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October 26, 2025

Langchain v1 Support

Hassieb Pakzad

Langfuse SDKs now support Langchain v1 for both Python and JS/TS. The integration remains stable and backward compatible.

We’re happy to announce that Langfuse now supports Langchain v1 in both the Python SDK (>=3.8.0) and the JS/TS SDK (>=4.3.0).

The integration has remained largely stable and continues to use the CallbackHandler pattern for both Python and JavaScript/TypeScript implementations. No changes are required to your existing instrumentation code - your current Langchain integrations will continue to work seamlessly.

What’s supported

• Python SDK: Langchain v1 support in Langfuse Python SDK >=3.8.0
• JS/TS SDK: Langchain v1 support in Langfuse JS SDK >=4.3.0
• Full backward compatibility with existing code
• Same CallbackHandler pattern for instrumentation

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