Next.js + AI SDK Instrumentation Example

Overview

We’ll explore a simple emotional support chat application built with Next.js that:

Provides a chat interface for users seeking emotional support
Uses OpenAI’s GPT model to generate empathetic responses
Traces the entire process with Laminar
Utilizes Vercel’s AI SDK for AI interactions

Setup

You can use the example app from our GitHub repo.

Alternatively, for a clean install, follow these steps:

Initialize a Next.js app

npx create-next-app@latest

Learn more in the Next.js docs.

Install Dependencies

Let’s now install the required packages:

npm install ai @ai-sdk/openai @lmnr-ai/lmnr

Environment Setup

cp .env.local.example .env.local

And then fill in the .env.local file. Get Laminar project API key. Get OpenAI API key

Update next.config.ts

Add the following to your next.config.ts file:

next.config.ts
const nextConfig = {
  serverExternalPackages: ['@lmnr-ai/lmnr'],
};

export default nextConfig;

This is because Laminar depends on OpenTelemetry, which uses some Node.js-specific functionality, and we need to inform Next.js about it. Learn more in the Next.js docs.

Project Structure

The project has the following structure:

nextjs-app/
├── .env.local
├── app/
│   ├── api/
│   │   └── chat/
│   │       └── route.ts
│   ├── page.tsx
│   └── layout.tsx
├── components/
│   └── chat-ui.tsx
├── instrumentation.ts
└── ...

Implementation

Let’s look at the key components of our Next.js application with Laminar tracing:

1. instrumentation.ts

This file is crucial as it initializes Laminar for tracing. Next.js automatically loads this file during initialization.

instrumentation.ts
export async function register() {
  if (process.env.NEXT_RUNTIME === 'nodejs') {
    const { Laminar } = await import('@lmnr-ai/lmnr')
    
    // Make sure to initialize Laminar **after** you initialize other 
    // tracing libraries, e.g. `registerOTel` from `@vercel/otel`.
    Laminar.initialize({
      apiKey: process.env.LMNR_PROJECT_API_KEY,
    })
  }
}

Laminar only works in the ‘nodejs’ runtime of Next.js.

Learn more about the instrumentation.ts file in the Next.js docs.

Laminar must be initialized at the entry point of the application, but after other tracing libraries are initialized. For Next.js, the instrumentation.ts file is ideal for this purpose as it’s loaded early in the application lifecycle.

2. app/page.tsx

This file contains the main page layout for our chat application:

app/page.tsx
import ChatUI from "@/components/chat-ui";

export default function Home() {
  return (
    <div className="grid grid-rows-[auto_1fr_auto] min-h-screen p-4 sm:p-6 font-[family-name:var(--font-geist-sans)]">
      <header className="py-4 text-center">
        <h1 className="text-2xl font-bold text-blue-600 mb-1">Therapy Chat</h1>
        <p className="text-sm text-gray-600 dark:text-gray-400 max-w-lg mx-auto">
          A safe space to share your thoughts and receive supportive guidance.
          Your conversation is private and confidential.
        </p>
      </header>
      <main className="w-full max-w-4xl mx-auto my-4">
        <ChatUI />
      </main>
      <footer className="py-4 text-center text-sm text-gray-500 dark:text-gray-400">
        <p>AI-powered support | Not a substitute for professional medical advice</p>
      </footer>
    </div>
  );
}

3. app/api/chat/route.ts

This file contains the API route handler that processes chat messages and communicates with the OpenAI API.

Make sure to enable experimental_telemetry in the generateText function and pass the tracer to it.

app/api/chat/route.ts
import { openai } from "@ai-sdk/openai";
import { generateText } from "ai";
import { getTracer } from "@lmnr-ai/lmnr";
import { NextRequest, NextResponse } from "next/server";

export async function POST(request: NextRequest) {
  try {
    const body = await request.json();
    const { messages } = body;

    // Create system message with therapeutic instructions
    const systemMessage = {
      role: 'system',
      content: `You are an AI-powered therapist assistant. Respond with empathy,
understanding, and professionalism. Your goal is to provide supportive responses
that help the user process their feelings and thoughts. Never give medical
advice or diagnose conditions.`
    };

    // Use the messages parameter directly with the system message as the first
    // element
    const response = await generateText({
      model: openai("gpt-4.1-nano"),
      messages: [systemMessage, ...messages],
      experimental_telemetry: {
        isEnabled: true,
        tracer: getTracer(),
      }
    });

    return NextResponse.json({ message: response.text });
  } catch (error) {
    console.error("Error in chat API:", error);
    return NextResponse.json(
      { error: "Failed to process request" },
      { status: 500 }
    );
  }
}

4. components/chat-ui.tsx

This component handles the chat interface and manages the chat state.

Feel free to modify the UI as you see fit, this is just an example.

components/chat-ui.tsx

"use client";

import { useState } from "react";

type Message = {
  role: "user" | "assistant";
  content: string;
};

export default function ChatUI() {
  const [messages, setMessages] = useState<Message[]>([]);
  const [input, setInput] = useState("");
  const [isLoading, setIsLoading] = useState(false);

  const handleSubmit = async (e: React.FormEvent) => {
    e.preventDefault();
    if (!input.trim()) return;

    // Add user message to chat
    const userMessage: Message = { role: "user", content: input.trim() };
    setMessages((prev) => [...prev, userMessage]);
    setInput("");
    setIsLoading(true);

    try {
      // Send message to API
      const response = await fetch("/api/chat", {
        method: "POST",
        headers: {
          "Content-Type": "application/json",
        },
        body: JSON.stringify({
          messages: [...messages, userMessage],
        }),
      });

      if (!response.ok) {
        throw new Error("Failed to get response");
      }

      const data = await response.json();
      
      // Add assistant response to chat
      setMessages((prev) => [
        ...prev,
        { role: "assistant", content: data.message },
      ]);
    } catch (error) {
      console.error("Error:", error);
      // Add error message
      setMessages((prev) => [
        ...prev,
        {
          role: "assistant",
          content: "Sorry, I couldn't process the request. Please try again.",
        },
      ]);
    } finally {
      setIsLoading(false);
    }
  };

  return (
    <div className={"flex flex-col h-[70vh] border rounded-lg " +
      "overflow-hidden bg-white dark:bg-gray-800"}>
      <div className="flex-1 overflow-y-auto p-4 space-y-4">
        {messages.length === 0 ? (
          <div className="text-center text-gray-500 dark:text-gray-400 mt-20">
            <p className="text-lg font-medium mb-2">Welcome to Therapy Chat</p>
            <p className="max-w-md mx-auto">
              Share what's on your mind, and I'll do my best to provide
              supportive guidance. Your privacy is important - this conversation
              stays between us.
            </p>
          </div>
        ) : (
          messages.map((msg, index) => (
            <div
              key={index}
              className={`flex ${
                msg.role === "user" ? "justify-end" : "justify-start"
              }`}
            >
              <div
                className={`max-w-[80%] rounded-lg px-4 py-2 ${
                  msg.role === "user"
                    ? "bg-blue-500 text-white"
                    : "bg-gray-100 dark:bg-gray-700 text-gray-800 " +
                      "dark:text-gray-200"
                }`}
              >
                {msg.content}
              </div>
            </div>
          ))
        )}
        {isLoading && (
          <div className="flex justify-start">
            <div className={"max-w-[80%] rounded-lg px-4 py-2 " +
              "bg-gray-100 dark:bg-gray-700 text-gray-800 dark:text-gray-200"}>
              <div className="flex space-x-2 items-center">
                <div className="w-2 h-2 rounded-full bg-gray-400 animate-pulse">
                </div>
                <div className={"w-2 h-2 rounded-full bg-gray-400 " +
                "animate-pulse delay-150"}></div>
                <div className={"w-2 h-2 rounded-full bg-gray-400 " + 
                "animate-pulse delay-300"}></div>
              </div>
            </div>
          </div>
        )}
      </div>
      <form
        onSubmit={handleSubmit}
        className="border-t dark:border-gray-700 p-4 flex space-x-2"
      >
        <input
          type="text"
          value={input}
          onChange={(e) => setInput(e.target.value)}
          placeholder="Type your message..."
          className={"flex-1 border rounded-md px-3 py-2 focus:outline-none " +
            "focus:ring-2 focus:ring-blue-500 dark:bg-gray-700 " +
            "dark:border-gray-600 dark:text-white"}
          disabled={isLoading}
        />
        <button
          type="submit"
          disabled={isLoading || !input.trim()}
          className={"bg-blue-500 text-white rounded-md px-4 py-2 " +
            "hover:bg-blue-600 focus:outline-none focus:ring-2 " +
            "focus:ring-blue-500 disabled:opacity-50 " + 
            "disabled:cursor-not-allowed"}
        >
          Send
        </button>
      </form>
    </div>
  );
}

Running the Application

Start the Next.js development server:

npm run dev

Testing the Application

Navigate to http://localhost:3000 in your browser
Interact with the chat interface by typing messages

Viewing Traces

After interacting with the chat, you can view the traces in your Laminar dashboard at https://www.lmnr.ai. The trace will show:

The Next.js API route execution
The OpenAI API call made through Vercel’s AI SDK
Token usage and response details

Key Features Demonstrated

Next.js Instrumentation: Using Next.js’s instrumentation API to initialize Laminar
AI SDK Integration: Seamless integration with Vercel’s AI SDK
OpenAI Tracing: Automatic tracing of OpenAI API calls
Token Usage: Automatic calculation of tokens used for each OpenAI call
Cost Estimation: Automatic estimation of the cost of each OpenAI call

Example Traces

A screenshot of a trace from the example app.

Troubleshooting

If you encounter issues:

Check that your API keys are correctly set in the .env.local file
Verify that Laminar is properly initialized in the instrumentation.ts file
Verify that the next.config.ts file is correctly configured
Ensure all dependencies are installed
Review the Next.js logs for any application errors

​Overview

​Setup

​Implementation

​1. instrumentation.ts

​2. app/page.tsx

​3. app/api/chat/route.ts

​4. components/chat-ui.tsx

​Running the Application

​Testing the Application

​Viewing Traces

​Key Features Demonstrated

​Example Traces

​Troubleshooting

Overview

Setup

Implementation

1. instrumentation.ts

2. app/page.tsx

3. app/api/chat/route.ts

4. components/chat-ui.tsx

Running the Application

Testing the Application

Viewing Traces

Key Features Demonstrated

Example Traces

Troubleshooting