When you build a retrieval-augmented system, most of the tuning work happens before the LLM ever sees a document. How you split text determines what gets retrieved — and bad splits mean bad answers, even with a great model.

The problem with long documents

LLMs have a context window. You can't …

A chain follows the map you drew. An agent draws its own.

LangChain gives you two ways to wire an LLM into a workflow: chains and agents. Both connect prompts, tools, and models into something useful, but the control flow works in opposite directions.

Chains: fixed routes

A chain is …