diff --git a/mempalace/palace_graph.py b/mempalace/palace_graph.py
index 5e6ccbf..3296cd5 100644
--- a/mempalace/palace_graph.py
+++ b/mempalace/palace_graph.py
@@ -15,6 +15,11 @@ Enables queries like:
 No external graph DB needed — built from ChromaDB metadata.
 """
 
+# PEP 604 (``str | None``) needs 3.10+ at runtime; the project still
+# supports 3.9, so defer annotation evaluation to keep the union syntax
+# working on the older interpreter.
+from __future__ import annotations
+
 import hashlib
 import json
 import logging