fix: billing topup fix

src/canton_mcp_server/canton_billing.py

@@ -730,7 +730,7 @@ async def _query_active_contracts_via_updates(
     party: str,
     extract: Callable[[str, dict, str], Optional[_T]],
     stop_when: Optional[Callable[[_T], bool]] = None,
-    page_size: int = 1000,
+    page_size: int = 100,
     end_offset: Optional[int] = None,
 ) -> list[_T]:
     """
@@ -780,7 +780,59 @@ async def _query_active_contracts_via_updates(
             break
 
         max_offset_this_page = begin
+
+        def _item_offset(item: dict) -> Optional[int]:
+            """Return the offset for any update variant (Transaction,
+            OffsetCheckpoint, Reassignment, TopologyTransaction, ...) so the
+            cursor advances even on pages that contain no Transactions. If we
+            only looked at Transactions, a page of pure OffsetCheckpoints
+            would leave `max_offset_this_page == begin` and the outer loop
+            would break prematurely — missing all later transactions.
+            """
+            upd = item.get("update", {}) if isinstance(item, dict) else {}
+            if not isinstance(upd, dict):
+                return None
+            # Try every known variant wrapper, both capitalized and flat.
+            for variant in (
+                "Transaction",
+                "OffsetCheckpoint",
+                "Reassignment",
+                "TopologyTransaction",
+            ):
+                wrapper = upd.get(variant)
+                if isinstance(wrapper, dict):
+                    value = wrapper.get("value")
+                    if isinstance(value, dict) and value.get("offset") is not None:
+                        return _coerce_offset(value.get("offset"))
+            for variant in (
+                "transaction",
+                "offsetCheckpoint",
+                "reassignment",
+                "topologyTransaction",
+            ):
+                value = upd.get(variant)
+                if isinstance(value, dict) and value.get("offset") is not None:
+                    return _coerce_offset(value.get("offset"))
+            return None
+
+        def _coerce_offset(raw) -> Optional[int]:
+            if isinstance(raw, (int, float)):
+                return int(raw)
+            if isinstance(raw, str):
+                try:
+                    return int(raw)
+                except ValueError:
+                    return None
+            return None
+
         for item in items:
+            # Always try to advance the page cursor — regardless of whether
+            # the item is a Transaction. This is the fix for checkpoint-only
+            # pages that would otherwise terminate the walk prematurely.
+            item_off = _item_offset(item)
+            if item_off is not None and item_off > max_offset_this_page:
+                max_offset_this_page = item_off
+
             update = item.get("update", {}) if isinstance(item, dict) else {}
             tx_wrapper = update.get("Transaction") or {}
             tx = tx_wrapper.get("value") if isinstance(tx_wrapper, dict) else None
@@ -789,19 +841,6 @@ async def _query_active_contracts_via_updates(
             if not tx:
                 continue
 
-            raw_offset = tx.get("offset")
-            if isinstance(raw_offset, str):
-                try:
-                    tx_offset = int(raw_offset)
-                except ValueError:
-                    tx_offset = max_offset_this_page
-            elif isinstance(raw_offset, (int, float)):
-                tx_offset = int(raw_offset)
-            else:
-                tx_offset = max_offset_this_page
-            if tx_offset > max_offset_this_page:
-                max_offset_this_page = tx_offset
-
             for ev in tx.get("events", []) or []:
                 created = ev.get("CreatedEvent") or ev.get("createdEvent")
                 if created: