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 # Familienarchiv — C4 Architecture Diagrams
 
 > For domain terminology used in these diagrams, see [docs/GLOSSARY.md](../GLOSSARY.md).
+>
+> **Cross-diagram stubs:** Components placed outside a `System_Boundary` block with a "See diagram X" annotation are reference stubs — they represent a component fully defined in another sub-diagram and appear here only to show the cross-domain dependency without duplicating the full definition.
 
 ## Level 1 — System Context