diff --git a/src/error/PhutilAggregateException.php b/src/error/PhutilAggregateException.php
--- a/src/error/PhutilAggregateException.php
+++ b/src/error/PhutilAggregateException.php
@@ -27,25 +27,29 @@
 
   private $exceptions = array();
 
-  public function __construct($message, array $other_exceptions) {
+  public function __construct($message, array $exceptions) {
     // We don't call assert_instances_of($other_exceptions, 'Exception') to not
     // throw another exception in this exception.
 
-    $this->exceptions = $other_exceptions;
+    $this->exceptions = $exceptions;
+    parent::__construct($message);
+  }
+
+  public function __toString() {
+    $message = array();
+    $message[] = $this->getMessage();
 
-    $full_message = array();
-    $full_message[] = $message;
-    foreach ($other_exceptions as $key => $exception) {
+    foreach ($this->exceptions as $key => $exception) {
       $ex_message =
         (is_string($key) ? $key.': ' : '').
         get_class($exception).': '.
         $exception->getMessage();
       $ex_message = '    - '.str_replace("\n", "\n      ", $ex_message);
 
-      $full_message[] = $ex_message;
+      $message[] = $ex_message;
     }
 
-    parent::__construct(implode("\n", $full_message), count($other_exceptions));
+    return implode("\n", $message);
   }
 
   public function getExceptions() {
diff --git a/src/error/PhutilErrorHandler.php b/src/error/PhutilErrorHandler.php
--- a/src/error/PhutilErrorHandler.php
+++ b/src/error/PhutilErrorHandler.php
@@ -77,6 +77,28 @@
 
 
   /**
+   * Gets all exceptions of an aggregate/proxy exception as an iterator.
+   *
+   * @param   Exception      Exception to unnest.
+   * @return  ArrayIterator  Iterator for nested exceptions.
+   * @task    exutil
+   */
+  public static function getAllExceptions(Exception $ex) {
+    if ($ex instanceof PhutilAggregateException) {
+      $exceptions = $ex->getExceptions();
+      array_unshift($exceptions, $ex);
+    } else {
+      $exceptions = array();
+
+      do {
+        $exceptions[] = $ex;
+      } while ($ex = self::getPreviousException($ex));
+    }
+
+    return new ArrayIterator($exceptions);
+  }
+
+  /**
    * Gets the previous exception of a nested exception. Prior to PHP 5.3 you
    * can use @{class:PhutilProxyException} to nest exceptions; after PHP 5.3
    * all exceptions are nestable.
@@ -365,9 +387,11 @@
       case self::EXCEPTION:
         $messages = array();
         $current = $value;
-        do {
-          $messages[] = '('.get_class($current).') '.$current->getMessage();
-        } while ($current = self::getPreviousException($current));
+
+        foreach (self::getAllExceptions($current) as $ex) {
+          $messages[] = '('.get_class($ex).') '.$ex->getMessage();
+        }
+
         $messages = implode(' {>} ', $messages);
 
         if (strlen($messages) > 4096) {
@@ -384,6 +408,13 @@
         $metadata['default_message'] = $default_message;
         error_log($default_message);
         self::outputStacktrace(self::getRootException($value)->getTrace());
+
+        if ($value instanceof PhutilAggregateException) {
+          foreach ($current->getExceptions() as $ex) {
+            self::outputStacktrace($ex->getTrace());
+          }
+        }
+
         break;
       case self::PHLOG:
         $default_message = sprintf(