An isomorphic JS library for logging data to Braintrust.

Version information

2.x is the current stable release. Zod is now a peer dependency instead of a bundled dependency. This gives you control over the Zod version in your project and reduces bundle size if you’re already using Zod.

The SDK requires Zod v3.25.34 or later.

Upgrading from 1.x

See the Migrate from v1.x to v2.x guide for instructions.

Upgrading from 0.x

First follow the Migrate from v0.x to v1.x guide, then proceed to the Migrate from v1.x to v2.x guide.

Note: If you do not have OpenTelemetry you can upgrade directly from v0.x to v2.x.

Quickstart

Install the library with npm (or yarn).

npm install braintrust zod

Then, run a simple experiment with the following code (replace YOUR_API_KEY with your Braintrust API key):

import * as braintrust from "braintrust";

async function main() {
  const experiment = await braintrust.init("NodeTest", {
    apiKey: "YOUR_API_KEY",
  });
  experiment.log({
    input: { test: 1 },
    output: "foo",
    expected: "bar",
    scores: {
      n: 0.5,
    },
    metadata: {
      id: 1,
    },
  });
  console.log(await experiment.summarize());
}

main().catch(console.error);