Set Up Hooks to Run Commands Automatically Before or After Tool Calls

Hooks let you attach shell commands to Claude's tool calls — they fire automatically before or after Claude reads a file, writes code, or runs a command. No prompting required.

{
  "hooks": {
    "PostToolUse": [
      {
        "matcher": "Write|Edit",
        "command": "vendor/bin/pint --dirty --format agent"
      }
    ]
  }
}

Drop that in your .claude/settings.json and every time Claude edits or writes a PHP file, Pint runs automatically to fix formatting. Claude sees the hook output and adjusts if needed.

You can hook into different events:

• PreToolUse — runs before a tool executes (can block it by returning a non-zero exit code)
• PostToolUse — runs after a tool completes
• Notification — runs when Claude sends a notification

The matcher field filters which tool triggers the hook. Match specific tools like Write, Edit, Bash, or use a regex pattern to match several.

{
  "hooks": {
    "PostToolUse": [
      {
        "matcher": "Write|Edit",
        "command": "npx eslint --fix $CLAUDE_FILE_PATH"
      },
      {
        "matcher": "Bash",
        "command": "echo \"$(date): $CLAUDE_TOOL_INPUT\" >> ~/.claude-commands.log"
      }
    ],
    "PreToolUse": [
      {
        "matcher": "Bash",
        "command": "echo 'Review this command carefully' >&2"
      }
    ]
  }
}

Hooks run in your shell with access to environment variables like $CLAUDE_FILE_PATH and $CLAUDE_TOOL_INPUT, so you can build context-aware automation around Claude's actions.

Hooks turn Claude Code from an assistant you instruct into a workflow that enforces your standards automatically.

via Claude Code