When would you use a deterministic workflow instead of an agent?

Example Answer

The way I'd think about it is this: I use a deterministic workflow when the path is known, the allowed branches are limited, and the business mainly cares about consistency. If I can describe the job as a clear state machine with explicit rules, I would rather encode that directly than pay for model judgment I do not need.

Agents earn their complexity when the work involves ambiguity, open-ended planning, or tool selection under uncertainty. Deterministic flows are stronger when the task is repetitive, auditable, and sensitive to unexpected variation.

The practical question is not whether agents are more impressive. It is whether the workflow actually benefits from model reasoning. If the answer is no, a deterministic path is usually faster, cheaper, and easier to trust.

Common Poor Answer

A weak answer is saying deterministic workflows are for simple tasks and agents are for complex ones. The real distinction is whether the path needs flexible reasoning or should stay tightly controlled.