[BUG] issue #19047

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?

Cowork fails to start on macOS Tahoe 26.3 (25D125). The error is identical to the one reported in #19047 (M4 Mac seccomp killed), but that issue was marked stale without a confirmed fix, and the problem persists on the latest Claude Desktop version after updating and clearing cache.

What Should Happen?

Claude co-work should start and execute without errors.

Error Messages/Logs

CLI output was not valid JSON. This may indicate an error during startup. 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

Open Claude Desktop (latest version)
Navigate to the Cowork tab
Enter any message or task
Observe error: "CLI output was not valid JSON. This may indicate an error during startup."

Claude Model

Sonnet (default)

Is this a regression?

Yes, this worked in a previous version

Last Working Version

Claude 1.1.5368 (d12d02) 2026-03-05T17:29:33.000Z

Claude Code Version

Claude 1.1.5368 (d12d02) 2026-03-05T17:29:33.000Z

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_