LangChain 'ModuleNotFoundError: No module named langchain_community' (or imports from langchain.llms / langchain.chat_models failing): what changed and how do I fix it, given langchain-community is now archived?

Cause: LangChain's integrations live in separate packages rather than the core langchain package. Its docs say integrations "live in independent provider packages" such as langchain-openai, langchain-anthropic and langchain-ollama. Older code imports integrations from langchain_community (installed with pip install langchain-community), and you get ModuleNotFoundError if that package is missing from the environment. Be aware that, per PyPI and the GitHub README, langchain-community has been sunset: the repository was archived in June 2026, it no longer receives updates, and the latest release listed is 0.4.2. The README points to issue #674 in that repository for guidance. Fix (best first): 1. Prefer the dedicated provider package for what you use: pip install -U langchain-openai (ChatOpenAI), langchain-anthropic, langchain-ollama, langchain-aws and so on, then import from that package (for example from langchain_openai import ChatOpenAI). The Python docs also describe extras such as langchain[openai]. 2. If you only need a community integration with no provider package, install it explicitly with pip install langchain-community into the same environment that runs your code (check with python -m pip show langchain-community and which python), but plan to migrate, since it is archived and will not get fixes. Read issue #674 for the maintainers' guidance. 3. Pin compatible versions of langchain, langchain-core and the integration package in requirements.txt or pyproject.toml and rebuild the virtualenv or container image so all agree. 4. Use a virtual environment per project; an error that appears only in a notebook or IDE usually means a different interpreter. Verify: python -c "import langchain_openai" (or your provider package) succeeds in the runtime environment, and your app starts without import errors. Sources: https://docs.langchain.com/oss/python/langchain/install https://pypi.org/project/langchain-community/ https://github.com/langchain-ai/langchain-community