You can use a Claude PreToolUse command hook to prevent write (or even read) access to specific files.

With this approach you can enforce that Claude cannot access to specific files. It’s a guarantee and will always work, unlike a prompt or Claude.md which is just a suggestion that can be forgotten or ignored.

This post has an example hook for blocking access to sensitive files:

https://aiorg.dev/blog/claude-code-hooks#:~:text=Protect%20s...