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

npm install @mastra/braintrust@latest

pnpm

pnpm add @mastra/braintrust@latest

Yarn

yarn add @mastra/braintrust@latest

Bun

bun add @mastra/braintrust@latest

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

# Optional
BRAINTRUST_ENDPOINT=https://api.braintrust.dev  # Custom endpoint if needed

Zero-Config Setup

With environment variables set, use the exporter with no configuration:

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()],
      },
    },
  }),
});

Explicit Configuration

You can also pass credentials directly (takes precedence over environment variables):

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: "my-project",
          }),
        ],
      },
    },
  }),
});

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
});

Related

• Tracing Overview
• Braintrust Documentation