SSH Code: "Ambiguous output redirect" on remote servers with csh/tcsh default shell

Bug Description

Claude Desktop SSH Code fails to probe remote machines that use csh/tcsh as the default shell. The error occurs during the probe phase, before any CLI deployment.

Error message in UI: Failed to probe remote machine: Ambiguous output redirect. Try again

Also shows: Path is invalid. when attempting to select a remote folder.

Regression

This worked correctly in the previous version. After updating Claude Desktop, all new sessions fail with this error. Existing sessions from before the update still work fine.

Environment

• Claude Desktop: latest (updated 2026-04-10)
• macOS: 26.0.1 (arm64, Apple M4)
• Remote server default shell: /bin/csh
• SSH connection itself succeeds (confirmed in ssh.log)

SSH Log

[SSH2Connection] Connected to server:4543
[RemoteServerController] Connection failed (4991ms): Failed to probe remote machine: Ambiguous output redirect.

The SSH connection is established successfully every time. The failure happens when the probe command is executed on the remote shell — csh does not support bash-style stderr redirection (2>/dev/null), which causes "Ambiguous output redirect".

Root Cause

The remote server uses /bin/csh as the default shell (common in semiconductor/EDA industry). The probe command sent by Claude Desktop likely contains bash-specific syntax that is incompatible with csh.

Suggested Fix

Wrap the probe command with bash -c '...' or detect the remote shell before probing.

Workaround

Existing sessions from before the update continue to work. Changing the default shell to bash is not feasible in enterprise environments where csh is required by toolchains.