Quickstart

npm i langfuse
# or
yarn add langfuse
 
# Node.js < 18
npm i langfuse-node
 
# Deno
import { Langfuse } from "https://esm.sh/langfuse"

import { Langfuse } from "langfuse";
 
const langfuse = new Langfuse({
  secretKey: process.env.LANGFUSE_SECRET_KEY, // sk-lf-...
  publicKey: process.env.LANGFUSE_PUBLIC_KEY, // pk-lf-...
  // baseUrl: defaults to "https://cloud.langfuse.com"
});
 
// Example generation creation
const generation = trace.generation({
  name: "chat-completion",
  model: "gpt-3.5-turbo",
  modelParameters: {
    temperature: 0.9,
    maxTokens: 2000,
  },
  prompt: messages,
});
 
// Application code
const chatCompletion = await llm.respond(prompt);
 
// End generation - sets endTime
generation.end({
  completion: chatCompletion,
});

import { LangfuseWeb } from "langfuse";
 
export default function UserFeedbackComponent(props: { traceId: string }) {
  const langfuseWeb = new LangfuseWeb({
    publicKey: process.env.NEXT_PUBLIC_LANGFUSE_PUBLIC_KEY, // pk-lf-...
    // baseUrl: defaults to "https://cloud.langfuse.com"
  });
 
  const handleFeedback = async (value: number) => {
    await langfuseWeb.score({
      traceId: props.traceId,
      name: "user_feedback", // arbitrary name to identify the type of score
      value, // float, optional: scale it to e.g. 0..1
    });
  };
 
  return (
    <>
      <button onClick={() => handleFeedback(1)}>👍</button>
      <button onClick={() => handleFeedback(0)}>👎</button>
    </>
  );
}