The distinction. Task (single call) vs Workflow (predefined control flow — you own the plumbing) vs Agent (model owns the plumbing).
Five workflow patterns: prompt chaining, routing, parallelization, orchestrator-workers, evaluator-optimizer.
Design rule: start simple, measure everything, add complexity only when it produces measurable value. "Don't build agents for everything."
Our default sequence for client design reviews. Walk every proposed automation up the workflow → agent ladder.