The AI Engineer

Production Agent Patterns:
From Concept to Code

Deep dives into agent architectures, elegant loop patterns, and reusable abstractions. Learn the crystallized patterns from building real-world autonomous systems. Then master the frontend interfaces that bring these agents to life.

Nov 6, 2025

The Anatomy of a Production Agent: From Single Turn to Human-in-the-Loop

Agentic Loop Fei Wang · The AI Engineer

A practical guide to production agent architecture, covering the four core primitives: single-turn API calls, tool execution with error handling, multi-turn loops with context engineering, and conversation state management. Learn how tools become feedback mechanisms, how loops enable autonomy while preventing overflow, and how message management handles caching, persistence, and human-in-the-loop interactions—patterns discovered through real production systems.

Nov 10, 2025

Building Production Agent APIs with FastAPI: Implementation Guide

Agent APIs Fei Wang · The AI Engineer

Transform agent architecture concepts into working production code. This implementation guide builds the complete MessageManager class with Redis L1 caching and PostgreSQL L2 persistence, implements session management with state tracking, creates streaming response handlers using Server-Sent Events, shows how interactive tools pause and resume across requests, and designs the frontend integration layer. Each pattern is demonstrated with real code that handles production traffic, error recovery, and scalability concerns.

Nov 11, 2025

Building Agent Interfaces I: From React Fundamentals to Design Systems

Agent Interface Fei Wang · The AI Engineer

AI tools can generate frontend code, but understanding the structure makes you far more effective. This guide reveals React's secret ingredient—the mental model shift from imperative to declarative programming. Master React's unidirectional data flow and component composition, learn modern tooling (Tailwind, CVA, shadcn/ui), and build token-based design systems for production agent interfaces.

Nov 12, 2025

Building Agent Interfaces II: Functional Foundations for Data-Driven UI

Agent Interface Fei Wang · The AI Engineer

React's data-driven UI model stems from functional programming—pure functions, immutability, and controlled side effects form the execution backbone. This guide builds a complete mental model through three progressive layers: FP principles that shape React's design, state management patterns (URL, component, global, persistent), and API integration from basic fetching to production patterns. Interactive examples and reference tables transform abstract concepts into practical decision-making tools, preparing you to build any complex interface from foundational patterns.

Nov 16, 2025

Building Agent Interfaces III: Authentication Foundations for Production Apps

Infrastructure Fei Wang · The AI Engineer

Almost every production application requires authentication—users log in, sessions persist, routes protect sensitive data. This guide builds authentication from foundational concepts: OAuth 2.0 flows (why Google login works), JWT tokens (stateless sessions), and coordinated frontend-backend state management. Three progressive layers: understanding SSO and OAuth architecture, implementing backend token generation and validation with FastAPI, and managing authentication state in React with protected routes and automatic token refresh. By mastering these patterns, you'll implement secure authentication for any application, not just agent interfaces.