As LLM applications move from experiments to production systems, prompts stop being one-off strings in a notebook. They become part of the system contract.

In real applications, prompts need to be reusable, parameterized, versioned, tested, and observable, like any other behavior that affects users. A hardcoded prompt that works for one input is not enough when the system processes thousands of requests with different data.

This is where prompt templates and prompt pipelines come in.

This chapter shows how to design prompt templates, version them, test them, and compose them into multi-step pipelines.