Langchain

Last updated Aug 26, 2026 is the most popular framework for building AI applications powered by large language models (LLMs).

LangChain publishes multiple Python packages. The following are provided by the Workers runtime:

Get Started

Clone the cloudflare/python-workers-examples repository and run the LangChain example:

git clone https://github.com/cloudflare/python-workers-examples
cd python-workers-examples/langchain
uv run pywrangler dev

Example code

from workers import WorkerEntrypoint, Response
from langchain_core.prompts import PromptTemplate
from langchain_openai import OpenAI

class Default(WorkerEntrypoint):
    async def fetch(self, request):
        prompt = PromptTemplate.from_template("Complete the following sentence: I am a {profession} and ")
        llm = OpenAI(api_key=self.env.API_KEY)
        chain = prompt | llm

        res = await chain.ainvoke({"profession": "electrician"})
        return Response(res.split(".")[0].strip())

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