Spec-Driven Development Is Not Waterfall

Spec-driven development and Waterfall both use upfront documentation, but they differ fundamentally in behavior. Waterfall freezes specs as gates requiring formal approval, while spec-driven development treats specs as living tools that change continuously alongside code. Four observable behaviors distinguish them: when specs change (continuously vs. at milestones), how design and specs relate (in parallel vs. sequentially), how 'done' is defined (acceptance criteria inside the spec vs. separate sign-off), and who edits the spec (everyone including developers vs. only analysts). The post also introduces the term 'Agentic Delivery Process' as a broader label for this shift, and provides concrete diagnostic signals to tell whether a team is genuinely practicing spec-driven development or just relabeling Waterfall.