Slack

Server Source code Package

Send walkerOS events to Slack as formatted messages. Supports both Incoming Webhooks (simple, single-channel) and the Web API (multi-channel routing, threading, DMs, ephemeral messages, Block Kit).

Where this fits

Slack is a server destination in the walkerOS flow:

Turns events into Slack messages for real-time alerts, sales notifications, moderation queues, or incident routing, without coupling your product code to Slack.

Installation

npm install @walkeros/server-destination-slack

Integrated

import { startFlow } from '@walkeros/collector';
import { destinationSlack } from '@walkeros/server-destination-slack';

await startFlow({
  destinations: {
    slack: {
      code: destinationSlack,
      config: {
        settings: {
          token: 'xoxb-your-bot-token',
          channel: '#notifications',
        },
      },
    },
  },
});

Bundled

Add to your flow.json destinations:

"destinations": {
  "slack": {
    "package": "@walkeros/server-destination-slack",
    "import": "destinationSlack",
    "config": {
      "settings": {
        "token": "xoxb-your-bot-token",
        "channel": "#notifications"
      }
    }
  }
}

See bundled mode setup | CLI reference

Configuration

This destination uses the standard destination config wrapper (consent, data, env, id, ...). For the shared fields see destination configuration. Package-specific fields live under config.settings and are listed below.

Settings

Property	Type	Description	More
token	string	Slack Bot token (xoxb-...). Enables Web API mode. Mutually exclusive with webhookUrl.
webhookUrl	string	Incoming Webhook URL. Enables webhook mode. Mutually exclusive with token.
channel	string	Default Slack channel ID or name (e.g. "#alerts" or "C024BE91L"). Required for Web API mode unless every rule supplies one. Ignored in webhook mode.
text	string	Default text template. Supports `${data.field}` interpolation against the walkerOS event.
blocks	Array<object>	Default Block Kit blocks applied when no mapping override is set.
includeHeader	boolean	Auto-add an event-name header block when generating default blocks. Default: true.
unfurlLinks	boolean	Enable link unfurling. Default: false (cleaner for automated alerts).
unfurlMedia	boolean	Enable media unfurling. Default: false.
mrkdwn	boolean	Use mrkdwn formatting in text. Default: true.
threadTs	string	Static thread_ts for replies (rarely set at destination level).
retryConfig		Retry policy passed to WebClient. Default: "default".

Mapping

Per-event rules under config.mapping. For the standard rule fields (consent, condition, data, batch, name, policy) see mapping.

Property	Type	Description	More
channel	string	Override the destination channel for this rule. Web API mode only -- ignored in webhook mode.
text	string	Override the text template for this rule. Supports `${data.field}` interpolation.
blocks	Array<object>	Override Block Kit blocks for this rule.
threadTs	string	thread_ts for posting as a reply in a thread.
replyBroadcast	boolean	Also broadcast the threaded reply back to the channel.
ephemeral	boolean	Send via chat.postEphemeral. Requires `user`.
user	string	Slack user ID for ephemeral or DM delivery.
dm	boolean	Send as DM via conversations.open + chat.postMessage. Requires `user`.

Examples

Default blocks

With no custom text the destination auto-generates a Block Kit message from event data and source.

Event

{
  "name": "lead submit",
  "data": {
    "name": "Acme",
    "email": "sales@acme.test"
  },
  "context": {
    "dev": [
      "test",
      1
    ]
  },
  "globals": {
    "lang": "elb"
  },
  "custom": {
    "completely": "random"
  },
  "user": {
    "id": "us3r",
    "device": "c00k13",
    "session": "s3ss10n"
  },
  "nested": [
    {
      "entity": "child",
      "data": {
        "is": "subordinated"
      }
    }
  ],
  "consent": {
    "functional": true
  },
  "id": "6323df53b76a3e4e",
  "trigger": "test",
  "entity": "lead",
  "action": "submit",
  "timestamp": 1700000600,
  "timing": 3.14,
  "source": {
    "count": 1,
    "trace": "0a1b2c3d4e5f60718293a4b5c6d7e8f9",
    "type": "crm",
    "platform": "server"
  }
}

Mapping

{
  "settings": {
    "channel": "#growth"
  }
}

Out

slackClient.chat.postMessage({
  "channel": "#growth",
  "text": "lead submit",
  "blocks": [
    {
      "type": "header",
      "text": {
        "type": "plain_text",
        "text": "lead submit"
      }
    },
    {
      "type": "section",
      "fields": [
        {
          "type": "mrkdwn",
          "text": "*name:*\nAcme"
        },
        {
          "type": "mrkdwn",
          "text": "*email:*\nsales@acme.test"
        }
      ]
    },
    {
      "type": "context",
      "elements": [
        {
          "type": "mrkdwn",
          "text": "Source: crm"
        }
      ]
    }
  ],
  "unfurl_links": false,
  "unfurl_media": false,
  "mrkdwn": true
})

Webhook deploy

Without a token the destination posts to an incoming Slack webhook URL with the rendered message body.

Event

{
  "name": "deploy complete",
  "data": {
    "version": "1.4.2",
    "environment": "prod"
  },
  "context": {
    "dev": [
      "test",
      1
    ]
  },
  "globals": {
    "lang": "elb"
  },
  "custom": {
    "completely": "random"
  },
  "user": {
    "id": "us3r",
    "device": "c00k13",
    "session": "s3ss10n"
  },
  "nested": [
    {
      "entity": "child",
      "data": {
        "is": "subordinated"
      }
    }
  ],
  "consent": {
    "functional": true
  },
  "id": "ee3c3eb93f9f29a7",
  "trigger": "test",
  "entity": "deploy",
  "action": "complete",
  "timestamp": 1700000700,
  "timing": 3.14,
  "source": {
    "count": 1,
    "trace": "0a1b2c3d4e5f60718293a4b5c6d7e8f9",
    "type": "collector",
    "schema": "4"
  }
}

Mapping

{
  "settings": {
    "text": ":rocket: Deployment complete: ${data.version} to ${data.environment}"
  }
}

Out

sendServer("https://hooks.slack.com/services/T00/B00/xxx", "{\"text\":\":rocket: Deployment complete: 1.4.2 to prod\",\"unfurl_links\":false,\"unfurl_media\":false,\"mrkdwn\":true}")

Ephemeral message

A quota warning posts an ephemeral Slack message visible only to a target admin user.

Event

{
  "name": "quota warning",
  "data": {
    "remaining": 5
  },
  "context": {
    "dev": [
      "test",
      1
    ]
  },
  "globals": {
    "lang": "elb"
  },
  "custom": {
    "completely": "random"
  },
  "user": {
    "id": "us3r",
    "device": "c00k13",
    "session": "s3ss10n"
  },
  "nested": [
    {
      "entity": "child",
      "data": {
        "is": "subordinated"
      }
    }
  ],
  "consent": {
    "functional": true
  },
  "id": "b4661f4fb739585e",
  "trigger": "test",
  "entity": "quota",
  "action": "warning",
  "timestamp": 1700000500,
  "timing": 3.14,
  "source": {
    "count": 1,
    "trace": "0a1b2c3d4e5f60718293a4b5c6d7e8f9",
    "type": "collector",
    "schema": "4"
  }
}

Mapping

{
  "settings": {
    "channel": "#admin",
    "ephemeral": true,
    "user": "U-ADMIN-1",
    "text": "Heads up: ${data.remaining} requests remaining"
  }
}

Out

slackClient.chat.postEphemeral({
  "channel": "#admin",
  "text": "Heads up: 5 requests remaining",
  "unfurl_links": false,
  "unfurl_media": false,
  "mrkdwn": true,
  "user": "U-ADMIN-1"
})

Error alert

An error event posts a critical alert to an engineering channel using a mapping-level channel override.

Event

{
  "name": "error occur",
  "data": {
    "message": "Payment gateway timeout",
    "code": "PGW_TIMEOUT",
    "severity": "critical"
  },
  "context": {
    "dev": [
      "test",
      1
    ]
  },
  "globals": {
    "lang": "elb"
  },
  "custom": {
    "completely": "random"
  },
  "user": {
    "id": "us3r",
    "device": "c00k13",
    "session": "s3ss10n"
  },
  "nested": [
    {
      "entity": "child",
      "data": {
        "is": "subordinated"
      }
    }
  ],
  "consent": {
    "functional": true
  },
  "id": "266b5d4d24184a0e",
  "trigger": "test",
  "entity": "error",
  "action": "occur",
  "timestamp": 1700000200,
  "timing": 3.14,
  "source": {
    "count": 1,
    "trace": "0a1b2c3d4e5f60718293a4b5c6d7e8f9",
    "type": "collector",
    "schema": "4"
  }
}

Mapping

{
  "settings": {
    "channel": "#engineering-alerts",
    "text": ":rotating_light: Error: ${data.message}"
  }
}

Out

slackClient.chat.postMessage({
  "channel": "#engineering-alerts",
  "text": ":rotating_light: Error: Payment gateway timeout",
  "unfurl_links": false,
  "unfurl_media": false,
  "mrkdwn": true
})

Purchase alert

A completed order posts a templated message to a sales channel via the Slack Web API.

Event

{
  "name": "order complete",
  "data": {
    "id": "ORD-500",
    "total": 299.99,
    "currency": "EUR",
    "product": "Pro Plan"
  },
  "context": {
    "shopping": [
      "complete",
      0
    ]
  },
  "globals": {
    "pagegroup": "shop"
  },
  "custom": {
    "completely": "random"
  },
  "user": {
    "id": "buyer-42"
  },
  "nested": [
    {
      "entity": "product",
      "data": {
        "id": "ers",
        "name": "Everyday Ruck Snack",
        "color": "black",
        "size": "l",
        "price": 420
      },
      "context": {
        "shopping": [
          "complete",
          0
        ]
      },
      "nested": []
    },
    {
      "entity": "product",
      "data": {
        "id": "cc",
        "name": "Cool Cap",
        "size": "one size",
        "price": 42
      },
      "context": {
        "shopping": [
          "complete",
          0
        ]
      },
      "nested": []
    },
    {
      "entity": "gift",
      "data": {
        "name": "Surprise"
      },
      "context": {
        "shopping": [
          "complete",
          0
        ]
      },
      "nested": []
    }
  ],
  "consent": {
    "functional": true
  },
  "id": "1859567d2dbc0398",
  "trigger": "load",
  "entity": "order",
  "action": "complete",
  "timestamp": 1700000100,
  "timing": 3.14,
  "source": {
    "count": 1,
    "trace": "0a1b2c3d4e5f60718293a4b5c6d7e8f9",
    "type": "collector",
    "schema": "4"
  }
}

Mapping

{
  "settings": {
    "channel": "#sales",
    "text": ":moneybag: New order: ${data.id} - ${data.total} ${data.currency}"
  }
}

Out

slackClient.chat.postMessage({
  "channel": "#sales",
  "text": ":moneybag: New order: ORD-500 - 299.99 EUR",
  "unfurl_links": false,
  "unfurl_media": false,
  "mrkdwn": true
})

Threaded reply

A checkout step posts as a threaded reply in Slack via thread_ts with broadcast to the channel.

Event

{
  "name": "checkout step",
  "data": {
    "step": "payment",
    "sessionTs": "1700000000.000050"
  },
  "context": {
    "dev": [
      "test",
      1
    ]
  },
  "globals": {
    "lang": "elb"
  },
  "custom": {
    "completely": "random"
  },
  "user": {
    "id": "us3r",
    "device": "c00k13",
    "session": "s3ss10n"
  },
  "nested": [
    {
      "entity": "child",
      "data": {
        "is": "subordinated"
      }
    }
  ],
  "consent": {
    "functional": true
  },
  "id": "ab9d56e47de5cf53",
  "trigger": "test",
  "entity": "checkout",
  "action": "step",
  "timestamp": 1700000400,
  "timing": 3.14,
  "source": {
    "count": 1,
    "trace": "0a1b2c3d4e5f60718293a4b5c6d7e8f9",
    "type": "collector",
    "schema": "4"
  }
}

Mapping

{
  "settings": {
    "channel": "#sales",
    "text": "Checkout step: ${data.step}",
    "threadTs": "1700000000.000050",
    "replyBroadcast": true
  }
}

Out

slackClient.chat.postMessage({
  "channel": "#sales",
  "text": "Checkout step: payment",
  "unfurl_links": false,
  "unfurl_media": false,
  "mrkdwn": true,
  "thread_ts": "1700000000.000050",
  "reply_broadcast": true
})

Welcome DM

A user signup opens a Slack DM channel and posts a welcome message with the selected plan.

Event

{
  "name": "user signup",
  "data": {
    "plan": "enterprise"
  },
  "context": {
    "dev": [
      "test",
      1
    ]
  },
  "globals": {
    "lang": "elb"
  },
  "custom": {
    "completely": "random"
  },
  "user": {
    "id": "U-NEW-USER"
  },
  "nested": [
    {
      "entity": "child",
      "data": {
        "is": "subordinated"
      }
    }
  ],
  "consent": {
    "functional": true
  },
  "id": "4f1aa47b22d48b4f",
  "trigger": "test",
  "entity": "user",
  "action": "signup",
  "timestamp": 1700000300,
  "timing": 3.14,
  "source": {
    "count": 1,
    "trace": "0a1b2c3d4e5f60718293a4b5c6d7e8f9",
    "type": "collector",
    "schema": "4"
  }
}

Mapping

{
  "settings": {
    "dm": true,
    "user": "U-NEW-USER",
    "text": ":wave: Welcome aboard! You signed up for the ${data.plan} plan."
  }
}

Out

slackClient.conversations.open({
  "users": "U-NEW-USER"
});

slackClient.chat.postMessage({
  "channel": "D-MOCK-DM",
  "text": ":wave: Welcome aboard! You signed up for the enterprise plan.",
  "unfurl_links": false,
  "unfurl_media": false,
  "mrkdwn": true
})

Webhook vs Web API modes

Pick exactly one auth method per destination. Each mode trades capability for simplicity.

Capability	Incoming Webhook (webhookUrl)	Web API (token)
Setup	Paste a URL, done	Create a Slack app, install bot, manage scopes
Channels	Fixed to the webhook's channel	Any channel the bot is in, routable per rule
Threading	Not supported	threadTs + replyBroadcast
Direct messages	Not supported	dm: true + user
Ephemeral messages	Not supported	ephemeral: true
Retries	Plain HTTP	SDK-managed (retryConfig)
Block Kit	Yes	Yes

Use webhooks for a single firehose channel and minimal setup. Use the Web API whenever you need routing, threading, DMs, or ephemeral messages.

Channel routing

With Web API mode, route events to different channels using nested entity > action mapping. Each rule can override channel, text, blocks, and threading behavior.

"destinations": {
  "slack": {
    "package": "@walkeros/server-destination-slack",
    "import": "destinationSlack",
    "config": {
      "settings": {
        "token": "$env.SLACK_BOT_TOKEN",
        "channel": "#events"
      },
      "mapping": {
        "order": {
          "complete": {
            "settings": {
              "channel": "#sales",
              "text": "New order ${data.id}: ${data.total} ${data.currency}"
            }
          }
        },
        "error": {
          "report": {
            "settings": {
              "channel": "#incidents",
              "threadTs": "data.incidentTs"
            }
          }
        },
        "user": {
          "signup": {
            "settings": {
              "channel": "#growth"
            }
          }
        }
      }
    }
  }
}

Events that don't match any rule fall back to the default channel in settings.

Message formatting

Messages support two formatting styles, set at destination level or per rule:

• Text templates: ${data.field} placeholders interpolate against the walkerOS event. Good for terse alerts.
• Block Kit: structured layouts via Slack's Block Kit (headers, sections, buttons, context). Use the blocks setting when you need rich formatting.

When neither text nor blocks is provided, the destination generates a default message with an event-name header (toggle via includeHeader).