[Bug] Windows: Creates undeletable nul files in working directory

Bug Description

When using Claude Code on Windows, it repeatedly creates files named nul in the working directory and subdirectories. These files are extremely difficult to delete because NUL is a Windows reserved device name.

Environment

• OS: Windows Server 2019 (10.0.18362.295)
• Claude Code Version: Latest
• Shell: PowerShell / cmd

Steps to Reproduce

1. Run Claude Code on Windows in any directory
2. After some operations, check the directory
3. A file named nul appears in the working directory

Expected Behavior

No nul files should be created.

Actual Behavior

• Files named nul are created in the working directory
• These files cannot be deleted using normal methods (del, Remove-Item, etc.)
• Requires special Win32 API calls with \\?\ prefix to delete

Workaround

Use this Python script to delete the files:

import ctypes
from ctypes import wintypes
import os

kernel32 = ctypes.WinDLL('kernel32', use_last_error=True)
DeleteFileW = kernel32.DeleteFileW
DeleteFileW.argtypes = [wintypes.LPCWSTR]
DeleteFileW.restype = wintypes.BOOL

path = '\\\\?\\' + os.path.abspath('nul')
DeleteFileW(path)

Root Cause Hypothesis

Likely caused by output redirection using > nul or similar commands that behave differently in certain Windows shell environments, creating actual files instead of redirecting to the null device.