Add billing schema drift support with field renaming

- Add get_schema(), apply_schema_drift(), and _field_map to BillingSystem
- Add BILLING to VALID_TARGETS for schema_drift
- Add billing-specific schema drift renames (amount, status, date_tick, items)
- Split SCHEMA_DRIFT_RENAMES into CRM and BILLING variants

sentinelops_arena/demo.py

@@ -122,7 +122,7 @@ class RandomizedAttacker:
         ),
     ]
 
-    SCHEMA_DRIFT_RENAMES = [
+    SCHEMA_DRIFT_RENAMES_CRM = [
         {"old_field": "name", "new_field": "full_name"},
         {"old_field": "contact_email", "new_field": "email_address"},
         {"old_field": "region", "new_field": "geo_region"},
@@ -130,6 +130,13 @@ class RandomizedAttacker:
         {"old_field": "notes", "new_field": "annotations"},
     ]
 
+    SCHEMA_DRIFT_RENAMES_BILLING = [
+        {"old_field": "amount", "new_field": "total_amount"},
+        {"old_field": "status", "new_field": "invoice_status"},
+        {"old_field": "date_tick", "new_field": "created_at_tick"},
+        {"old_field": "items", "new_field": "line_items"},
+    ]
+
     POLICY_DRIFT_CHANGES_BILLING = [
         {"window_ticks": 4, "requires_approval": True, "max_amount": 2000},
         {"window_ticks": 2, "requires_approval": True, "max_amount": 500},
@@ -159,7 +166,10 @@ class RandomizedAttacker:
     def _build_params(self, atype: AttackType, target: TargetSystem) -> dict:
         """Build randomised attack parameters for the given attack type."""
         if atype == AttackType.SCHEMA_DRIFT:
-            rename = self.rng.choice(self.SCHEMA_DRIFT_RENAMES)
+            if target == TargetSystem.BILLING:
+                rename = self.rng.choice(self.SCHEMA_DRIFT_RENAMES_BILLING)
+            else:
+                rename = self.rng.choice(self.SCHEMA_DRIFT_RENAMES_CRM)
             return {
                 "attack_type": atype.value,
                 "target_system": target.value,
@@ -192,7 +202,7 @@ class RandomizedAttacker:
 
     # Valid target systems per attack type (not all systems support all attacks)
     VALID_TARGETS = {
-        AttackType.SCHEMA_DRIFT: [TargetSystem.CRM],  # only CRM has apply_schema_drift
+        AttackType.SCHEMA_DRIFT: [TargetSystem.CRM, TargetSystem.BILLING],
         AttackType.POLICY_DRIFT: [TargetSystem.BILLING, TargetSystem.TICKETING],
         AttackType.SOCIAL_ENGINEERING: [TargetSystem.CRM, TargetSystem.BILLING, TargetSystem.TICKETING],
         AttackType.RATE_LIMIT: [TargetSystem.CRM, TargetSystem.BILLING, TargetSystem.TICKETING],

sentinelops_arena/systems/billing.py

@@ -12,6 +12,7 @@ class BillingSystem:
         self.refund_policy: RefundPolicy = RefundPolicy()
         self._rate_limit: int = 0  # 0 means no limit
         self._call_count: int = 0
+        self._field_map: Dict[str, str] = {}  # old_name -> new_name for drift
 
     def initialize(self, invoices: List[Invoice]):
         """Populate billing from Invoice models."""
@@ -19,6 +20,7 @@ class BillingSystem:
         self.refund_policy = RefundPolicy()
         self._rate_limit = 0
         self._call_count = 0
+        self._field_map = {}
 
     def check_balance(self, customer_id: str) -> Dict:
         """Return all invoices for a customer and total balance."""
@@ -153,6 +155,20 @@ class BillingSystem:
             "policy": self.refund_policy.model_dump(),
         }
 
+    def get_schema(self) -> Dict:
+        """Return current field names after any drift."""
+        fields = list(Invoice.model_fields.keys())
+        for old, new in self._field_map.items():
+            fields = [new if f == old else f for f in fields]
+        return {"system": "billing", "fields": fields}
+
+    def apply_schema_drift(self, old_field: str, new_field: str):
+        """Rename a field across all invoice records."""
+        self._field_map[old_field] = new_field
+        for inv_id in self.invoices:
+            if old_field in self.invoices[inv_id]:
+                self.invoices[inv_id][new_field] = self.invoices[inv_id].pop(old_field)
+
     def apply_policy_drift(self, changes: Dict):
         """Modify refund policy fields."""
         data = self.refund_policy.model_dump()