# UNDF: UNDF-2026-000000115
--- a/src/jamidht/conversation.cpp
+++ b/src/jamidht/conversation.cpp
@@ -783,7 +783,7 @@ Conversation::loadMessages(...)
-    std::vector<std::string> replies;
+    std::unordered_set<std::string> replies;
     std::vector<std::shared_ptr<libjami::SwarmMessage>> msgList;
     repository_->log(
         /* preCondition */
@@ -826,14 +826,11 @@ Conversation::loadMessages(...)
             auto message = optMessage.value();
             if (message.find("reply-to") != message.end()) {
-                auto it = std::find(replies.begin(), replies.end(), message.at("reply-to"));
-                if (it == replies.end()) {
-                    replies.emplace_back(message.at("reply-to"));
-                }
+                replies.insert(message.at("reply-to"));      // O(1) avg; duplicates ignored
             }
-            auto it = std::find(replies.begin(), replies.end(), message.at("id"));
-            if (it != replies.end()) {
-                replies.erase(it);
-            }
+            replies.erase(message.at("id"));                 // O(1) avg; no-op if absent