# Invariant Doc Entity
### Scope
- **Purpose**: Define properties that must always hold throughout all code paths in mod_interface.
- **Responsibility**: Catalog of invariant doc instances governing the namespace layer propagation system.
- **In Scope**: Invariant statements, enforcement mechanisms, and violation consequences.
- **Out of Scope**: Implementation algorithms; those belong in algorithm/ doc instances if created.
### Overview Table
| 001 | [Propagation Rules](001_propagation_rules.md) | Layer-to-parent propagation invariants for the five-layer cascade | ✅ |