diff --git a/resources/celerity/map.php b/resources/celerity/map.php
--- a/resources/celerity/map.php
+++ b/resources/celerity/map.php
@@ -200,6 +200,7 @@
     'rsrc/externals/javelin/lib/Router.js' => '29274e2b',
     'rsrc/externals/javelin/lib/URI.js' => '6eff08aa',
     'rsrc/externals/javelin/lib/Vector.js' => 'cc1bd0b0',
+    'rsrc/externals/javelin/lib/WebSocket.js' => '897b80bf',
     'rsrc/externals/javelin/lib/Workflow.js' => 'd149e002',
     'rsrc/externals/javelin/lib/__tests__/Cookie.js' => '5ed109e8',
     'rsrc/externals/javelin/lib/__tests__/DOM.js' => 'c984504b',
@@ -685,6 +686,7 @@
     'javelin-view-interpreter' => '0c33c1a0',
     'javelin-view-renderer' => '6c2b09a2',
     'javelin-view-visitor' => 'efe49472',
+    'javelin-websocket' => '897b80bf',
     'javelin-workflow' => 'd149e002',
     'lightbox-attachment-css' => '7acac05d',
     'maniphest-batch-editor' => '8f380ebc',
@@ -1360,6 +1362,9 @@
       'javelin-view-interpreter',
       'javelin-view-renderer',
     ),
+    '897b80bf' => array(
+      'javelin-install',
+    ),
     '8a41885b' => array(
       'javelin-install',
       'javelin-dom',
diff --git a/webroot/rsrc/externals/javelin/lib/WebSocket.js b/webroot/rsrc/externals/javelin/lib/WebSocket.js
new file mode 100644
--- /dev/null
+++ b/webroot/rsrc/externals/javelin/lib/WebSocket.js
@@ -0,0 +1,178 @@
+/**
+ * @requires javelin-install
+ * @provides javelin-websocket
+ * @javelin
+ */
+
+/**
+ * Wraps a WebSocket.
+ */
+JX.install('WebSocket', {
+
+  construct: function(uri) {
+    this.setURI(uri);
+  },
+
+  properties: {
+    URI: null,
+
+    /**
+     * Called when a connection is established or re-established after an
+     * interruption.
+     */
+    openHandler: null,
+
+    /**
+     * Called when a message is received.
+     */
+    messageHandler: null,
+
+    /**
+     * Called when the connection is closed.
+     *
+     * You can return `true` to prevent the socket from reconnecting.
+     */
+    closeHandler: null
+  },
+
+  members: {
+    /**
+     * The underlying WebSocket.
+     */
+    _socket: null,
+
+    /**
+     * Is the socket connected?
+     */
+    _isOpen: false,
+
+    /**
+     * Has the caller asked us to close?
+     *
+     * By default, we reconnect when the connection is interrupted.
+     * This stops us from reconnecting if @{method:close} was called.
+     */
+    _shouldClose: false,
+
+    /**
+     * Number of milliseconds to wait after a connection failure before
+     * attempting to reconnect.
+     */
+    _delayUntilReconnect: null,
+
+
+    /**
+     * Open the connection.
+     */
+    open: function() {
+      if (!window.WebSocket) {
+        return;
+      }
+
+      this._shouldClose = false;
+      this._resetDelay();
+
+      this._socket = new WebSocket(this.getURI());
+      this._socket.onopen = JX.bind(this, this._onopen);
+      this._socket.onmessage = JX.bind(this, this._onmessage);
+      this._socket.onclose = JX.bind(this, this._onclose);
+    },
+
+
+    /**
+     * Send a message.
+     *
+     * If the connection is not currently open, this method has no effect and
+     * the messages vanishes into the ether.
+     */
+    send: function(message) {
+      if (this._isOpen) {
+        this._socket.send(message);
+      }
+    },
+
+
+    /**
+     * Close the connection.
+     */
+    close: function() {
+      if (!$this._isOpen) {
+        return;
+      }
+      this._shouldClose = true;
+      this._socket.close();
+    },
+
+
+    /**
+     * Callback for connection open.
+     */
+    _onopen: function(e) {
+      this._isOpen = true;
+
+      // Reset the reconnect delay, since we connected successfully.
+      this._resetDelay();
+
+      var handler = this.getOpenHandler();
+      if (handler) {
+        handler();
+      }
+    },
+
+
+    /**
+     * Reset the reconnect delay to its base value.
+     */
+    _resetDelay: function() {
+      this._delayUntilReconnect = 2000;
+    },
+
+
+    /**
+     * Callback for message received.
+     */
+    _onmessage: function(e) {
+      var data = e.data;
+
+      var handler = this.getMessageHandler();
+      if (handler) {
+        handler(data);
+      }
+    },
+
+
+    /**
+     * Callback for connection close.
+     */
+    _onclose: function(e) {
+      this._isOpen = false;
+
+      var done = false;
+
+      var handler = this.getCloseHandler();
+      if (handler) {
+        done = handler();
+      }
+
+      // If we didn't explicitly see a close() call and the close handler
+      // did not return `true` to stop the reconnect, wait a little while
+      // and try to reconnect.
+      if (!done && !this._shouldClose) {
+        setTimeout(JX.bind(this, this._reconnect), this._delayUntilReconnect);
+      }
+    },
+
+
+    /**
+     * Reconnect an interrupted socket.
+     */
+    _reconnect: function() {
+      // Increase the reconnect delay by a factor of 2. If we fail to open the
+      // connection, the close handler will send us back here. We'll reconnect
+      // more and more slowly until we eventually get a valid connection.
+      this._delayUntilReconnect = this._delayUntilReconnect * 2;
+      this.open();
+    }
+
+  }
+});