[BUG] Bash tool fails on Windows — "Session environment not yet supported on Windows" (v2.1.45)

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?

Environment:

• OS: Windows 11 Pro (10.0.26200)
• Shell: Git Bash (C:\Program Files\Git\bin\bash.exe)
• Claude Code version: 2.1.45

Behavior:
Every Bash tool call fails with exit code 1 and no output. The debug log shows this fires before every failure:
Session environment not yet supported on Windows
Bash tool error (Xms): Shell command failed

Affected commands: All shell built-ins (echo, pwd) and Unix utilities (cat, grep). Windows .exe commands (e.g.
where.exe) succeed.

Not affected: Read, Grep, Glob, Edit, Write tools all work normally.

Reproducer:

1. Install Claude Code v2.1.45 on Windows with Git Bash
2. Open any session
3. Run echo hello via Bash tool → exit code 1, no output

Note: Affects all profiles (default ~/.claude/ and custom CLAUDE_CONFIG_DIR profiles equally).

What Should Happen?

Claude should examine and suggest fix

Error Messages/Logs

Steps to Reproduce

not sure

Claude Model

Not sure / Multiple models

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.45

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Windows Terminal

Additional Information

_No response_