diff --git a/resources/celerity/map.php b/resources/celerity/map.php
--- a/resources/celerity/map.php
+++ b/resources/celerity/map.php
@@ -46,7 +46,7 @@
     'rsrc/css/application/config/config-options.css' => '16c920ae',
     'rsrc/css/application/config/config-template.css' => '20babf50',
     'rsrc/css/application/config/setup-issue.css' => '5eed85b2',
-    'rsrc/css/application/config/unhandled-exception.css' => '9da8fdab',
+    'rsrc/css/application/config/unhandled-exception.css' => '9ecfc00d',
     'rsrc/css/application/conpherence/color.css' => 'b17746b0',
     'rsrc/css/application/conpherence/durable-column.css' => '2d57072b',
     'rsrc/css/application/conpherence/header-pane.css' => 'c9a3db8e',
@@ -877,7 +877,7 @@
     'syntax-highlighting-css' => '8a16f91b',
     'tokens-css' => 'ce5a50bd',
     'typeahead-browse-css' => 'b7ed02d2',
-    'unhandled-exception-css' => '9da8fdab',
+    'unhandled-exception-css' => '9ecfc00d',
   ),
   'requires' => array(
     '01384686' => array(
diff --git a/src/aphront/configuration/AphrontApplicationConfiguration.php b/src/aphront/configuration/AphrontApplicationConfiguration.php
--- a/src/aphront/configuration/AphrontApplicationConfiguration.php
+++ b/src/aphront/configuration/AphrontApplicationConfiguration.php
@@ -118,6 +118,12 @@
       $database_exception = $ex;
     }
 
+    // If we're in developer mode, set a flag so that top-level exception
+    // handlers can add more information.
+    if (PhabricatorEnv::getEnvConfig('phabricator.developer-mode')) {
+      $sink->setShowStackTraces(true);
+    }
+
     if ($database_exception) {
       $issue = PhabricatorSetupIssue::newDatabaseConnectionIssue(
         $database_exception,
diff --git a/src/aphront/response/AphrontUnhandledExceptionResponse.php b/src/aphront/response/AphrontUnhandledExceptionResponse.php
--- a/src/aphront/response/AphrontUnhandledExceptionResponse.php
+++ b/src/aphront/response/AphrontUnhandledExceptionResponse.php
@@ -4,8 +4,20 @@
   extends AphrontStandaloneHTMLResponse {
 
   private $exception;
+  private $showStackTraces;
+
+  public function setShowStackTraces($show_stack_traces) {
+    $this->showStackTraces = $show_stack_traces;
+    return $this;
+  }
+
+  public function getShowStackTraces() {
+    return $this->showStackTraces;
+  }
+
+  public function setException($exception) {
+    // NOTE: We accept an Exception or a Throwable.
 
-  public function setException(Exception $exception) {
     // Log the exception unless it's specifically a silent malformed request
     // exception.
 
@@ -61,10 +73,36 @@
     $body = $ex->getMessage();
     $body = phutil_escape_html_newlines($body);
 
+    $classes = array();
+    $classes[] = 'unhandled-exception-detail';
+
+    $stack = null;
+    if ($this->getShowStackTraces()) {
+      try {
+        $stack = id(new AphrontStackTraceView())
+          ->setTrace($ex->getTrace());
+
+        $stack = hsprintf('%s', $stack);
+
+        $stack = phutil_tag(
+          'div',
+          array(
+            'class' => 'unhandled-exception-stack',
+          ),
+          $stack);
+
+        $classes[] = 'unhandled-exception-with-stack';
+      } catch (Exception $trace_exception) {
+        $stack = null;
+      } catch (Throwable $trace_exception) {
+        $stack = null;
+      }
+    }
+
     return phutil_tag(
       'div',
       array(
-        'class' => 'unhandled-exception-detail',
+        'class' => implode(' ', $classes),
       ),
       array(
         phutil_tag(
@@ -79,6 +117,7 @@
             'class' => 'unhandled-exception-body',
           ),
           $body),
+        $stack,
       ));
   }
 
diff --git a/src/aphront/sink/AphrontHTTPSink.php b/src/aphront/sink/AphrontHTTPSink.php
--- a/src/aphront/sink/AphrontHTTPSink.php
+++ b/src/aphront/sink/AphrontHTTPSink.php
@@ -5,14 +5,22 @@
  * Normally this is just @{class:AphrontPHPHTTPSink}, which uses "echo" and
  * "header()" to emit responses.
  *
- * Mostly, this class allows us to do install security or metrics hooks in the
- * output pipeline.
- *
  * @task write  Writing Response Components
  * @task emit   Emitting the Response
  */
 abstract class AphrontHTTPSink extends Phobject {
 
+  private $showStackTraces = false;
+
+  final public function setShowStackTraces($show_stack_traces) {
+    $this->showStackTraces = $show_stack_traces;
+    return $this;
+  }
+
+  final public function getShowStackTraces() {
+    return $this->showStackTraces;
+  }
+
 
 /* -(  Writing Response Components  )---------------------------------------- */
 
diff --git a/src/view/widget/AphrontStackTraceView.php b/src/view/widget/AphrontStackTraceView.php
--- a/src/view/widget/AphrontStackTraceView.php
+++ b/src/view/widget/AphrontStackTraceView.php
@@ -10,7 +10,6 @@
   }
 
   public function render() {
-    $user = $this->getUser();
     $trace = $this->trace;
 
     $libraries = PhutilBootloader::getInstance()->getAllLibraries();
diff --git a/webroot/index.php b/webroot/index.php
--- a/webroot/index.php
+++ b/webroot/index.php
@@ -44,6 +44,7 @@
     try {
       $response = new AphrontUnhandledExceptionResponse();
       $response->setException($main_exception);
+      $response->setShowStackTraces($sink->getShowStackTraces());
 
       PhabricatorStartup::endOutputCapture();
       $sink->writeResponse($response);
diff --git a/webroot/rsrc/css/application/config/unhandled-exception.css b/webroot/rsrc/css/application/config/unhandled-exception.css
--- a/webroot/rsrc/css/application/config/unhandled-exception.css
+++ b/webroot/rsrc/css/application/config/unhandled-exception.css
@@ -8,12 +8,12 @@
   background: #fff;
   border: 1px solid #c0392b;
   border-radius: 3px;
-  padding: 0 8px;
+  padding: 8px;
 }
 
 .unhandled-exception-detail .unhandled-exception-title {
   color: #c0392b;
-  padding: 12px 8px;
+  padding: 4px 8px 12px;
   border-bottom: 1px solid #f4dddb;
   font-size: 16px;
   font-weight: 500;
@@ -23,3 +23,31 @@
 .unhandled-exception-detail .unhandled-exception-body {
   padding: 16px 12px;
 }
+
+.unhandled-exception-with-stack {
+  max-width: 95%;
+}
+
+.unhandled-exception-stack {
+  background: #fcfcfc;
+  overflow-x: auto;
+  overflow-y: hidden;
+}
+
+.unhandled-exception-stack table {
+  border-spacing: 0;
+  border-collapse: collapse;
+  width: 100%;
+  border: 1px solid #d7d7d7;
+}
+
+.unhandled-exception-stack th {
+  background: #e7e7e7;
+  border-bottom: 1px solid #d7d7d7;
+  padding: 8px;
+}
+
+.unhandled-exception-stack td {
+  padding: 4px 8px;
+  white-space: nowrap;
+}