20 Safety and Review

Claude Code is powerful—which means it’s important to use it responsibly. This chapter covers safety practices.

20.1 The Approval Workflow

Claude Code asks for approval before: - Creating or modifying files - Running shell commands - Deleting anything

Always read what Claude proposes before approving.

20.2 Reading Before Approving

20.2.1 For File Changes

When Claude shows a file change, look for:

What file? Is it the right file?
What change? Does it match what you asked?
Side effects? Will this break anything else?

20.2.2 For Commands

When Claude proposes a command, check:

What will it do? Understand the command
Is it safe? Check for dangerous flags
Scope? What files/directories will it affect?

20.3 Dangerous Commands to Watch For

20.3.1 Deletion Commands

rm -rf *           # Deletes everything!
rm -rf /           # Deletes your entire system
rm -rf ~           # Deletes your home directory

Always check rm commands for: - The path being deleted - The -rf flags (recursive, force)

20.3.2 Git Commands

git reset --hard     # Loses uncommitted changes
git push --force     # Overwrites remote history
git clean -fd        # Deletes untracked files

20.3.3 Permission Commands

sudo rm ...          # Admin-level deletion
chmod 777 ...        # Opens files to everyone
sudo chown ...       # Changes file ownership

20.3.4 Network Commands

curl ... | bash      # Runs downloaded script
wget ... && ./script # Downloads and executes

20.4 Safe Practices

20.4.1 Work in a Project Directory

Don’t run Claude Code from your home directory or root:

# Good - in a specific project
cd ~/Projects/my-project
claude

# Bad - too broad
cd ~
claude

20.4.2 Use Git

Commit often so you can revert mistakes:

> Before making major changes, let's commit what we have

If something goes wrong:

git diff                    # See what changed
git checkout -- filename    # Revert a specific file
git reset --hard HEAD       # Revert everything (careful!)

20.4.3 Test in Isolation

For risky operations:

> Let's test this on a copy of the file first

cp important_file.csv test_copy.csv
# Test on copy first

20.4.4 Understand Before Approving

If you don’t understand a command:

> What does this command do exactly?

Or:

> Explain the flags in this command

20.5 Sensitive Data

20.5.2 Environment Variables

Never put secrets in code:

# Bad - secret in code
api_key = "sk-12345..."

# Good - from environment
import os
api_key = os.getenv("API_KEY")

20.5.3 .gitignore

Ensure sensitive files aren’t committed:

> Add .env and any data files to .gitignore

20.6 When Things Go Wrong

20.6.1 Undo File Changes

# See what changed
git status

# Revert a file
git checkout -- path/to/file

# Revert everything
git reset --hard HEAD

20.6.2 Stop a Running Command

Press Ctrl + C to interrupt a running process.

20.6.3 Recovery from Deletion

If you accidentally delete something: - Check your trash/recycle bin - Check Time Machine or other backups - Check git history if it was committed

20.7 Claude’s Limitations

20.7.1 Claude Can Be Wrong

Code might have bugs
Commands might have unintended effects
Suggestions might not be optimal

Your job: Verify that outputs make sense.

20.7.2 Claude Doesn’t Know Your Context

Your file system specifics
Your institutional policies
Your security requirements

Your job: Provide relevant context and apply domain judgment.

20.7.3 Claude Doesn’t Persist State

Between sessions: - Claude doesn’t remember previous conversations - It re-reads files each time - Settings don’t persist automatically

20.8 Institutional Considerations

20.8.1 Data Use Agreements

If your data has restrictions: - Check if using AI tools is permitted - Consider what data is sent to external servers - Consult your IRB or data governance team

20.8.2 Publication and Authorship

When using AI assistance: - Follow journal guidelines on AI use - Document AI assistance appropriately - Ensure you understand and can defend all content

20.8.3 Reproducibility

For research: - Keep records of prompts used - Version control everything - Document AI-assisted steps

20.9 Checklist: Before Approving

For file changes: - [ ] Correct file? - [ ] Change looks right? - [ ] Won’t break other things?

For commands: - [ ] Understand what it does? - [ ] Safe flags? - [ ] Correct paths?

For sensitive operations: - [ ] Backed up? - [ ] Can undo if wrong? - [ ] Not affecting production?

20.10 Summary

Safety with Claude Code: - Read before approving every change - Watch for dangerous commands (rm, sudo, git reset) - Use git for easy recovery - Protect sensitive data from accidental exposure - Verify outputs match expectations

20.11 Next Steps

Continue to When Claude Code Struggles.