Slack

Run a workflow on Slack activity — a message posted, a mention, any event your Slack app subscribes to. The Slack Events API envelope becomes the workflow's input.

For behavior shared by every provider (the delivery URL, testing), see the webhook triggers reference.

Setup

Slack sends events to a Request URL you configure on a Slack app, so you wire it up in Slack:

1. Add a From an app trigger and pick Slack. Cotera gives you a delivery URL.
2. In your Slack app's Event Subscriptions, set the Request URL to Cotera's URL.
3. Subscribe to the events you want (for example message.channels). Slack only sends the events you subscribe to.

There's nothing to tear down on Cotera's side; remove the subscription in Slack to stop deliveries.

Events

The Slack trigger is a passthrough: every event Slack delivers runs the workflow. There's no per-event filtering in Cotera — you scope what fires by choosing which events to subscribe to in Slack (and, if needed, by branching inside the workflow on event.type).

Payload

The raw Slack Events API event_callback envelope is passed through as the workflow input. A message event looks like:

{
  "token": "cotera-test-verification-token",
  "team_id": "T0123456789",
  "api_app_id": "A0123456789",
  "type": "event_callback",
  "event_id": "Ev0123456789",
  "event_time": 1716111111,
  "event": {
    "type": "message",
    "channel": "C0123456789",
    "user": "U0123456789",
    "text": "Hello from Cotera",
    "ts": "1716111111.000100",
    "channel_type": "channel"
  },
  "authorizations": [
    { "enterprise_id": null, "team_id": "T0123456789", "user_id": "U0123456789", "is_bot": true }
  ]
}

Signature verification

Slack signs each delivery with the X-Slack-Signature header in the form v0=<hex> — an HMAC-SHA256 over v0:{timestamp}:{body}, where the timestamp comes from the X-Slack-Request-Timestamp header. Cotera verifies it against the trigger's signing secret on every delivery and rejects anything that fails.