diff --git a/src/applications/differential/render/DifferentialChangesetOneUpRenderer.php b/src/applications/differential/render/DifferentialChangesetOneUpRenderer.php
index d84a6838e0..fc50b0d605 100644
--- a/src/applications/differential/render/DifferentialChangesetOneUpRenderer.php
+++ b/src/applications/differential/render/DifferentialChangesetOneUpRenderer.php
@@ -1,280 +1,471 @@
 <?php
 
 final class DifferentialChangesetOneUpRenderer
   extends DifferentialChangesetHTMLRenderer {
 
   public function isOneUpRenderer() {
     return true;
   }
 
   protected function getRendererTableClass() {
     return 'diff-1up';
   }
 
   public function getRendererKey() {
     return '1up';
   }
 
   protected function renderColgroup() {
     return phutil_tag('colgroup', array(), array(
       phutil_tag('col', array('class' => 'num')),
       phutil_tag('col', array('class' => 'num')),
       phutil_tag('col', array('class' => 'copy')),
       phutil_tag('col', array('class' => 'unified')),
     ));
   }
 
   public function renderTextChange(
     $range_start,
     $range_len,
     $rows) {
 
     $primitives = $this->buildPrimitives($range_start, $range_len);
     return $this->renderPrimitives($primitives, $rows);
   }
 
   protected function renderPrimitives(array $primitives, $rows) {
     list($left_prefix, $right_prefix) = $this->getLineIDPrefixes();
 
     $no_copy = phutil_tag('td', array('class' => 'copy'));
     $no_coverage = null;
 
     $column_width = 4;
 
     $aural_minus = javelin_tag(
       'span',
       array(
         'aural' => true,
       ),
       '- ');
 
     $aural_plus = javelin_tag(
       'span',
       array(
         'aural' => true,
       ),
       '+ ');
 
     $out = array();
     foreach ($primitives as $k => $p) {
       $type = $p['type'];
       switch ($type) {
         case 'old':
         case 'new':
         case 'old-file':
         case 'new-file':
           $is_old = ($type == 'old' || $type == 'old-file');
 
           $cells = array();
           if ($is_old) {
             if ($p['htype']) {
               if (empty($p['oline'])) {
                 $class = 'left old old-full';
               } else {
                 $class = 'left old';
               }
               $aural = $aural_minus;
             } else {
               $class = 'left';
               $aural = null;
             }
 
             if ($type == 'old-file') {
               $class = "{$class} differential-old-image";
             }
 
             if ($left_prefix) {
               $left_id = $left_prefix.$p['line'];
             } else {
               $left_id = null;
             }
 
             $line = $p['line'];
 
             $cells[] = phutil_tag(
               'td',
               array(
                 'id' => $left_id,
                 'class' => $class.' n',
                 'data-n' => $line,
               ));
 
             $render = $p['render'];
             if ($aural !== null) {
               $render = array($aural, $render);
             }
 
             $cells[] = phutil_tag(
               'td',
               array(
                 'class' => $class.' n',
               ));
             $cells[] = $no_copy;
             $cells[] = phutil_tag('td', array('class' => $class), $render);
             $cells[] = $no_coverage;
           } else {
             if ($p['htype']) {
               if (empty($p['oline'])) {
                 $class = 'right new new-full';
               } else {
                 $class = 'right new';
               }
               $cells[] = phutil_tag(
                 'td',
                 array(
                   'class' => $class.' n',
                 ));
               $aural = $aural_plus;
             } else {
               $class = 'right';
               if ($left_prefix) {
                 $left_id = $left_prefix.$p['oline'];
               } else {
                 $left_id = null;
               }
 
               $oline = $p['oline'];
 
               $cells[] = phutil_tag(
                 'td',
                 array(
                   'id' => $left_id,
                   'class' => 'n',
                   'data-n' => $oline,
                 ));
               $aural = null;
             }
 
             if ($type == 'new-file') {
               $class = "{$class} differential-new-image";
             }
 
             if ($right_prefix) {
               $right_id = $right_prefix.$p['line'];
             } else {
               $right_id = null;
             }
 
             $line = $p['line'];
 
             $cells[] = phutil_tag(
               'td',
               array(
                 'id' => $right_id,
                 'class' => $class.' n',
                 'data-n' => $line,
               ));
 
             $render = $p['render'];
             if ($aural !== null) {
               $render = array($aural, $render);
             }
 
             $cells[] = $no_copy;
             $cells[] = phutil_tag('td', array('class' => $class), $render);
             $cells[] = $no_coverage;
           }
 
           $out[] = phutil_tag('tr', array(), $cells);
 
           break;
         case 'inline':
           $inline = $this->buildInlineComment(
             $p['comment'],
             $p['right']);
           $out[] = $this->getRowScaffoldForInline($inline);
           break;
         case 'no-context':
           $out[] = phutil_tag(
             'tr',
             array(),
             phutil_tag(
               'td',
               array(
                 'class' => 'show-more',
                 'colspan' => $column_width,
               ),
               pht('Context not available.')));
           break;
         case 'context':
           $top = $p['top'];
           $len = $p['len'];
 
           $links = $this->renderShowContextLinks($top, $len, $rows);
 
           $out[] = javelin_tag(
             'tr',
             array(
               'sigil' => 'context-target',
             ),
             phutil_tag(
               'td',
               array(
                 'class' => 'show-more',
                 'colspan' => $column_width,
               ),
               $links));
           break;
         default:
           $out[] = hsprintf('<tr><th /><th /><td>%s</td></tr>', $type);
           break;
       }
     }
 
     if ($out) {
       return $this->wrapChangeInTable(phutil_implode_html('', $out));
     }
 
     return null;
   }
 
   public function renderDocumentEngineBlocks(
     PhabricatorDocumentEngineBlocks $block_list,
     $old_changeset_key,
     $new_changeset_key) {
 
-    // TODO: This should eventually merge into the normal primitives pathway,
-    // but fake it for now and just share as much code as possible.
-
-    $primitives = array();
-    foreach ($block_list->newOneUpLayout() as $block) {
-      $primitives[] = array(
-        'type' => 'old-file',
-        'htype' => '',
-        'line' => $block->getBlockKey(),
-        'render' => $block->getContent(),
-      );
+    $engine = $this->getDocumentEngine();
+    $layout = $block_list->newTwoUpLayout();
+
+    $old_comments = $this->getOldComments();
+    $new_comments = $this->getNewComments();
+
+    $unchanged = array();
+    foreach ($layout as $key => $row) {
+      list($old, $new) = $row;
+
+      if (!$old) {
+        continue;
+      }
+
+      if (!$new) {
+        continue;
+      }
+
+      if ($old->getDifferenceType() !== null) {
+        continue;
+      }
+
+      if ($new->getDifferenceType() !== null) {
+        continue;
+      }
+
+      $unchanged[$key] = true;
     }
 
-    // TODO: We'd like to share primitive code here, but buildPrimitives()
-    // currently chokes on changesets with no textual data.
-    foreach ($this->getOldComments() as $line => $group) {
-      foreach ($group as $comment) {
-        $primitives[] = array(
-          'type' => 'inline',
-          'comment' => $comment,
-          'right' => false,
+    $rows = array();
+    $count = count($layout);
+    for ($ii = 0; $ii < $count;) {
+      $start = $ii;
+
+      for ($jj = $ii; $jj < $count; $jj++) {
+        list($old, $new) = $layout[$jj];
+
+        if (empty($unchanged[$jj])) {
+          break;
+        }
+
+        $rows[] = array(
+          'type' => 'unchanged',
+          'layoutKey' => $jj,
         );
       }
-    }
+      $ii = $jj;
+
+      for ($jj = $ii; $jj < $count; $jj++) {
+        list($old, $new) = $layout[$jj];
 
-    foreach ($this->getNewComments() as $line => $group) {
-      foreach ($group as $comment) {
-        $primitives[] = array(
-          'type' => 'inline',
-          'comment' => $comment,
-          'right' => true,
+        if (!empty($unchanged[$jj])) {
+          break;
+        }
+
+        $rows[] = array(
+          'type' => 'old',
+          'layoutKey' => $jj,
         );
       }
+
+      for ($jj = $ii; $jj < $count; $jj++) {
+        list($old, $new) = $layout[$jj];
+
+        if (!empty($unchanged[$jj])) {
+          break;
+        }
+
+        $rows[] = array(
+          'type' => 'new',
+          'layoutKey' => $jj,
+        );
+      }
+      $ii = $jj;
+
+      // We always expect to consume at least one row when iterating through
+      // the loop and make progress. If we don't, bail out to avoid spinning
+      // to death.
+      if ($ii === $start) {
+        throw new Exception(
+          pht(
+            'Failed to make progress during 1up diff layout.'));
+      }
+    }
+
+    $old_ref = null;
+    $new_ref = null;
+    $refs = $block_list->getDocumentRefs();
+    if ($refs) {
+      list($old_ref, $new_ref) = $refs;
+    }
+
+    $view = array();
+    foreach ($rows as $row) {
+      $row_type = $row['type'];
+      $layout_key = $row['layoutKey'];
+      $row_layout = $layout[$layout_key];
+      list($old, $new) = $row_layout;
+
+      if ($old) {
+        $old_key = $old->getBlockKey();
+      } else {
+        $old_key = null;
+      }
+
+      if ($new) {
+        $new_key = $new->getBlockKey();
+      } else {
+        $new_key = null;
+      }
+
+      $cells = array();
+      $cell_classes = array();
+
+      if ($row_type === 'unchanged') {
+        $cell_content = $engine->newBlockContentView(
+          $old_ref,
+          $old);
+      } else if ($old && $new) {
+        $block_diff = $engine->newBlockDiffViews(
+          $old_ref,
+          $old,
+          $new_ref,
+          $new);
+
+        // TODO: We're currently double-rendering this: once when building
+        // the old row, and once when building the new one. In both cases,
+        // we throw away the other half of the output. We could cache this
+        // to improve performance.
+
+        if ($row_type === 'old') {
+          $cell_content = $block_diff->getOldContent();
+          $cell_classes = $block_diff->getOldClasses();
+        } else {
+          $cell_content = $block_diff->getNewContent();
+          $cell_classes = $block_diff->getNewClasses();
+        }
+      } else if ($row_type === 'old') {
+        $cell_content = $engine->newBlockContentView(
+          $old_ref,
+          $old);
+        $cell_classes[] = 'old';
+        $cell_classes[] = 'old-full';
+
+        $new_key = null;
+      } else if ($row_type === 'new') {
+        $cell_content = $engine->newBlockContentView(
+          $new_ref,
+          $new);
+        $cell_classes[] = 'new';
+        $cell_classes[] = 'new-full';
+
+        $old_key = null;
+      }
+
+      if ($old_key === null) {
+        $old_id = null;
+      } else {
+        $old_id = "C{$old_changeset_key}OL{$old_key}";
+      }
+
+      if ($new_key === null) {
+        $new_id = null;
+      } else {
+        $new_id = "C{$new_changeset_key}NL{$new_key}";
+      }
+
+      $cells[] = phutil_tag(
+        'td',
+        array(
+          'id' => $old_id,
+          'data-n' => $old_key,
+          'class' => 'n',
+        ));
+
+      $cells[] = phutil_tag(
+        'td',
+        array(
+          'id' => $new_id,
+          'data-n' => $new_key,
+          'class' => 'n',
+        ));
+
+      $cells[] = phutil_tag(
+        'td',
+        array(
+          'class' => 'copy',
+        ));
+
+      $cell_classes[] = 'diff-flush';
+      $cell_classes = implode(' ', $cell_classes);
+
+      $cells[] = phutil_tag(
+        'td',
+        array(
+          'class' => $cell_classes,
+          'data-copy-mode' => 'copy-unified',
+        ),
+        $cell_content);
+
+      $view[] = phutil_tag(
+        'tr',
+        array(),
+        $cells);
+
+      if ($old_key !== null) {
+        $old_inlines = idx($old_comments, $old_key, array());
+        foreach ($old_inlines as $inline) {
+          $inline = $this->buildInlineComment(
+            $inline,
+            $on_right = false);
+          $view[] = $this->getRowScaffoldForInline($inline);
+        }
+      }
+
+      if ($new_key !== null) {
+        $new_inlines = idx($new_comments, $new_key, array());
+        foreach ($new_inlines as $inline) {
+          $inline = $this->buildInlineComment(
+            $inline,
+            $on_right = true);
+          $view[] = $this->getRowScaffoldForInline($inline);
+        }
+      }
     }
 
-    $output = $this->renderPrimitives($primitives, 1);
+    $output = $this->wrapChangeInTable($view);
     return $this->renderChangesetTable($output);
   }
 
   public function getRowScaffoldForInline(PHUIDiffInlineCommentView $view) {
     return id(new PHUIDiffOneUpInlineCommentRowScaffold())
       ->addInlineView($view);
   }
 
 }
diff --git a/src/infrastructure/diff/view/PHUIDiffOneUpInlineCommentRowScaffold.php b/src/infrastructure/diff/view/PHUIDiffOneUpInlineCommentRowScaffold.php
index fe5cab8622..02477186ff 100644
--- a/src/infrastructure/diff/view/PHUIDiffOneUpInlineCommentRowScaffold.php
+++ b/src/infrastructure/diff/view/PHUIDiffOneUpInlineCommentRowScaffold.php
@@ -1,41 +1,42 @@
 <?php
 
 /**
  * Row scaffold for `1up` (unified) changeset views.
  *
  * This scaffold is straightforward.
  */
 final class PHUIDiffOneUpInlineCommentRowScaffold
   extends PHUIDiffInlineCommentRowScaffold {
 
   public function render() {
     $inlines = $this->getInlineViews();
     if (count($inlines) != 1) {
       throw new Exception(
         pht('One-up inline row scaffold must have exactly one inline view!'));
     }
     $inline = head($inlines);
 
     $attrs = array(
-      'colspan' => 3,
+      'colspan' => 2,
       'id' => $inline->getScaffoldCellID(),
     );
 
     if ($inline->getIsOnRight()) {
       $left_hidden = null;
       $right_hidden = $inline->newHiddenIcon();
     } else {
       $left_hidden = $inline->newHiddenIcon();
       $right_hidden = null;
     }
 
     $cells = array(
       phutil_tag('td', array('class' => 'n'), $left_hidden),
       phutil_tag('td', array('class' => 'n'), $right_hidden),
+      phutil_tag('td', array('class' => 'copy')),
       phutil_tag('td', $attrs, $inline),
     );
 
     return javelin_tag('tr', $this->getRowAttributes(), $cells);
   }
 
 }