ADR-0002 Layer names
#Context
The layer model derives its tiers from the question "what authority does this have over attention?" The names must survive being said out loud in a job interview without explanation, and must not turn the astronomy of the project's name into a costume for the architecture. Substrate, Emitter, and View were settled in Draft 1; Arbiter and Scope were provisional.
#Decision
The five layers are Substrate, Emitter, Arbiter, Scope, View. All five are accepted and closed.
Scope's collision with general programming vocabulary is an asset, not a hazard: it means exactly what a developer already assumes — a bounded region that owns what happens inside it. A name that arrives pre-explained is worth more than a name that is merely unique.
#Rejected options
Astronomy names (photosphere, corona, chromosphere). On-theme and memorable. Rejected because they require a glossary to use, and a system whose architecture needs translation before discussion has failed the interview test. Novel structure, ordinary words.
Atomic tiers (atom, molecule, organism). Familiar to every reviewer. Rejected because the chemistry metaphor has no real boundaries in software — the tiers don't answer any question about a given component, which is the failure this model exists to fix. Borrowing them would import the ambiguity along with the familiarity.
Region in place of Scope. Avoids the programming collision and reads naturally in layout conversation. Rejected because the collision is the feature: Scope carries the ownership-and-boundary semantics for free, while Region is purely spatial and says nothing about authority.
Referee or Resolver in place of Arbiter. Same meaning. Rejected on register: Referee is sports vocabulary in a professional document, and Resolver is overloaded in networking and GraphQL. Arbiter says rank-and-decide plainly and collides with nothing.
#Consequences
The vocabulary is frozen and binding in code, Figma, docs, and conversation: package names, type names, and lint rule identifiers all use these five nouns. Any future rename is a superseding ADR plus a codemod, not an edit.