safety-hooks.md

safety hooks in 5 minutes

block force pushes, rm -rf /, DROP TABLE, and curl | bash with one hook script.

setup

1. copy the script:

cp hooks/safety-guard.sh ~/.claude/hooks/safety-guard.sh
chmod +x ~/.claude/hooks/safety-guard.sh

2. register it in your global settings:

// ~/.claude/settings.json
{
  "hooks": {
    "PreToolUse": [
      {
        "matcher": "Bash",
        "hooks": [
          {
            "type": "command",
            "command": "~/.claude/hooks/safety-guard.sh"
          }
        ]
      }
    ]
  }
}

3. done. every Bash command claude runs now gets checked first.

what it blocks

pattern	why
git push --force to main/master	protects shared branches
rm -rf / and variants	prevents catastrophic deletes
DROP TABLE, DROP DATABASE	protects databases
chmod 777 on sensitive paths	prevents permission disasters
curl | bash, wget | sh	blocks remote code execution

note (v2.1.160+): in addition to safety-guard.sh blocking, claude code now prompts before writing to shell startup files and build-tool config files. this provides a second layer of protection for sensitive writes.

how it works

the hook receives JSON on stdin with the tool name and input. it checks the bash command against known dangerous patterns. exit 0 = allow, exit 2 = block.

#!/usr/bin/env bash
set -euo pipefail
INPUT=$(cat)
CMD=$(echo "$INPUT" | jq -r '.tool_input.command // empty')

# check for dangerous patterns
if echo "$CMD" | grep -qiE 'push.*--force|push.*-f'; then
  echo "blocked: force push detected" >&2
  exit 2
fi

the full safety-guard.sh covers 6 categories. this example shows the pattern.

try it

after setup, test it:

> run: git push --force origin main

claude will see: "blocked: force push detected" and won't execute it.

full hooks guide →