This is exactly why I made a deep-dive video — LangChain changed massively since v0.0.x. All the old tutorials break because:

- Imports like `ConversationalRetrievalChain` moved or were deprecated

- Chains like `LLMChain` are gone

- You now use `.invoke()` instead of `.run()`

- New versions rely on Pydantic v2 and modular packages (like `langchain_core`, `langchain_openai`, etc.)

🎥 LangChain v0.3 Upgrade Fixes (YouTube)

💻 GitHub

Still learning myself, but this covers what broke and how to fix it in current LangChain.