npm i
npm run build
npm run start
curl http://localhost:3000/make-req

Afterwards, look at the server logs.

Inside make-req/route.ts, we are making an http.get() call to check/route.ts. This http.get() call should be instrumented, meaning tracing headers should be attached. The check/route.ts endpoint simply returns the headers it receives, but no tracing headers are attached, meaning the instrumentation didn't work.

You might be inclined to say "yo the folks at Sentry did something wrong", but I don't think this is the case. For the sake of simplicity I used the Sentry SDK which uses the OpenTelemetry instrumentation under the hood. You could probably also reproduce this by using the OpenTelemetry HTTP instrumentation + any OTEL HTTP propagator, and the propagation would also fail.