This tier is for developers and coding agents. It uses the internal interface words on purpose: family, shell, guard, and the closed set of kinds. Agency-facing how-to lives in [Help](/docs). Domain definitions live in [Early Intervention](/early-intervention).

<Cards>
  <Card title="Interface vocabulary" href="/docs/developers/interface" description="Families, shells, the route index, and the guards that keep them honest." />

  <Card title="Comprehensive app model" href="/docs/developers/app-model" description="Architecture, domain model, shipped surface, and product target." />
</Cards>