Note: This article was written in July 2026 using LangChain 0.3.x. APIs may change in future versions — check the LangChain docs if something doesn't work.
When I started learning LangChain, I got overwhelmed. There are chains, agents, memory, retrievers, output parsers — dozens of abstractions. Then I realized: most of them are deprecated.
LangGraph (by the same team) has replaced the orchestration layer. But you still need LangChain's core building blocks inside LangGraph nodes. So I figured out the minimum you actually need to learn.
Here's everything, in one file.
The 4 Things That Matter
