LangChain docs/examples don't seem to align with LangChain v1 apis

[dan-massey]

I am looking at these docs: https://langfuse.com/integrations/frameworks/langchain#langchain-example

I have created an sdk instance and called sdk.start() and an instance of CallbackHandler.

The Langchain API no longer supports passing the handler to agent.invoke.

In the examples:

  await agent.invoke(
    { messages: [{ role: "user", content: "What's the weather in San Francisco?" }] }, 
    { callbacks: [langfuseHandler] }
)

but callbacks is not an acceptable key for the second object, and I get this typescript error:

Object literal may only specify known properties, and 'callbacks' does not exist in type 'Partial<Pick<PregelOptions<any, any, any, StreamMode | StreamMode[] | undefined, boolean, "text/event-stream" | undefined>, CreateAgentPregelOptions>> & { ...; }'

I see support for Langchain v1 was added in #9866 by @hassiebp but I don't think the docs are updated yet?

[inkeep-ai-assistant[bot]]

---

The Langfuse documentation for LangChain JS/TS integration shows passing the CallbackHandler via the callbacks config option(1)(2). However, based on your TypeScript error, it appears LangChain v1 may have changed how callbacks are passed to agents.

The documented approach is:

await agent.invoke(
  { messages: [{ role: "user", content: "What's the weather in San Francisco?" }] }, 
  { callbacks: [langfuseHandler] }
)

(1)

With LangChain v1, you may need to pass callbacks differently depending on the agent type. The Langfuse integration relies on LangChain's callback system, so if LangChain v1 changed the API for passing callbacks to agent.invoke, you'll need to follow LangChain's updated patterns while still using the Langfuse CallbackHandler.

I don't have specific documentation showing the exact LangChain v1 callback syntax in the available sources. You may want to check LangChain's v1 migration guide for how callbacks are now passed to agents, then apply that pattern with the Langfuse CallbackHandler instance you've created.

If you continue to experience issues, I recommend opening a GitHub discussion with the Langfuse team about LangChain v1 compatibility, as the documentation may need updates to reflect the new API patterns.

📚 Sources:

1. LangChain & LangGraph Integration
2. Cookbook: Langchain Integration (JS/TS)

---

Have another question? Just tag @inkeep.

[jannikmaierhoefer]

Hi @dan-massey, thanks for your patience. I am not able to reproduce this. Which version of LangChain and Langfuse were you using?