diff --git a/app.js b/app.js
index 1aba7743..c184f9b1 100644
--- a/app.js
+++ b/app.js
@@ -253,6 +253,7 @@ const script = {
         "moto/load-svg",
         "moto/load-url",
         "moto/load-file",
+        "moto/broker",
         "moto/db",
         "kiri/ui",
         "kiri/do",
@@ -308,6 +309,7 @@ const script = {
         "geo/gyroid",
         "geo/mesh",
         "moto/pack",
+        "moto/broker",
         "kiri/slice",
         "kiri/slicer",
         "kiri/slicer2",
@@ -378,6 +380,7 @@ const script = {
         "geo/polygon",
         "geo/polygons",
         "moto/kv",
+        "moto/broker",
         "moto/load-obj",
         "moto/load-stl",
         "kiri/conf",
diff --git a/src/kiri/main.js b/src/kiri/main.js
index 0104172d..de66101c 100644
--- a/src/kiri/main.js
+++ b/src/kiri/main.js
@@ -16,6 +16,7 @@
         SETUP   = parseOpt(LOC.search.substring(1)),
         SECURE  = isSecure(LOC.protocol),
         LOCAL   = self.debug && !SETUP.remote,
+        EVENT   = new Broker(),
         SDB     = MOTO.KV,
         ODB     = KIRI.odb = new MOTO.Storage(SETUP.d ? SETUP.d[0] : 'kiri'),
         // K3DB    = KIRI.wdb = new MOTO.Storage('kiri3', { stores:["file","work"] }).init(),
@@ -40,7 +41,6 @@
         STACKS = KIRI.stacks,
         DRIVER = undefined,
         complete = {},
-        onEvent = {},
         selectedMeshes = [],
         localFilterKey ='kiri-gcode-filters',
         localFilters = js2o(SDB.getItem(localFilterKey)) || [],
@@ -654,22 +654,12 @@
          return showFavorites;
      }
 
-     function sendOnEvent(name, data) {
-         if (name && onEvent[name]) {
-             onEvent[name].forEach(function(fn) {
-                 fn(data, name);
-             });
-         }
+     function sendOnEvent(name, data, options) {
+         EVENT.publish(name, data, options);
      }
 
      function addOnEvent(name, handler) {
-         if (Array.isArray(name)) {
-             return name.forEach(n => addOnEvent(n, handler));
-         }
-         if (name && typeof(name) === 'string' && typeof(handler) === 'function') {
-             onEvent[name] = onEvent[name] || [];
-             onEvent[name].push(handler);
-         }
+         EVENT.subscribe(name, handler);
          return API.event;
      }
 
diff --git a/src/moto/broker.js b/src/moto/broker.js
new file mode 100644
index 00000000..d58b21c6
--- /dev/null
+++ b/src/moto/broker.js
@@ -0,0 +1,49 @@
+class Broker {
+    constructor() {
+        this.topics = {};
+    }
+
+    topics() {
+        return Object.keys(this.topics);
+    }
+
+    subscribe(topic, listener) {
+        let topics = this.topics;
+        let channel = topics[topic];
+        if (!channel) {
+            channel = topics[topic] = [];
+        }
+        if (channel.indexOf(listener) < 0) {
+            channel.push(listener);
+            this.publish(".topic.add", topic);
+        }
+    }
+
+    unsubscribe(topic, listener) {
+        let channel = this.topics[topic];
+        if (!channel) {
+            return;
+        }
+        let index = channel.indexOf(listener);
+        if (index < 0) {
+            return;
+        }
+        channel.splice(index,1);
+        if (channel.length === 0) {
+            delete this.topics[topic];
+            this.publish(".topic.remove", topic);
+        }
+    }
+
+    publish(topic, message, options = {}) {
+        if (topic !== ".topic.publish") {
+            this.publish(".topic.publish", {topic, message, options});
+        }
+        let channel = this.topics[topic];
+        if (channel && channel.length) {
+            for (let listener of channel) {
+                listener(message, topic, options);
+            }
+        }
+    }
+}