Slack Bot Builder
Build Slack apps using the Bolt framework across Python, JavaScript, and Java. Covers Block Kit for rich UIs, interactive components, slash commands, event handling, OAuth installation flows, and Workflow Builder integration. Focus on best practices for production-ready Slack apps.
Patterns
Bolt App Foundation Pattern
The Bolt framework is Slack's recommended approach for building apps. It handles authentication, event routing, request verification, and HTTP request processing so you can focus on app logic.
Key benefits:
- Event handling in a few lines of code
- Security checks and payload validation built-in
- Organized, consistent patterns
- Works for experiments and production
Available in: Python, JavaScript (Node.js), Java
When to use: Starting any new Slack app,Migrating from legacy Slack APIs,Building production Slack integrations
Python Bolt App
from slack_bolt import App from slack_bolt.adapter.socket_mode import SocketModeHandler import os
Initialize with tokens from environment
app = App( token=os.environ["SLACK_BOT_TOKEN"], signing_secret=os.environ["SLACK_SIGNING_SECRET"] )
Handle messages containing "hello"
@app.message("hello") def handle_hello(message, say): """Respond to messages containing 'hello'.""" user = message["user"] say(f"Hey there <@{user}>!")
Handle slash command
@app.command("/ticket") def handle_ticket_command(ack, body, client): """Handle /ticket slash command.""" # Acknowledge immediately (within 3 seconds) ack()
# Open a modal for ticket creation client.views_open( trigger_id=body["trigger_id"], view={ "type": "modal", "callback_id": "ticket_modal", "title": {"type": "plain_text", "text": "Create Ticket"}, "submit": {"type": "plain_text", "text": "Submit"}, "blocks": [ { "type": "input", "block_id": "title_block", "element": { "type": "plain_text_input", "action_id": "title_input" }, "label": {"type": "plain_text", "text": "Title"} }, { "type": "input", "block_id": "desc_block", "element": { "type": "plain_text_input", "multiline": True, "action_id": "desc_input" }, "label": {"type": "plain_text", "text": "Description"} }, { "type": "input", "block_id": "priority_block", "element": { "type": "static_select", "action_id": "priority_select", "options": [ {"text": {"type": "plain_text", "text": "Low"}, "value": "low"}, {"text": {"type": "plain_text", "text": "Medium"}, "value": "medium"}, {"text": {"type": "plain_text", "text": "High"}, "value": "high"} ] }, "label": {"type": "plain_text", "text": "Priority"} } ] } )
Handle modal submission
@app.view("ticket_modal") def handle_ticket_submission(ack, body, client, view): """Handle ticket modal submission.""" ack()
# Extract values from the view values = view["state"]["values"] title = values["title_block"]["title_input"]["value"] desc = values["desc_block"]["desc_input"]["value"] priority = values["priority_block"]["priority_select"]["selected_option"]["value"] user_id = body["user"]["id"]
# Create ticket in your system ticket_id = create_ticket(title, desc, priority, user_id)
# Notify user client.chat_postMessage( channel=user_id, text=f"Ticket #{ticket_id} created: {title}" )
Handle button clicks
@app.action("approve_button") def handle_approval(ack, body, client): """Handle approval button click.""" ack()
# Get context from the action user = body["user"]["id"] action_value = body["actions"][0]["value"]
# Update the message to remove interactive elements # (Best practice: prevent double-clicks) client.chat_update( channel=body["channel"]["id"], ts=body["message"]["ts"], text=f"Approved by <@{user}>", blocks=[] # Remove interactive blocks )
Listen for app_home_opened events
@app.event("app_home_opened") def update_home_tab(client, event): """Update the Home tab when user opens it.""" client.views_publish( user_id=event["user"], view={ "type": "home", "blocks": [ { "type": "section", "text": { "type": "mrkdwn", "text": "Welcome to the Ticket Bot!" } }, { "type": "actions", "elements": [ { "type": "button", "text": {"type": "plain_text", "text": "Create Ticket"}, "action_id": "create_ticket_button" } ] } ] } )
Socket Mode for development (no public URL needed)
if __name__ == "__main__": handler = SocketModeHandler(app, os.environ["SLACK_APP_TOKEN"]) handler.start()
For production, use HTTP mode with a web server
from flask import Flask, request
from slack_bolt.adapter.flask import SlackRequestHandler
#
flask_app = Flask(__name__)
handler = SlackRequestHandler(app)
#
@flask_app.route("/slack/events", methods=["POST"])
def slack_events():
return handler.handle(request)
Anti_patterns
- Not acknowledging requests within 3 seconds
- Blocking operations in the ack handler
- Hardcoding tokens in source code
- Not using Socket Mode for development
Block Kit UI Pattern
Block Kit is Slack's UI framework for building rich, interactive messages. Compose messages using blocks (sections, actions, inputs) and elements (buttons, menus, text inputs).
Limits:
- Up to 50 blocks per message
- Up to 100 blocks in modals/Home tabs
- Block text limited to 3000 characters
Use Block Kit Builder to prototype: https://app.slack.com/block-kit-builder
When to use: Building rich message layouts,Adding interactive components to messages,Creating forms in modals,Building Home tab experiences
from slack_bolt import App import os
app = App(token=os.environ["SLACK_BOT_TOKEN"])
def build_notification_blocks(incident: dict) -> list: """Build Block Kit blocks for incident notification.""" severity_emoji = { "critical": ":red_circle:", "high": ":large_orange_circle:", "medium": ":large_yellow_circle:", "low": ":white_circle:" }
return [ # Header { "type": "header", "text": { "type": "plain_text", "text": f"{severity_emoji.get(incident['severity'], '')} Incident Alert" } }, # Details section { "type": "section", "fields": [ { "type": "mrkdwn", "text": f"Incident:\n{incident['title']}" }, { "type": "mrkdwn", "text": f"Severity:\n{incident['severity'].upper()}" }, { "type": "mrkdwn", "text": f"Service:\n{incident['service']}" }, { "type": "mrkdwn", "text": f"*Re