Bundled and serverless runtimes

Bundled and serverless tracing requires two things: one server-side SDK instance must load before traced clients in a TypeScript bundle, and completed roots must flush before a serverless runtime freezes. Use this page for bundlers such as Next.js and for serverless runtimes that can stop after responding.

TypeScript bundlers

Load tracing from the runtime's instrumentation or bootstrap path before you import traced model clients. Confirm the bundler puts that module in the server runtime.

A bundled runtime can give each entry point its own copy of judgeval or @opentelemetry/api. The copy you initialized is then not the copy your handler uses, so nothing records. Keep one server-side copy of both packages.

For Next.js:

export default {
  serverExternalPackages: ["judgeval", "@opentelemetry/api"],
};

Log once at initialization. A second log when a handler loads points to a second copy.

In TypeScript, auto-instrumentation needs all three of the following: a preloaded instrumentation file, OpenTelemetry instrumentations registered on Tracer before Tracer.init(), and a CommonJS build. See Reference for the setup.

Serverless runtimes

A serverless runtime can freeze as soon as it sends the response, which may discard spans still waiting to export. In TypeScript, await Tracer.forceFlush() after the root ends and before the handler returns. In Python, call Tracer.force_flush() at the same point. Initialize the tracer once per runtime instance and shut it down only when the process stops, not after each request.

Verify

First run the shared verification checklist. Then deploy and export a full trace on a cold call, meaning the first request after the runtime spins up. The init log should appear once, and the completed trace should arrive before the runtime freezes. Silent export loss is the failure mode here: the app works while the platform shows nothing.

Related pages

• How spans attach to the right trace
• Streaming for handlers that return a response before generation ends
• Durable work for serverless handlers that enqueue work for a later worker