Langchain Framework

This is the go-to framework for building LLM applications with proper structure. You get chains for composing prompts and model calls using the pipe operator syntax, RAG implementation with document loaders and vector stores, and agents that can use tools to take actions. The LCEL (LangChain Expression Language) approach makes everything composable and gives you streaming and async out of the box. It's overkill if you just need a single API call, but once you're splitting documents, retrieving context, or chaining multiple LLM operations together, it handles the plumbing so you can focus on the logic. The abstraction layer means you can swap between Claude, GPT-4, or other models without rewriting your pipeline.