Complex tasks in Claude Code can take a while. Run a few in parallel across different repos and it gets hard to track which ones are done and which ones need input.

Claude Code supports hooks - shell commands that run in response to events. Hook into the Stop and Notification events to send a Slack message when a task completes or when Claude needs attention.

The notification script

Using PEP 723 inline metadata to keep everything in one file:

# /// script
# requires-python = ">=3.10"
# dependencies = [
#   "httpx",
# ]
# ///

import json
import os
import sys

SLACK_WEBHOOK_URL = os.environ.get("SLACK_WEBHOOK_URL")

def send_slack_message(text: str) -> None:
    if not SLACK_WEBHOOK_URL:
        print("SLACK_WEBHOOK_URL not set", file=sys.stderr)
        return

    import httpx
    httpx.post(SLACK_WEBHOOK_URL, json={"text": text})

def main():
    hook_data = json.load(sys.stdin)
    event = hook_data.get("event")
    cwd = hook_data.get("cwd", "unknown")
    project = cwd.split("/")[-1]

    if event == "stop":
        send_slack_message(f":white_check_mark: Claude Code finished in `{project}`")
    elif event == "notification":
        message = hook_data.get("notification", {}).get("message", "")
        send_slack_message(f":bell: Claude Code needs attention in `{project}`: {message}")

if __name__ == "__main__":
    main()

The script reads hook data from stdin (JSON with event type, working directory, etc.), formats a message with the project name, and posts to Slack.

Setting up the webhook

  1. Go to Slack API Apps and create a new app
  2. Enable “Incoming Webhooks”
  3. Add a webhook to your workspace and choose a channel
  4. Copy the webhook URL

Set it as an environment variable:

export SLACK_WEBHOOK_URL="https://hooks.slack.com/services/..."

Configuring Claude Code hooks

Add this to ~/.claude/settings.json:

{
  "hooks": {
    "Notification": [
      {
        "matcher": "",
        "hooks": [
          "uv run /path/to/claude-code-slack-notify.py"
        ]
      }
    ],
    "Stop": [
      {
        "matcher": "",
        "hooks": [
          "uv run /path/to/claude-code-slack-notify.py"
        ]
      }
    ]
  }
}

Replace /path/to/claude-code-slack-notify.py with the actual path.

Now when Claude Code finishes a task or needs input, you get a Slack message with the project name. Useful when running tasks across multiple repos or when you’re away from your terminal.

The full gist is here.