diff --git a/workspace/frontend/lib/sidebar-agents.ts b/workspace/frontend/lib/sidebar-agents.ts
index 0941f3d1d..2728c2c14 100644
--- a/workspace/frontend/lib/sidebar-agents.ts
+++ b/workspace/frontend/lib/sidebar-agents.ts
@@ -3,5 +3,20 @@ import type { WorkspaceAgent } from './types';
 /** The personal roster never includes other people's or unclaimed agents. */
 export function ownedSidebarAgents(agents: WorkspaceAgent[], email: string) {
   const owner = email.trim().toLowerCase();
-  return owner ? agents.filter((agent) => agent.ownerEmail?.trim().toLowerCase() === owner && agent.status !== 'removed') : [];
+  return owner
+    ? agents
+        .filter((agent) => agent.ownerEmail?.trim().toLowerCase() === owner && agent.status !== 'removed')
+        .sort((a, b) => {
+          const aJoinedAt = a.joinedAt ? Date.parse(a.joinedAt) : Number.NaN;
+          const bJoinedAt = b.joinedAt ? Date.parse(b.joinedAt) : Number.NaN;
+          const aHasJoinedAt = Number.isFinite(aJoinedAt);
+          const bHasJoinedAt = Number.isFinite(bJoinedAt);
+
+          if (aHasJoinedAt && bHasJoinedAt && aJoinedAt !== bJoinedAt) {
+            return aJoinedAt - bJoinedAt;
+          }
+          if (aHasJoinedAt !== bHasJoinedAt) return aHasJoinedAt ? -1 : 1;
+          return a.agentName.localeCompare(b.agentName);
+        })
+    : [];
 }