Chapter 5: Middleware (cross-cutting concerns)

Goal of this chapter: understand the middleware pattern and implement Tool error handling and ChatModel retry.

Why Middleware

Once you add tools (Chapter 4), failures become normal in real-world systems:

• Tool failures: file not found, invalid args, missing permissions, etc.
• ChatModel failures: rate limits (429), network timeouts, temporary outages, etc.

Middleware provides a single place to handle these cross-cutting concerns without scattering logic throughout your business code.

Code location

• Entry code: cmd/ch05/main.go

Full tutorial

• ch05_middleware.md

What you learn

• How to wrap tool execution with consistent error handling.
• How to add retry policies around ChatModel calls in a composable way.
• How middleware keeps the Agent core clean and extensible.