diff --git a/mercurymesh_federated_reproducible_marke/governance.py b/mercurymesh_federated_reproducible_marke/governance.py
index bd8618b..e2d64f1 100644
--- a/mercurymesh_federated_reproducible_marke/governance.py
+++ b/mercurymesh_federated_reproducible_marke/governance.py
@@ -13,6 +13,8 @@ from dataclasses import dataclass, asdict
 from typing import Dict, Any, Optional
 import json
 
+# Import cross-module primitives for PlanDelta references
+from .core import PlanDelta
 
 @dataclass
 class FoundationModelBlock:
diff --git a/mercurymesh_federated_reproducible_marke/registry.py b/mercurymesh_federated_reproducible_marke/registry.py
index a4d8aed..c515205 100644
--- a/mercurymesh_federated_reproducible_marke/registry.py
+++ b/mercurymesh_federated_reproducible_marke/registry.py
@@ -22,7 +22,7 @@ class ContractSpec:
 
     name: str
     version: str
-    schema: Dict[str, Any] | None = None
+    schema: Optional[Dict[str, Any]] = None
 
     def to_dict(self) -> Dict[str, Any]:
         return asdict(self)