diff --git a/apps/web/src/components/Sidebar.tsx b/apps/web/src/components/Sidebar.tsx
index ddc7ad1e7bd2..0868554b50ff 100644
--- a/apps/web/src/components/Sidebar.tsx
+++ b/apps/web/src/components/Sidebar.tsx
@@ -337,6 +337,8 @@ interface SidebarThreadPartitionInput {
   readonly serverConfigs: ReadonlyMap<EnvironmentId, EnvironmentServerConfig>;
   readonly optimisticDrop: SidebarOptimisticDrop | null;
   readonly workingShelfEnabled: boolean;
+  /** Boring mode: folders list active threads by the user's latest message. */
+  readonly sortActiveBySend: boolean;
   // Snooze wakes, the queued-turn grace and the Working shelf's exit grace depend
   // on the clock, so the minute tick, the precise snooze-wake tick and the inbox
   // tracker's expiry version are inputs: a new key repartitions.
@@ -458,6 +460,7 @@ function useSidebarThreads(input: {
     serverConfigs,
     optimisticDrop,
     workingShelfEnabled,
+    sortActiveBySend: folderGroups !== null,
     clockKey: `${nowMinute}:${snoozeWakeClock}:${inboxReturnsVersion}`,
   });
 
@@ -592,6 +595,7 @@ function partitionSidebarThreads(input: SidebarThreadPartitionInput) {
     serverConfigs,
     optimisticDrop,
     workingShelfEnabled,
+    sortActiveBySend,
   } = input;
   const preciseNow = new Date().toISOString();
   const visible = filterSidebarV2VisibleThreads(threads, scopedProjectKeys, delegatedUnderParent);
@@ -650,9 +654,11 @@ function partitionSidebarThreads(input: SidebarThreadPartitionInput) {
   }
   // A loaded config gates dragging only; the sort must not depend on it, so web and mobile agree.
   const sortedPinned = sortPinnedThreadsForSidebar(pinned);
-  const sortedActive = workingShelfEnabled
-    ? sortInboxThreadsByReturn(active, inboxObservation.returnedAt)
-    : sortThreadsForSidebar(active);
+  const sortedActive = sortActiveBySend
+    ? sortWorkingThreadsBySend(active)
+    : workingShelfEnabled
+      ? sortInboxThreadsByReturn(active, inboxObservation.returnedAt)
+      : sortThreadsForSidebar(active);
   return {
     pinnedThreads:
       optimisticDrop?.section !== "pinned" || optimisticDrop.order === null