Concept
Reuse the layer’s contract, never coin a new one
When a layer already answers the question, its format name is vocabulary the stack owns — a design implements the existing contract rather than inventing a parallel one.
Pinned to
web4/1 — the nine-layer stack mapThe canonical source this concept is taught from. If it moves, the lesson is regenerated — teaching is pinned to code, not retyped.
On the frontier
No course teaches this concept yet — it is a named gap on the content graph, not a hole nobody sees. A gap is the roadmap, not an embarrassment: the count only falls by teaching.