New HeliconeLogBuilder for Improved Stream Handling

March 5, 2025

We’re excited to introduce the HeliconeLogBuilder, a new approach to handling streaming responses with better error handling and a simplified workflow.

Introducing HeliconeLogBuilder

The new HeliconeLogBuilder class provides a simplified way to handle streaming LLM responses with improved error handling and async support. This new approach makes it easier to:

• Handle errors gracefully with the setError method
• Simplify stream handling with the toReadableStream method
• Use more flexible async/await patterns with sendLog
• Track proper error status codes

Example Usage with Next.js App Router

import { HeliconeManualLogger } from "@helicone/helpers";
import { after } from "next/server";
import Together from "together-ai";

const together = new Together();
const helicone = new HeliconeManualLogger({
  apiKey: process.env.HELICONE_API_KEY!,
});

export async function POST(request: Request) {
  const { question } = await request.json();
  const body = {
    model: "meta-llama/Meta-Llama-3.1-8B-Instruct-Turbo",
    messages: [{ role: "user", content: question }],
    stream: true,
  };

  const heliconeLogBuilder = helicone.logBuilder(body, {
    "Helicone-Property-Environment": "dev",
  });

  try {
    const response = await together.chat.completions.create(body);
    return new Response(heliconeLogBuilder.toReadableStream(response));
  } catch (error) {
    heliconeLogBuilder.setError(error);
    throw error;
  } finally {
    after(async () => {
      // This will be executed after the response is sent to the client
      await heliconeLogBuilder.sendLog();
    });
  }
}

Benefits Over Previous Methods

The logBuilder approach offers several advantages over the previous streaming methods:

• Better Error Handling: Automatically captures and logs errors with the setError method
• Simplified Stream Handling: Combines stream processing and logging in one step
• More Flexible Async Patterns: Better support for async workflows with the sendLog method
• Proper Status Code Tracking: Accurately records HTTP status codes, including errors
• Improved Time-to-First-Token Metrics: More reliable tracking of streaming performance

This new approach is now the recommended way to handle streaming responses with Helicone. For more information, check out our Manual Logger with Streaming guide.