[BUG] Session freezes completely during SSH/Bash commands - UI becomes unresponsive

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 CLI sessions intermittently freeze completely when executing SSH commands to remote servers.

During the freeze:

• The spinner animation stops completely (e.g., "Embellishing..." text freezes)
• Keyboard input is not accepted (Escape, Ctrl+C have no effect)
• The entire TUI becomes unresponsive
• The session recovers on its own after ~7 minutes

What Should Happen?

• The session should remain responsive during command execution
• If a pre-flight check is slow, it should not block the UI/input handling
• Keyboard interrupts (Escape) should work to cancel operations

Error Messages/Logs

Debug Log Findings                                                                                                                                                                                                         
                                                                                                                                                                                                                             
  From ~/.claude/debug/f557c072-fd8e-4587-a647-c519a0efbb2f.txt:                                                                                                                                                             
                                                                                                                                                                                                                             
  1. BashTool Pre-flight Check Timeout (likely root cause)                                                                                                                                                                   
  2026-02-03T05:56:34.566Z [ERROR] Error: Error: console.error: ⚠️  [BashTool] Pre-flight check is taking longer than expected. Run with ANTHROPIC_LOG=debug to check for failed or slow API requests.                       
      at Timeout._onTimeout (file:///opt/homebrew/lib/node_modules/@anthropic-ai/claude-code/cli.js:4799:7138)                                                                                                               
                                                                                                                                                                                                                             
  There's a 7+ minute gap in the debug log (05:49:01 → 05:56:34) during which nothing was logged - this corresponds to the freeze duration.                                                                                  
                                                                                                                                                                                                                             
  2. Repeated "Bun is not defined" Errors (17 occurrences)                                                                                                                                                                   
  2026-02-03T05:48:33.478Z [ERROR] ReferenceError: ReferenceError: Bun is not defined                                                                                                                                        
      at Z34 (file:///opt/homebrew/lib/node_modules/@anthropic-ai/claude-code/cli.js:1602:27809)                                                                                                                             
      at f34 (file:///opt/homebrew/lib/node_modules/@anthropic-ai/claude-code/cli.js:1614:83)                                                                                                                                
      at C5q (file:///opt/homebrew/lib/node_modules/@anthropic-ai/claude-code/cli.js:4787:6330)                                                                                                                              
                                                                                                                                                                                                                             
  Process Analysis During Freeze                                                                                                                                                                                             
                                                                                                                                                                                                                             
  Using sample on the frozen process (PID 80360):                                                                                                                                                                            
  - Process state: S+ (sleeping, foreground)                                                                                                                                                                                 
  - 97% of samples in kevent (waiting for I/O in event loop)                                                                                                                                                                 
  - Event loop IS running, but UI not responding to input                                                                                                                                                                    
  - Terminal in raw mode with -isig (signals disabled, as expected for TUI)                                                                                                                                                  
  - No child SSH process remained (command had completed)                                                                                                                                                                    
  - No active TCP connections to the process

Steps to Reproduce

1. Start a Claude Code session
2. Have Claude execute multiple SSH commands to a remote server in sequence
3. Example command that triggered freeze:

ssh constellation 'cat ~/constellation/docs/decisions/ADR-001.md 2>/dev/null || find ~/constellation -name "ADR-001" -type f 2>/dev/null'

1. Session freezes mid-execution

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.29

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

Additional Context

• The Bun is not defined error suggests there's Bun-specific code being called in a Node.js environment
• Issue occurs specifically during SSH commands to remote servers
• Not every SSH command triggers the freeze (intermittent)