> ## Documentation Index
> Fetch the complete documentation index at: https://docs.belvedir.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Fractal SDK Environment Variables: Setup and Best Practices

> Learn which environment variables the Fractal SDK requires and how to set them in local development, Vercel, and other hosting platforms.

The SDK itself only reads what you pass to `initialize()`. In practice most apps wire the following env vars to the SDK options:

| Variable           | Maps to   | Notes                                                 |
| ------------------ | --------- | ----------------------------------------------------- |
| `FRACTAL_API_KEY`  | `apiKey`  | Required. Starts with `fr_live_`.                     |
| `FRACTAL_BASE_URL` | `baseUrl` | Optional. Defaults to `https://platform.belvedir.ai`. |

## Benchmark harness variables

If your code runs inside a Belvedir [benchmark](/benchmarks/overview) sandbox, three extra variables are injected at run time — `FRACTAL_API_KEY` (a per-run ingest key), `FRACTAL_BASE_URL`, and `FRACTAL_RUN_ID`. The SDK does **not** read them automatically; pass them to `initialize()` and use `FRACTAL_RUN_ID` as the `sessionId`.

## Local development

Set the vars in `.env.local` (Next.js) or export them in your shell. If traces aren't arriving, check your terminal for SDK warnings on startup and verify `FRACTAL_API_KEY` is loaded before `initialize()` runs.