Hooks

A hook is your own command that runs automatically when a specific Claude Code event fires — no need to ask for it each time. The classic example: auto-formatting code the moment Claude edits a file, rather than remembering to say “now run the formatter” at the end of every session.

A worked example

Here’s a PostToolUse hook that runs after any Edit or Write tool call, in .claude/settings.json:

{
  "hooks": {
    "PostToolUse": [
      {
        "matcher": "Edit|Write",
        "hooks": [
          { "type": "command", "command": "bun run format" }
        ]
      }
    ]
  }
}

Swap bun run format for whatever your project actually uses — for a Flutter/Dart repo that’s likely dart format ..

Once this is in place, every time Claude edits or writes a file, your formatter runs immediately afterward, automatically. You never have to remember to ask.

More events exist beyond PostToolUse

The set of supported hook events can grow over time. PostToolUse (after a tool runs) is the one shown here, but check the current hooks reference docs for the full list — there are hooks for other points in the session lifecycle too.

Hooks live in the same tiered settings system as everything else in .claude/settings.json — see Configuration for how project, user, and local settings stack. For a Dart-specific hook idea (running dart format or flutter analyze automatically post-edit), see Claude Code for Flutter Teams.

Check yourselfWhat's a hook actually for, versus just asking Claude to run the formatter each time?

A hook guarantees the action happens every single time the triggering event occurs — it’s enforced by Claude Code itself, not dependent on you remembering to ask or Claude remembering to do it unprompted. Asking each time is optional and easy to forget; a hook makes the behavior automatic and consistent across the whole team, since it’s checked into .claude/settings.json rather than living in anyone’s habits.