[BUG] Claude Desktop (Windows MSIX) — MSIX registry silo prevents all C:\Windows\System32\OpenSSH\ binaries from executing in child processes

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?

Claude Desktop's MSIX packaging on Windows creates a registry silo that prevents Windows System OpenSSH binaries from initializing in any child process spawned by the app. All four binaries in C:\Windows\System32\OpenSSH\ (ssh.exe, ssh-add.exe, ssh-keygen.exe, scp.exe) silently exit with code 255 and produce zero output — including ssh -V, which requires no network connection. Other System32 binaries and Git's bundled OpenSSH work normally from the same child processes.

This breaks any MCP server or workflow that relies on Windows System OpenSSH for remote server management.

bug-report-final.md
procmon_ssh.CSV

What Should Happen?

Child processes spawned by Claude Desktop should be able to execute all Windows System binaries, including those in C:\Windows\System32\OpenSSH\. The MSIX registry silo should not interfere with OpenSSH binary initialization. ssh.exe -V should return exit code 0 and print its version string regardless of whether it's launched from a user terminal or from a Claude Desktop child process.

Error Messages/Logs

Steps to Reproduce

bug-report-steps.md
procmon_ssh.CSV
ssh_msix_test.js

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

1.1.9493.0 (Claude desktop)

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Other

Additional Information

this bug affects child processes spawned by Claude Desktop, not a specific terminal shell. MCP tools tested include Desktop Commander v0.2.38 (spawns via cmd.exe) and Windows-MCP (spawns via PowerShell). Both are affected. The issue does not occur in any standalone terminal (PowerShell, cmd, VS Code integrated terminal).