Bash tool fails with exit code 1 on Windows - stdout capture broken

Description

All Bash tool commands that produce stdout output fail with exit code 1 on Windows. Commands that produce no output (like true) succeed. Writing to files works correctly.

Environment

• Claude Code version: 2.1.45
• OS: Windows 11 Pro for Workstations (10.0.26100)
• Shell: Git Bash (MINGW64), GNU bash 5.2.37(1)-release (x86_64-pc-msys)
• Platform: MINGW64_NT-10.0-26100, x86_64

Steps to Reproduce

1. Launch Claude Code on Windows with Git Bash
2. Ask Claude to run any command that produces stdout output

Observed Behavior

| Command | Result |
|---------|--------|
| true | exit 0 ✅ |
| echo "test" | exit 1 ❌ |
| pwd | exit 1 ❌ |
| ls | exit 1 ❌ |
| builtin echo "test" | exit 1 ❌ |
| echo "test" > /tmp/file.txt 2>&1; true | exit 0 ✅ (file contains "test") |

Terminal shows: /usr/bin/echo: /usr/bin/echo: cannot execute binary file

Diagnostics

• /usr/bin/echo.exe is a valid Windows binary: PE32+ executable for MS Windows 5.02 (console), x86-64
• /usr/bin/ls.exe is also a valid PE32+ executable
• Bash builtins work when output is redirected to a file
• The issue appears to be with stdout capture by Claude Code, not with the binaries themselves
• MSYSTEM=MINGW64, TERM=xterm-256color

What I've Tried

• Setting $env:SHELL to various Git Bash paths (C:\Program Files\Git\bin\bash.exe, C:\Program Files\Git\usr\bin\bash.exe)
• Deleting ~/.claude/shell-snapshots/
• Reinstalling Git for Windows
• Updating Claude Code to latest version (2.1.45)
• Running from different terminals (PowerShell, CMD, Git Bash)
• Setting $env:SHELL = "powershell" (Claude Code still uses bash)

Expected Behavior

Bash commands should execute and their stdout output should be captured and returned to the agent.