Claude Code Hooks Generator

10 examples you can load

Each button adds the hook to the generator above. Read the command before you keep it.

How a hook runs

When an event fires, Claude Code looks up the groups registered for it, filters them by matcher, and runs each handler. A command handler gets the event as JSON on stdin. Its exit code and output tell Claude Code what to do next.

• Exit 0: success. Stdout can carry JSON such as hookSpecificOutput.additionalContext.
• Exit 2: a blocking error on events that can block. Stderr goes back to Claude. On events that cannot block, stderr is only shown.
• Any other exit code: a non-blocking error. Execution continues.

The shape of the JSON

{
  "hooks": {
    "PreToolUse": [
      {
        "matcher": "Bash",
        "hooks": [
          { "type": "command", "command": "./check.sh", "timeout": 30 }
        ]
      }
    ]
  }
}

Events map to an array of groups. Each group has an optional matcher and a hooks array of handlers. Optional handler fields listed in the docs include if, timeout, statusMessage, async and once.

Events and what the matcher compares

Checked against code.claude.com/docs/en/hooks on 2026-10-20. The docs change often, so confirm the event you depend on. unverified: whether SessionEnd blocks nothing in every version; treat it as informational.

Pitfalls

• Hooks run with your user permissions and no sandbox. A hook script that reads untrusted input needs the same care as any shell script.
• Quote file paths. tool_input.file_path can contain spaces.
• A hook that prints extra text on stdout can break JSON parsing. Redirect noisy tools to stderr or /dev/null.
• After you edit a settings file, start a new session to be sure the change applies. unverified: whether a running session reloads hooks on its own.