diff --git a/resources/celerity/map.php b/resources/celerity/map.php
index 487da6a02e..69f28b9738 100644
--- a/resources/celerity/map.php
+++ b/resources/celerity/map.php
@@ -78,7 +78,7 @@ return array(
     'rsrc/css/application/files/global-drag-and-drop.css' => '1d2713a4',
     'rsrc/css/application/flag/flag.css' => '2b77be8d',
     'rsrc/css/application/harbormaster/harbormaster.css' => '8dfe16b2',
-    'rsrc/css/application/herald/herald-test.css' => 'e004176f',
+    'rsrc/css/application/herald/herald-test.css' => '7e7bbdae',
     'rsrc/css/application/herald/herald.css' => '648d39e2',
     'rsrc/css/application/maniphest/report.css' => '3d53188b',
     'rsrc/css/application/maniphest/task-edit.css' => '272daa84',
@@ -587,7 +587,7 @@ return array(
     'harbormaster-css' => '8dfe16b2',
     'herald-css' => '648d39e2',
     'herald-rule-editor' => '2633bef7',
-    'herald-test-css' => 'e004176f',
+    'herald-test-css' => '7e7bbdae',
     'inline-comment-summary-css' => '81eb368d',
     'javelin-aphlict' => '022516b4',
     'javelin-behavior' => '1b6acc2a',
diff --git a/src/__phutil_library_map__.php b/src/__phutil_library_map__.php
index 79d318b76d..7b6c30ab71 100644
--- a/src/__phutil_library_map__.php
+++ b/src/__phutil_library_map__.php
@@ -1566,6 +1566,7 @@ phutil_register_library_map(array(
     'HeraldCommentContentField' => 'applications/herald/field/HeraldCommentContentField.php',
     'HeraldCommitAdapter' => 'applications/diffusion/herald/HeraldCommitAdapter.php',
     'HeraldCondition' => 'applications/herald/storage/HeraldCondition.php',
+    'HeraldConditionResult' => 'applications/herald/storage/transcript/HeraldConditionResult.php',
     'HeraldConditionTranscript' => 'applications/herald/storage/transcript/HeraldConditionTranscript.php',
     'HeraldContentSourceField' => 'applications/herald/field/HeraldContentSourceField.php',
     'HeraldController' => 'applications/herald/controller/HeraldController.php',
@@ -7793,6 +7794,7 @@ phutil_register_library_map(array(
       'HarbormasterBuildableAdapterInterface',
     ),
     'HeraldCondition' => 'HeraldDAO',
+    'HeraldConditionResult' => 'Phobject',
     'HeraldConditionTranscript' => 'Phobject',
     'HeraldContentSourceField' => 'HeraldField',
     'HeraldController' => 'PhabricatorController',
diff --git a/src/applications/herald/adapter/HeraldAdapter.php b/src/applications/herald/adapter/HeraldAdapter.php
index 58e0143799..ce6f371d91 100644
--- a/src/applications/herald/adapter/HeraldAdapter.php
+++ b/src/applications/herald/adapter/HeraldAdapter.php
@@ -520,21 +520,29 @@ abstract class HeraldAdapter extends Phobject {
       case self::CONDITION_NOT_REGEXP:
         $result_if_match = ($condition_type == self::CONDITION_REGEXP);
 
+        // We add the 'S' flag because we use the regexp multiple times.
+        // It shouldn't cause any troubles if the flag is already there
+        // - /.*/S is evaluated same as /.*/SS.
+        $condition_pattern = $condition_value.'S';
+
         foreach ((array)$field_value as $value) {
-          // We add the 'S' flag because we use the regexp multiple times.
-          // It shouldn't cause any troubles if the flag is already there
-          // - /.*/S is evaluated same as /.*/SS.
-          $result = @preg_match($condition_value.'S', $value);
-          if ($result === false) {
-            throw new HeraldInvalidConditionException(
-              pht(
-                'Regular expression "%s" in Herald rule "%s" is not valid, '.
-                'or exceeded backtracking or recursion limits while '.
-                'executing. Verify the expression and correct it or rewrite '.
-                'it with less backtracking.',
-                $condition_value,
-                $rule->getMonogram()));
+          try {
+            $result = phutil_preg_match($condition_pattern, $value);
+          } catch (PhutilRegexException $ex) {
+            $message = array();
+            $message[] = pht(
+              'Regular expression "%s" in Herald rule "%s" is not valid, '.
+              'or exceeded backtracking or recursion limits while '.
+              'executing. Verify the expression and correct it or rewrite '.
+              'it with less backtracking.',
+              $condition_value,
+              $rule->getMonogram());
+            $message[] = $ex->getMessage();
+            $message = implode("\n\n", $message);
+
+            throw new HeraldInvalidConditionException($message);
           }
+
           if ($result) {
             return $result_if_match;
           }
diff --git a/src/applications/herald/controller/HeraldTranscriptController.php b/src/applications/herald/controller/HeraldTranscriptController.php
index 7755afaf74..a7498abdb7 100644
--- a/src/applications/herald/controller/HeraldTranscriptController.php
+++ b/src/applications/herald/controller/HeraldTranscriptController.php
@@ -269,34 +269,20 @@ final class HeraldTranscriptController extends HeraldController {
           ->setTarget(phutil_tag('strong', array(), pht('Conditions'))));
 
       foreach ($cond_xscripts as $cond_xscript) {
-        if ($cond_xscript->isForbidden()) {
-          $icon = 'fa-ban';
-          $color = 'indigo';
-          $result = pht('Forbidden');
-        } else if ($cond_xscript->getResult()) {
-          $icon = 'fa-check';
-          $color = 'green';
-          $result = pht('Passed');
-        } else {
-          $icon = 'fa-times';
-          $color = 'red';
-          $result = pht('Failed');
-        }
+        $result = $cond_xscript->getResult();
 
-        if ($cond_xscript->getNote()) {
-          $note_text = $cond_xscript->getNote();
-          if ($cond_xscript->isForbidden()) {
-            $note_text = HeraldStateReasons::getExplanation($note_text);
-          }
+        $icon = $result->getIconIcon();
+        $color = $result->getIconColor();
+        $name = $result->getName();
 
-          $note = phutil_tag(
+        $result_details = $result->newDetailsView();
+        if ($result_details !== null) {
+          $result_details = phutil_tag(
             'div',
             array(
               'class' => 'herald-condition-note',
             ),
-            $note_text);
-        } else {
-          $note = null;
+            $result_details);
         }
 
         // TODO: This is not really translatable and should be driven through
@@ -309,8 +295,8 @@ final class HeraldTranscriptController extends HeraldController {
 
         $cond_item = id(new PHUIStatusItemView())
           ->setIcon($icon, $color)
-          ->setTarget($result)
-          ->setNote(array($explanation, $note));
+          ->setTarget($name)
+          ->setNote(array($explanation, $result_details));
 
         $cond_list->addItem($cond_item);
       }
diff --git a/src/applications/herald/engine/HeraldEngine.php b/src/applications/herald/engine/HeraldEngine.php
index 9ca72821e7..78a3c6c695 100644
--- a/src/applications/herald/engine/HeraldEngine.php
+++ b/src/applications/herald/engine/HeraldEngine.php
@@ -8,7 +8,8 @@ final class HeraldEngine extends Phobject {
   protected $activeRule;
   protected $transcript;
 
-  protected $fieldCache = array();
+  private $fieldCache = array();
+  private $fieldExceptions = array();
   protected $object;
   private $dryRun;
 
@@ -64,6 +65,7 @@ final class HeraldEngine extends Phobject {
     $this->transcript = new HeraldTranscript();
     $this->transcript->setObjectPHID((string)$object->getPHID());
     $this->fieldCache = array();
+    $this->fieldExceptions = array();
     $this->results = array();
     $this->rules   = $rules;
     $this->object  = $object;
@@ -74,6 +76,7 @@ final class HeraldEngine extends Phobject {
 
       $is_first_only = $rule->isRepeatFirst();
 
+      $caught = null;
       try {
         if (!$this->getDryRun() &&
             $is_first_only &&
@@ -119,7 +122,21 @@ final class HeraldEngine extends Phobject {
                 $names));
         }
         $rule_matches = false;
+      } catch (Exception $ex) {
+        $caught = $ex;
+      } catch (Throwable $ex) {
+        $caught = $ex;
       }
+
+      if ($caught) {
+        $this->newRuleTranscript($rules[$phid])
+          ->setResult(false)
+          ->setReason(
+            pht(
+              'Rule encountered an exception while evaluting.'));
+        $rule_matches = false;
+      }
+
       $this->results[$phid] = $rule_matches;
 
       if ($rule_matches) {
@@ -323,42 +340,18 @@ final class HeraldEngine extends Phobject {
       $result = false;
     } else {
       foreach ($conditions as $condition) {
-        try {
-          $this->getConditionObjectValue($condition, $object);
-        } catch (Exception $ex) {
-          $reason = pht(
-            'Field "%s" does not exist!',
-            $condition->getFieldName());
-          $result = false;
-          break;
-        }
-
-        // Here, we're profiling the cost to match the condition value against
-        // whatever test is configured. Normally, this cost should be very
-        // small (<<1ms) since it amounts to a single comparison:
-        //
-        //   [ Task author ][ is any of ][ alice ]
-        //
-        // However, it may be expensive in some cases, particularly if you
-        // write a rule with a very creative regular expression that backtracks
-        // explosively.
-        //
-        // At time of writing, the "Another Herald Rule" field is also
-        // evaluated inside the matching function. This may be arbitrarily
-        // expensive (it can prompt us to execute any finite number of other
-        // Herald rules), although we'll push the profiler stack appropriately
-        // so we don't count the evaluation time against this rule in the final
-        // profile.
-
         $caught = null;
 
-        $this->pushProfilerRule($rule);
         try {
-          $match = $this->doesConditionMatch($rule, $condition, $object);
+          $match = $this->doesConditionMatch(
+            $rule,
+            $condition,
+            $object);
         } catch (Exception $ex) {
           $caught = $ex;
+        } catch (Throwable $ex) {
+          $caught = $ex;
         }
-        $this->popProfilerRule($rule);
 
         if ($caught) {
           throw $ex;
@@ -419,63 +412,176 @@ final class HeraldEngine extends Phobject {
     return $result;
   }
 
-  protected function doesConditionMatch(
+  private function doesConditionMatch(
     HeraldRule $rule,
     HeraldCondition $condition,
-    HeraldAdapter $object) {
+    HeraldAdapter $adapter) {
 
-    $object_value = $this->getConditionObjectValue($condition, $object);
     $transcript = $this->newConditionTranscript($rule, $condition);
 
+    $caught = null;
+    $result_data = array();
+
     try {
-      $result = $object->doesConditionMatch(
-        $this,
+      $field_key = $condition->getFieldName();
+
+      $field_value = $this->getProfiledObjectFieldValue(
+        $adapter,
+        $field_key);
+
+      $is_match = $this->getProfiledConditionMatch(
+        $adapter,
         $rule,
         $condition,
-        $object_value);
+        $field_value);
+      if ($is_match) {
+        $result_code = HeraldConditionResult::RESULT_MATCHED;
+      } else {
+        $result_code = HeraldConditionResult::RESULT_FAILED;
+      }
     } catch (HeraldInvalidConditionException $ex) {
-      $result = false;
-      $transcript->setNote($ex->getMessage());
+      $result_code = HeraldConditionResult::RESULT_INVALID;
+      $caught = $ex;
+    } catch (Exception $ex) {
+      $result_code = HeraldConditionResult::RESULT_EXCEPTION;
+      $caught = $ex;
+    } catch (Throwable $ex) {
+      $result_code = HeraldConditionResult::RESULT_EXCEPTION;
+      $caught = $ex;
     }
 
+    if ($caught) {
+      $result_data = array(
+        'exception.class' => get_class($caught),
+        'exception.message' => $ex->getMessage(),
+      );
+    }
+
+    $result = HeraldConditionResult::newFromResultCode($result_code)
+      ->setResultData($result_data);
+
     $transcript->setResult($result);
 
-    return $result;
-  }
-
-  protected function getConditionObjectValue(
-    HeraldCondition $condition,
-    HeraldAdapter $object) {
-
-    $field = $condition->getFieldName();
-
-    return $this->getObjectFieldValue($field);
-  }
-
-  public function getObjectFieldValue($field) {
-    if (!array_key_exists($field, $this->fieldCache)) {
-      $adapter = $this->object;
-
-      $adapter->willGetHeraldField($field);
-
-      $caught = null;
-
-      $this->pushProfilerField($field);
-      try {
-        $value = $adapter->getHeraldField($field);
-      } catch (Exception $ex) {
-        $caught = $ex;
-      }
-      $this->popProfilerField($field);
-
-      if ($caught) {
-        throw $caught;
-      }
-
-      $this->fieldCache[$field] = $value;
+    if ($caught) {
+      throw $caught;
     }
 
-    return $this->fieldCache[$field];
+    return $result->getIsMatch();
+  }
+
+  private function getProfiledConditionMatch(
+    HeraldAdapter $adapter,
+    HeraldRule $rule,
+    HeraldCondition $condition,
+    $field_value) {
+
+    // Here, we're profiling the cost to match the condition value against
+    // whatever test is configured. Normally, this cost should be very
+    // small (<<1ms) since it amounts to a single comparison:
+    //
+    //   [ Task author ][ is any of ][ alice ]
+    //
+    // However, it may be expensive in some cases, particularly if you
+    // write a rule with a very creative regular expression that backtracks
+    // explosively.
+    //
+    // At time of writing, the "Another Herald Rule" field is also
+    // evaluated inside the matching function. This may be arbitrarily
+    // expensive (it can prompt us to execute any finite number of other
+    // Herald rules), although we'll push the profiler stack appropriately
+    // so we don't count the evaluation time against this rule in the final
+    // profile.
+
+    $this->pushProfilerRule($rule);
+
+    $caught = null;
+    try {
+      $is_match = $adapter->doesConditionMatch(
+        $this,
+        $rule,
+        $condition,
+        $field_value);
+    } catch (Exception $ex) {
+      $caught = $ex;
+    } catch (Throwable $ex) {
+      $caught = $ex;
+    }
+
+    $this->popProfilerRule($rule);
+
+    if ($caught) {
+      throw $caught;
+    }
+
+    return $is_match;
+  }
+
+  private function getProfiledObjectFieldValue(
+    HeraldAdapter $adapter,
+    $field_key) {
+
+    // Before engaging the profiler, make sure the field class is loaded.
+
+    $adapter->willGetHeraldField($field_key);
+
+    // The first time we read a field value, we'll actually generate it, which
+    // may be slow.
+
+    // After it is generated for the first time, this will just read it from a
+    // cache, which should be very fast.
+
+    // We still want to profile the request even if it goes to cache so we can
+    // get an accurate count of how many times we access the field value: when
+    // trying to improve the performance of Herald rules, it's helpful to know
+    // how many rules rely on the value of a field which is slow to generate.
+
+    $caught = null;
+
+    $this->pushProfilerField($field_key);
+    try {
+      $value = $this->getObjectFieldValue($field_key);
+    } catch (Exception $ex) {
+      $caught = $ex;
+    } catch (Throwable $ex) {
+      $caught = $ex;
+    }
+    $this->popProfilerField($field_key);
+
+    if ($caught) {
+      throw $caught;
+    }
+
+    return $value;
+  }
+
+  private function getObjectFieldValue($field_key) {
+    if (array_key_exists($field_key, $this->fieldExceptions)) {
+      throw $this->fieldExceptions[$field_key];
+    }
+
+    if (array_key_exists($field_key, $this->fieldCache)) {
+      return $this->fieldCache[$field_key];
+    }
+
+    $adapter = $this->object;
+
+    $caught = null;
+    try {
+      $value = $adapter->getHeraldField($field_key);
+    } catch (Exception $ex) {
+      $caught = $ex;
+    } catch (Throwable $ex) {
+      $caught = $ex;
+    }
+
+    if ($caught) {
+      $this->fieldExceptions[$field_key] = $caught;
+      throw $caught;
+    }
+
+    $this->fieldCache[$field_key] = $value;
+
+    return $value;
   }
 
   protected function getRuleEffects(
@@ -639,9 +745,16 @@ final class HeraldEngine extends Phobject {
 
       $forbidden_reason = $this->forbiddenFields[$field_key];
       if ($forbidden_reason !== null) {
+        $result_code = HeraldConditionResult::RESULT_OBJECT_STATE;
+        $result_data = array(
+          'reason' => $forbidden_reason,
+        );
+
+        $result = HeraldConditionResult::newFromResultCode($result_code)
+          ->setResultData($result_data);
+
         $this->newConditionTranscript($rule, $condition)
-          ->setResult(HeraldConditionTranscript::RESULT_FORBIDDEN)
-          ->setNote($forbidden_reason);
+          ->setResult($result);
 
         $is_forbidden = true;
       }
diff --git a/src/applications/herald/storage/transcript/HeraldConditionResult.php b/src/applications/herald/storage/transcript/HeraldConditionResult.php
new file mode 100644
index 0000000000..16e240b3f8
--- /dev/null
+++ b/src/applications/herald/storage/transcript/HeraldConditionResult.php
@@ -0,0 +1,177 @@
+<?php
+
+final class HeraldConditionResult
+  extends Phobject {
+
+  const RESULT_MATCHED = 'matched';
+  const RESULT_FAILED = 'failed';
+  const RESULT_OBJECT_STATE = 'object-state';
+  const RESULT_INVALID = 'invalid';
+  const RESULT_EXCEPTION = 'exception';
+  const RESULT_UNKNOWN = 'unknown';
+
+  private $resultCode;
+  private $resultData = array();
+
+  public function toMap() {
+    return array(
+      'code' => $this->getResultCode(),
+      'data' => $this->getResultData(),
+    );
+  }
+
+  public static function newFromMap(array $map) {
+    $result_code = idx($map, 'code');
+    $result = self::newFromResultCode($result_code);
+
+    $result_data = idx($map, 'data', array());
+    $result->setResultData($result_data);
+
+    return $result;
+  }
+
+  public static function newFromResultCode($result_code) {
+    $map = self::getResultSpecification($result_code);
+
+    $result = new self();
+    $result->resultCode = $result_code;
+
+    return $result;
+  }
+
+  public function getResultCode() {
+    return $this->resultCode;
+  }
+
+  private function getResultData() {
+    return $this->resultData;
+  }
+
+  public function getIconIcon() {
+    return $this->getSpecificationProperty('icon');
+  }
+
+  public function getIconColor() {
+    return $this->getSpecificationProperty('color.icon');
+  }
+
+  public function getIsMatch() {
+    return ($this->getSpecificationProperty('match') === true);
+  }
+
+  public function getName() {
+    return $this->getSpecificationProperty('name');
+  }
+
+  public function newDetailsView() {
+    switch ($this->resultCode) {
+      case self::RESULT_OBJECT_STATE:
+        $reason = $this->getDataProperty('reason');
+        $details = HeraldStateReasons::getExplanation($reason);
+        break;
+      case self::RESULT_INVALID:
+      case self::RESULT_EXCEPTION:
+        $error_class = $this->getDataProperty('exception.class');
+        $error_message = $this->getDataProperty('exception.message');
+
+        if (!strlen($error_class)) {
+          $error_class = pht('Unknown Error');
+        }
+
+        switch ($error_class) {
+          case 'HeraldInvalidConditionException':
+            $error_class = pht('Invalid Condition');
+            break;
+        }
+
+        if (!strlen($error_message)) {
+          $error_message = pht(
+            'An unknown error occurred while evaluating this condition. No '.
+            'additional information is available.');
+        }
+
+        $details = pht(
+          '%s: %s',
+          phutil_tag('strong', array(), $error_class),
+          phutil_escape_html_newlines($error_message));
+        break;
+        $details = 'exception';
+        break;
+      default:
+        $details = null;
+        break;
+    }
+
+    return $details;
+  }
+
+  public function setResultData(array $result_data) {
+    $this->resultData = $result_data;
+    return $this;
+  }
+
+  private function getDataProperty($key) {
+    $data = $this->getResultData();
+    return idx($data, $key);
+  }
+
+  private function getSpecificationProperty($key) {
+    $map = self::getResultSpecification($this->resultCode);
+    return $map[$key];
+  }
+
+  private static function getResultSpecification($result_code) {
+    $map = self::getResultSpecificationMap();
+
+    if (!isset($map[$result_code])) {
+      throw new Exception(
+        pht(
+          'Condition result "%s" is unknown.',
+          $result_code));
+    }
+
+    return $map[$result_code];
+  }
+
+  private static function getResultSpecificationMap() {
+    return array(
+      self::RESULT_MATCHED => array(
+        'match' => true,
+        'icon' => 'fa-check',
+        'color.icon' => 'green',
+        'name' => pht('Passed'),
+      ),
+      self::RESULT_FAILED => array(
+        'match' => false,
+        'icon' => 'fa-times',
+        'color.icon' => 'red',
+        'name' => pht('Failed'),
+      ),
+      self::RESULT_OBJECT_STATE => array(
+        'match' => null,
+        'icon' => 'fa-ban',
+        'color.icon' => 'indigo',
+        'name' => pht('Forbidden'),
+      ),
+      self::RESULT_INVALID => array(
+        'match' => null,
+        'icon' => 'fa-exclamation-triangle',
+        'color.icon' => 'yellow',
+        'name' => pht('Invalid'),
+      ),
+      self::RESULT_EXCEPTION => array(
+        'match' => null,
+        'icon' => 'fa-exclamation-triangle',
+        'color.icon' => 'red',
+        'name' => pht('Exception'),
+      ),
+      self::RESULT_UNKNOWN => array(
+        'match' => null,
+        'icon' => 'fa-question',
+        'color.icon' => 'grey',
+        'name' => pht('Unknown'),
+      ),
+    );
+  }
+
+}
diff --git a/src/applications/herald/storage/transcript/HeraldConditionTranscript.php b/src/applications/herald/storage/transcript/HeraldConditionTranscript.php
index a7096b6880..2e66cea1fb 100644
--- a/src/applications/herald/storage/transcript/HeraldConditionTranscript.php
+++ b/src/applications/herald/storage/transcript/HeraldConditionTranscript.php
@@ -7,10 +7,17 @@ final class HeraldConditionTranscript extends Phobject {
   protected $fieldName;
   protected $condition;
   protected $testValue;
-  protected $note;
-  protected $result;
+  protected $resultMap;
 
-  const RESULT_FORBIDDEN = 'forbidden';
+  // See T13586. Older versions of this record stored a boolean true, boolean
+  // false, or the string "forbidden" in the "$result" field. They stored a
+  // human-readable English-language message or a state code in the "$note"
+  // field.
+
+  // The modern record does not use either field.
+
+  protected $result;
+  protected $note;
 
   public function setRuleID($rule_id) {
     $this->ruleID = $rule_id;
@@ -57,26 +64,39 @@ final class HeraldConditionTranscript extends Phobject {
     return $this->testValue;
   }
 
-  public function setNote($note) {
-    $this->note = $note;
-    return $this;
-  }
-
-  public function getNote() {
-    return $this->note;
-  }
-
-  public function setResult($result) {
-    $this->result = $result;
+  public function setResult(HeraldConditionResult $result) {
+    $this->resultMap = $result->toMap();
     return $this;
   }
 
   public function getResult() {
-    return $this->result;
-  }
+    $map = $this->resultMap;
 
-  public function isForbidden() {
-    return ($this->getResult() === self::RESULT_FORBIDDEN);
+    if (is_array($map)) {
+      $result = HeraldConditionResult::newFromMap($map);
+    } else {
+      $legacy_result = $this->result;
+
+      $result_data = array();
+
+      if ($legacy_result === 'forbidden') {
+        $result_code = HeraldConditionResult::RESULT_OBJECT_STATE;
+        $result_data = array(
+          'reason' => $this->note,
+        );
+      } else if ($legacy_result === true) {
+        $result_code = HeraldConditionResult::RESULT_MATCHED;
+      } else if ($legacy_result === false) {
+        $result_code = HeraldConditionResult::RESULT_FAILED;
+      } else {
+        $result_code = HeraldConditionResult::RESULT_UNKNOWN;
+      }
+
+      $result = HeraldConditionResult::newFromResultCode($result_code)
+        ->setResultData($result_data);
+    }
+
+    return $result;
   }
 
 }
diff --git a/webroot/rsrc/css/application/herald/herald-test.css b/webroot/rsrc/css/application/herald/herald-test.css
index 67b49145d5..e673020464 100644
--- a/webroot/rsrc/css/application/herald/herald-test.css
+++ b/webroot/rsrc/css/application/herald/herald-test.css
@@ -4,6 +4,8 @@
 
 .herald-condition-note {
   color: {$red};
+  padding: 4px 0;
+  margin: 4px 0 8px;
 }
 
 textarea.herald-field-value-transcript {