Potential bug in Context Runnable

[eyurtsev]

Privileged issue

• I am a LangChain maintainer, or was asked directly by a LangChain maintainer to create an issue here.

Issue Content

Minimal reproduction

from langchain_core.prompts import ChatPromptTemplate
from langchain_core.runnables import RunnablePassthrough, RunnableGenerator
from langchain_core.beta.runnables.context import Context

async def to_dict(input):
    async for chunk in input:
        yield {
            'foo': chunk
        }

chain = Context.setter('input') | model | to_dict | Context.getter('input')

async for chunk in chain.astream('hello'):
    print(chunk)

[eyurtsev]

langchain-ai/langserve#504

[eyurtsev]

investigate if related to: langchain-ai/langgraph#136