Windows Developer Guide

When to Load

Automatically loaded on Windows (platform_trigger: "win32"). Applies to: .py, .ps1, .bat, .cmd files and any Windows-specific workflow.

Python on Windows

Encoding (CRITICAL)

Windows defaults to cp1251 / cp1252 for file I/O. Always specify UTF-8 explicitly:

with open("file.txt", "r", encoding="utf-8") as f:
    content = f.read()

Path("file.txt").read_text(encoding="utf-8")
Path("file.txt").write_text(content, encoding="utf-8")

import json
json.load(open("data.json", encoding="utf-8"))

At script entry point, reconfigure stdout:

import sys
sys.stdout.reconfigure(encoding="utf-8")
sys.stderr.reconfigure(encoding="utf-8")

For subprocess calls:

subprocess.run(cmd, capture_output=True, text=True, encoding="utf-8")

Python Command

Use python (not python3) on Windows. The python3 alias is not reliably available.

python -m pytest tests/
python -m pip install -e .
python scripts/run.py

Path Handling

Use pathlib.Path or os.path — never hardcode forward/backslashes:

from pathlib import Path
config = Path(__file__).parent / "config" / "settings.json"

Terminal Encoding

Git Bash (Preferred for Claude Code)

Git Bash handles UTF-8 well by default. Recommended as primary shell.

CMD / PowerShell

Set code page to UTF-8 before running scripts:

chcp 65001

PowerShell profile setup:

[Console]::OutputEncoding = [System.Text.Encoding]::UTF8
$OutputEncoding = [System.Text.Encoding]::UTF8

Environment Variable

Set globally for consistent behavior:

[Environment]::SetEnvironmentVariable("PYTHONIOENCODING", "utf-8", "User")

Common Windows Pitfalls

1. File locking: Windows locks open files — close handles before rename/delete
2. Max path length: Enable long paths via Group Policy or registry if paths exceed 260 chars
3. Line endings: Configure git: git config core.autocrlf true
4. Temp files: Use tempfile.NamedTemporaryFile(delete=False) — Windows cannot open a temp file while it's held
5. Process cleanup: Use taskkill /F /PID instead of kill -9
6. Permission errors on rmtree: Use onerror handler for read-only files:

import shutil, stat
def rm_readonly(func, path, _):
    os.chmod(path, stat.S_IWRITE)
    func(path)
shutil.rmtree(dir_path, onerror=rm_readonly)