Distributed Tracing

Stitch spans across services — frontend to backend, or service to service — into one trace.

EvalKit spans are W3C-compatible: trace IDs and span IDs follow the W3C traceparent spec, so they interoperate with OpenTelemetry collectors and Jaeger. Inbound is read automatically by the web framework middleware; outbound HTTP is instrumented automatically and injects the header for you.

Bridging a browser to your API manually

import * as evalkit from 'syntropylabs-evalkit';

fetch('/api/chat', {
  headers: {
    'Content-Type': 'application/json',
    traceparent: evalkit.getTraceparent(),
  },
  body: JSON.stringify({ message }),
});

On the receiving service, the framework middleware reads the header automatically and creates a child span — so a request that starts in the browser, hits an API gateway, and fans out to two backend services all shows up as one trace in the dashboard.