Designing Multi-Agent Systems

Official code repository for Designing Multi-Agent Systems: Principles, Patterns, and Implementation for AI Agents by Victor Dibia.

Learn to build effective multi-agent systems from first principles through complete, tested implementations. This repository includes PicoAgents—a full-featured multi-agent framework built entirely from scratch for the sole purpose of teaching you how multi-agent systems work. Every component, from agent reasoning loops to orchestration patterns, is implemented with clarity and transparency.

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Why This Book & Code Repository?

As the AI agent space evolves rapidly, clear patterns are emerging for building effective multi-agent systems. This book focuses on identifying these patterns and providing practical guidance for applying them effectively.

What makes this approach unique:

• Fundamentals-first: Build from scratch to understand every component and design decision
• Complete implementations: Every theoretical concept backed by working, tested code
• Framework-agnostic: Core patterns that transcend any specific framework (avoids the lock in or outdated api issue common with books that focus on a single framework)
• Production considerations: Evaluation, optimization, and deployment guidance from real-world experience

What You'll Learn & Build

The book is organized across 4 parts, taking you from theory to production:

Part I: Foundations of Multi-Agent Systems

Chapter	Title	Code	Learning Outcome
Ch 1	Understanding Multi-Agent Systems	Poet/critic example, references yc_analysis/	Understand when multi-agent systems are needed
Ch 2	Multi-Agent Patterns	-	Master coordination strategies (workflows vs autonomous)
Ch 3	UX Design Principles for Multi-Agent Systems	-	Principles for building intuitive agent interfaces

Part II: Building Multi-Agent Systems from Scratch

Chapter	Title	Code	Learning Outcome
Ch 4	Building Your First Agent	agents/_agent.py, basic-agent.py, memory.py, middleware.py	Build agents with tools, memory, streaming, and middleware
Ch 5	Computer Use Agents	agents/_computer_use/, computer_use.py	Build browser automation agents with multimodal reasoning
Ch 6	Building Multi-Agent Workflows	workflow/, workflows/	Build type-safe workflows with streaming observability
Ch 7	Autonomous Multi-Agent Orchestration	orchestration/, round-robin.py, ai-driven.py, plan-based.py	Implement GroupChat, LLM-driven, and plan-based orchestration (Magentic One patterns)
Ch 8	Building Modern Agent UX Applications	app/ (minimal FastAPI+SSE example), webui/ (production React UI)	Build interactive agent applications with web UI, auto-discovery, and real-time streaming
Ch 9	Multi-Agent Frameworks	-	Evaluate and choose the right multi-agent framework

Part III: Evaluating and Optimizing Multi-Agent Systems

Chapter	Title	Code	Learning Outcome
Ch 10	Evaluating Multi-Agent Systems	eval/, agent-evaluation.py	Build evaluation frameworks with LLM-as-judge and metrics

Part IV: Real-World Applications

Chapter	Title	Code	Learning Outcome
Ch 16	Business Questions from Unstructured Data	yc_analysis/	Production case study: Analyze 5,000+ companies with cost optimization and checkpointing
Ch 17	Software Engineering Agent	swe_agent/	Build a complete software engineering agent with coding tools and workspace management

Getting Started

Option 1: Interactive Notebooks

Click Colab badges in the chapter tables above to run examples in your browser. No installation required.

Option 2: GitHub Codespaces

Pre-configured development environment in your browser. Once open:

1. Add your API key: export OPENAI_API_KEY='your-key'
2. Run examples: python examples/agents/basic-agent.py
3. Launch Web UI: picoagents ui

Free tier: 60 hours/month

Option 3: Local Installation

# Clone the repository
git clone https://github.com/victordibia/designing-multiagent-systems.git
cd designing-multiagent-systems

# Navigate to the PicoAgents framework directory
cd picoagents

# Create virtual environment (recommended)
python -m venv venv
source venv/bin/activate  # On Windows: venv\Scripts\activate

# Basic installation
pip install -e .

# Or install with optional features
pip install -e ".[web]"           # Web UI and API server
pip install -e ".[computer-use]"  # Browser automation
pip install -e ".[examples]"      # Run example scripts
pip install -e ".[all]"           # Everything

# Set up your API key
export OPENAI_API_KEY="your-api-key-here"

Quick Start: Your First Agent

In this book, we will cover the fundamentals of building multi-agent systems, and incrementally build up the Agents abstractions shown below:

from picoagents import Agent, OpenAIChatCompletionClient

def get_weather(location: str) -> str:
    """Get current weather for a given location."""
    return f"The weather in {location} is sunny, 75°F"

# Create an agent
agent = Agent(
    name="assistant",
    instructions="You are helpful. Use tools when appropriate.",
    model_client=OpenAIChatCompletionClient(model="gpt-4.1-mini"),
    tools=[get_weather]
)

# Use the agent
response = await agent.run("What's the weather in Paris?")
print(response.messages[-1].content)

Model Client Setup

PicoAgents supports multiple LLM providers through a unified interface. Each provider requires minimal setup—just API credentials and switching the client class. Chapter 4 covers building custom model clients for any provider.

Provider	Client Class	Setup	Example	Source
OpenAI	OpenAIChatCompletionClient	1. Get API key from platform.openai.com 2. export OPENAI_API_KEY='sk-...'	basic-agent.py	_openai.py
Azure OpenAI	AzureOpenAIChatCompletionClient	1. Deploy model on Azure Portal 2. Set endpoint, key, deployment name	agent_azure.py	_azure_openai.py
Anthropic	AnthropicChatCompletionClient	1. Get API key from console.anthropic.com 2. export ANTHROPIC_API_KEY='sk-...'	agent_anthropic.py	_anthropic.py
GitHub Models	OpenAIChatCompletionClient + base_url	1. Get token from github.com/settings/tokens 2. export GITHUB_TOKEN='ghp_...' 3. Set base_url="https://models.github.ai/inference"	agent_githubmodels.py	Uses _openai.py
Local/Custom	OpenAIChatCompletionClient + base_url	Point to any OpenAI-compatible endpoint (Ollama, LM Studio, vLLM, etc.)	Use base_url="http://localhost:8000"	Uses _openai.py

Quick Examples:

# OpenAI (default)
from picoagents import OpenAIChatCompletionClient
client = OpenAIChatCompletionClient(model="gpt-4.1-mini")

# Anthropic
from picoagents import AnthropicChatCompletionClient
client = AnthropicChatCompletionClient(model="claude-3-5-sonnet-20241022")

# GitHub Models (free tier)
client = OpenAIChatCompletionClient(
    model="openai/gpt-4.1-mini",
    api_key=os.getenv("GITHUB_TOKEN"),
    base_url="https://models.github.ai/inference"
)

# Local LLM (e.g., Ollama)
client = OpenAIChatCompletionClient(
    model="llama3.2",
    base_url="http://localhost:11434/v1"
)

Launch the Web UI

# Auto-discover agents, orchestrators, and workflows in current directory
picoagents ui

# Or specify a directory
picoagents ui --dir ./examples

The Web UI provides streaming chat, real-time debug events, session management, and automatic discovery of all agents and workflows in your codebase.

Run Examples

Examples are now at the root level for easy access:

# Basic agent with tools (Chapter 4)
python examples/agents/basic-agent.py

# Browser automation agent (Chapter 5)
python examples/agents/computer_use.py

# Autonomous orchestration (Chapter 6)
python examples/orchestration/round-robin.py
python examples/orchestration/ai-driven.py

# Production workflow (Chapter 13)
python examples/workflows/yc_analysis/workflow.py

PicoAgents Framework

This repository is organized into two main components:

1. Framework Source (picoagents/)

Complete multi-agent framework built from scratch:

picoagents/
├── src/picoagents/
│   ├── agents/            # Core Agent implementation (Ch 4)
│   │   ├── _agent.py      # Complete agent with streaming, tools, memory
│   │   └── _computer_use/ # Browser automation agents (Ch 5)
│   ├── workflow/          # Type-safe workflow engine (Ch 5)
│   │   ├── core/          # DAG-based execution with streaming
│   │   └── steps/         # Reusable workflow steps
│   ├── orchestration/     # Autonomous coordination (Ch 6)
│   │   ├── _round_robin.py  # Sequential turn-taking
│   │   ├── _ai.py           # LLM-driven speaker selection
│   │   └── _plan.py         # Plan-based orchestration (Magentic One)
│   ├── tools/             # 15+ built-in tools (core, research, coding)
│   ├── eval/              # Evaluation framework (Ch 8)
│   │   ├── judges/        # LLM-as-judge, reference-based
│   │   └── _runner.py     # Test execution and metrics
│   ├── webui/             # Web UI with auto-discovery (Ch 6)
│   ├── llm/               # OpenAI and Azure clients
│   ├── memory/            # Memory implementations
│   ├── termination/       # 9 termination conditions
│   └── middleware/        # Extensible middleware system
└── tests/                 # Comprehensive test suite

### 2. Examples ([`examples/`](examples/))
50+ runnable examples organized by chapter:

examples/
├── agents/            # Ch 4: Basic agents, tools, memory, computer use
├── workflows/         # Ch 5: Sequential, parallel, production workflows
├── orchestration/     # Ch 6: Round-robin, AI-driven, plan-based
└── evaluation/        # Ch 8: Agent evaluation patterns

Key Features

Production-Ready Patterns

Illustrated through real-world case studies (see YC Analysis workflow):

• Cost optimization: Two-stage filtering for 90% LLM cost reduction
• Type safety: Structured outputs with Pydantic validation
• Reliability: Checkpointing and resumable workflows
• Advanced reasoning: Think tool for improved problem-solving (54% performance gain)

Computer Use Agents

• Playwright-based browser automation
• Multimodal reasoning with vision models
• Built-in tools: navigate, click, type, scroll, extract content

Web UI & CLI

• Auto-discovery of agents, orchestrators, workflows
• Real-time streaming with Server-Sent Events
• Session management with conversation history
• Launch: picoagents ui

Evaluation Framework

• LLM-as-judge evaluation patterns
• Reference-based validation (exact, fuzzy, contains)
• Composite scoring with multiple judges
• Comprehensive metrics collection

Get the Book

"Designing Multi-Agent Systems: Principles, Patterns, and Implementation for AI Agents"

This repository implements every concept from the book. The book provides the theory, design trade-offs, and production considerations you need to build effective multi-agent systems.

• Buy Digital Edition
• Paperback on Amazon
• Hardcover on Amazon

Questions and Feedback

Questions or feedback about the book or code? Please open an issue.

Citation

@book{dibia2025multiagent,
  title={Designing Multi-Agent Systems: Principles, Patterns, and Implementation for AI Agents},
  author={Dibia, Victor},
  year={2025},
  github={https://github.com/victordibia/designing-multiagent-systems}
}