diff --git a/apps/hub/src/server.ts b/apps/hub/src/server.ts
index c0f685b78e..0e6e8ac32a 100644
--- a/apps/hub/src/server.ts
+++ b/apps/hub/src/server.ts
@@ -478,6 +478,9 @@ export async function createHubServer({
       bus: mailboxBus,
     }),
   };
+  // The sidecar router captured `lookups` before this wrapper existed; an
+  // agent's outbound mail must also land in principal inboxes.
+  lookups.persistMail = mailboxLookups.persistMail;
 
   const artifactContentStore = InlineContentStore;