Langfuse

Langfuse is an open-source observability platform designed specifically for LLM applications.

Note: Currently, only AI-related calls will contain detailed telemetry data. Other operations will create traces but with limited information.

Configuration

To use Langfuse with Mastra, you can configure it using either environment variables or directly in your Mastra configuration.

Using Environment Variables

Set the following environment variables:

OTEL_EXPORTER_OTLP_ENDPOINT="https://cloud.langfuse.com/api/public/otel/v1/traces" # 🇪🇺 EU data region
# OTEL_EXPORTER_OTLP_ENDPOINT="https://us.cloud.langfuse.com/api/public/otel/v1/traces" # 🇺🇸 US data region

OTEL_EXPORTER_OTLP_HEADERS="Authorization=Basic ${AUTH_STRING}"

Where AUTH_STRING is the base64-encoded combination of your public and secret keys (see below).

Generating AUTH_STRING

The authorization uses basic auth with your Langfuse API keys. You can generate the base64-encoded auth string using:

echo -n "pk-lf-1234567890:sk-lf-1234567890" | base64

For long API keys on GNU systems, you may need to add -w 0 to prevent auto-wrapping:

echo -n "pk-lf-1234567890:sk-lf-1234567890" | base64 -w 0

Implementation

Here's how to configure Mastra to use Langfuse with OpenTelemetry:

import { Mastra } from "@mastra/core";

export const mastra = new Mastra({
  // ... other config
  telemetry: {
    enabled: true,
    export: {
      type: "otlp",
      endpoint: "https://cloud.langfuse.com/api/public/otel/v1/traces", // or your preferred endpoint
      headers: {
        Authorization: `Basic ${AUTH_STRING}`, // Your base64-encoded auth string
      },
    },
  },
});

Alternatively, if you're using environment variables, you can simplify the configuration:

import { Mastra } from "@mastra/core";

export const mastra = new Mastra({
  // ... other config
  telemetry: {
    enabled: true,
    export: {
      type: "otlp",
      // endpoint and headers will be read from OTEL_EXPORTER_OTLP_* env vars
    },
  },
});

Dashboard

Once configured, you can view your traces and analytics in the Langfuse dashboard at cloud.langfuse.com