Code Chains Graphs State Machines: An Engineer's Field Guide to AI Patterns

I Rewrote the Same AI Agent 4 Times. Here's the Architecture That Finally Stuck. I built an AI agent that could classify customer queries, pull up the right data, and generate a helpful response — all in about 40 lines of LangChain code. My manager watched it handle a compound question about a return and a delivery change in the same message, and said: "Ship it." So I did. It fell apart in production within a week. I rebuilt it as a graph. That lasted three months before a 23-node, 47-e...