Thesis
Specification, not documentation.
Automated tooling accelerates interface generation. It does not produce governance. Design systems without enforceable structure reduce to informal convention — undeclared, unenforced, and untranslatable across system boundaries.
The Invariant Design Language defines the specification layer that automated execution requires. Structure is not documented. It is specified. Specification carries enforcement. Documentation does not.
Architecture
Three layers. One system.
IDL operates across three layers. Each layer depends only on layers beneath it. Cross-layer dependencies are a specification violation.
Token Architecture
Grammar, not guidelines.
The token system defines three tiers: primitive, semantic, and component. Each tier has derivation rules. Lower tiers may not reference higher tiers. Violations are compile-time errors, not style warnings.
The component system extends this model. Components declare props, slots, variants, and state machines. Composition is explicit. Inheritance is prohibited. Every structure is traceable to a token, and every token resolves to a primitive.
Governance
Governed evolution.
IDL versioning is semantic and binding. Minor releases are additive only. No breaking changes are introduced within a minor version boundary. The stability contract is enforced by the governance model, not by convention.
This is the architectural property that makes IDL suitable as a dependency for automated pipelines. Downstream systems can rely on the stability contract. Breaking changes require a major version increment and a documented migration path.