> ## 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 FAQ: Runtime, Traces, API Keys, and Multi-App

> Answers to common questions about the Fractal SDK: runtime support, LLM client setup, trace delivery timing, API key safety, and multi-app usage.

## Which runtimes are supported?

The Node SDK requires the Node.js runtime — the Edge runtime on Vercel and similar platforms won't work because OpenTelemetry needs Node APIs. The Python SDK works anywhere CPython does. See [Vercel](/guides/vercel) for the runtime opt-in.

## Do I need to set `baseUrl`?

No. It defaults to `https://platform.belvedir.ai`. Only set it if you're targeting a self-hosted or staging platform host.

## How long until traces appear in the dashboard?

Traces appear within seconds. Tasks and groups form \~30 seconds after a session goes quiet — segmentation only runs once a session is idle.

## Is my API key safe in `instrumentation.ts`?

Yes — `instrumentation.ts` runs on the server. Never expose `FRACTAL_API_KEY` to client-side code.

## Can I use one project for multiple apps?

Yes. Set a different `appName` per app when calling `initialize()`; traces from each app are labeled and can be filtered in the dashboard.

## What if my agent uses more than one LLM provider?

Pass every provider you use to `instrumentModules`, e.g. `{ openAI: openai.OpenAI, anthropic }`. Every span records which provider and model served it, so you can compare them in the dashboard.

## Can I route between local and hosted models?

Yes — see [Mixture of Models](/inference/mixture-of-models).