Maple Next.js style

For Next.js apps, use the framework entrypoint, instrumentation.ts with @vercel/otel.

// instrumentation.ts
import { registerOTel } from "@vercel/otel"

const MAPLE_ENDPOINT = "https://ingest.maple.dev" // EU: https://ingest.eu.maple.dev
const MAPLE_KEY = "MAPLE_TEST" // public ingest key (maple_pk_…), or MAPLE_TEST until the user has one