LangChain fundamentals: the mental model that makes everything click

Before you touch agents or RAG pipelines, you need to understand one pattern. Everything else builds on it. The problem LangChain solves Most LLM applications share the same structural patterns — connect a prompt to a model, parse the output, pass it somewhere else. Without a framework, you end up reinventing that plumbing on every project. LangChain standardizes those patterns. It gives you modular components that work across different model providers — OpenAI, Anthropic, Gemini — and slot toge