[BUG] Cowork crashes on startup: apply-seccomp Killed in VM sandbox (macOS ARM64)

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?

Bug Description
The Cowork feature in Claude Desktop fails to start, showing the error:

CLI output was not valid JSON. This may indicate an error during start up.
Output: /usr/bin/bash: line 4: 5 Killed /usr/local/lib/node_modules_global/lib/node_modules/@anthropic-ai/sandbox-runtime/vendor/seccomp/arm64/apply-seccomp /usr/local/lib/node_modules_g...

The apply-seccomp binary inside the VM sandbox is being killed (signal 9 / SIGKILL) on startup. The path /usr/local/lib/node_modules_global/ exists only inside the VM's rootfs.img — it does not exist on the host macOS filesystem.

What Should Happen?

Run Cowork normally.

Error Messages/Logs

CLI output was not valid JSON. This may indicate an error during start up.
Output: /usr/bin/bash: line 4:     5 Killed                  /usr/local/lib/node_modules_global/lib/node_modules/@anthropic-ai/sandbox-runtime/vendor/seccomp/arm64/apply-seccomp /usr/local/lib/node_modules_g...

Steps to Reproduce

The apply-seccomp binary inside the VM sandbox is being killed (signal 9 / SIGKILL) on startup. The path /usr/local/lib/node_modules_global/ exists only inside the VM's rootfs.img — it does not exist on the host macOS filesystem.

Steps to Reproduce

1. Open Claude Desktop (v1.1.5368)
2. Navigate to the Cowork tab
3. Attempt to start a Cowork session
4. Error appears immediately: "Something went wrong — CLI output was not valid JSON"

Attempted Fixes (none resolved the issue)

• Quit and reopen Claude Desktop (Cmd+Q → relaunch)
• Cleared app cache: rm -rf ~/Library/Caches/com.anthropic.claudefordesktop
• Deleted VM bundles to force recreation: rm -rf ~/Library/Application\ Support/Claude/vm_bundles — the VM was recreated on next launch but the same error persists
• Installed Claude Code CLI via npm — CLI works fine in Terminal, only Cowork in Desktop is broken
• Verified app auto-update completed successfully

Environment

| Component | Version |
|---|---|
| macOS | 26.3 (Build 25D125) |
| Architecture | Apple Silicon (arm64) |
| Claude Desktop | 1.1.5368 |
| Claude Code CLI | 2.1.71 (works fine standalone) |
| Node.js | v25.8.0 |

Diagnostic Details

• VM bundle path: ~/Library/Application Support/Claude/vm_bundles/claudevm.bundle/
• The rootfs.img is recreated after deletion but produces the same crash
• Origin hash: fb30784dadb34104626c8cf6d8f90dd47cd393cc
• Signal 9 (SIGKILL) suggests OOM inside VM, seccomp policy violation, or corrupted binary in rootfs
• Host has 32GB RAM — not a host memory issue
• CLI claude in Terminal works perfectly — only the Cowork VM sandbox is affected

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

Claude Code CLI v2.1.71

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_