Implementation:Langfuse Langfuse SlackService

Knowledge Sources	Langfuse
Domains	Integrations, Slack, Notifications
Last Updated	2026-02-14 00:00 GMT

Overview

The SlackService is a singleton service class that manages Slack OAuth integration, channel listing, and message sending for Langfuse projects using the official Slack SDK libraries.

Description

The SlackService class handles the complete Slack integration lifecycle for Langfuse projects. It is implemented as a singleton (via getInstance()) and wraps the Slack SDK's InstallProvider for OAuth flow management and WebClient for API operations.

Key components and behaviors:

OAuth flow management - Uses @slack/oauth InstallProvider with a custom installationStore that persists Slack installations to PostgreSQL via the slackIntegration Prisma model. Each project maps to one Slack workspace integration.
Encrypted token storage - Bot tokens are encrypted via encrypt() before storage and decrypted via decrypt() on retrieval, ensuring sensitive credentials are not stored in plaintext.
Metadata-based project mapping - Installation metadata carries the projectId, parsed and validated by parseSlackInstallationMetadata. The fetchInstallation callback supports lookup by both teamId and projectId.
Channel listing - getChannels recursively fetches all public, non-archived channels using cursor-based pagination, respecting the SLACK_FETCH_LIMIT environment variable.
Message sending - sendMessage posts Block Kit messages to a specified channel with link unfurling disabled.
Client management - getWebClientForProject authorizes and returns a WebClient instance for a given project.
Client validation - validateClient tests whether a WebClient is still valid via auth.test().
Integration deletion - deleteIntegration removes the Slack integration for a project.

The requested OAuth scopes are: channels:read, chat:write, chat:write.public.

Usage

Use this service when you need to:

Initiate or handle the Slack OAuth installation flow for a project.
Retrieve the list of Slack channels a bot can post to.
Send notification messages (e.g., evaluation alerts) to a Slack channel.
Validate or refresh a Slack connection for a project.
Remove a Slack integration from a project.

Code Reference

Source Location

Repository: Langfuse
File: packages/shared/src/server/services/SlackService.ts
Lines: 1-427

Signature

export interface SlackChannel {
  id: string;
  name: string;
  isPrivate: boolean;
  isMember: boolean;
}

export interface SlackMessageParams {
  client: WebClient;
  channelId: string;
  blocks: any[];
  text?: string;
}

export interface SlackMessageResponse {
  messageTs: string;
  channel: string;
}

export function parseSlackInstallationMetadata(
  metadata: unknown,
): SlackInstallationMetadata;

export class SlackService {
  static getInstance(): SlackService;
  static resetInstance(): void;
  getInstaller(): InstallProvider;
  async deleteIntegration(projectId: string): Promise<void>;
  async getWebClientForProject(projectId: string): Promise<WebClient>;
  async getChannels(client: WebClient): Promise<SlackChannel[]>;
  async sendMessage(params: SlackMessageParams): Promise<SlackMessageResponse>;
  async validateClient(client: WebClient): Promise<boolean>;
}

Import

import { SlackService, SlackChannel, SlackMessageParams } from "@langfuse/shared/src/server/services/SlackService";

I/O Contract

Inputs

Name	Type	Required	Description
projectId	string	Yes	The project ID for retrieving or deleting Slack integrations
client	WebClient	Yes (for channels/messages)	An authorized Slack WebClient instance
channelId	string	Yes (for sending)	The Slack channel ID to send a message to
blocks	any[]	Yes (for sending)	Slack Block Kit blocks composing the message body
text	string	No	Fallback plain text for the message (defaults to "Langfuse Notification")
metadata	unknown	Yes (for parsing)	Raw installation metadata string containing projectId JSON

Outputs

Name	Type	Description
SlackService	SlackService	Singleton instance of the service
WebClient	WebClient	Authorized Slack Web API client for a specific project
SlackChannel[]	array	List of accessible Slack channels with id, name, privacy, and membership status
SlackMessageResponse	object	Contains messageTs (Slack timestamp ID) and channel for the sent message
boolean	boolean	Client validation result (true if auth.test succeeds)

Usage Examples

import { SlackService } from "@langfuse/shared/src/server/services/SlackService";

// Get the singleton instance
const slackService = SlackService.getInstance();

// Get a WebClient for a project
const client = await slackService.getWebClientForProject("proj-123");

// List available channels
const channels = await slackService.getChannels(client);

// Send a notification message
const response = await slackService.sendMessage({
  client,
  channelId: "C01234567",
  blocks: [
    {
      type: "section",
      text: {
        type: "mrkdwn",
        text: "Evaluation *accuracy* completed with score 0.95",
      },
    },
  ],
  text: "Evaluation accuracy completed with score 0.95",
});

// Validate the client connection
const isValid = await slackService.validateClient(client);

// Delete integration for a project
await slackService.deleteIntegration("proj-123");

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