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Braintrust Exporter

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

When to Use Braintrust​

Braintrust excels at:

  • Evaluation workflows - Systematic quality measurement
  • Experiment tracking - Compare model versions and prompts
  • Dataset management - Curate test cases and golden datasets
  • Regression testing - Ensure improvements don't break existing functionality
  • Team collaboration - Share experiments and insights

Installation​

npm install @mastra/braintrust

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 { BraintrustExporter } from "@mastra/braintrust";

export const mastra = new Mastra({
  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
});