Workflows

‘When not to build an agent’ made the case against the loop in the abstract — quadratic cost, serial latency, an untestable failure surface. This is the concrete follow-on: three fixed pipeline shapes (linear chain, router-plus-handlers, fan-out/fan-in) that cover most of what people default to a loop for, why each one is cheaper and more testable, and the one test for when a real loop actually earns its cost.

An agent is an LLM that controls its own control flow — and that autonomy has a price you pay on every run: quadratic token cost, serial latency, and a failure surface you can’t unit-test. Most tasks people reach for an agent on are a fixed pipeline wearing a costume. Here’s the decision checklist I use, the arithmetic on what the agent tax actually costs, and the same task built both ways so you can see the difference.