# Backup Before Edit

Before editing any file, back up the original to a `.backup/` directory in the same parent folder.

## Why

Disk space is cheap. Lost work is expensive. AI assistants sometimes make destructive edits — overwriting files, truncating content, or introducing bugs that are hard to reverse. A `.backup/` directory provides instant recovery without relying on git history (which may not exist yet, or may have uncommitted changes).

## How

Before modifying `src/config.py`:

```bash
mkdir -p src/.backup
cp src/config.py src/.backup/config.py
```

For files that get edited multiple times, timestamp the backup:

```bash
cp src/config.py src/.backup/config.py.$(date +%Y%m%d-%H%M%S)
```

## Gitignore

Add `.backup/` to your `.gitignore` so backups are never committed:

```
.backup/
```

## When to Apply

- **Always** before editing existing files, especially configuration or infrastructure files
- **Always** when an AI assistant is making changes to files you haven't read yet
- **Skip** for files you just created in this session (nothing to back up)
- **Skip** for test files during rapid iteration (git handles recovery)

## Where This Rule Lives

This belongs in your global `~/.claude/CLAUDE.md` so it applies to every project without per-project configuration. It's the one rule that should be universal and unconditional.