Design Patterns in Action: Building an Intelligent Agent Workflow

Software design patterns often feel abstract until you see them working together in a real system. I recently built a simple tool that demonstrates how these patterns create elegant solutions to complex problems. Here's how classic patterns like Observer, Chain of Responsibility, and Strategy combine to create a flexible agent workflow.

A Real-World Example

Here's how these patterns work with a practical example. This changelog monitoring agent watches a website for changes - like a security camera watching a door. When something changes, it takes a snapshot and sends it to an AI assistant. The AI looks at what changed and decides if it's important enough to tell me about. If it is, I get a message on my phone through Telegram asking "Should I post about this on social media?" I can tap "yes" or "no," and if I say yes, it automatically creates and publishes the post.

The Hidden Patterns Making It Work

Think of this system like a well-organized team, where each person has a specific job:

The Watcher (Observer Pattern)

• Like a security guard who only speaks up when something happens
• Doesn't need to know what to do about changes, just reports them

The Assembly Line (Chain of Responsibility)

• Each team member handles their part: Watcher → AI Analyzer → Me (approval) → Social Media Poster
• Like passing a baton in a relay race - each person does their job then hands off to the next

The Playbook (Strategy Pattern)

• "Post to social media" is just one play in our playbook
• Tomorrow I could add "send an email" or "update a spreadsheet" without changing how the rest works

The Permission Slip (Command Pattern)

• My "yes" on Telegram is like signing a permission slip that says exactly what should happen
• The system waits for my signature before taking action

The Coordinator (Mediator Pattern)

• Like a project manager who makes sure everyone talks to the right person at the right time
• The website watcher doesn't need to know how Telegram works, and Telegram doesn't need to know about social media APIs

This design means I can easily swap out any piece - use a different chat app, watch different websites, or post to different platforms - without rebuilding everything. It's like having LEGO blocks that click together in standard ways, making the whole system flexible and easy to modify.

Key Patterns in Detail

1. Observer Pattern

Your page monitor is the classic Observer, watching for state changes. When changes occur, it notifies interested parties (in this case, the LLM processor). This decouples the detection mechanism from the processing logic.

2. Chain of Responsibility Pattern

The workflow passes through distinct handlers: Observer → LLM Analyzer → Human Approver → Action Executor. Each component has a specific responsibility and can pass control to the next. Any handler can interrupt the chain (e.g., LLM decides no action needed, human rejects).

3. Strategy Pattern

The "social media post" is one concrete strategy. The system could easily accommodate other strategies (email notification, database update, etc.). The execution logic is separated from the decision logic.

4. Command Pattern

The Telegram approval creates a command object that encapsulates the action to be taken. This allows for queuing, logging, or even undo operations. The human approval essentially "parameterizes" the command before execution.

5. Mediator Pattern

Your orchestration layer acts as a mediator between components. The Observer doesn't directly talk to Telegram or the social media API. This reduces coupling between components.

Why This Architecture Matters

This agent workflow demonstrates how classical design patterns create a flexible, maintainable automation system. The Observer pattern enables passive monitoring, while Chain of Responsibility ensures each decision point is isolated. The Command pattern through Telegram approval adds human oversight without tight coupling, and the Strategy pattern allows the system to adapt to different output channels. Together, these patterns create a loosely-coupled pipeline that's easy to extend and modify.

This architecture is particularly elegant because it balances automation with human judgment, using patterns to keep each concern separated and testable. By building on these time-tested patterns, we create systems that are not just functional today, but adaptable for tomorrow's requirements.