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The Slack adapter posts notifications to a Slack channel using an Incoming Webhook. Optionally, if you provide a Bot Token, file attachments are uploaded as real Slack files.

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Configuration

{
  "settings": {
    "notifications": {
      "channels": {
        "slack-alerts": {
          "type": "slack",
          "webhookUrl": "https://hooks.slack.com/services/T00/B00/xxx"
        }
      }
    }
  }
}
FieldTypeRequiredDescription
type"slack"YesChannel type
webhookUrlstringYesSlack Incoming Webhook URL
apiKeystringNoSlack Bot Token — enables real file uploads via files.upload
Both webhookUrl and apiKey support ${ENV_VAR} syntax: 
{
  "type": "slack",
  "webhookUrl": "${SLACK_WEBHOOK_URL}",
  "apiKey": "${SLACK_BOT_TOKEN}"
}

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Message Format

Messages use Slack’s rich attachment format with a color-coded sidebar:
SeverityColor
infoGreen (#36a64f)
warningGoldenrod (#daa520)
criticalRed (#ff0000)
Each message includes the notification title, body, a footer with the source event name, and a timestamp.

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Attachments

When a notification rule has includeOutcomes: true, task outcomes (files, logs) are attached to the Slack message. Without Bot Token — attachments are rendered as follow-up text messages. File content is shown in code blocks (truncated to 2800 characters). File metadata (name, size) is included. With Bot Token — binary files are uploaded to Slack via the files.upload API as real downloadable files, each with a title and comment.

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Connectivity Test

The test() check validates that the webhook URL hostname contains slack.com or hooks.slack.com. It does not make a network call — to verify end-to-end delivery, use the Send Direct API.

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Setup

  1. Create a Slack App at api.slack.com/apps
  2. Enable Incoming Webhooks in the app settings
  3. Add a webhook to your target channel — copy the webhook URL
  4. Add to Polpo config: 
    {
  "type": "slack",
  "webhookUrl": "https://hooks.slack.com/services/T00/B00/xxx"
}
  5. (Optional) For file upload support, add a Bot Token with files:write scope