Langfuse Upgrade Migration

set -euo pipefail
# Check what you have
npm list langfuse @langfuse/client @langfuse/tracing 2>/dev/null

# Check latest available
npm info @langfuse/client version
npm info @langfuse/tracing version
npm info langfuse version

# Python
pip show langfuse 2>/dev/null | grep Version
pip index versions langfuse 2>/dev/null | head -3

set -euo pipefail
# Install v4+ packages
npm install @langfuse/client @langfuse/tracing @langfuse/otel @opentelemetry/sdk-node

# Keep langfuse v3 temporarily for comparison
# Remove after migration: npm uninstall langfuse

// BEFORE (v3):
import { Langfuse } from "langfuse";
const langfuse = new Langfuse({
  publicKey: process.env.LANGFUSE_PUBLIC_KEY,
  secretKey: process.env.LANGFUSE_SECRET_KEY,
  baseUrl: process.env.LANGFUSE_HOST,
});

// AFTER (v4+):
import { LangfuseClient } from "@langfuse/client";
import { LangfuseSpanProcessor } from "@langfuse/otel";
import { NodeSDK } from "@opentelemetry/sdk-node";

// OTel setup (once at entry point)
const sdk = new NodeSDK({
  spanProcessors: [new LangfuseSpanProcessor()],
});
sdk.start();

// Client for prompts, datasets, scores
const langfuse = new LangfuseClient();

// BEFORE (v3): Manual trace/span/generation
const trace = langfuse.trace({ name: "my-op", input: data });
const span = trace.span({ name: "step-1", input: data });
await doWork();
span.end({ output: result });
const gen = trace.generation({ name: "llm", model: "gpt-4o" });
gen.end({ output: response, usage: { promptTokens: 10 } });
await langfuse.flushAsync();

// AFTER (v4+): startActiveObservation with auto-nesting
import { startActiveObservation, updateActiveObservation } from "@langfuse/tracing";

await startActiveObservation("my-op", async () => {
  updateActiveObservation({ input: data });

  await startActiveObservation("step-1", async () => {
    updateActiveObservation({ input: data });
    const result = await doWork();
    updateActiveObservation({ output: result });
  });

  await startActiveObservation({ name: "llm", asType: "generation" }, async () => {
    updateActiveObservation({ model: "gpt-4o" });
    const response = await callLLM();
    updateActiveObservation({ output: response, usage: { promptTokens: 10 } });
  });
});

// BEFORE (v3):
import { observeOpenAI } from "langfuse";

// AFTER (v4+):
import { observeOpenAI } from "@langfuse/openai";
// npm install @langfuse/openai

# BEFORE: LANGFUSE_HOST or LANGFUSE_BASEURL
# AFTER:  LANGFUSE_BASE_URL (LANGFUSE_BASEURL still works in v4 but not v5)

// BEFORE (v3):
const prompt = await langfuse.getPrompt("my-prompt", 2); // version as positional arg

// AFTER (v4+):
const prompt = await langfuse.prompt.get("my-prompt", {
  version: 2, // version in options object
  type: "text", // explicit type
});

// BEFORE (v3):
await langfuse.shutdownAsync();

// AFTER (v4+):
await sdk.shutdown(); // Shuts down OTel SDK + flushes spans

# BEFORE (v2):
from langfuse import Langfuse
langfuse = Langfuse()

@langfuse.observe()
def my_function():
    pass

# AFTER (v3):
from langfuse.decorators import observe, langfuse_context

@observe()
def my_function():
    langfuse_context.update_current_observation(
        metadata={"key": "value"}
    )

set -euo pipefail
# Run existing test suite
npm test

# Verify traces appear in dashboard
node -e "
  const { startActiveObservation, updateActiveObservation } = require('@langfuse/tracing');
  startActiveObservation('upgrade-verify', async () => {
    updateActiveObservation({ input: { test: true }, output: { migrated: true } });
  }).then(() => console.log('Migration verified'));
"

set -euo pipefail
# After all tests pass
npm uninstall langfuse

# Verify no lingering imports
grep -rn "from ['\"]langfuse['\"]" src/ || echo "No old imports found"