Validation does not come from the producer
The same model that generated a graph is not asked to certify that graph as correct. Structural and semantic validation are deterministic repository-owned mechanisms.
Structural validation
Structural validation checks the shape of the application document: required fields, node forms, binding shapes and other schema-level constraints.
Semantic validation
Semantic validation checks relations the schema alone cannot express cleanly: whether references resolve, bindings are type-compatible, capability-specific constraints hold and graph-level invariants remain coherent.
Validation is not execution
A contract-valid graph can still fall outside the current proof-runtime support slice. Known runtime restrictions belong in the support boundary rather than being silently inferred from validator success.