> ## Documentation Index
> Fetch the complete documentation index at: https://docs.cassidyai.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Slack message trigger

> Start a Workflow when a message is posted in a Slack channel or sent as a DM to Cassidy.

The Slack Message trigger starts your [Workflow](/workflows/overview) whenever a message is posted in a Slack channel or sent as a direct message to Cassidy. Use it to automate follow-up, route requests, or process inbound messages automatically.

<Steps>
  <Step title="Add the Slack Message trigger">
    Create a workflow with a Slack Message trigger, use an existing workflow with a Slack Message trigger, or change an existing workflow's trigger type to a Slack Message trigger.

    <Frame>
      <img src="https://mintcdn.com/cassidy/g8fyfImJ_SyinsRX/images/reference/slack-message-trigger-img-0.png?fit=max&auto=format&n=g8fyfImJ_SyinsRX&q=85&s=af6ca23f51b4d91ed176bca800f85ba7" alt="Workflow builder showing the Slack Message trigger selected" width="579" height="187" data-path="images/reference/slack-message-trigger-img-0.png" />
    </Frame>
  </Step>

  <Step title="Connect your Slack account">
    If you haven't already, connect your Slack account to Cassidy.

    <Frame>
      <img src="https://mintcdn.com/cassidy/g8fyfImJ_SyinsRX/images/reference/slack-message-trigger-img-1.png?fit=max&auto=format&n=g8fyfImJ_SyinsRX&q=85&s=f67288e02140ea6d9c1be1f42b43df17" alt="Slack connection prompt in the trigger configuration" width="636" height="595" data-path="images/reference/slack-message-trigger-img-1.png" />
    </Frame>
  </Step>

  <Step title="Choose the message event type">
    Select either **Message in Channel** to run the workflow when a message is posted in a Slack channel, or **Direct Message** to trigger the workflow when a direct message is sent to Cassidy.
  </Step>

  <Step title="Select the channel">
    If you chose **Message in Channel**, select the Slack channel where you want the trigger to listen for messages.

    <Frame>
      <img src="https://mintcdn.com/cassidy/g8fyfImJ_SyinsRX/images/reference/slack-message-trigger-img-2.png?fit=max&auto=format&n=g8fyfImJ_SyinsRX&q=85&s=f552720a75d92b5952ab3682154d7af0" alt="Channel selector dropdown in the Slack Message trigger" width="630" height="459" data-path="images/reference/slack-message-trigger-img-2.png" />
    </Frame>

    <Tip>Private channels only appear after Cassidy has been added. In the desired channel, send `/invite @Cassidy`.</Tip>
  </Step>

  <Step title="Reference the trigger variables">
    In subsequent Workflow steps, you can reference the following variables from this trigger:

    * **Message Contents** — the content of the message posted in Slack
    * **Message with History** — full conversation history from the Slack channel, including previous messages and responses from Cassidy and other users
    * **Message with Thread History** — thread-specific conversation history if the message is part of a thread
    * **Thread ID** — the unique identifier for the thread if the message is part of a thread
    * **Channel ID** — the unique identifier for the Slack channel where the message was posted
    * **Message ID** — the unique identifier for the specific message
    * **Message Attachments** — any files or attachments included with the message
    * **Sent By User** — user information for the person who sent the message, including their Slack user ID, display name, and other profile details

    <Frame>
      <img src="https://mintcdn.com/cassidy/g8fyfImJ_SyinsRX/images/reference/slack-message-trigger-img-3.png?fit=max&auto=format&n=g8fyfImJ_SyinsRX&q=85&s=0587a5f5df1678c12bcddcc21274f732" alt="Variable picker showing available Slack Message trigger outputs" width="1510" height="774" data-path="images/reference/slack-message-trigger-img-3.png" />
    </Frame>
  </Step>

  <Step title="Activate the trigger">
    In the Slack Message trigger block, click the toggle switch to turn it on.

    <Frame>
      <img src="https://mintcdn.com/cassidy/g8fyfImJ_SyinsRX/images/reference/slack-message-trigger-img-4.png?fit=max&auto=format&n=g8fyfImJ_SyinsRX&q=85&s=8dc75a2c4a3c31a07f31f44f097e187d" alt="Toggle switch to activate the Slack Message trigger" width="569" height="185" data-path="images/reference/slack-message-trigger-img-4.png" />
    </Frame>
  </Step>
</Steps>

## Related

* [Send Slack Message](/integrations/slack/send-slack-message)
* [Slack for Workflows](/integrations/slack/workflows)
* [Deploy an Agent to Slack](/integrations/slack/deploy-agent)