diff --git a/packages/web/src/App.svelte b/packages/web/src/App.svelte
index 287b8d6..baf788f 100644
--- a/packages/web/src/App.svelte
+++ b/packages/web/src/App.svelte
@@ -423,9 +423,13 @@
     }
   }
 
-  /** Every targeted cast goes out through here so attachments never drop. */
+  /** Every targeted cast goes out through here so attachments never drop —
+   * the attached NUMBER included, unless the call site already carried it. */
   function withMods<T extends Parameters<typeof net.command>[0] & { type: "cast" }>(cmd: T): T {
     applyMods(cmd);
+    if (attachedNumber && !cmd.numberInstanceIds) {
+      cmd.numberInstanceIds = [attachedNumber.instanceId];
+    }
     return cmd;
   }