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xAI provides access to the Grok family of language models designed for reasoning and real-time information processing. Braintrust integrates seamlessly with xAI through direct API access, wrapper functions for automatic tracing, and proxy support.

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Setup

To use xAI models, configure your xAI API key in Braintrust.
  1. Get an xAI API key from xAI Console
  2. Add the xAI API key to your organization’s AI providers or to a project’s AI providers
  3. Set the xAI API key and your Braintrust API key as environment variables
.env
XAI_API_KEY=<your-xai-api-key>
BRAINTRUST_API_KEY=<your-braintrust-api-key>

# If you are self-hosting Braintrust, set the URL of your hosted dataplane
# BRAINTRUST_API_URL=<your-braintrust-api-url>
API keys are encrypted at rest using transparent data encryption with a unique 256-bit key and nonce.

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Use xAI with Braintrust AI proxy

The Braintrust AI Proxy allows you to access xAI models through a unified OpenAI-compatible interface. First, install the braintrust and openai packages. 
# pnpm
pnpm add braintrust openai
# npm
npm install braintrust openai
Then, initialize the client and make a request to a xAI model via the Braintrust AI Proxy. 
import { OpenAI } from "openai";

const client = new OpenAI({
  baseURL: "https://api.braintrust.dev/v1/proxy",
  apiKey: process.env.BRAINTRUST_API_KEY,
});

const response = await client.chat.completions.create({
  model: "grok-4",
  messages: [{ role: "user", content: "Hello, world!" }],
});

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Trace logs with xAI

Trace your xAI LLM calls for observability and monitoring. When using the Braintrust AI Proxy, API calls are automatically logged to the specified project. 
import { OpenAI } from "openai";
import { initLogger } from "braintrust";

initLogger({
  projectName: "My Project",
  apiKey: process.env.BRAINTRUST_API_KEY,
});

const client = new OpenAI({
  baseURL: "https://api.braintrust.dev/v1/proxy",
  apiKey: process.env.BRAINTRUST_API_KEY,
});

// All API calls are automatically logged
const result = await client.chat.completions.create({
  model: "grok-4",
  messages: [{ role: "user", content: "What is machine learning?" }],
});
The Braintrust AI Proxy is not required. For more control, learn how to customize traces.

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Evaluate with xAI

Evaluations distill the non-deterministic outputs of xAI models into an effective feedback loop that enables you to ship more reliable, higher quality products. Braintrust Eval is a simple function composed of a dataset of user inputs, a task, and a set of scorers. To learn more about evaluations, check out the Experiments guide. 
import { Eval } from "braintrust";
import { OpenAI } from "openai";

const client = new OpenAI({
  baseURL: "https://api.braintrust.dev/v1/proxy",
  apiKey: process.env.BRAINTRUST_API_KEY,
});

Eval("xAI Evaluation", {
  data: () => [
    { input: "What is 2+2?", expected: "4" },
    { input: "What is the capital of France?", expected: "Paris" },
  ],
  task: async (input) => {
    const response = await client.chat.completions.create({
      model: "grok-4",
      messages: [{ role: "user", content: input }],
    });
    return response.choices[0].message.content;
  },
  scores: [
    {
      name: "accuracy",
      scorer: (args) => (args.output === args.expected ? 1 : 0),
    },
  ],
});
To learn more about tool use, multimodal support, attachments, and masking sensitive data with xAI, visit the customize traces guide.