diff --git a/src/__phutil_library_map__.php b/src/__phutil_library_map__.php
--- a/src/__phutil_library_map__.php
+++ b/src/__phutil_library_map__.php
@@ -3453,6 +3453,7 @@
     'PhabricatorFileAES256StorageFormat' => 'applications/files/format/PhabricatorFileAES256StorageFormat.php',
     'PhabricatorFileAltTextTransaction' => 'applications/files/xaction/PhabricatorFileAltTextTransaction.php',
     'PhabricatorFileAttachment' => 'applications/files/storage/PhabricatorFileAttachment.php',
+    'PhabricatorFileAttachmentQuery' => 'applications/files/query/PhabricatorFileAttachmentQuery.php',
     'PhabricatorFileBundleLoader' => 'applications/files/query/PhabricatorFileBundleLoader.php',
     'PhabricatorFileChunk' => 'applications/files/storage/PhabricatorFileChunk.php',
     'PhabricatorFileChunkIterator' => 'applications/files/engine/PhabricatorFileChunkIterator.php',
@@ -9892,7 +9893,12 @@
     ),
     'PhabricatorFileAES256StorageFormat' => 'PhabricatorFileStorageFormat',
     'PhabricatorFileAltTextTransaction' => 'PhabricatorFileTransactionType',
-    'PhabricatorFileAttachment' => 'PhabricatorFileDAO',
+    'PhabricatorFileAttachment' => array(
+      'PhabricatorFileDAO',
+      'PhabricatorPolicyInterface',
+      'PhabricatorExtendedPolicyInterface',
+    ),
+    'PhabricatorFileAttachmentQuery' => 'PhabricatorCursorPagedPolicyAwareQuery',
     'PhabricatorFileBundleLoader' => 'Phobject',
     'PhabricatorFileChunk' => array(
       'PhabricatorFileDAO',
diff --git a/src/applications/files/query/PhabricatorFileAttachmentQuery.php b/src/applications/files/query/PhabricatorFileAttachmentQuery.php
new file mode 100644
--- /dev/null
+++ b/src/applications/files/query/PhabricatorFileAttachmentQuery.php
@@ -0,0 +1,110 @@
+<?php
+
+final class PhabricatorFileAttachmentQuery
+  extends PhabricatorCursorPagedPolicyAwareQuery {
+
+  private $objectPHIDs;
+  private $needFiles;
+
+  public function withObjectPHIDs(array $object_phids) {
+    $this->objectPHIDs = $object_phids;
+    return $this;
+  }
+
+  public function needFiles($need) {
+    $this->needFiles = $need;
+    return $this;
+  }
+
+  public function newResultObject() {
+    return new PhabricatorFileAttachment();
+  }
+
+  protected function loadPage() {
+    return $this->loadStandardPage($this->newResultObject());
+  }
+
+  protected function buildWhereClauseParts(AphrontDatabaseConnection $conn) {
+    $where = parent::buildWhereClauseParts($conn);
+
+    if ($this->objectPHIDs !== null) {
+      $where[] = qsprintf(
+        $conn,
+        'attachments.objectPHID IN (%Ls)',
+        $this->objectPHIDs);
+    }
+
+    return $where;
+  }
+
+  protected function willFilterPage(array $attachments) {
+    $viewer = $this->getViewer();
+    $object_phids = array();
+
+    foreach ($attachments as $attachment) {
+      $object_phid = $attachment->getObjectPHID();
+      $object_phids[$object_phid] = $object_phid;
+    }
+
+    if ($object_phids) {
+      $objects = id(new PhabricatorObjectQuery())
+        ->setViewer($viewer)
+        ->setParentQuery($this)
+        ->withPHIDs($object_phids)
+        ->execute();
+      $objects = mpull($objects, null, 'getPHID');
+    } else {
+      $objects = array();
+    }
+
+    foreach ($attachments as $key => $attachment) {
+      $object_phid = $attachment->getObjectPHID();
+      $object = idx($objects, $object_phid);
+
+      if (!$object) {
+        $this->didRejectResult($attachment);
+        unset($attachments[$key]);
+        continue;
+      }
+
+      $attachment->attachObject($object);
+    }
+
+    if ($this->needFiles) {
+      $file_phids = array();
+      foreach ($attachments as $attachment) {
+        $file_phid = $attachment->getFilePHID();
+        $file_phids[$file_phid] = $file_phid;
+      }
+
+      if ($file_phids) {
+        $files = id(new PhabricatorFileQuery())
+          ->setViewer($viewer)
+          ->setParentQuery($this)
+          ->withPHIDs($file_phids)
+          ->execute();
+        $files = mpull($files, null, 'getPHID');
+      } else {
+        $files = array();
+      }
+
+      foreach ($attachments as $key => $attachment) {
+        $file_phid = $attachment->getFilePHID();
+        $file = idx($files, $file_phid);
+
+        $attachment->attachFile($file);
+      }
+    }
+
+    return $attachments;
+  }
+
+  protected function getPrimaryTableAlias() {
+    return 'attachments';
+  }
+
+  public function getQueryApplicationClass() {
+    return 'PhabricatorFilesApplication';
+  }
+
+}
diff --git a/src/applications/files/query/PhabricatorFileQuery.php b/src/applications/files/query/PhabricatorFileQuery.php
--- a/src/applications/files/query/PhabricatorFileQuery.php
+++ b/src/applications/files/query/PhabricatorFileQuery.php
@@ -374,8 +374,12 @@
     if ($this->shouldJoinAttachmentsTable()) {
       $joins[] = qsprintf(
         $conn,
-        'JOIN %R attachments ON attachments.filePHID = f.phid',
-        new PhabricatorFileAttachment());
+        'JOIN %R attachments ON attachments.filePHID = f.phid
+          AND attachmentMode IN (%Ls)',
+        new PhabricatorFileAttachment(),
+        array(
+          PhabricatorFileAttachment::MODE_ATTACH,
+        ));
     }
 
     return $joins;
diff --git a/src/applications/files/storage/PhabricatorFileAttachment.php b/src/applications/files/storage/PhabricatorFileAttachment.php
--- a/src/applications/files/storage/PhabricatorFileAttachment.php
+++ b/src/applications/files/storage/PhabricatorFileAttachment.php
@@ -1,13 +1,19 @@
 <?php
 
 final class PhabricatorFileAttachment
-  extends PhabricatorFileDAO {
+  extends PhabricatorFileDAO
+  implements
+    PhabricatorPolicyInterface,
+    PhabricatorExtendedPolicyInterface {
 
   protected $objectPHID;
   protected $filePHID;
   protected $attacherPHID;
   protected $attachmentMode;
 
+  private $object = self::ATTACHABLE;
+  private $file = self::ATTACHABLE;
+
   const MODE_ATTACH = 'attach';
   const MODE_REFERENCE = 'reference';
   const MODE_DETACH = 'detach';
@@ -40,4 +46,53 @@
     );
   }
 
+  public function attachObject($object) {
+    $this->object = $object;
+    return $this;
+  }
+
+  public function getObject() {
+    return $this->assertAttached($this->object);
+  }
+
+  public function attachFile(PhabricatorFile $file = null) {
+    $this->file = $file;
+    return $this;
+  }
+
+  public function getFile() {
+    return $this->assertAttached($this->file);
+  }
+
+
+/* -(  PhabricatorPolicyInterface  )----------------------------------------- */
+
+
+  public function getCapabilities() {
+    return array(
+      PhabricatorPolicyCapability::CAN_VIEW,
+    );
+  }
+
+  public function getPolicy($capability) {
+    switch ($capability) {
+      case PhabricatorPolicyCapability::CAN_VIEW:
+        return PhabricatorPolicies::getMostOpenPolicy();
+    }
+  }
+
+  public function hasAutomaticCapability($capability, PhabricatorUser $viewer) {
+    return false;
+  }
+
+
+/* -(  PhabricatorExtendedPolicyInterface  )--------------------------------- */
+
+
+  public function getExtendedPolicy($capability, PhabricatorUser $viewer) {
+    return array(
+      array($this->getObject(), $capability),
+    );
+  }
+
 }
diff --git a/src/applications/files/storage/__tests__/PhabricatorFileTestCase.php b/src/applications/files/storage/__tests__/PhabricatorFileTestCase.php
--- a/src/applications/files/storage/__tests__/PhabricatorFileTestCase.php
+++ b/src/applications/files/storage/__tests__/PhabricatorFileTestCase.php
@@ -100,7 +100,12 @@
     $xactions[] = id(new ManiphestTransaction())
       ->setTransactionType(
         ManiphestTaskDescriptionTransaction::TRANSACTIONTYPE)
-      ->setNewValue('{'.$file->getMonogram().'}');
+      ->setNewValue('{'.$file->getMonogram().'}')
+      ->setMetadataValue(
+        'attachedFilePHIDs',
+        array(
+          $file->getPHID(),
+        ));
 
     id(new ManiphestTransactionEditor())
       ->setActor($author)
diff --git a/src/applications/transactions/editor/PhabricatorApplicationTransactionEditor.php b/src/applications/transactions/editor/PhabricatorApplicationTransactionEditor.php
--- a/src/applications/transactions/editor/PhabricatorApplicationTransactionEditor.php
+++ b/src/applications/transactions/editor/PhabricatorApplicationTransactionEditor.php
@@ -2266,7 +2266,14 @@
     $viewer = $this->getActor();
 
     $old_blocks = mpull($remarkup_changes, 'getOldValue');
+    foreach ($old_blocks as $key => $old_block) {
+      $old_blocks[$key] = phutil_string_cast($old_block);
+    }
+
     $new_blocks = mpull($remarkup_changes, 'getNewValue');
+    foreach ($new_blocks as $key => $new_block) {
+      $new_blocks[$key] = phutil_string_cast($new_block);
+    }
 
     $old_refs = PhabricatorMarkupEngine::extractFilePHIDsFromEmbeddedFiles(
       $viewer,