diff --git a/web/js/state.js b/web/js/state.js
index de6b559..5692ffc 100644
--- a/web/js/state.js
+++ b/web/js/state.js
@@ -21,4 +21,5 @@ export const state = {
   logSource: null,
   pointSocket: null,
   apiDocLoaded: false,
+  runtimes: new Map(),  // unit_id -> UnitRuntime
 };