Running a LangGraph ReAct Agent in Production: OpenAI-Compatible API + Multi-Model Gateway + One-Line Tracing

Most LangGraph content stops at the notebook. You build a cute ReAct loop, it answers one question, and the article ends before the hard part: how do you actually serve this thing, swap models without a rewrite, and see what it's doing when it misbehaves? This post walks through a small but producti