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The Vercel AI SDK includes built-in telemetry support that works seamlessly with Lemma’s OpenTelemetry-based tracing. This guide shows you how to set up tracing for your AI SDK applications.

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How It Works

Once the tracer provider is registered, the AI SDK automatically captures spans for all generateText and streamText calls with telemetry enabled. Lemma receives:
  • Model calls and responses
  • Token usage (prompt tokens, completion tokens)
  • Tool invocations
  • Streaming events
  • Timing and latency

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Getting Started

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Install Dependencies

npm install @uselemma/tracing

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Set Up the Tracer Provider

Create an instrumentation.ts (or instrumentation.js) file in your project root. Next.js will automatically run this code when your application starts: 
// instrumentation.ts
export async function register() {
  if (process.env.NEXT_RUNTIME === 'nodejs') {
    const { registerOTel } = await import('@uselemma/tracing');
    registerOTel();
  }
}

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Node.js (Non-Next.js)

Create a tracer setup file and import it at the top of your entry point: 
// tracer.ts
import { registerOTel } from '@uselemma/tracing';
registerOTel();
Then import it at the top of your application entry point: 
// index.ts or server.ts
import './tracer'; // Must be first!
// ... rest of your imports

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Options

registerOTel reads from LEMMA_API_KEY and LEMMA_PROJECT_ID environment variables by default. You can also pass options explicitly: 
registerOTel({
  apiKey: 'sk_...',
  projectId: '...',
  baseUrl: 'https://api.uselemma.ai', // default
});
Set the LEMMA_API_KEY and LEMMA_PROJECT_ID environment variables in your application. You can find these in your Lemma project settings.

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Enable Telemetry in AI SDK

To capture traces from the Vercel AI SDK, enable telemetry in your streamText or generateText calls: 
import { streamText } from 'ai';
import { anthropic } from '@ai-sdk/anthropic';

const result = await streamText({
  model: anthropic('claude-sonnet-4'),
  messages: [
    { role: 'user', content: 'What is the capital of France?' }
  ],
  experimental_telemetry: {
    isEnabled: true, // required
  },
});

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Examples

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Non-Streaming

import { agent } from "@uselemma/tracing";
import { generateText } from 'ai';
import { anthropic } from '@ai-sdk/anthropic';

export const callAgent = async (userMessage: string) => {
  const wrappedFn = agent(
    "my-agent",
    async (input) => {
      const { text } = await generateText({
        model: anthropic('claude-sonnet-4'),
        messages: [{ role: 'user', content: input.userMessage }],
        experimental_telemetry: { isEnabled: true },
      });
      return text; // wrapper auto-captures output and closes the span
    }
  );

  const { result, runId } = await wrappedFn({ userMessage });
  return { result, runId };
};

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Streaming

Pass { streaming: true } to opt into manual span lifecycle, then call ctx.complete() inside the onFinish callback once the full output is assembled: 
import { agent } from "@uselemma/tracing";
import { streamText } from 'ai';
import { anthropic } from '@ai-sdk/anthropic';

export const callAgent = async (userMessage: string) => {
  const wrappedFn = agent(
    "my-agent",
    async (input, ctx) => {
      const result = await streamText({
        model: anthropic('claude-sonnet-4'),
        messages: [{ role: 'user', content: input.userMessage }],
        experimental_telemetry: { isEnabled: true },
        onFinish({ text }) {
          ctx.complete(text); // closes the run span once the full output is known
        },
      });
      return result.toDataStreamResponse();
    },
    { streaming: true }
  );

  const { result, runId } = await wrappedFn({ userMessage });
  return { result, runId };
};

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Next Steps