Braintrust Exporter

Braintrust is an evaluation and monitoring platform that helps you measure and improve LLM application quality. The Braintrust exporter sends your traces to Braintrust, enabling systematic evaluation, scoring, and experimentation.

Installation

npm install @mastra/braintrust@beta

Configuration

Prerequisites

1. Braintrust Account: Sign up at braintrust.dev
2. Project: Create or select a project for your traces
3. API Key: Generate in Braintrust Settings → API Keys
4. Environment Variables: Set your credentials:

.env

BRAINTRUST_API_KEY=sk-xxxxxxxxxxxxxxxx
BRAINTRUST_PROJECT_NAME=my-project  # Optional, defaults to 'mastra-tracing'

Basic Setup

src/mastra/index.ts

import { Mastra } from "@mastra/core";
import { Observability } from "@mastra/observability";
import { BraintrustExporter } from "@mastra/braintrust";

export const mastra = new Mastra({
  observability: new Observability({
    configs: {
      braintrust: {
        serviceName: "my-service",
        exporters: [
          new BraintrustExporter({
            apiKey: process.env.BRAINTRUST_API_KEY,
            projectName: process.env.BRAINTRUST_PROJECT_NAME,
          }),
        ],
      },
    },
  }),
});

Complete Configuration

new BraintrustExporter({
  // Required
  apiKey: process.env.BRAINTRUST_API_KEY!,

  // Optional settings
  projectName: "my-project", // Default: 'mastra-tracing'
  endpoint: "https://api.braintrust.dev", // Custom endpoint if needed
  logLevel: "info", // Diagnostic logging: debug | info | warn | error
});

Using Tags

Tags help you categorize and filter traces in the Braintrust dashboard. Add tags when executing agents or workflows:

const result = await agent.generate({
  messages: [{ role: "user", content: "Hello" }],
  tracingOptions: {
    tags: ["production", "experiment-v2", "user-request"],
  },
});

Tags appear in Braintrust's trace view and can be used to filter and search traces. Common use cases include:

• Environment labels: "production", "staging"
• Experiment tracking: "experiment-v1", "control-group"
• Priority levels: "priority-high", "batch-job"

Related

• Tracing Overview
• Braintrust Documentation