and com.anthropic.claude.plist, then reinstalled from claude.ai/download
• Confirmed no VPN, firewall software, or network extensions active
• Granted Full Disk Access and Accessibility permissions to Claude Desktop
• Followed all steps in https://gist.github.com/chillskellingtom/5b810654ad8ee357ec0d226acf2a137f

Additional Context

The kernel panic occurs at the earliest possible point in VM boot (timestamp ~1.6s), before any Cowork-specific process starts. This appears to be an incompatibility between the VM image (Ubuntu 22.04 / kernel 6.8.0-106) and Apple Virtualization Framework on macOS 26.3.1. This is not a networking or VPN issue — the kernel never reaches network initialization.

What Should Happen?

Task executes and returns a result.

Error Messages/Logs

VM crashes during session startup. The coworkd.log shows a Linux kernel panic inside the VM immediately after boot:


[KERNEL] [1.610319] Kernel panic - not syncing: Attempted to kill the idle task!
[KERNEL] [1.610653] SMP: stopping secondary CPUs
[KERNEL] [0.409183] Internal error: Oops - FPAC: 0000000072000000 [#1] SMP
[KERNEL] [0.409716] pstate: 610000c5 (nZCv daIF -PAN -UAO -TCO +DIT -SSBS BTYPE=--)
[KERNEL] [0.409739] pc : arch_cpu_idle+0x1c/0x38
[KERNEL] [0.409760] lr : default_idle_call+0x44/0x1b8
[KERNEL] Hardware name: Apple Inc. Apple Virtualization Generic Platform, BIOS 2094.80.5.0.0 01/16/2026


The guest Ubuntu 22.04 kernel (6.8.0-106-generic) panics at `arch_cpu_idle` on both CPU 0 and CPU 1 during the idle loop, before coworkd can initialize.

Steps to Reproduce

1. Open Claude Desktop → Cowork tab
2. Workspace setup completes ("Setting up Claude's workspace…" spinner clears)
3. Enter any task and send
4. "Starting session…" spinner appears
5. Switch to another tab and return — the session is gone
6. Occasionally the "Finishing up…" exit dialog appears before reset

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.0.32

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_