llama-index-llms-langchain

What it is and what it does

This package provides a wrapper that lets you use any LangChain-compatible language model as a LlamaIndex LLM. It acts as an adapter layer, translating between LlamaIndex's LLM interface and LangChain's model implementations. You instantiate a LangChain model (such as OpenAI) and wrap it with LangChainLLM, then use it directly in LlamaIndex workflows for indexing, querying, and response generation.

The integration supports both standard completion and streaming responses. It depends on langchain and llama-index-core. This is useful when you want to leverage LlamaIndex's retrieval and indexing capabilities while using a specific LangChain provider or model that may not have a direct LlamaIndex integration.

Use it for:

• Use LangChain's OpenAI wrapper within LlamaIndex to build RAG pipelines with specific model configurations
• Integrate a custom or lesser-known LangChain LLM provider into LlamaIndex without writing your own adapter
• Stream responses from LangChain models through LlamaIndex's completion API for real-time output
• Combine LlamaIndex's document indexing with a LangChain LLM you already have configured in another project

Worth the install?

AI-flagged interpretation of the facts on this page — verify before relying

Bridges LlamaIndex with LangChain LLM providers, allowing you to use any LangChain-compatible language model within LlamaIndex's indexing and retrieval framework.

Yes, if you are already using both LlamaIndex and LangChain and want to use a LangChain LLM provider within LlamaIndex. The low install friction, active maintenance, MIT license, and zero known vulnerabilities make it a straightforward choice. Install it only if you have a specific LangChain provider you need to integrate; if LlamaIndex has a direct integration for your model, that is likely simpler.

Install

llama-index-llms-langchain on PyPI

pip install llama-index-llms-langchain

uv add llama-index-llms-langchain

poetry add llama-index-llms-langchain

Installing llama-index-llms-langchain

Before you install

Low friction installation with only two runtime dependencies. The package is actively maintained with a recent release.

License in practice

MIT license permits free use, modification, and distribution with minimal restrictions—suitable for both open-source and commercial projects.

Quickstart

pip install llama-index-llms-langchain

from langchain.llms import OpenAI
from llama_index.llms.langchain import LangChainLLM

llm = LangChainLLM(llm=OpenAI())
response_gen = llm.stream_complete("Hi this is")
for delta in response_gen:
    print(delta.delta, end="")

Requires Python 3.10 or later

Verify before relying

• Whether all LangChain LLM implementations are fully compatible with LlamaIndex's streaming and completion interfaces
• Performance characteristics when using LangChain providers compared to native LlamaIndex integrations

Package facts

Evidence: llama_index_llms_langchain-0.8.0-py3-none-any.whl

Tags

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