[BUG] Claude Code Desktop SSH connection fails on Windows with Synology NAS on non-standard port

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 Code Desktop app on Windows fails to establish SSH connection to a Synology NAS on a non-standard port (6069). App briefly shows "Installing Claude Code..." then silently fails with "Connection failed". No error details shown. Terminal SSH to the same host works perfectly.

Environment:

• Client: Windows 11, OpenSSH 9.5p2 (C:\Windows\System32\OpenSSH\ssh.exe)
• Remote: Synology NAS (DSM), OpenSSH 8.2, port 6069
• Auth: ed25519 key (no passphrase)
• Claude Code on remote: v2.1.109 at ~/.local/bin/claude
• Node.js on remote: v20.19.5

Debugging already attempted:

• Terminal SSH works: ssh -v -p 6069 -i ~/.ssh/id_ed25519 doyeon@192.168.1.238 succeeds
• Added host key via ssh-keyscan -p 6069 >> ~/.ssh/known_hosts
• Confirmed ~/.local/bin in PATH on remote (.bashrc and .bash_profile)
• Tried alias-based host (nas) and explicit user@ip — both fail
• Created symlink C:\usr\bin\ssh -> C:\Windows\System32\OpenSSH\ssh.exe — no effect

Suspected cause: app uses internal Node.js ssh2 library, not system OpenSSH, and fails to handle non-standard ports or Windows key paths correctly. Related: #25659, #26809, #32734

What Should Happen?

Successful SSH connection and Claude Code session, same as terminal SSH.

Error Messages/Logs

No error message displayed in app UI. App shows "Connection failed" only.

Steps to Reproduce

1. Open Claude Code Desktop app on Windows 11
2. Add SSH connection: host doyeon@192.168.1.238, port 6069, identity file ~/.ssh/id_ed25519
3. App shows "Installing Claude Code..." briefly
4. App shows "Connection failed" with no further details

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.109 (Claude Code)

Platform

Other

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

This is a Desktop app SSH remote connection issue, not a CLI issue. The app connects to a Synology NAS (192.168.1.238) via SSH on port 6069. The remote server has Claude Code installed and working. The issue appears to be that the Desktop app uses an internal Node.js ssh2 library rather than the system OpenSSH binary, causing it to fail silently with non-standard port configurations on Windows.