Upgrade Langfuse SDK versions and migrate between API changes.
Use when upgrading Langfuse SDK, handling breaking changes,
or migrating between Langfuse versions.
Trigger with phrases like "upgrade langfuse", "langfuse migration",
"update langfuse SDK", "langfuse breaking changes", "langfuse version".
!npm list langfuse @langfuse/client @langfuse/tracing @langfuse/otel 2>/dev/null | head -10 || echo 'No langfuse packages found'
!pip show langfuse 2>/dev/null | grep -E "Name|Version" || echo 'Python langfuse not installed'
Overview
Step-by-step guide for upgrading the Langfuse SDK across major versions. Covers v3 to v4 (OTel rewrite), v4 to v5, breaking changes, and automated codemods.
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
Step 2: v3 to v4 Migration (TypeScript)
This is the biggest migration -- v4 rewrites tracing on OpenTelemetry.
2a. Install new packages:
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
2b. Update initialization:
// 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):
import { observeOpenAI } from "langfuse";
// AFTER (v4+):
import { observeOpenAI } from "@langfuse/openai";
// npm install @langfuse/openai
2e. Update environment variable:
# BEFORE: LANGFUSE_HOST or LANGFUSE_BASEURL
# AFTER: LANGFUSE_BASE_URL (LANGFUSE_BASEURL still works in v4 but not v5)
2f. Update prompt management:
// 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
});
2g. Update shutdown:
// BEFORE (v3):
await langfuse.shutdownAsync();
// AFTER (v4+):
await sdk.shutdown(); // Shuts down OTel SDK + flushes spans
Step 3: Python SDK Migration (v2 to v3)
# 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"}
)
Step 4: Run Tests and Verify
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'));
"
Step 5: Remove Old Package
set -euo pipefail
# After all tests pass
npm uninstall langfuse
# Verify no lingering imports
grep -rn "from ['\"]langfuse['\"]" src/ || echo "No old imports found"
