The LangChain Ecosystem in 2026: Why Three Frameworks Exist (And When to Use Each)

You call create_agent every day. Do you know what graph it builds internally? Most developers don't. You have probably seen the tutorials. Paste some imports, call create_agentWatch the chatbot respond, feel good about it. Then two weeks later, when your agent starts hallucinating tool arguments, loses conversation history after a restart, or burns through your token budget in a single session, you open the LangChain docs and realize you have no idea what is actually running underneath your code. That gap is not a skill problem. It is a mental model problem.