Windows: NUL files created in every directory (Git Bash)

Description

On Windows with Git Bash, Claude Code creates a file literally named NUL in virtually every directory it touches during a session. Since NUL is a reserved device name on Windows, these files cannot be deleted through normal means (Explorer, del, Remove-Item), requiring the \?\ prefix path workaround.

Environment

• OS: Windows 11
• Shell: Git Bash (via Claude Code's Bash tool)
• Claude Code: latest

Steps to reproduce

1. Run Claude Code on Windows (Git Bash environment)
2. Perform any task that involves file/directory operations
3. Check directories with Get-ChildItem -Filter 'NUL' -Recurse

Observed behavior

• A NUL file is created in nearly every directory that Claude Code accesses
• In one session, 1290 NUL files were found under a single parent directory
• Files are recreated every session even after deletion
• Files cannot be deleted via normal Windows tools due to the reserved device name

Expected behavior

No NUL files should be created. Output suppression should use /dev/null (Git Bash) or the actual NUL device, not create literal files.

Root cause hypothesis

Claude Code or its internal tooling likely uses > NUL style redirection (Windows convention) while running under Git Bash, where NUL is not interpreted as a device name but as a literal filename. The fix would be to use > /dev/null in Bash contexts, or ensure the redirection targets the actual null device.

Workaround

Delete using \?\ prefix to bypass reserved name parsing:

Get-ChildItem -Path . -Filter 'NUL' -File -Recurse -Force | ForEach-Object {
    [System.IO.File]::Delete("\?\$($_.FullName)")
}