---
title: "Agent architectures"
id: "architectures"
pass: "Pass 1: Architectures"
canonical_url: "https://renatomignone.github.io/From-LLMs-to-Secure-Agents/architectures/"
total_chapters: 8
---

# Agent architectures

> **Section Overview:** Teach stable orchestration patterns before component and framework detail.
> **Pass:** Pass 1: Architectures · **Published chapters:** 8

## Learning Outcomes
The reader can choose and diagram single-agent loops, routers, pipelines, parallel workers, evaluator-optimizer loops, plan-execute systems, supervisors, handoffs, and event-driven graphs.

## Published chapters
- [Architecture selection criteria](https://renatomignone.github.io/From-LLMs-to-Secure-Agents/architectures/01-architecture-selection-criteria/) - Establishes a systematic decision framework and trade-off matrix for selecting among deterministic workflows, single-agent loops, and multi-agent coordination patterns based on latency, cost, determinism, and failure containment.
- [Single-agent and reactive loops](https://renatomignone.github.io/From-LLMs-to-Secure-Agents/architectures/02-single-agent-and-reactive-loops/) - Explores the internal mechanics, state progression, and failure modes of single-agent ReAct loops, detailing how models interleave reasoning with dynamic tool actions and how host runtimes enforce termination guardrails.
- [Sequential, routing, and parallel workflows](https://renatomignone.github.io/From-LLMs-to-Secure-Agents/architectures/03-sequential-routing-and-parallel-workflows/) - Deep dive into deterministic workflow orchestration topologies including linear prompt chaining, conditional routing, parallel sectioning, and consensus voting, emphasizing error isolation and validation gates.
- [Plan and execute](https://renatomignone.github.io/From-LLMs-to-Secure-Agents/architectures/04-plan-and-execute/) - Explores the plan-and-execute architectural pattern, detailing how separating strategic task planning from tactical action execution and dynamic replanning improves reliability on complex long-horizon tasks.
- [Evaluator-optimizer and reflection](https://renatomignone.github.io/From-LLMs-to-Secure-Agents/architectures/05-evaluator-optimizer-and-reflection/) - Explores the evaluator-optimizer and reflection patterns, detailing how decoupled generator and evaluator models iteratively critique, score, and refine outputs against deterministic tests and semantic rubrics.
- [State machines and event-driven graphs](https://renatomignone.github.io/From-LLMs-to-Secure-Agents/architectures/06-state-machines-and-event-driven-graphs/) - Explores state machines and event-driven graphs for AI agents, detailing typed state schemas, cyclic nodes, conditional edge routing, durable checkpointing, and asynchronous human-in-the-loop interruption.
- [Supervisors, handoffs, and agent-as-tool](https://renatomignone.github.io/From-LLMs-to-Secure-Agents/architectures/07-supervisors-handoffs-and-agent-as-tool/) - Explores multi-agent coordination architectures, comparing centralized supervisors (manager-worker), decentralized peer handoffs (swarm), and encapsulated subagents (agent-as-a-tool).
- [Architecture trade-offs](https://renatomignone.github.io/From-LLMs-to-Secure-Agents/architectures/08-architecture-trade-offs/) - Compares orchestration patterns across determinism, latency, token expenditure, observability, failure propagation, and termination guarantees to guide minimal architecture selection.