Langfuse JS/TS SDKs

langfuse-js

Modular mono repo for the Langfuse JS/TS client libraries.

Packages

Important

The SDK was rewritten in v5 and released in March 2026. Refer to the v5 migration guide for instructions on updating your code.

The unscoped npm packages langfuse, langfuse-core, langfuse-node, and langfuse-langchain belong to the legacy v3 SDK. For new integrations use the @langfuse/* scoped packages below — start with @langfuse/tracing + @langfuse/otel for tracing.

Package	Description	Environments
@langfuse/client	Langfuse API client for universal JavaScript environments	Universal JS
@langfuse/browser	Langfuse browser SDK for public-key score ingestion	Browser
@langfuse/tracing	Langfuse instrumentation methods based on OpenTelemetry	Node.js 20+
@langfuse/otel	Langfuse OpenTelemetry export helpers	Node.js 20+
@langfuse/openai	Langfuse integration for OpenAI SDK	Universal JS
@langfuse/langchain	Langfuse integration for LangChain	Universal JS
@langfuse/vercel-ai-sdk	Langfuse integration for AI SDK v7	Universal JS

Documentation

Development

This is a monorepo managed with pnpm. See CONTRIBUTING.md for detailed development instructions.

Quick start:

pnpm install    # Install dependencies
pnpm build      # Build all packages
pnpm test       # Run tests
pnpm ci         # Run full CI suite

License

MIT