[BUG] Claude Desktop Code tab SSH connection fails with "All configured authentication methods failed" — offers zero keys to server (Windows)

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?

The Code tab's SSH connection to a remote server consistently fails with
"All configured authentication methods failed," regardless of key format,
passphrase status, or connection field configuration (host as IP, host as
SSH-config alias). Server-side verbose logging confirms the client offers
zero SSH keys on every attempt — not a wrong key, not a malformed key, no
key at all.

What Should Happen?

The Code tab's SSH client should load and offer the configured private
key, matching the behavior of a standard SSH client using the same key
and path.

Error Messages/Logs

All configured authentication methods failed

Server-side sshd verbose log (every failed attempt shows this identical
pattern):
Connection from <client IP> port <port> on <server IP> port 22
Received disconnect from <client IP> port <port>:11:  [preauth]
Disconnected from authenticating user <username> <client IP> port <port> [preauth]

No "Failed publickey" line ever appears, which sshd logs for any offered
key, even a rejected one -- confirming zero keys were ever offered by
the client.

Steps to Reproduce

1. In Claude Desktop's Code tab, add a new SSH connection with host,

port 22, username, and a private key path

1. Attempt to connect
2. Connection fails with "All configured authentication methods failed"

Diagnostic steps taken to isolate the cause:

• Converted the private key from OpenSSH format to PEM/PKCS8 -- no change
• Generated a second, passphrase-free key specifically for this

connection, added to the server's authorized_keys -- still zero keys
offered

• Tried both a literal file path and an SSH config file with a Host

alias -- the alias approach failed differently (getaddrinfo ENOTFOUND),
suggesting the Code tab's SSH client does not read the system's SSH
config at all

• Control test: using the exact same key file and path directly via

"ssh -i <path> user@host" from a regular terminal connects
successfully every time -- proving the key, path, and server are all
correct, and the fault is isolated specifically to Claude Desktop's
own key-loading logic

Claude Model

None

Is this a regression?

No, this never worked

Last Working Version

_No response_

Claude Code Version

2.1.77 (Claude Code)

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

This is a networking/connection bug isolated to the Code tab's SSH
client specifically -- the Chat tab and terminal-based Claude Code (via
regular SSH from PowerShell) both work correctly with the same server
and credentials. Full diagnostic process, including the sshd verbose
log excerpts, is in the "Error Messages/Logs" and "Steps to Reproduce"
sections above.