react

How LLM agents actually run: the iterative prompt-action-observation loop, the ReAct shape, the smallest tool-calling loop in twelve lines, why you always stack three termination layers, what the model sees on iteration N, and when a single prompt is the better answer.

Move beyond toy ReAct loops. Learn how to build a production-grade agent harness with a robust control loop, tool registry, schema validation, retry logic, token budgets, abort signals, and a persistent journal that survives crashes.

From hand-rolled useEffect fetches to TanStack Query v5 and SWR: race conditions, caching, mutations, optimistic updates, error boundaries, and when to push fetching to the server.

useState, useEffect, useReducer, and useContext in React 19: the rules, snapshot semantics, dependency arrays, when NOT to useEffect, and the dependency-array footgun that bites everyone.

Master React 19's core primitive: function components, JSX, props, children, composition, conditional rendering, and stable keys — built around a small TODO list you can ship.

What separates an agent from a plain chatbot, the perceive-think-act loop they all share, and how to design one that doesn't loop forever or burn through your token budget.