Traces and logs for TanStack Start apps

What works for traces and logs depends on where your TanStack Start app runs. Errors work everywhere with @belvador/tanstack-start.

On your own Node.js server#

The built server is an ES module, so use the ES modules launch line — both the loader hook and the register file:

export OTEL_SEMCONV_STABILITY_OPT_IN=httpexport OTEL_NODE_RESOURCE_DETECTORS=env,host,osnode --experimental-loader=@opentelemetry/instrumentation/hook.mjs --import @opentelemetry/auto-instrumentations-node/register app.mjs

Replace app.mjs with your server entry. The auto-instrumentations create a server span for each request and client spans for outgoing fetch and database calls; server functions show up as requests to their /_serverFn/… URLs, not as named spans. For named spans around your own code, use @opentelemetry/api (tracer.startActiveSpan).

Pass the same API to the Belvador SDK's otel option so server errors carry the active span's ids — see Link requests.

On your own Cloudflare account#

Add the two destinations and the observability block from Cloudflare Workers to the app's wrangler.jsonc. Cloudflare then traces every request, fetch and binding call with no code.

On Lovable hosting#

Lovable publishes your app to Cloudflare under its own account, so you cannot add Cloudflare export destinations, and starting a Node.js SDK in a Worker is not possible. Use the Belvador SDK for errors and its trace headers to link browser and server errors. In-app OpenTelemetry for Workers exists in community libraries, but Belvador has not tested any.

Status#

The Node.js launch line is the certified Node.js recipe; Belvador has not run it on a TanStack Start build specifically. The Cloudflare route follows Cloudflare's documentation and is untested.