Claude overwrote a user-edited .docx without confirmation, destroying manual work

What happened

Claude Code overwrote a .docx file that I had edited in Word and saved and closed. All of my manual work was destroyed.

Steps

1. Claude generated a .docx
2. I edited it extensively in Word (layout, line breaks, font sizes, rewrote the copy), then saved and closed it
3. I asked Claude to read my edited version and ADD a supplementary section
4. Claude read the text content and aggregate font-size statistics from the .docx
5. Claude then regenerated the entire .docx from Markdown and overwrote the same path
6. All of my manual edits were lost
7. Claude claimed it could restore the file because it had "read" it — it could not
8. It then failed several more restore attempts, consuming even more of my time

Problems

1. Overwrote a user-edited file without confirmation. I asked it to add a section, not to regenerate the document.
2. Claimed the file was restorable without verifying it. It only had the text and aggregate font sizes — not per-paragraph formatting, line breaks, or bold ranges.
3. No backup was taken before overwriting.

Requested fixes

• Block or warn before overwriting a file whose mtime is newer than the assistant's last write to it (i.e. a human touched it)
• Automatically back up any user-touched file before overwriting
• Do not claim a file can be restored without verifying that it actually can be

Impact

Lost the layout work I had spent significant time on, and had to redo it. The failed recovery attempts wasted additional working time.

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（日本語）
Wordで編集して保存・終了したdocxを、Claudeが断りなく上書きして消しました。
「補足を足してほしい」と頼んだだけなのに、Markdownから全体を作り直して同じパスに上書きしています。
さらに「読み取ったので戻せる」と言いながら復元できず、復旧の試行錯誤にも時間を奪われました。
人が触ったファイルへの上書きは、既定で止めるか、必ずバックアップを取るようにしてください。