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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