Workflow Operator on Slack

Workflow Operator on Slack uses a Slack bot to map each Slack channel to a persistent Dagu AI agent session using Socket Mode (WebSocket-based, no public HTTP endpoint required). Messages sent in Slack are forwarded to the built-in AI agent, and agent responses are posted back. When a DAG run completes, Workflow Operator can also send AI-generated notifications so follow-up stays in the same conversation.

Prerequisites

Before setting up Workflow Operator on Slack, configure the AI agent in the Web UI. Go to Agent Settings (/agent-settings) and set up the agent model, tool policy, and other defaults first. The Slack bot forwards messages to the built-in agent, so it must be configured before Slack can use it. Start with Agent Settings, then use Models & Providers and Tool Permissions & Bash Policy for the concrete setup pieces.

Creating a Slack App

Before configuring Dagu, you need to create a Slack app with Socket Mode enabled.

1. Create the app

1. Go to https://api.slack.com/apps and click Create New App → From scratch.
2. Name it (e.g., Dagu) and select your workspace. Click Create App.

2. Enable Socket Mode and get the App-Level Token

1. Go to Settings → Socket Mode in the left sidebar.
2. Toggle Enable Socket Mode to ON.
3. When prompted, create an App-Level Token:
   • Name: anything (e.g., dagu-socket)
   • Scope: connections:write
   • Click Generate
4. Copy the token. It starts with xapp-. This is the value for bots.slack.app_token.

3. Add Bot Token Scopes

1. Go to Features → OAuth & Permissions.
2. Under Bot Token Scopes, add:
   • app_mentions:read
   • chat:write
   • channels:history (for messages in public channels)
   • groups:history (for messages in private channels)
   • im:history (for direct messages)

4. Subscribe to Events

1. Go to Features → Event Subscriptions.

2. Toggle Enable Events to ON.

3. Under Subscribe to bot events, add the events for the channel types you use:

   Event	Required for
   app_mention	@mention support (all channel types)
   message.channels	Messages in public channels
   message.groups	Messages in private channels
   message.im	Direct messages
   message.mpim	Group direct messages

   At minimum, add app_mention and the event(s) matching your channel type. If the bot doesn't respond to messages without @mention, the most common cause is a missing event subscription here (e.g., using a private channel without message.groups).

4. Click Save Changes.

5. (Optional) Add Slash Commands

If you want /dagu-new and /dagu-cancel slash commands:

1. Go to Features → Slash Commands.
2. Create two commands:
   • Command: /dagu-new, Description: Start a new session, Request URL: leave empty (Socket Mode handles it)
   • Command: /dagu-cancel, Description: Cancel current session, Request URL: leave empty

6. Enable Interactivity

For interactive buttons (agent prompts) to work:

1. Go to Features → Interactivity & Shortcuts.
2. Toggle Interactivity to ON.
3. No Request URL is needed when Socket Mode is enabled.

7. Enable Direct Messages

To allow users to DM the bot directly (without @mentioning in a channel):

1. Go to Features → App Home.
2. Under Show Tabs, check Messages Tab.
3. Optionally check Allow users to send Slash commands and messages from the messages tab.

Without this, users will see "Sending messages to this app has been turned off" when trying to DM the bot.

8. Install the app

1. Go to Settings → Install App.
2. Click Install to Workspace → Allow.
3. Copy the Bot User OAuth Token. It starts with xoxb-. This is the value for bots.slack.bot_token.

If you already installed the app before adding scopes or enabling features, you need to reinstall it. Go to Settings → Install App and click Reinstall to Workspace.

9. Invite the bot to a channel

In the Slack channel where you want to use the bot, type:

/invite @Dagu

(Replace @Dagu with whatever you named your app.)

Finding your Channel ID

Right-click the channel name in Slack → View channel details. The Channel ID is at the bottom of the details panel (e.g., C07ABC123DE).

Alternatively, open the channel in Slack's web interface. The URL contains the channel ID:

https://app.slack.com/client/T.../C07ABC123DE

The C07ABC123DE part is the channel ID.

Running

The Slack connector for Workflow Operator starts automatically when bots.provider is set to slack and you run either:

dagu server

or

dagu start-all

In both modes, the connector shares the server's agent API instance.

Configuration

Set provider: slack under bots and configure the Slack-specific fields. Only one connector can be active at a time.

bots:
  provider: slack
  safe_mode: true
  slack:
    bot_token: "xoxb-your-bot-token"
    app_token: "xapp-your-app-token"
    allowed_channel_ids:
      - "C07ABC123DE"
      - "C08XYZ456FG"
    respond_to_all: true

bots fields

Field	Type	Default	Description
provider	string	"" (disabled)	Which connector to run. Set to "slack" for Slack. If empty, no bot starts.
safe_mode	bool	true	Passed to the agent's ChatRequest.SafeMode field. Applies to all bot connectors.

bots.slack fields

Field	Type	Default	Description
bot_token	string	(required)	Bot User OAuth Token from the Slack app. Starts with xoxb-.
app_token	string	(required)	App-Level Token with connections:write scope. Starts with xapp-.
allowed_channel_ids	[]string	(required)	Slack channel IDs authorized to use the bot. Messages from other channels are silently ignored.
respond_to_all	bool	true	When true, the bot responds to every message in allowed channels without requiring an @mention. When false, the bot only responds to @mentions and thread replies where it is already participating. DMs are always handled regardless of this setting.

Environment variables

Variable	Config equivalent
DAGU_BOTS_PROVIDER	bots.provider
DAGU_BOTS_SAFE_MODE	bots.safe_mode
DAGU_BOTS_SLACK_BOT_TOKEN	bots.slack.bot_token
DAGU_BOTS_SLACK_APP_TOKEN	bots.slack.app_token
DAGU_BOTS_SLACK_ALLOWED_CHANNEL_IDS	bots.slack.allowed_channel_ids
DAGU_BOTS_SLACK_RESPOND_TO_ALL	bots.slack.respond_to_all

Environment variables take precedence over the config file for bot_token and app_token. For allowed_channel_ids, use a comma-separated string:

export DAGU_BOTS_SLACK_ALLOWED_CHANNEL_IDS=C07ABC123DE,C08XYZ456FG

Event Handling

The bot handles three types of Socket Mode events:

Events API (app_mention, message)

• app_mention: When someone @mentions the bot in a channel. The <@BOTID> prefix is stripped from the text. The bot replies in a thread starting from that message. Once the bot is in a thread, subsequent replies in that thread do not require @mentioning.
• message: Regular channel messages. Bot messages, message edits, and other subtypes are ignored (only messages where SubType is empty and BotID is empty are processed). The routing depends on the message context:
  1. DMs (ChannelType == "im"): always handled, regardless of respond_to_all.
  2. Thread replies in a thread the bot is already participating in: handled without requiring @mention.
  3. Channel messages (not a thread reply, not a DM): only handled when respond_to_all is true. When handled this way, they are treated like DM messages (no thread is created).

Messages from channels not in allowed_channel_ids are silently dropped.

Slash Commands

If you registered /dagu-new and /dagu-cancel as slash commands in the Slack app:

Command	Behavior
/dagu-new	Resets the channel's session state and clears the current agent session
/dagu-cancel	Cancels the currently active agent session

Text Commands

If you don't register slash commands, you can also type these as plain messages (or after @mentioning the bot):

Text	Behavior
new	Same as /dagu-new
cancel	Same as /dagu-cancel

Any text starting with new or cancel is treated as a command. All other text is forwarded to the agent.

Interactive Components (Button Presses)

When the agent emits a UserPrompt with options, the bot renders it as a Block Kit message with a SectionBlock (question text) and an ActionBlock containing ButtonBlockElement elements. Each button's action_id is formatted as prompt:<promptID>:<optionID>.

When a user clicks a button, the bot submits the selected option to the agent and updates the original message to show the selection.

Button labels are truncated to 75 characters (Slack's limit for button text).

If the prompt allows free text (AllowFreeText: true), the user can also reply with a regular text message instead of clicking a button.

Session Rotation

When the current session is idle and has no pending prompt, Dagu checks the latest assistant-reported prompt token count. If it reaches 80% of the model context window, Dagu compacts the session. If the model does not declare a context window, Dagu uses a fallback of 200,000 tokens.

1. Builds a transcript from prior user, assistant, error, and prompt messages.
2. Asks the model for a handoff summary.
3. Creates a continuation session and stores that summary as an assistant message prefixed with Session handoff summary:\n.
4. Switches the conversation to the new session.

The stored handoff summary is marked as already delivered for chat bridges, so Slack does not replay it as a visible message.

DAG Run Notifications

When the centralized event store is available (the default in both server and start-all modes), the bot starts a DAG run monitor that reads persisted DAG-run events and sends notifications. If the event store is disabled or unavailable, Slack chat works normally but DAG-run notifications stay disabled.

Monitored statuses

Notifications are sent for these DAG run statuses:

• succeeded
• failed
• aborted
• partially_succeeded
• rejected
• waiting (for human approval requests)

How notifications work

1. The monitor polls the event store every 10 seconds and reads only new DAG-run events, using durable on-disk state so restarts do not lose pending notifications.
2. On first startup, it seeds its cursor at the current event-store head, so existing channels only receive future events.
3. For each destination, it batches pending DAG-run notifications. Urgent single-run batches try to generate the message with the agent; all other batches use deterministic formatting. Batch delivery uses a 30-second flush timeout.
4. For direct-message destinations, the notification is appended to the DM-scoped session. For channel destinations, Slack posts a new thread root message and binds that thread to a session so follow-up replies continue there.
5. Delivered entries are retained for 2 hours to suppress duplicate event replays, while failed deliveries remain pending and are retried.

Fallback

If the agent API is unavailable or times out, the bot sends a plain text fallback:

<emoji> DAG '<name>' <status>
Error: <error message if any>

Where the emoji is: ✅ succeeded/partial, ❌ failed/rejected, ⚠️ aborted, ⏳ waiting.

Message Length

Messages longer than 4,000 characters are split at paragraph boundaries (\n\n), falling back to line boundaries (\n) if no paragraph break exists in the second half of the text.

User Identity

All Slack users are mapped to agent sessions with auth.RoleAdmin. The user ID format is slack:<slack_user_id> (e.g., slack:U01ABC23DEF). For DAG run notifications, the user ID is slack:<channel_id>.