Tokens 3-tier, primitives → semantics → components
3-tier architecture pattern for design tokens: 3 strict layers (primitives → semantics → components) where each layer references ONLY the layer below. Documented by Nathan Curtis (eightshapes.com), taught by Brad Frost / Ian Frost in the Subatomic course, validated in production by Atlassian Atlaskit, Shopify Polaris, IBM Carbon.