diff --git a/src/assets/javascripts/ui/document/index.ts b/src/assets/javascripts/agent/document/index.ts
similarity index 100%
rename from src/assets/javascripts/ui/document/index.ts
rename to src/assets/javascripts/agent/document/index.ts
diff --git a/src/assets/javascripts/agent/element/index.ts b/src/assets/javascripts/agent/element/index.ts
new file mode 100644
index 000000000..2b549dfb1
--- /dev/null
+++ b/src/assets/javascripts/agent/element/index.ts
@@ -0,0 +1,57 @@
+/*
+ * Copyright (c) 2016-2019 Martin Donath <martin.donath@squidfunk.com>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to
+ * deal in the Software without restriction, including without limitation the
+ * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+ * sell copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+/* ----------------------------------------------------------------------------
+ * Functions
+ * ------------------------------------------------------------------------- */
+
+/**
+ * Retrieve an element matching the query selector
+ *
+ * @template T - Element type
+ *
+ * @param selector - Query selector
+ * @param node - Node of reference
+ *
+ * @return Element
+ */
+export function getElement<T extends HTMLElement>(
+  selector: string, node: ParentNode = document
+): T | undefined {
+  return node.querySelector<T>(selector) || undefined
+}
+
+/**
+ * Retrieve all elements matching the query selector
+ *
+ * @template T - Element type
+ *
+ * @param selector - Query selector
+ * @param node - Node of reference
+ *
+ * @return Elements
+ */
+export function getElements<T extends HTMLElement>(
+  selector: string, node: ParentNode = document
+): T[] {
+  return Array.from(node.querySelectorAll<T>(selector))
+}
diff --git a/src/assets/javascripts/ui/index.ts b/src/assets/javascripts/agent/index.ts
similarity index 96%
rename from src/assets/javascripts/ui/index.ts
rename to src/assets/javascripts/agent/index.ts
index 7ad3ab452..798e51472 100644
--- a/src/assets/javascripts/ui/index.ts
+++ b/src/assets/javascripts/agent/index.ts
@@ -21,6 +21,8 @@
  */
 
 export * from "./document"
+export * from "./element"
 export * from "./location"
 export * from "./media"
 export * from "./viewport"
+export * from "./worker"
diff --git a/src/assets/javascripts/ui/location/index.ts b/src/assets/javascripts/agent/location/index.ts
similarity index 100%
rename from src/assets/javascripts/ui/location/index.ts
rename to src/assets/javascripts/agent/location/index.ts
diff --git a/src/assets/javascripts/ui/media/index.ts b/src/assets/javascripts/agent/media/index.ts
similarity index 100%
rename from src/assets/javascripts/ui/media/index.ts
rename to src/assets/javascripts/agent/media/index.ts
diff --git a/src/assets/javascripts/ui/viewport/index.ts b/src/assets/javascripts/agent/viewport/index.ts
similarity index 100%
rename from src/assets/javascripts/ui/viewport/index.ts
rename to src/assets/javascripts/agent/viewport/index.ts
diff --git a/src/assets/javascripts/ui/worker/index.ts b/src/assets/javascripts/agent/worker/index.ts
similarity index 90%
rename from src/assets/javascripts/ui/worker/index.ts
rename to src/assets/javascripts/agent/worker/index.ts
index 2df48f648..739c4550d 100644
--- a/src/assets/javascripts/ui/worker/index.ts
+++ b/src/assets/javascripts/agent/worker/index.ts
@@ -21,14 +21,7 @@
  */
 
 import { Observable, fromEvent } from "rxjs"
-import {
-  pluck,
-  shareReplay,
-  switchMap,
-  take,
-  tap,
-  throttle
-} from "rxjs/operators"
+import { pluck, share, switchMapTo, tap, throttle } from "rxjs/operators"
 
 /* ----------------------------------------------------------------------------
  * Types
@@ -75,22 +68,19 @@ export function watchWorker<T extends WorkerMessage>(
   worker: Worker, { message$ }: Options<T>
 ): Observable<T> {
 
-  /* Receive messages from web worker */
+  /* Observable for messages from web worker */
   const worker$ = fromEvent(worker, "message")
     .pipe(
-      pluck<Event, T>("data")
+      pluck<Event, T>("data"),
+      share()
     )
 
-  /* Send request and wait for response */
+  /* Send and receive messages, return hot observable */
   return message$
     .pipe(
       throttle(() => worker$, { leading: true, trailing: true }),
       tap(message => worker.postMessage(message)),
-      switchMap(() => worker$
-        .pipe(
-          take(1)
-        )
-      ),
-      shareReplay(1)
+      switchMapTo(worker$),
+      share()
     )
 }