diff --git a/src/__phutil_library_map__.php b/src/__phutil_library_map__.php
index 849d4d4702..f4a410ad2e 100644
--- a/src/__phutil_library_map__.php
+++ b/src/__phutil_library_map__.php
@@ -860,6 +860,7 @@ phutil_register_library_map(array(
     'DiffusionRepositoryEditDangerousController' => 'applications/diffusion/controller/DiffusionRepositoryEditDangerousController.php',
     'DiffusionRepositoryEditDeleteController' => 'applications/diffusion/controller/DiffusionRepositoryEditDeleteController.php',
     'DiffusionRepositoryEditEngine' => 'applications/diffusion/editor/DiffusionRepositoryEditEngine.php',
+    'DiffusionRepositoryEditEnormousController' => 'applications/diffusion/controller/DiffusionRepositoryEditEnormousController.php',
     'DiffusionRepositoryEditUpdateController' => 'applications/diffusion/controller/DiffusionRepositoryEditUpdateController.php',
     'DiffusionRepositoryFunctionDatasource' => 'applications/diffusion/typeahead/DiffusionRepositoryFunctionDatasource.php',
     'DiffusionRepositoryHistoryManagementPanel' => 'applications/diffusion/management/DiffusionRepositoryHistoryManagementPanel.php',
@@ -1007,6 +1008,7 @@ phutil_register_library_map(array(
     'DrydockBlueprintCustomField' => 'applications/drydock/customfield/DrydockBlueprintCustomField.php',
     'DrydockBlueprintDatasource' => 'applications/drydock/typeahead/DrydockBlueprintDatasource.php',
     'DrydockBlueprintDisableController' => 'applications/drydock/controller/DrydockBlueprintDisableController.php',
+    'DrydockBlueprintDisableTransaction' => 'applications/drydock/xaction/DrydockBlueprintDisableTransaction.php',
     'DrydockBlueprintEditConduitAPIMethod' => 'applications/drydock/conduit/DrydockBlueprintEditConduitAPIMethod.php',
     'DrydockBlueprintEditController' => 'applications/drydock/controller/DrydockBlueprintEditController.php',
     'DrydockBlueprintEditEngine' => 'applications/drydock/editor/DrydockBlueprintEditEngine.php',
@@ -1015,12 +1017,15 @@ phutil_register_library_map(array(
     'DrydockBlueprintImplementationTestCase' => 'applications/drydock/blueprint/__tests__/DrydockBlueprintImplementationTestCase.php',
     'DrydockBlueprintListController' => 'applications/drydock/controller/DrydockBlueprintListController.php',
     'DrydockBlueprintNameNgrams' => 'applications/drydock/storage/DrydockBlueprintNameNgrams.php',
+    'DrydockBlueprintNameTransaction' => 'applications/drydock/xaction/DrydockBlueprintNameTransaction.php',
     'DrydockBlueprintPHIDType' => 'applications/drydock/phid/DrydockBlueprintPHIDType.php',
     'DrydockBlueprintQuery' => 'applications/drydock/query/DrydockBlueprintQuery.php',
     'DrydockBlueprintSearchConduitAPIMethod' => 'applications/drydock/conduit/DrydockBlueprintSearchConduitAPIMethod.php',
     'DrydockBlueprintSearchEngine' => 'applications/drydock/query/DrydockBlueprintSearchEngine.php',
     'DrydockBlueprintTransaction' => 'applications/drydock/storage/DrydockBlueprintTransaction.php',
     'DrydockBlueprintTransactionQuery' => 'applications/drydock/query/DrydockBlueprintTransactionQuery.php',
+    'DrydockBlueprintTransactionType' => 'applications/drydock/xaction/DrydockBlueprintTransactionType.php',
+    'DrydockBlueprintTypeTransaction' => 'applications/drydock/xaction/DrydockBlueprintTypeTransaction.php',
     'DrydockBlueprintViewController' => 'applications/drydock/controller/DrydockBlueprintViewController.php',
     'DrydockCommand' => 'applications/drydock/storage/DrydockCommand.php',
     'DrydockCommandError' => 'applications/drydock/exception/DrydockCommandError.php',
@@ -5923,6 +5928,7 @@ phutil_register_library_map(array(
     'DiffusionRepositoryEditDangerousController' => 'DiffusionRepositoryManageController',
     'DiffusionRepositoryEditDeleteController' => 'DiffusionRepositoryManageController',
     'DiffusionRepositoryEditEngine' => 'PhabricatorEditEngine',
+    'DiffusionRepositoryEditEnormousController' => 'DiffusionRepositoryManageController',
     'DiffusionRepositoryEditUpdateController' => 'DiffusionRepositoryManageController',
     'DiffusionRepositoryFunctionDatasource' => 'PhabricatorTypeaheadCompositeDatasource',
     'DiffusionRepositoryHistoryManagementPanel' => 'DiffusionRepositoryManagementPanel',
@@ -6100,6 +6106,7 @@ phutil_register_library_map(array(
     'DrydockBlueprintCustomField' => 'PhabricatorCustomField',
     'DrydockBlueprintDatasource' => 'PhabricatorTypeaheadDatasource',
     'DrydockBlueprintDisableController' => 'DrydockBlueprintController',
+    'DrydockBlueprintDisableTransaction' => 'DrydockBlueprintTransactionType',
     'DrydockBlueprintEditConduitAPIMethod' => 'PhabricatorEditEngineAPIMethod',
     'DrydockBlueprintEditController' => 'DrydockBlueprintController',
     'DrydockBlueprintEditEngine' => 'PhabricatorEditEngine',
@@ -6108,12 +6115,15 @@ phutil_register_library_map(array(
     'DrydockBlueprintImplementationTestCase' => 'PhabricatorTestCase',
     'DrydockBlueprintListController' => 'DrydockBlueprintController',
     'DrydockBlueprintNameNgrams' => 'PhabricatorSearchNgrams',
+    'DrydockBlueprintNameTransaction' => 'DrydockBlueprintTransactionType',
     'DrydockBlueprintPHIDType' => 'PhabricatorPHIDType',
     'DrydockBlueprintQuery' => 'DrydockQuery',
     'DrydockBlueprintSearchConduitAPIMethod' => 'PhabricatorSearchEngineAPIMethod',
     'DrydockBlueprintSearchEngine' => 'PhabricatorApplicationSearchEngine',
-    'DrydockBlueprintTransaction' => 'PhabricatorApplicationTransaction',
+    'DrydockBlueprintTransaction' => 'PhabricatorModularTransaction',
     'DrydockBlueprintTransactionQuery' => 'PhabricatorApplicationTransactionQuery',
+    'DrydockBlueprintTransactionType' => 'PhabricatorModularTransactionType',
+    'DrydockBlueprintTypeTransaction' => 'DrydockBlueprintTransactionType',
     'DrydockBlueprintViewController' => 'DrydockBlueprintController',
     'DrydockCommand' => array(
       'DrydockDAO',
diff --git a/src/applications/diffusion/application/PhabricatorDiffusionApplication.php b/src/applications/diffusion/application/PhabricatorDiffusionApplication.php
index 5a426ec299..5797b8ba7c 100644
--- a/src/applications/diffusion/application/PhabricatorDiffusionApplication.php
+++ b/src/applications/diffusion/application/PhabricatorDiffusionApplication.php
@@ -89,6 +89,7 @@ final class PhabricatorDiffusionApplication extends PhabricatorApplication {
         'edit/' => array(
           'activate/' => 'DiffusionRepositoryEditActivateController',
           'dangerous/' => 'DiffusionRepositoryEditDangerousController',
+          'enormous/' => 'DiffusionRepositoryEditEnormousController',
           'delete/' => 'DiffusionRepositoryEditDeleteController',
           'update/' => 'DiffusionRepositoryEditUpdateController',
           'testautomation/' => 'DiffusionRepositoryTestAutomationController',
diff --git a/src/applications/diffusion/controller/DiffusionCommitController.php b/src/applications/diffusion/controller/DiffusionCommitController.php
index 11463ef97d..b4d06989c2 100644
--- a/src/applications/diffusion/controller/DiffusionCommitController.php
+++ b/src/applications/diffusion/controller/DiffusionCommitController.php
@@ -277,9 +277,9 @@ final class DiffusionCommitController extends DiffusionController {
           'This commit is empty and does not affect any paths.'));
     } else if ($was_limited) {
       $info_panel = $this->renderStatusMessage(
-        pht('Enormous Commit'),
+        pht('Very Large Commit'),
         pht(
-          'This commit is enormous, and affects more than %d files. '.
+          'This commit is very large, and affects more than %d files. '.
           'Changes are not shown.',
           $hard_limit));
     } else if (!$this->getCommitExists()) {
diff --git a/src/applications/diffusion/controller/DiffusionRepositoryEditEnormousController.php b/src/applications/diffusion/controller/DiffusionRepositoryEditEnormousController.php
new file mode 100644
index 0000000000..d4eeb118d7
--- /dev/null
+++ b/src/applications/diffusion/controller/DiffusionRepositoryEditEnormousController.php
@@ -0,0 +1,90 @@
+<?php
+
+final class DiffusionRepositoryEditEnormousController
+  extends DiffusionRepositoryManageController {
+
+  public function handleRequest(AphrontRequest $request) {
+    $response = $this->loadDiffusionContextForEdit();
+    if ($response) {
+      return $response;
+    }
+
+    $viewer = $this->getViewer();
+    $drequest = $this->getDiffusionRequest();
+    $repository = $drequest->getRepository();
+
+    $panel_uri = id(new DiffusionRepositoryBasicsManagementPanel())
+      ->setRepository($repository)
+      ->getPanelURI();
+
+    if (!$repository->canAllowEnormousChanges()) {
+      return $this->newDialog()
+        ->setTitle(pht('Unprotectable Repository'))
+        ->appendParagraph(
+          pht(
+            'This repository can not be protected from enormous changes '.
+            'because Phabricator does not control what users are allowed '.
+            'to push to it.'))
+        ->addCancelButton($panel_uri);
+    }
+
+    if ($request->isFormPost()) {
+      $xaction = id(new PhabricatorRepositoryTransaction())
+        ->setTransactionType(PhabricatorRepositoryTransaction::TYPE_ENORMOUS)
+        ->setNewValue(!$repository->shouldAllowEnormousChanges());
+
+      $editor = id(new PhabricatorRepositoryEditor())
+        ->setContinueOnNoEffect(true)
+        ->setContentSourceFromRequest($request)
+        ->setActor($viewer)
+        ->applyTransactions($repository, array($xaction));
+
+      return id(new AphrontReloadResponse())->setURI($panel_uri);
+    }
+
+    if ($repository->shouldAllowEnormousChanges()) {
+      $title = pht('Prevent Enormous Changes');
+
+      $body = pht(
+        'It will no longer be possible to push enormous changes to this '.
+        'repository.');
+
+      $submit = pht('Prevent Enormous Changes');
+    } else {
+      $title = pht('Allow Enormous Changes');
+
+      $body = array(
+        pht(
+          'If you allow enormous changes, users can push commits which are '.
+          'too large for Herald to process content rules for. This can allow '.
+          'users to evade content rules implemented in Herald.'),
+        pht(
+          'You can selectively configure Herald by adding rules to prevent a '.
+          'subset of enormous changes (for example, based on who is trying '.
+          'to push the change).'),
+      );
+
+      $submit = pht('Allow Enormous Changes');
+    }
+
+    $more_help = pht(
+      'Enormous changes are commits which are too large to process with '.
+      'content rules because: the diff text for the change is larger than '.
+      '%s bytes; or the diff text takes more than %s seconds to extract.',
+      new PhutilNumber(HeraldCommitAdapter::getEnormousByteLimit()),
+      new PhutilNumber(HeraldCommitAdapter::getEnormousTimeLimit()));
+
+    $response = $this->newDialog();
+
+      foreach ((array)$body as $paragraph) {
+        $response->appendParagraph($paragraph);
+      }
+
+    return $response
+      ->setTitle($title)
+      ->appendParagraph($more_help)
+      ->addSubmitButton($submit)
+      ->addCancelButton($panel_uri);
+  }
+
+}
diff --git a/src/applications/diffusion/editor/DiffusionRepositoryEditEngine.php b/src/applications/diffusion/editor/DiffusionRepositoryEditEngine.php
index b3baafbd06..dcb79a6c86 100644
--- a/src/applications/diffusion/editor/DiffusionRepositoryEditEngine.php
+++ b/src/applications/diffusion/editor/DiffusionRepositoryEditEngine.php
@@ -309,6 +309,19 @@ final class DiffusionRepositoryEditEngine
         ->setConduitDescription(pht('Allow or prevent dangerous changes.'))
         ->setConduitTypeDescription(pht('New protection setting.'))
         ->setValue($object->shouldAllowDangerousChanges()),
+      id(new PhabricatorBoolEditField())
+        ->setKey('allowEnormousChanges')
+        ->setLabel(pht('Allow Enormous Changes'))
+        ->setIsCopyable(true)
+        ->setIsConduitOnly(true)
+        ->setOptions(
+          pht('Prevent Enormous Changes'),
+          pht('Allow Enormous Changes'))
+        ->setTransactionType(PhabricatorRepositoryTransaction::TYPE_ENORMOUS)
+        ->setDescription(pht('Permit enormous changes to be made.'))
+        ->setConduitDescription(pht('Allow or prevent enormous changes.'))
+        ->setConduitTypeDescription(pht('New protection setting.'))
+        ->setValue($object->shouldAllowEnormousChanges()),
       id(new PhabricatorSelectEditField())
         ->setKey('status')
         ->setLabel(pht('Status'))
diff --git a/src/applications/diffusion/engine/DiffusionCommitHookEngine.php b/src/applications/diffusion/engine/DiffusionCommitHookEngine.php
index 7fe45834b3..99df0e54af 100644
--- a/src/applications/diffusion/engine/DiffusionCommitHookEngine.php
+++ b/src/applications/diffusion/engine/DiffusionCommitHookEngine.php
@@ -34,6 +34,7 @@ final class DiffusionCommitHookEngine extends Phobject {
   private $rejectCode = PhabricatorRepositoryPushLog::REJECT_BROKEN;
   private $rejectDetails;
   private $emailPHIDs = array();
+  private $changesets = array();
 
 
 /* -(  Config  )------------------------------------------------------------- */
@@ -131,6 +132,15 @@ final class DiffusionCommitHookEngine extends Phobject {
       $this->applyHeraldRefRules($ref_updates, $all_updates);
 
       $content_updates = $this->findContentUpdates($ref_updates);
+
+      try {
+        $this->rejectEnormousChanges($content_updates);
+      } catch (DiffusionCommitHookRejectException $ex) {
+        // If we're rejecting enormous changes, flag everything.
+        $this->rejectCode = PhabricatorRepositoryPushLog::REJECT_ENORMOUS;
+        throw $ex;
+      }
+
       $all_updates = array_merge($all_updates, $content_updates);
 
       $this->applyHeraldContentRules($content_updates, $all_updates);
@@ -1079,7 +1089,37 @@ final class DiffusionCommitHookEngine extends Phobject {
       ->setEpoch(time());
   }
 
-  public function loadChangesetsForCommit($identifier) {
+  private function rejectEnormousChanges(array $content_updates) {
+    $repository = $this->getRepository();
+    if ($repository->shouldAllowEnormousChanges()) {
+      return;
+    }
+
+    foreach ($content_updates as $update) {
+      $identifier = $update->getRefNew();
+      try {
+        $changesets = $this->loadChangesetsForCommit($identifier);
+        $this->changesets[$identifier] = $changesets;
+      } catch (Exception $ex) {
+        $this->changesets[$identifier] = $ex;
+
+        $message = pht(
+          'ENORMOUS CHANGE'.
+          "\n".
+          'Enormous change protection is enabled for this repository, but '.
+          'you are pushing an enormous change ("%s"). Edit the repository '.
+          'configuration before making enormous changes.'.
+          "\n\n".
+          "Content Exception: %s",
+          $identifier,
+          $ex->getMessage());
+
+        throw new DiffusionCommitHookRejectException($message);
+      }
+    }
+  }
+
+  private function loadChangesetsForCommit($identifier) {
     $byte_limit = HeraldCommitAdapter::getEnormousByteLimit();
     $time_limit = HeraldCommitAdapter::getEnormousTimeLimit();
 
@@ -1126,9 +1166,10 @@ final class DiffusionCommitHookEngine extends Phobject {
     if (strlen($raw_diff) >= $byte_limit) {
       throw new Exception(
         pht(
-          'The raw text of this change is enormous (larger than %d '.
-          'bytes). Herald can not process it.',
-          $byte_limit));
+          'The raw text of this change ("%s") is enormous (larger than %s '.
+          'bytes).',
+          $identifier,
+          new PhutilNumber($byte_limit)));
     }
 
     if (!strlen($raw_diff)) {
@@ -1143,6 +1184,20 @@ final class DiffusionCommitHookEngine extends Phobject {
     return $diff->getChangesets();
   }
 
+  public function getChangesetsForCommit($identifier) {
+    if (isset($this->changesets[$identifier])) {
+      $cached = $this->changesets[$identifier];
+
+      if ($cached instanceof Exception) {
+        throw $cached;
+      }
+
+      return $cached;
+    }
+
+    return $this->loadChangesetsForCommit($identifier);
+  }
+
   public function loadCommitRefForCommit($identifier) {
     $repository = $this->getRepository();
     $vcs = $repository->getVersionControlSystem();
diff --git a/src/applications/diffusion/herald/HeraldPreCommitContentAdapter.php b/src/applications/diffusion/herald/HeraldPreCommitContentAdapter.php
index f4d7e794a2..c93ba32345 100644
--- a/src/applications/diffusion/herald/HeraldPreCommitContentAdapter.php
+++ b/src/applications/diffusion/herald/HeraldPreCommitContentAdapter.php
@@ -37,7 +37,7 @@ final class HeraldPreCommitContentAdapter extends HeraldPreCommitAdapter {
   public function getDiffContent($type) {
     if ($this->changesets === null) {
       try {
-        $this->changesets = $this->getHookEngine()->loadChangesetsForCommit(
+        $this->changesets = $this->getHookEngine()->getChangesetsForCommit(
           $this->getObject()->getRefNew());
       } catch (Exception $ex) {
         $this->changesets = $ex;
diff --git a/src/applications/diffusion/management/DiffusionRepositoryBasicsManagementPanel.php b/src/applications/diffusion/management/DiffusionRepositoryBasicsManagementPanel.php
index 6e527e81b5..af5e9b2881 100644
--- a/src/applications/diffusion/management/DiffusionRepositoryBasicsManagementPanel.php
+++ b/src/applications/diffusion/management/DiffusionRepositoryBasicsManagementPanel.php
@@ -43,6 +43,7 @@ final class DiffusionRepositoryBasicsManagementPanel
     $delete_uri = $repository->getPathURI('edit/delete/');
     $encoding_uri = $this->getEditPageURI('encoding');
     $dangerous_uri = $repository->getPathURI('edit/dangerous/');
+    $enormous_uri = $repository->getPathURI('edit/enormous/');
 
     if ($repository->isTracked()) {
       $activate_label = pht('Deactivate Repository');
@@ -59,6 +60,15 @@ final class DiffusionRepositoryBasicsManagementPanel
       $can_dangerous = ($can_edit && $repository->canAllowDangerousChanges());
     }
 
+    $should_enormous = $repository->shouldAllowEnormousChanges();
+    if ($should_enormous) {
+      $enormous_name = pht('Prevent Enormous Changes');
+      $can_enormous = $can_edit;
+    } else {
+      $enormous_name = pht('Allow Enormous Changes');
+      $can_enormous = ($can_edit && $repository->canAllowEnormousChanges());
+    }
+
     $action_list->addAction(
       id(new PhabricatorActionView())
         ->setName(pht('Edit Basic Information'))
@@ -80,6 +90,13 @@ final class DiffusionRepositoryBasicsManagementPanel
         ->setDisabled(!$can_dangerous)
         ->setWorkflow(true));
 
+    $action_list->addAction(
+      id(new PhabricatorActionView())
+        ->setName($enormous_name)
+        ->setHref($enormous_uri)
+        ->setDisabled(!$can_enormous)
+        ->setWorkflow(true));
+
     $action_list->addAction(
       id(new PhabricatorActionView())
         ->setHref($activate_uri)
@@ -198,6 +215,20 @@ final class DiffusionRepositoryBasicsManagementPanel
 
     $view->addProperty(pht('Dangerous Changes'), $dangerous);
 
+    $can_enormous = $repository->canAllowEnormousChanges();
+    if (!$can_enormous) {
+      $enormous = phutil_tag('em', array(), pht('Not Preventable'));
+    } else {
+      $should_enormous = $repository->shouldAllowEnormousChanges();
+      if ($should_enormous) {
+        $enormous = pht('Allowed');
+      } else {
+        $enormous = pht('Not Allowed');
+      }
+    }
+
+    $view->addProperty(pht('Enormous Changes'), $enormous);
+
     return $view;
   }
 
diff --git a/src/applications/diffusion/ssh/DiffusionMercurialServeSSHWorkflow.php b/src/applications/diffusion/ssh/DiffusionMercurialServeSSHWorkflow.php
index 4508ae53da..5701a4bac1 100644
--- a/src/applications/diffusion/ssh/DiffusionMercurialServeSSHWorkflow.php
+++ b/src/applications/diffusion/ssh/DiffusionMercurialServeSSHWorkflow.php
@@ -66,17 +66,6 @@ final class DiffusionMercurialServeSSHWorkflow
       ->setWillWriteCallback(array($this, 'willWriteMessageCallback'))
       ->execute();
 
-    // TODO: It's apparently technically possible to communicate errors to
-    // Mercurial over SSH by writing a special "\n<error>\n-\n" string. However,
-    // my attempt to implement that resulted in Mercurial closing the socket and
-    // then hanging, without showing the error. This might be an issue on our
-    // side (we need to close our half of the socket?), or maybe the code
-    // for this in Mercurial doesn't actually work, or maybe something else
-    // is afoot. At some point, we should look into doing this more cleanly.
-    // For now, when we, e.g., reject writes for policy reasons, the user will
-    // see "abort: unexpected response: empty string" after the diagnostically
-    // useful, e.g., "remote: This repository is read-only over SSH." message.
-
     if (!$err && $this->didSeeWrite) {
       $repository->writeStatusMessage(
         PhabricatorRepositoryStatusMessage::TYPE_NEEDS_UPDATE,
@@ -109,14 +98,7 @@ final class DiffusionMercurialServeSSHWorkflow
       $this->didSeeWrite = true;
     }
 
-    $raw_message = $message['raw'];
-    if ($command == 'capabilities') {
-      $raw_message = DiffusionMercurialWireProtocol::filterBundle2Capability(
-        $raw_message);
-    }
-
-    // If we're good, return the raw message data.
-    return $raw_message;
+    return $message['raw'];
   }
 
   protected function raiseWrongVCSException(
diff --git a/src/applications/diffusion/ssh/DiffusionMercurialWireClientSSHProtocolChannel.php b/src/applications/diffusion/ssh/DiffusionMercurialWireClientSSHProtocolChannel.php
index 5150ef9352..8eb026d8fe 100644
--- a/src/applications/diffusion/ssh/DiffusionMercurialWireClientSSHProtocolChannel.php
+++ b/src/applications/diffusion/ssh/DiffusionMercurialWireClientSSHProtocolChannel.php
@@ -180,6 +180,15 @@ final class DiffusionMercurialWireClientSSHProtocolChannel
           $this->state = 'arguments';
         }
       } else if ($this->state == 'data-length') {
+
+        // We're reading the length of a chunk of raw data. It looks like
+        // this:
+        //
+        //   <length-in-bytes>\n
+        //
+        // The length is human-readable text (for example, "4096"), and
+        // may be 0.
+
         $line = $this->readProtocolLine();
         if ($line === null) {
           break;
@@ -192,10 +201,27 @@ final class DiffusionMercurialWireClientSSHProtocolChannel
           $this->state = 'data-bytes';
         }
       } else if ($this->state == 'data-bytes') {
+
+        // We're reading some known, nonzero number of raw bytes of data.
+
+        // If we don't have any more bytes on the buffer yet, just bail:
+        // otherwise, we'll emit a pointless and possibly harmful 0-byte data
+        // frame. See T13036 for discussion.
+        if (!strlen($this->buffer)) {
+          break;
+        }
+
         $bytes = substr($this->buffer, 0, $this->expectBytes);
         $this->buffer = substr($this->buffer, strlen($bytes));
         $this->expectBytes -= strlen($bytes);
 
+        // NOTE: We emit a data frame as soon as we read some data. This can
+        // cause us to repackage frames: for example, if we receive one large
+        // frame slowly, we may emit it as several smaller frames. In theory
+        // this is good; in practice, Mercurial never seems to select a frame
+        // size larger than 4096 bytes naturally and this may be more
+        // complexity and trouble than it is worth. See T13036.
+
         $messages[] = $this->newDataMessage($bytes);
 
         if (!$this->expectBytes) {
diff --git a/src/applications/drydock/conduit/DrydockBlueprintEditConduitAPIMethod.php b/src/applications/drydock/conduit/DrydockBlueprintEditConduitAPIMethod.php
index 764c077d87..7a120f7c5b 100644
--- a/src/applications/drydock/conduit/DrydockBlueprintEditConduitAPIMethod.php
+++ b/src/applications/drydock/conduit/DrydockBlueprintEditConduitAPIMethod.php
@@ -13,8 +13,7 @@ final class DrydockBlueprintEditConduitAPIMethod
 
   public function getMethodSummary() {
     return pht(
-      'WARNING: Apply transactions to edit an existing blueprint. This method '.
-      'can not create new blueprints.');
+      'Apply transactions to create or edit a blueprint.');
   }
 
 }
diff --git a/src/applications/drydock/controller/DrydockBlueprintDisableController.php b/src/applications/drydock/controller/DrydockBlueprintDisableController.php
index 525e55228b..60fc8b0d74 100644
--- a/src/applications/drydock/controller/DrydockBlueprintDisableController.php
+++ b/src/applications/drydock/controller/DrydockBlueprintDisableController.php
@@ -28,7 +28,8 @@ final class DrydockBlueprintDisableController
       $xactions = array();
 
       $xactions[] = id(new DrydockBlueprintTransaction())
-        ->setTransactionType(DrydockBlueprintTransaction::TYPE_DISABLED)
+        ->setTransactionType(
+          DrydockBlueprintDisableTransaction::TRANSACTIONTYPE)
         ->setNewValue($is_disable ? 1 : 0);
 
       $editor = id(new DrydockBlueprintEditor())
diff --git a/src/applications/drydock/editor/DrydockBlueprintEditEngine.php b/src/applications/drydock/editor/DrydockBlueprintEditEngine.php
index 020fe7514c..6bd1366ef0 100644
--- a/src/applications/drydock/editor/DrydockBlueprintEditEngine.php
+++ b/src/applications/drydock/editor/DrydockBlueprintEditEngine.php
@@ -51,6 +51,38 @@ final class DrydockBlueprintEditEngine
     return $blueprint;
   }
 
+  protected function newEditableObjectFromConduit(array $raw_xactions) {
+    $type = null;
+    foreach ($raw_xactions as $raw_xaction) {
+      if ($raw_xaction['type'] !== 'type') {
+        continue;
+      }
+
+      $type = $raw_xaction['value'];
+    }
+
+    if ($type === null) {
+      throw new Exception(
+        pht(
+          'When creating a new Drydock blueprint via the Conduit API, you '.
+          'must provide a "type" transaction to select a type.'));
+    }
+
+    $map = DrydockBlueprintImplementation::getAllBlueprintImplementations();
+    if (!isset($map[$type])) {
+      throw new Exception(
+        pht(
+          'Blueprint type "%s" is unrecognized. Valid types are: %s.',
+          $type,
+          implode(', ', array_keys($map))));
+    }
+
+    $impl = clone $map[$type];
+    $this->setBlueprintImplementation($impl);
+
+    return $this->newEditableObject();
+  }
+
   protected function newEditableObjectForDocumentation() {
     // In order to generate the proper list of fields/transactions for a
     // blueprint, a blueprint's type needs to be known upfront, and there's
@@ -112,16 +144,27 @@ final class DrydockBlueprintEditEngine
     $impl = $object->getImplementation();
 
     return array(
+      // This field appears in the web UI
       id(new PhabricatorStaticEditField())
-        ->setKey('type')
+        ->setKey('displayType')
         ->setLabel(pht('Blueprint Type'))
         ->setDescription(pht('Type of blueprint.'))
         ->setValue($impl->getBlueprintName()),
+      id(new PhabricatorTextEditField())
+        ->setKey('type')
+        ->setLabel(pht('Type'))
+        ->setIsConduitOnly(true)
+        ->setTransactionType(
+          DrydockBlueprintTypeTransaction::TRANSACTIONTYPE)
+        ->setDescription(pht('When creating a blueprint, set the type.'))
+        ->setConduitDescription(pht('Set the blueprint type.'))
+        ->setConduitTypeDescription(pht('Blueprint type.'))
+        ->setValue($object->getClassName()),
       id(new PhabricatorTextEditField())
         ->setKey('name')
         ->setLabel(pht('Name'))
         ->setDescription(pht('Name of the blueprint.'))
-        ->setTransactionType(DrydockBlueprintTransaction::TYPE_NAME)
+        ->setTransactionType(DrydockBlueprintNameTransaction::TRANSACTIONTYPE)
         ->setIsRequired(true)
         ->setValue($object->getBlueprintName()),
     );
diff --git a/src/applications/drydock/editor/DrydockBlueprintEditor.php b/src/applications/drydock/editor/DrydockBlueprintEditor.php
index 125c36811a..aac3e7a020 100644
--- a/src/applications/drydock/editor/DrydockBlueprintEditor.php
+++ b/src/applications/drydock/editor/DrydockBlueprintEditor.php
@@ -11,6 +11,14 @@ final class DrydockBlueprintEditor
     return pht('Drydock Blueprints');
   }
 
+  public function getCreateObjectTitle($author, $object) {
+    return pht('%s created this blueprint.', $author);
+  }
+
+  public function getCreateObjectTitleForFeed($author, $object) {
+    return pht('%s created %s.', $author, $object);
+  }
+
   protected function supportsSearch() {
     return true;
   }
@@ -21,99 +29,7 @@ final class DrydockBlueprintEditor
     $types[] = PhabricatorTransactions::TYPE_VIEW_POLICY;
     $types[] = PhabricatorTransactions::TYPE_EDIT_POLICY;
 
-    $types[] = DrydockBlueprintTransaction::TYPE_NAME;
-    $types[] = DrydockBlueprintTransaction::TYPE_DISABLED;
-
     return $types;
   }
 
-  protected function getCustomTransactionOldValue(
-    PhabricatorLiskDAO $object,
-    PhabricatorApplicationTransaction $xaction) {
-
-    switch ($xaction->getTransactionType()) {
-      case DrydockBlueprintTransaction::TYPE_NAME:
-        return $object->getBlueprintName();
-      case DrydockBlueprintTransaction::TYPE_DISABLED:
-        return (int)$object->getIsDisabled();
-    }
-
-    return parent::getCustomTransactionOldValue($object, $xaction);
-  }
-
-  protected function getCustomTransactionNewValue(
-    PhabricatorLiskDAO $object,
-    PhabricatorApplicationTransaction $xaction) {
-
-    switch ($xaction->getTransactionType()) {
-      case DrydockBlueprintTransaction::TYPE_NAME:
-        return $xaction->getNewValue();
-      case DrydockBlueprintTransaction::TYPE_DISABLED:
-        return (int)$xaction->getNewValue();
-    }
-
-    return parent::getCustomTransactionNewValue($object, $xaction);
-  }
-
-  protected function applyCustomInternalTransaction(
-    PhabricatorLiskDAO $object,
-    PhabricatorApplicationTransaction $xaction) {
-
-    switch ($xaction->getTransactionType()) {
-      case DrydockBlueprintTransaction::TYPE_NAME:
-        $object->setBlueprintName($xaction->getNewValue());
-        return;
-      case DrydockBlueprintTransaction::TYPE_DISABLED:
-        $object->setIsDisabled((int)$xaction->getNewValue());
-        return;
-    }
-
-    return parent::applyCustomInternalTransaction($object, $xaction);
-  }
-
-  protected function applyCustomExternalTransaction(
-    PhabricatorLiskDAO $object,
-    PhabricatorApplicationTransaction $xaction) {
-
-    switch ($xaction->getTransactionType()) {
-      case DrydockBlueprintTransaction::TYPE_NAME:
-      case DrydockBlueprintTransaction::TYPE_DISABLED:
-        return;
-    }
-
-    return parent::applyCustomExternalTransaction($object, $xaction);
-  }
-
-
-  protected function validateTransaction(
-    PhabricatorLiskDAO $object,
-    $type,
-    array $xactions) {
-
-    $errors = parent::validateTransaction($object, $type, $xactions);
-
-    switch ($type) {
-      case DrydockBlueprintTransaction::TYPE_NAME:
-        $missing = $this->validateIsEmptyTextField(
-          $object->getBlueprintName(),
-          $xactions);
-
-        if ($missing) {
-          $error = new PhabricatorApplicationTransactionValidationError(
-            $type,
-            pht('Required'),
-            pht('You must choose a name for this blueprint.'),
-            nonempty(last($xactions), null));
-
-          $error->setIsMissingFieldError(true);
-          $errors[] = $error;
-          continue;
-        }
-
-        break;
-    }
-
-    return $errors;
-  }
-
 }
diff --git a/src/applications/drydock/storage/DrydockBlueprintTransaction.php b/src/applications/drydock/storage/DrydockBlueprintTransaction.php
index 0856f01fdb..68eebe8c1d 100644
--- a/src/applications/drydock/storage/DrydockBlueprintTransaction.php
+++ b/src/applications/drydock/storage/DrydockBlueprintTransaction.php
@@ -1,7 +1,7 @@
 <?php
 
 final class DrydockBlueprintTransaction
-  extends PhabricatorApplicationTransaction {
+  extends PhabricatorModularTransaction {
 
   const TYPE_NAME = 'drydock:blueprint:name';
   const TYPE_DISABLED = 'drydock:blueprint:disabled';
@@ -14,37 +14,8 @@ final class DrydockBlueprintTransaction
     return DrydockBlueprintPHIDType::TYPECONST;
   }
 
-  public function getTitle() {
-    $old = $this->getOldValue();
-    $new = $this->getNewValue();
-    $author_handle = $this->renderHandleLink($this->getAuthorPHID());
-
-    switch ($this->getTransactionType()) {
-      case self::TYPE_NAME:
-        if (!strlen($old)) {
-          return pht(
-            '%s created this blueprint.',
-            $author_handle);
-        } else {
-          return pht(
-            '%s renamed this blueprint from "%s" to "%s".',
-            $author_handle,
-            $old,
-            $new);
-        }
-      case self::TYPE_DISABLED:
-        if ($new) {
-          return pht(
-            '%s disabled this blueprint.',
-            $author_handle);
-        } else {
-          return pht(
-            '%s enabled this blueprint.',
-            $author_handle);
-        }
-    }
-
-    return parent::getTitle();
+  public function getBaseTransactionClass() {
+    return 'DrydockBlueprintTransactionType';
   }
 
 }
diff --git a/src/applications/drydock/xaction/DrydockBlueprintDisableTransaction.php b/src/applications/drydock/xaction/DrydockBlueprintDisableTransaction.php
new file mode 100644
index 0000000000..216cea35f4
--- /dev/null
+++ b/src/applications/drydock/xaction/DrydockBlueprintDisableTransaction.php
@@ -0,0 +1,48 @@
+<?php
+
+final class DrydockBlueprintDisableTransaction
+  extends DrydockBlueprintTransactionType {
+
+  const TRANSACTIONTYPE = 'drydock:blueprint:disabled';
+
+  public function generateOldValue($object) {
+    return (bool)$object->getIsDisabled();
+  }
+
+  public function generateNewValue($object, $value) {
+    return (bool)$value;
+  }
+
+  public function applyInternalEffects($object, $value) {
+    $object->setIsDisabled((int)$value);
+  }
+
+  public function getTitle() {
+    $new = $this->getNewValue();
+    if ($new) {
+      return pht(
+        '%s disabled this blueprint.',
+        $this->renderAuthor());
+    } else {
+      return pht(
+        '%s enabled this blueprint.',
+        $this->renderAuthor());
+    }
+  }
+
+  public function getTitleForFeed() {
+    $new = $this->getNewValue();
+    if ($new) {
+      return pht(
+        '%s disabled %s.',
+        $this->renderAuthor(),
+        $this->renderObject());
+    } else {
+      return pht(
+        '%s enabled %s.',
+        $this->renderAuthor(),
+        $this->renderObject());
+    }
+  }
+
+}
diff --git a/src/applications/drydock/xaction/DrydockBlueprintNameTransaction.php b/src/applications/drydock/xaction/DrydockBlueprintNameTransaction.php
new file mode 100644
index 0000000000..c3c17d0413
--- /dev/null
+++ b/src/applications/drydock/xaction/DrydockBlueprintNameTransaction.php
@@ -0,0 +1,60 @@
+<?php
+
+final class DrydockBlueprintNameTransaction
+  extends DrydockBlueprintTransactionType {
+
+  const TRANSACTIONTYPE = 'drydock:blueprint:name';
+
+  public function generateOldValue($object) {
+    return $object->getBlueprintName();
+  }
+
+  public function applyInternalEffects($object, $value) {
+    $object->setBlueprintName($value);
+  }
+
+  public function getTitle() {
+    return pht(
+      '%s renamed this blueprint from %s to %s.',
+      $this->renderAuthor(),
+      $this->renderOldValue(),
+      $this->renderNewValue());
+  }
+
+  public function getTitleForFeed() {
+    $old = $this->getOldValue();
+    $new = $this->getNewValue();
+
+    return pht(
+      '%s renamed %s from %s to %s.',
+      $this->renderAuthor(),
+      $this->renderObject(),
+      $this->renderOldValue(),
+      $this->renderNewValue());
+  }
+
+  public function validateTransactions($object, array $xactions) {
+    $errors = array();
+
+    $name = $object->getBlueprintName();
+    if ($this->isEmptyTextTransaction($name, $xactions)) {
+      $errors[] = $this->newRequiredError(
+        pht('Blueprints must have a name.'));
+    }
+
+    $max_length = $object->getColumnMaximumByteLength('blueprintName');
+    foreach ($xactions as $xaction) {
+      $new_value = $xaction->getNewValue();
+
+      $new_length = strlen($new_value);
+      if ($new_length > $max_length) {
+        $errors[] = $this->newInvalidError(
+          pht('Blueprint names can be no longer than %s characters.',
+          new PhutilNumber($max_length)));
+      }
+    }
+
+    return $errors;
+  }
+
+}
diff --git a/src/applications/drydock/xaction/DrydockBlueprintTransactionType.php b/src/applications/drydock/xaction/DrydockBlueprintTransactionType.php
new file mode 100644
index 0000000000..ecf021b3ad
--- /dev/null
+++ b/src/applications/drydock/xaction/DrydockBlueprintTransactionType.php
@@ -0,0 +1,4 @@
+<?php
+
+abstract class DrydockBlueprintTransactionType
+  extends PhabricatorModularTransactionType {}
diff --git a/src/applications/drydock/xaction/DrydockBlueprintTypeTransaction.php b/src/applications/drydock/xaction/DrydockBlueprintTypeTransaction.php
new file mode 100644
index 0000000000..024e6092fa
--- /dev/null
+++ b/src/applications/drydock/xaction/DrydockBlueprintTypeTransaction.php
@@ -0,0 +1,57 @@
+<?php
+
+final class DrydockBlueprintTypeTransaction
+  extends DrydockBlueprintTransactionType {
+
+  const TRANSACTIONTYPE = 'drydock.blueprint.type';
+
+  public function generateOldValue($object) {
+    return $object->getClassName();
+  }
+
+  public function applyInternalEffects($object, $value) {
+    $object->setClassName($value);
+  }
+
+  public function getTitle() {
+    // These transactions can only be applied during object creation and never
+    // generate a timeline event.
+    return null;
+  }
+
+  public function validateTransactions($object, array $xactions) {
+    $errors = array();
+
+    $name = $object->getClassName();
+    if ($this->isEmptyTextTransaction($name, $xactions)) {
+      $errors[] = $this->newRequiredError(
+        pht('You must select a blueprint type when creating a blueprint.'));
+    }
+
+    $map = DrydockBlueprintImplementation::getAllBlueprintImplementations();
+
+    foreach ($xactions as $xaction) {
+      if (!$this->isNewObject()) {
+        $errors[] = $this->newInvalidError(
+          pht(
+            'The type of a blueprint can not be changed once it has '.
+            'been created.'),
+          $xaction);
+        continue;
+      }
+
+      $new = $xaction->getNewValue();
+      if (!isset($map[$new])) {
+        $errors[] = $this->newInvalidError(
+          pht(
+            'Blueprint type "%s" is not valid. Valid types are: %s.',
+            $new,
+            implode(', ', array_keys($map))));
+        continue;
+      }
+    }
+
+    return $errors;
+  }
+
+}
diff --git a/src/applications/files/config/PhabricatorFilesConfigOptions.php b/src/applications/files/config/PhabricatorFilesConfigOptions.php
index 0f13a2fb4f..1493c54f59 100644
--- a/src/applications/files/config/PhabricatorFilesConfigOptions.php
+++ b/src/applications/files/config/PhabricatorFilesConfigOptions.php
@@ -134,7 +134,7 @@ final class PhabricatorFilesConfigOptions
             "Configure which uploaded file types may be viewed directly ".
             "in the browser. Other file types will be downloaded instead ".
             "of displayed. This is mainly a usability consideration, since ".
-            "browsers tend to freak out when viewing enormous binary files.".
+            "browsers tend to freak out when viewing very large binary files.".
             "\n\n".
             "The keys in this map are viewable MIME types; the values are ".
             "the MIME types they are delivered as when they are viewed in ".
diff --git a/src/applications/maniphest/controller/ManiphestReportController.php b/src/applications/maniphest/controller/ManiphestReportController.php
index 66aa154e8f..3ba597fb92 100644
--- a/src/applications/maniphest/controller/ManiphestReportController.php
+++ b/src/applications/maniphest/controller/ManiphestReportController.php
@@ -75,6 +75,7 @@ final class ManiphestReportController extends ManiphestController {
     $conn = $table->establishConnection('r');
 
     $joins = '';
+    $create_joins = '';
     if ($project_phid) {
       $joins = qsprintf(
         $conn,
@@ -84,6 +85,12 @@ final class ManiphestReportController extends ManiphestController {
         PhabricatorEdgeConfig::TABLE_NAME_EDGE,
         PhabricatorProjectObjectHasProjectEdgeType::EDGECONST,
         $project_phid);
+      $create_joins = qsprintf(
+        $conn,
+        'JOIN %T p ON p.src = t.phid AND p.type = %d AND p.dst = %s',
+        PhabricatorEdgeConfig::TABLE_NAME_EDGE,
+        PhabricatorProjectObjectHasProjectEdgeType::EDGECONST,
+        $project_phid);
     }
 
     $data = queryfx_all(
@@ -99,13 +106,68 @@ final class ManiphestReportController extends ManiphestController {
         ManiphestTaskMergedIntoTransaction::TRANSACTIONTYPE,
       ));
 
+    // See PHI273. After the move to EditEngine, we no longer create a
+    // "status" transaction if a task is created directly into the default
+    // status. This likely impacted API/email tasks after 2016 and all other
+    // tasks after late 2017. Until Facts can fix this properly, use the
+    // task creation dates to generate synthetic transactions which look like
+    // the older transactions that this page expects.
+
+    $default_status = ManiphestTaskStatus::getDefaultStatus();
+    $duplicate_status = ManiphestTaskStatus::getDuplicateStatus();
+
+    // Build synthetic transactions which take status from `null` to the
+    // default value.
+    $create_rows = queryfx_all(
+      $conn,
+      'SELECT t.dateCreated FROM %T t %Q',
+      id(new ManiphestTask())->getTableName(),
+      $create_joins);
+    foreach ($create_rows as $key => $create_row) {
+      $create_rows[$key] = array(
+        'transactionType' => 'status',
+        'oldValue' => null,
+        'newValue' => $default_status,
+        'dateCreated' => $create_row['dateCreated'],
+      );
+    }
+
+    // Remove any actual legacy status transactions which take status from
+    // `null` to any open status.
+    foreach ($data as $key => $row) {
+      if ($row['transactionType'] != 'status') {
+        continue;
+      }
+
+      $oldv = trim($row['oldValue'], '"');
+      $newv = trim($row['oldValue'], '"');
+
+      // If this is a status change, preserve it.
+      if ($oldv != 'null') {
+        continue;
+      }
+
+      // If this task was created directly into a closed status, preserve
+      // the transaction.
+      if (!ManiphestTaskStatus::isOpenStatus($newv)) {
+        continue;
+      }
+
+      // If this is a legacy "create" transaction, discard it in favor of the
+      // synthetic one.
+      unset($data[$key]);
+    }
+
+    // Merge the synthetic rows into the real transactions.
+    $data = array_merge($create_rows, $data);
+    $data = array_values($data);
+    $data = isort($data, 'dateCreated');
+
     $stats = array();
     $day_buckets = array();
 
     $open_tasks = array();
 
-    $default_status = ManiphestTaskStatus::getDefaultStatus();
-    $duplicate_status = ManiphestTaskStatus::getDuplicateStatus();
     foreach ($data as $key => $row) {
       switch ($row['transactionType']) {
         case ManiphestTaskStatusTransaction::TRANSACTIONTYPE:
diff --git a/src/applications/repository/editor/PhabricatorRepositoryEditor.php b/src/applications/repository/editor/PhabricatorRepositoryEditor.php
index 401fca3668..768121de5a 100644
--- a/src/applications/repository/editor/PhabricatorRepositoryEditor.php
+++ b/src/applications/repository/editor/PhabricatorRepositoryEditor.php
@@ -28,6 +28,7 @@ final class PhabricatorRepositoryEditor
     $types[] = PhabricatorRepositoryTransaction::TYPE_AUTOCLOSE;
     $types[] = PhabricatorRepositoryTransaction::TYPE_PUSH_POLICY;
     $types[] = PhabricatorRepositoryTransaction::TYPE_DANGEROUS;
+    $types[] = PhabricatorRepositoryTransaction::TYPE_ENORMOUS;
     $types[] = PhabricatorRepositoryTransaction::TYPE_SLUG;
     $types[] = PhabricatorRepositoryTransaction::TYPE_SERVICE;
     $types[] = PhabricatorRepositoryTransaction::TYPE_SYMBOLS_LANGUAGE;
@@ -76,6 +77,8 @@ final class PhabricatorRepositoryEditor
         return $object->getPushPolicy();
       case PhabricatorRepositoryTransaction::TYPE_DANGEROUS:
         return $object->shouldAllowDangerousChanges();
+      case PhabricatorRepositoryTransaction::TYPE_ENORMOUS:
+        return $object->shouldAllowEnormousChanges();
       case PhabricatorRepositoryTransaction::TYPE_SLUG:
         return $object->getRepositorySlug();
       case PhabricatorRepositoryTransaction::TYPE_SERVICE:
@@ -110,6 +113,7 @@ final class PhabricatorRepositoryEditor
       case PhabricatorRepositoryTransaction::TYPE_VCS:
       case PhabricatorRepositoryTransaction::TYPE_PUSH_POLICY:
       case PhabricatorRepositoryTransaction::TYPE_DANGEROUS:
+      case PhabricatorRepositoryTransaction::TYPE_ENORMOUS:
       case PhabricatorRepositoryTransaction::TYPE_SERVICE:
       case PhabricatorRepositoryTransaction::TYPE_SYMBOLS_LANGUAGE:
       case PhabricatorRepositoryTransaction::TYPE_SYMBOLS_SOURCES:
@@ -184,6 +188,9 @@ final class PhabricatorRepositoryEditor
       case PhabricatorRepositoryTransaction::TYPE_DANGEROUS:
         $object->setDetail('allow-dangerous-changes', $xaction->getNewValue());
         return;
+      case PhabricatorRepositoryTransaction::TYPE_ENORMOUS:
+        $object->setDetail('allow-enormous-changes', $xaction->getNewValue());
+        return;
       case PhabricatorRepositoryTransaction::TYPE_SLUG:
         $object->setRepositorySlug($xaction->getNewValue());
         return;
@@ -248,6 +255,7 @@ final class PhabricatorRepositoryEditor
       case PhabricatorRepositoryTransaction::TYPE_AUTOCLOSE:
       case PhabricatorRepositoryTransaction::TYPE_PUSH_POLICY:
       case PhabricatorRepositoryTransaction::TYPE_DANGEROUS:
+      case PhabricatorRepositoryTransaction::TYPE_ENORMOUS:
       case PhabricatorRepositoryTransaction::TYPE_SLUG:
       case PhabricatorRepositoryTransaction::TYPE_SERVICE:
       case PhabricatorRepositoryTransaction::TYPE_SYMBOLS_SOURCES:
diff --git a/src/applications/repository/storage/PhabricatorRepository.php b/src/applications/repository/storage/PhabricatorRepository.php
index 702bb42780..435e5749e6 100644
--- a/src/applications/repository/storage/PhabricatorRepository.php
+++ b/src/applications/repository/storage/PhabricatorRepository.php
@@ -1672,6 +1672,18 @@ final class PhabricatorRepository extends PhabricatorRepositoryDAO
     return (bool)$this->getDetail('allow-dangerous-changes');
   }
 
+  public function canAllowEnormousChanges() {
+    if (!$this->isHosted()) {
+      return false;
+    }
+
+    return true;
+  }
+
+  public function shouldAllowEnormousChanges() {
+    return (bool)$this->getDetail('allow-enormous-changes');
+  }
+
   public function writeStatusMessage(
     $status_type,
     $status_code,
diff --git a/src/applications/repository/storage/PhabricatorRepositoryPushLog.php b/src/applications/repository/storage/PhabricatorRepositoryPushLog.php
index 4c449b4a84..4e099209c6 100644
--- a/src/applications/repository/storage/PhabricatorRepositoryPushLog.php
+++ b/src/applications/repository/storage/PhabricatorRepositoryPushLog.php
@@ -23,12 +23,14 @@ final class PhabricatorRepositoryPushLog
   const CHANGEFLAG_APPEND = 4;
   const CHANGEFLAG_REWRITE = 8;
   const CHANGEFLAG_DANGEROUS = 16;
+  const CHANGEFLAG_ENORMOUS = 32;
 
   const REJECT_ACCEPT = 0;
   const REJECT_DANGEROUS = 1;
   const REJECT_HERALD = 2;
   const REJECT_EXTERNAL = 3;
   const REJECT_BROKEN = 4;
+  const REJECT_ENORMOUS = 5;
 
   protected $repositoryPHID;
   protected $epoch;
diff --git a/src/applications/repository/storage/PhabricatorRepositoryTransaction.php b/src/applications/repository/storage/PhabricatorRepositoryTransaction.php
index e02b670f75..866800161e 100644
--- a/src/applications/repository/storage/PhabricatorRepositoryTransaction.php
+++ b/src/applications/repository/storage/PhabricatorRepositoryTransaction.php
@@ -16,6 +16,7 @@ final class PhabricatorRepositoryTransaction
   const TYPE_AUTOCLOSE = 'repo:autoclose';
   const TYPE_PUSH_POLICY = 'repo:push-policy';
   const TYPE_DANGEROUS = 'repo:dangerous';
+  const TYPE_ENORMOUS = 'repo:enormous';
   const TYPE_SLUG = 'repo:slug';
   const TYPE_SERVICE = 'repo:service';
   const TYPE_SYMBOLS_SOURCES = 'repo:symbol-source';
@@ -376,6 +377,16 @@ final class PhabricatorRepositoryTransaction
             '%s enabled protection against dangerous changes.',
             $this->renderHandleLink($author_phid));
         }
+      case self::TYPE_ENORMOUS:
+        if ($new) {
+          return pht(
+            '%s disabled protection against enormous changes.',
+            $this->renderHandleLink($author_phid));
+        } else {
+          return pht(
+            '%s enabled protection against enormous changes.',
+            $this->renderHandleLink($author_phid));
+        }
       case self::TYPE_SLUG:
         if (strlen($old) && !strlen($new)) {
           return pht(
diff --git a/src/applications/transactions/editengine/PhabricatorEditEngine.php b/src/applications/transactions/editengine/PhabricatorEditEngine.php
index 8ba49f4d77..1e9d936929 100644
--- a/src/applications/transactions/editengine/PhabricatorEditEngine.php
+++ b/src/applications/transactions/editengine/PhabricatorEditEngine.php
@@ -630,6 +630,17 @@ abstract class PhabricatorEditEngine
     return $this->isCreate;
   }
 
+  /**
+   * Initialize a new object for object creation via Conduit.
+   *
+   * @return object Newly initialized object.
+   * @param list<wild> Raw transactions.
+   * @task load
+   */
+  protected function newEditableObjectFromConduit(array $raw_xactions) {
+    return $this->newEditableObject();
+  }
+
   /**
    * Initialize a new object for documentation creation.
    *
@@ -2031,6 +2042,8 @@ abstract class PhabricatorEditEngine
           get_class($this)));
     }
 
+    $raw_xactions = $this->getRawConduitTransactions($request);
+
     $identifier = $request->getValue('objectIdentifier');
     if ($identifier) {
       $this->setIsCreate(false);
@@ -2039,7 +2052,7 @@ abstract class PhabricatorEditEngine
       $this->requireCreateCapability();
 
       $this->setIsCreate(true);
-      $object = $this->newEditableObject();
+      $object = $this->newEditableObjectFromConduit($raw_xactions);
     }
 
     $this->validateObject($object);
@@ -2049,7 +2062,11 @@ abstract class PhabricatorEditEngine
     $types = $this->getConduitEditTypesFromFields($fields);
     $template = $object->getApplicationTransactionTemplate();
 
-    $xactions = $this->getConduitTransactions($request, $types, $template);
+    $xactions = $this->getConduitTransactions(
+      $request,
+      $raw_xactions,
+      $types,
+      $template);
 
     $editor = $object->getApplicationTransactionEditor()
       ->setActor($viewer)
@@ -2078,23 +2095,7 @@ abstract class PhabricatorEditEngine
     );
   }
 
-
-  /**
-   * Generate transactions which can be applied from edit actions in a Conduit
-   * request.
-   *
-   * @param ConduitAPIRequest The request.
-   * @param list<PhabricatorEditType> Supported edit types.
-   * @param PhabricatorApplicationTransaction Template transaction.
-   * @return list<PhabricatorApplicationTransaction> Generated transactions.
-   * @task conduit
-   */
-  private function getConduitTransactions(
-    ConduitAPIRequest $request,
-    array $types,
-    PhabricatorApplicationTransaction $template) {
-
-    $viewer = $request->getUser();
+  private function getRawConduitTransactions(ConduitAPIRequest $request) {
     $transactions_key = 'transactions';
 
     $xactions = $request->getValue($transactions_key);
@@ -2124,7 +2125,33 @@ abstract class PhabricatorEditEngine
             $transactions_key,
             $key));
       }
+    }
 
+    return $xactions;
+  }
+
+
+  /**
+   * Generate transactions which can be applied from edit actions in a Conduit
+   * request.
+   *
+   * @param ConduitAPIRequest The request.
+   * @param list<wild> Raw conduit transactions.
+   * @param list<PhabricatorEditType> Supported edit types.
+   * @param PhabricatorApplicationTransaction Template transaction.
+   * @return list<PhabricatorApplicationTransaction> Generated transactions.
+   * @task conduit
+   */
+  private function getConduitTransactions(
+    ConduitAPIRequest $request,
+    array $xactions,
+    array $types,
+    PhabricatorApplicationTransaction $template) {
+
+    $viewer = $request->getUser();
+    $results = array();
+
+    foreach ($xactions as $key => $xaction) {
       $type = $xaction['type'];
       if (empty($types[$type])) {
         throw new Exception(
@@ -2137,8 +2164,6 @@ abstract class PhabricatorEditEngine
       }
     }
 
-    $results = array();
-
     if ($this->getIsCreate()) {
       $results[] = id(clone $template)
         ->setTransactionType(PhabricatorTransactions::TYPE_CREATE);