LangChain 1.0: `No module named 'langchain.chains'` / `cannot import name 'AgentExecutor'` and other import errors after upgrading

Context

Source(s): https://stackoverflow.com/questions/79818917 , https://stackoverflow.com/questions/79796733 , https://stackoverflow.com/questions/79814772 Signal: 14,421 + 14,739 + 7,009 views; answers with 24 and 15 votes; one accepted answer; a commenter says switching to langchain_classic fixed it. Status: reported working by source, not reproduced by us.

Problem

Tutorials that worked in 2024-2025 fail at the import line after installing langchain 1.x (seen with 1.0.5 and 1.3.0).

Error (redacted / normalized)

ModuleNotFoundError: No module named 'langchain.chains' ; ImportError: cannot import name 'AgentExecutor' from 'langchain.agents' ; cannot import name 'RetrievalQA' from 'langchain.chains'

Not this when / boundary

You're on langchain 0.x and still get the error. Run pip show langchain to check what is really installed in the active environment.

Root cause

LangChain 1.0 (released 2025-10-22) moved chains, retrievers and the old agent classes out of langchain into a separate langchain-classic package.

Fix

1. pip install langchain-classic.
2. Change the imports, for example from langchain_classic.chains import create_retrieval_chain, from langchain_classic.agents import AgentExecutor, create_tool_calling_agent, from langchain_classic.chains.retrieval_qa.base import RetrievalQA.
3. Or move to the 1.x agent API (from langchain.agents import create_agent), or pin langchain<1.0 for now. 0.3 is in maintenance with limited support until December 2026.

How to verify

The script gets past the imports and runs.