Slack Notification Skill

Part of Cardo — "Spawn many. Swarm the objective."

Send notifications to {{SLACK_CHANNEL}} channel. Always tag the project owner and reply to thread when available.

Prerequisites

bash

# Required environment variables
export SLACK_WEBHOOK_URL=https://hooks.slack.com/services/...
export SLACK_MEMBER_ID=U0XXXXXXX  # Project owner's Slack user ID

Thread Context

When triggered from Slack via @Claude, capture the thread timestamp from the triggering message at the start of your session:

bash

# Capture from the Slack message that triggered this session
# This keeps all replies in the same thread
THREAD_TS="<thread_ts from triggering slack message>"

If no thread context is available (e.g., triggered from web UI), notifications will post as new messages to the channel.

Helper Function

bash

slack_notify() {
  local message="$1"
  local thread_ts="${2:-}"  # Pass thread_ts as second argument if available

  # Tag project owner using member ID from environment
  local tagged_message="<@${SLACK_MEMBER_ID}> ${message}"

  if [ -n "$thread_ts" ]; then
    # Reply to existing thread
    curl -s -X POST -H 'Content-type: application/json' \
      --data "{\"text\":\"${tagged_message}\",\"thread_ts\":\"${thread_ts}\"}" \
      "$SLACK_WEBHOOK_URL"
  else
    # Post to channel (new thread)
    curl -s -X POST -H 'Content-type: application/json' \
      --data "{\"text\":\"${tagged_message}\"}" \
      "$SLACK_WEBHOOK_URL"
  fi
}

# Usage:
# slack_notify "PR ready for review" "$THREAD_TS"

Notification Templates

All templates pass $THREAD_TS to reply in the triggering thread.

PR Ready for Review

bash

slack_notify "PR Ready

PR: #${PR_NUMBER} - ${PR_TITLE}
Issue: Closes #${ISSUE_NUMBER}

Link: https://github.com/{{GITHUB_OWNER}}/{{GITHUB_REPO}}/pull/${PR_NUMBER}" "$THREAD_TS"

Blocked / Need Input

bash

slack_notify "Blocked

Issue: #${ISSUE_NUMBER} - ${ISSUE_TITLE}
Phase: ${CURRENT_PHASE}
Problem: ${ERROR_SUMMARY}

_Need your help to proceed._" "$THREAD_TS"

Input Needed

bash

slack_notify "Input Needed

Issue: #${ISSUE_NUMBER} - ${ISSUE_TITLE}
Question: ${QUESTION}

_Waiting for your response._" "$THREAD_TS"

Phase Complete

bash

slack_notify "${PHASE_NAME} Complete

Issue: #${ISSUE_NUMBER}
Next: ${NEXT_PHASE}" "$THREAD_TS"

PR Merged

bash

slack_notify "Merged!

PR: #${PR_NUMBER} merged
Issue: #${ISSUE_NUMBER} closed" "$THREAD_TS"

Comments Received on PR

bash

slack_notify "PR Feedback

PR: #${PR_NUMBER} has new review comments
Reviewer: ${REVIEWER}

Addressing feedback now..." "$THREAD_TS"

Morning Digest

bash

# Morning digest posts as new message (no thread context)
slack_notify "Morning Summary

*While you slept:*
Completed: ${COMPLETED_ISSUES}
PRs ready: ${READY_PRS}
Blocked: ${BLOCKED_ISSUES}
Needs input: ${NEEDS_INPUT}

*Budget:* \$${SPENT}/\$200 (${PERCENT}%) this month"

Raw Curl Commands

If helper function not available:

Post to Channel (New Thread)

bash

curl -s -X POST -H 'Content-type: application/json' \
  --data "{\"text\":\"<@${SLACK_MEMBER_ID}> Your message here\"}" \
  "$SLACK_WEBHOOK_URL"

Reply to Thread

bash

# Use THREAD_TS captured from session context
curl -s -X POST -H 'Content-type: application/json' \
  --data "{
    \"text\":\"<@${SLACK_MEMBER_ID}> Your message here\",
    \"thread_ts\":\"${THREAD_TS}\"
  }" \
  "$SLACK_WEBHOOK_URL"

With Formatting

bash

curl -s -X POST -H 'Content-type: application/json' \
  --data "{\"text\":\"<@${SLACK_MEMBER_ID}> *Bold* _italic_ \`code\`\n- Bullet point\n- Another point\",\"thread_ts\":\"${THREAD_TS}\"}" \
  "$SLACK_WEBHOOK_URL"

When to Notify

Event	Notify?	Template
Issue picked up	No	--
Phase complete	No (unless blocked)	--
Need human input	Yes	Input Needed
Blocked after 3 attempts	Yes	Blocked
PR created	Yes	PR Ready
PR has review comments	Yes	Comments Received
PR merged	Yes	PR Merged
Session ending (sleep hours)	Yes	Morning Digest

Setting Up SLACK_MEMBER_ID

To get your Slack member ID:

•Go to Slack
•Click on your profile
•Click "..." menu → "Copy member ID"
•Set as environment variable: export SLACK_MEMBER_ID=U0XXXXXXX

Error Handling

bash

response=$(slack_notify "Test message")
if echo "$response" | grep -q "ok"; then
  echo "Notification sent"
else
  echo "Failed to send notification: $response"
fi

Security Notes

•Never hardcode SLACK_WEBHOOK_URL in files
•Webhook URL is secret — treat like a password
•If compromised, regenerate in Slack app settings
•SLACK_MEMBER_ID is not sensitive but keep in env for consistency