Update server/sessionStore.js

server/sessionStore.js

@@ -53,6 +53,9 @@ function ensureSessionShape(raw, fallbackId = null) {
     created,
     history: Array.isArray(raw?.history) ? raw.history : [],
     model: raw?.model || null,
+    updatedAt: typeof raw?.updatedAt === 'string' && raw.updatedAt.trim()
+      ? raw.updatedAt
+      : nowIso(),
   };
 }
 
@@ -177,6 +180,7 @@ function sessionForList(meta, loaded) {
     created: Number.isFinite(source.created) ? source.created : Date.now(),
     history: loaded?.history || [],
     model: source.model || null,
+    updatedAt: source.updatedAt || null,
   };
 }