diff --git a/extensions/mattermost/src/mattermost/monitor.ts b/extensions/mattermost/src/mattermost/monitor.ts
index 433e01e49..e468b2ea3 100644
--- a/extensions/mattermost/src/mattermost/monitor.ts
+++ b/extensions/mattermost/src/mattermost/monitor.ts
@@ -516,7 +516,7 @@ export async function monitorMattermostProvider(opts: MonitorMattermostOpts = {}
     });
 
     const baseSessionKey = route.sessionKey;
-    const threadRootId = post.root_id?.trim() || undefined;
+    const threadRootId = post.root_id?.trim() || (kind !== "dm" ? post.id : undefined);
     const threadKeys = resolveThreadSessionKeys({
       baseSessionKey,
       threadId: threadRootId,