diff --git a/web/backend/app/services/designators.py b/web/backend/app/services/designators.py
index 47b8d4c..0e8cceb 100644
--- a/web/backend/app/services/designators.py
+++ b/web/backend/app/services/designators.py
@@ -170,30 +170,48 @@ def _split_expression_parts(expr: str) -> list[str]:
     return parts
 
 
-def _resolve_property(name: str, props: dict[str, str], designator: str = "") -> str:
+def _resolve_property(
+    name: str,
+    props: dict[str, str],
+    designator: str = "",
+    resolving: frozenset[str] | None = None,
+) -> str:
+    if resolving is None:
+        resolving = frozenset()
+    if name in resolving:
+        return ""
     if name == "Designator":
         raw = designator or props.get("Designator", "")
     else:
         raw = props.get(name, "")
     if not raw:
         return ""
-    if raw.startswith("=") or (raw.startswith('"') and raw.endswith('"') and len(raw) > 1):
-        return resolve_expression(raw, props, designator)
+    if raw.startswith("="):
+        return resolve_expression(raw, props, designator, resolving | {name})
     return raw
 
 
-def resolve_expression(value: str, props: dict[str, str], designator: str = "") -> str:
+def resolve_expression(
+    value: str,
+    props: dict[str, str],
+    designator: str = "",
+    resolving: frozenset[str] | None = None,
+) -> str:
     """
     Altium complex string: ='literal'+"Property"+Name
     - single quotes = literal text
     - double quotes = component property reference
     - bare identifiers = property reference
     """
+    if resolving is None:
+        resolving = frozenset()
+    if len(resolving) > 64:
+        return ""
     if not value:
         return ""
     value = value.strip()
     if value.startswith('"') and value.endswith('"') and not value.startswith('="'):
-        return _resolve_property(value[1:-1], props, designator)
+        return _resolve_property(value[1:-1], props, designator, resolving)
     if not value.startswith("="):
         return value
 
@@ -204,9 +222,9 @@ def resolve_expression(value: str, props: dict[str, str], designator: str = "")
         if part.startswith("'") and part.endswith("'") and len(part) >= 2:
             result.append(part[1:-1])
         elif part.startswith('"') and part.endswith('"') and len(part) >= 2:
-            result.append(_resolve_property(part[1:-1], props, designator))
+            result.append(_resolve_property(part[1:-1], props, designator, resolving))
         elif part == "Designator":
             result.append(designator or props.get("Designator", ""))
         else:
-            result.append(_resolve_property(part, props, designator))
+            result.append(_resolve_property(part, props, designator, resolving))
     return "".join(result)