Wiring the Vercel AI SDK to tracelet

The AI SDK only records spans into whatever OpenTelemetry tracer is active — you provide the exporter. Point it at tracelet's ingest endpoint and you're done.

Node / Express / Hono / standalone script

Install the OTel bits (these are the only deps, and only in your app):

npm i @opentelemetry/sdk-node @opentelemetry/exporter-trace-otlp-http

Create instrumentation.js and import it before anything that uses the AI SDK:

// instrumentation.js
import { NodeSDK } from '@opentelemetry/sdk-node';
import { OTLPTraceExporter } from '@opentelemetry/exporter-trace-otlp-http';

const sdk = new NodeSDK({
  traceExporter: new OTLPTraceExporter({
    url: 'http://localhost:4318/v1/traces', // ← tracelet
  }),
});
sdk.start();

// app.js
import './instrumentation.js'; // must be first
import { generateText } from 'ai';

const { text } = await generateText({
  model: 'anthropic/claude-sonnet-4.5',
  prompt: 'What is the weather in SF? Use the get_weather tool.',
  experimental_telemetry: { isEnabled: true, functionId: 'weather-agent' },
});

Run tracelet in one terminal (npx @jnmetacode/tracelet), your app in another, and the ai.generateText / ai.toolCall spans stream into the UI live.

Next.js

@vercel/otel reads the standard env vars, so no exporter code is needed:

npm i @vercel/otel

// instrumentation.ts
import { registerOTel } from '@vercel/otel';
export function register() {
  registerOTel({ serviceName: 'my-agent' });
}

# .env.local
OTEL_EXPORTER_OTLP_ENDPOINT=http://localhost:4318

Set experimental_telemetry: { isEnabled: true } on your generateText / streamText calls and you'll see traces in tracelet.

Either encoding works. tracelet ingests both OTLP/HTTP protobuf (the exporter default) and JSON, so you don't need to set OTEL_EXPORTER_OTLP_PROTOCOL at all.