[BUG] SessionStart hooks hang indefinitely on 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?

Bug Description

SessionStart hooks cause Claude Code to hang indefinitely on Windows. Even the simplest possible hook
(echo hello) causes the freeze. Other hook types (UserPromptSubmit, Stop, Notification, etc.) work
correctly.

What Should Happen?

Expected Behavior

The hook should execute and Claude should start normally, especially with "timeout": 5 set.

Actual Behavior

Claude freezes indefinitely. The "timeout" setting has no effect.

Environment

• Claude Code version: 2.1.34
• OS: Windows 11
• Shell: Git Bash (C:\Program Files\Git\bin\bash.exe)
• Platform: win32

Workaround

Remove SessionStart hooks entirely. The event can be approximated by emitting from a UserPromptSubmit
hook on first prompt instead.

Error Messages/Logs

Steps to Reproduce

Reproduction Steps

1. Add a SessionStart hook to ~/.claude/settings.json:

{
"hooks": {
"SessionStart": [
{
"hooks": [
{
"type": "command",
"command": "echo hello",
"timeout": 5
}
]
}
]
}
}

1. Launch claude in any git repository
2. Claude hangs and never shows the prompt

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.34

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

_No response_