diff --git a/nanobot/session/manager.py b/nanobot/session/manager.py
index 9c1e427..18e23b2 100644
--- a/nanobot/session/manager.py
+++ b/nanobot/session/manager.py
@@ -154,6 +154,7 @@ class SessionManager:
         with open(path, "w", encoding="utf-8") as f:
             metadata_line = {
                 "_type": "metadata",
+                "key": session.key,
                 "created_at": session.created_at.isoformat(),
                 "updated_at": session.updated_at.isoformat(),
                 "metadata": session.metadata,
@@ -186,8 +187,9 @@ class SessionManager:
                     if first_line:
                         data = json.loads(first_line)
                         if data.get("_type") == "metadata":
+                            key = data.get("key") or path.stem.replace("_", ":", 1)
                             sessions.append({
-                                "key": path.stem.replace("_", ":"),
+                                "key": key,
                                 "created_at": data.get("created_at"),
                                 "updated_at": data.get("updated_at"),
                                 "path": str(path)