Windows: Bash tool stdout capture broken when using Git Bash via CLAUDE_CODE_SHELL

Description

On Windows 11, when CLAUDE_CODE_SHELL is set to Git Bash (C:/Program Files/Git/bin/bash.exe) in ~/.claude/settings.json, the Bash tool's stdout/stderr capture is broken. Commands execute successfully but Claude Code receives no output and reports Exit code 1.

Reproduction

Settings (~/.claude/settings.json):

{
  "env": {
    "CLAUDE_CODE_SHELL": "C:/Program Files/Git/bin/bash.exe"
  }
}

Steps:

1. Set CLAUDE_CODE_SHELL to Git Bash as shown above
2. Start a new Claude Code session
3. Run any command via the Bash tool, e.g. echo hello

Expected: Output hello, exit code 0
Actual: Empty output, exit code 1

Key finding

Commands do execute — they just can't pipe output back to Claude Code:

| Command | Result |
|---|---|
| echo hello | Exit code 1, no output |
| echo hello > /tmp/test.txt | Success (file contains hello) |
| pwd > /tmp/test.txt | Success (correct working directory) |

Redirecting to a temp file and reading it back with the Read tool confirms bash is fully functional — the issue is specifically with stdout/stderr pipe capture.

Workaround

Redirect all output to a temp file, then use the Read tool to retrieve it:

echo hello > /tmp/out.txt 2>&1
# then Read /tmp/out.txt

Environment

• Claude Code: 2.1.45
• OS: Windows 11 Pro 10.0.26200 (MINGW64_NT-10.0-26200)
• Git Bash: 5.2.37(1)-release (Git for Windows 2.52.0)
• Node.js: v24.13.0
• Shell path: C:/Program Files/Git/bin/bash.exe (confirmed exists and works)

Notes

• Without CLAUDE_CODE_SHELL, Windows resolves C:\WINDOWS\system32\bash.EXE (WSL) which fails entirely if no WSL distro is installed. Setting CLAUDE_CODE_SHELL to Git Bash was the fix for that — and the shell does launch correctly, it's only the output piping that's broken.
• The CLAUDE_CODE_SHELL env var is set inside the "env" block of settings.json. This is the documented approach for setting environment variables.