[BUG] SSH connection fails after 2.xupdate — password-auth fallback no longer triggered

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?

le: SSH connection fails after 2.x update — password-auth fallback no longer triggered

Environment:

OS: Windows 11 Pro 10.0.26200
Claude Code CLI: 2.1.87
Claude desktop: upgraded from build 9e5781db... → cee98937dc... on 2026-04-14
Remote: Linux, ssh-server on port 22, accepting keyboard-interactive/password

Bug: SSH connections that worked in the previous build now fail with All configured authentication methods failed. Log shows keyboard-interactive attempted and failed, but unlike the previous build the client never retries with plain password auth.

New build log (broken): identical up to the error, but the "Retrying with password auth" step never fires.

Repro: Any SSH host that accepts only password (no keyboard-interactive PAM and no keys accepted) becomes unreachable.

What Should Happen?

login SSH for claude code session

Error Messages/Logs

Previous build log (working):
[SSH2Connection] Connecting ... (agent: false, key: false, proxy: false, keyboard: true)
[SSH2Connection] Connection error: All configured authentication methods failed
[SSH2Connection] Retrying with password auth (keyboard-interactive not available)
[SSH2Connection] Connected to infordata@192.168.x.x:22

Steps to Reproduce

Steps to Reproduce
Set up an SSH server that offers password authentication but either:
Does not advertise keyboard-interactive as a separate method, OR
Has a PAM/keyboard-interactive configuration that rejects the client's attempt (the fallback to plain password auth is what used to succeed)
Example /etc/ssh/sshd_config:

PasswordAuthentication yes
KbdInteractiveAuthentication yes
PubkeyAuthentication yes
No public key installed for the target user, so password is the only viable method.

Open Claude desktop (Windows, build cee98937dc257e6af64e712d71dbe4497eb82452 or later).
Add a new SSH host via the connection menu → Aggiungi host SSH… / Add SSH host:
Host: user@server-ip (e.g. user@192.168.x.x)
Port: 22
Leave identity file auto-detection on (7 keys found in ~/.ssh/ is fine — none of them are authorized on the server)
Select the newly added SSH host from the environment switcher.
Send any message in the Claude chat (this triggers RemoteServerController → BinaryDeployment → SSH2Connection).
Observe: the connection hangs on Connessione in corso… / Connecting… and eventually times out after ~120 seconds. The session never becomes usable.
Expected behavior
When keyboard-interactive fails, the client should automatically retry with plain password authentication (as it did in build 9e5781db566ba58c6c90b9ea712abbeb62c99eb5 and earlier), prompt for the password, and successfully open the remote session.

Actual behavior
Authentication fails immediately and the fallback to password auth is never attempted. Relevant log entries from %APPDATA%\Claude\logs\ssh.log:

[SSH2Connection] Connecting to user@host:22 (agent: false, key: false, proxy: false, keyboard: true)
[SSH2Connection] Connection error: All configured authentication methods failed
[RemoteServerController] Connection failed (120xxx ms, trigger: send_message): All configured authentication methods failed
No Retrying with password auth (keyboard-interactive not available) line is emitted, whereas the previous build reliably emitted it and completed the connection a few milliseconds later.

Additional notes
Same host, same credentials, same ~/.ssh/config: worked continuously for days on the previous build, breaks immediately after the desktop auto-update.
ssh user@host from Git Bash / PowerShell on the same machine still connects successfully with password — so the server and network are fine; the regression is isolated to Claude's SSH client.
Affects every SSH host configured in Claude, not a single one.

Claude Model

Not sure / Multiple models

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

Claude 1.2581.0 (f10398) 2026-04-14T17:16:40.000Z

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Windows Terminal

Additional Information

_No response_