Slack Trigger

Receives Slack events — messages, app mentions, and reactions — and starts workflow execution. Use this to build automations that react to activity in your Slack workspace.

When to Use

Use Slack Trigger when:

You want to run a workflow when someone posts a message or mentions your bot
You need to react to emoji reactions or channel activity
Slack is the event source and your workflow runs asynchronously

For sending messages back to Slack, pair this with Slack Send Message.

Setup

Create a Slack App at api.slack.com/apps
Enable Event Subscriptions and set the Request URL to your deployed trigger endpoint on triggers.tensorify.io
Subscribe to the bot events matching your event_types setting (e.g., message, app_mention, reaction_added)
Install the app to your workspace and copy the Bot User OAuth Token and Signing Secret
Add SLACK_BOT_TOKEN and SLACK_SIGNING_SECRET on the Env Vars page
Deploy the workflow to activate the endpoint

The plugin handles Slack's URL verification challenge automatically — no manual setup required.

Output

Handle	Type	Description
`payload`	object	Normalized Slack event payload

The payload (accessed as {{ slack.* }}) shape:

Field	Type	Description
`user`	string	Slack user ID of the event author
`channel`	string	Channel ID where the event occurred
`text`	string	Message text (for message and mention events)
`timestamp`	string	Slack message timestamp (`ts`)
`thread_ts`	string	Thread parent timestamp, if the message is in a thread
`event_type`	string	Event type (e.g., `message`, `app_mention`, `reaction_added`)
`raw_event`	object	Full Slack event object for advanced use cases

Settings

Setting	Type	Default	Description
`event_types`	multi-select	`message`, `app_mention`	Slack event types to listen for: `message`, `app_mention`, `reaction_added`, `message.channels`
`channel_filter`	string	—	Only trigger for events in this channel ID. Leave empty to accept all channels.
`mockPayload`	JSON	—	Test payload injected during canvas testing.

Authentication

Env Var	Description
`SLACK_BOT_TOKEN`	Bot User OAuth Token (`xoxb-...`) from your Slack app
`SLACK_SIGNING_SECRET`	Signing secret used to verify incoming Slack requests

Example

React to bot mentions and reply in the same thread:

Set event_types to app_mention
Add a Slack Send Message node after the trigger
Set Channel to {{ slack.channel }}
Set Thread Timestamp to {{ slack.thread_ts }} (or {{ slack.timestamp }} for top-level replies)
Set Message Text to a dynamic response

Access event data in downstream nodes:

{{ slack.user }}
{{ slack.text }}
{{ slack.channel }}
{{ slack.event_type }}

Common Gotchas

Bot messages ignored: Slack does not deliver bot-authored messages by default. Subscribe to app_mention if you want the bot to respond when tagged.
Missing scopes: Ensure your Slack app has the OAuth scopes required for the events you subscribe to (e.g., channels:history, app_mentions:read).
Channel filter: Use the channel ID (e.g., C01234ABCDE), not the channel name. Right-click a channel in Slack and copy the link to find the ID.
Signing secret required: Requests without a valid signature are rejected. Double-check SLACK_SIGNING_SECRET matches your app settings.