4.3. Workflow Templates and Reuse Models

💡 First Principle: All three reuse mechanisms answer "don't write this twice," but they differ in when the consumer binds to the definition — creation time, call time, or step-resolution time — and that single property determines maintenance cost, update propagation, and blast radius.

Why care: this is the most frequently confused triad on the exam, and it's confused in practice too. The symptom of getting it wrong is either forty divergent copies of a pipeline nobody can patch, or a central definition that changes under teams without warning. Phase 1.3 introduced the spectrum; here it becomes a decision you can defend.

⚠️ Common Misconception: "Templates keep receiving updates from the source." Starter workflows are copy-on-create. Once a repository creates a workflow from one, the copy is fully independent — editing the template later changes nothing that already exists. Only reusable workflows and actions are resolved at run time.