diff --git a/resources/celerity/map.php b/resources/celerity/map.php
index 755fd5a906..bebb1d3802 100644
--- a/resources/celerity/map.php
+++ b/resources/celerity/map.php
@@ -9,7 +9,7 @@ return array(
   'names' => array(
     'conpherence.pkg.css' => '3c8a0668',
     'conpherence.pkg.js' => '020aebcf',
-    'core.pkg.css' => '4451f9fd',
+    'core.pkg.css' => 'f8c53b6f',
     'core.pkg.js' => '6e5c894f',
     'differential.pkg.css' => '607c84be',
     'differential.pkg.js' => 'a0212a0b',
@@ -169,7 +169,7 @@ return array(
     'rsrc/css/phui/phui-pager.css' => 'd022c7ad',
     'rsrc/css/phui/phui-pinboard-view.css' => '1f08f5d8',
     'rsrc/css/phui/phui-policy-section-view.css' => '139fdc64',
-    'rsrc/css/phui/phui-property-list-view.css' => 'ad841f1c',
+    'rsrc/css/phui/phui-property-list-view.css' => '807b1632',
     'rsrc/css/phui/phui-remarkup-preview.css' => '91767007',
     'rsrc/css/phui/phui-segment-bar-view.css' => '5166b370',
     'rsrc/css/phui/phui-spacing.css' => 'b05cadc3',
@@ -868,7 +868,7 @@ return array(
     'phui-pager-css' => 'd022c7ad',
     'phui-pinboard-view-css' => '1f08f5d8',
     'phui-policy-section-view-css' => '139fdc64',
-    'phui-property-list-view-css' => 'ad841f1c',
+    'phui-property-list-view-css' => '807b1632',
     'phui-remarkup-preview-css' => '91767007',
     'phui-segment-bar-view-css' => '5166b370',
     'phui-spacing-css' => 'b05cadc3',
diff --git a/src/__phutil_library_map__.php b/src/__phutil_library_map__.php
index 5ac174701c..c35ac91e1d 100644
--- a/src/__phutil_library_map__.php
+++ b/src/__phutil_library_map__.php
@@ -3140,6 +3140,7 @@ phutil_register_library_map(array(
     'PhabricatorDivinerApplication' => 'applications/diviner/application/PhabricatorDivinerApplication.php',
     'PhabricatorDocumentEngine' => 'applications/files/document/PhabricatorDocumentEngine.php',
     'PhabricatorDocumentEngineBlock' => 'applications/files/diff/PhabricatorDocumentEngineBlock.php',
+    'PhabricatorDocumentEngineBlockDiff' => 'applications/files/diff/PhabricatorDocumentEngineBlockDiff.php',
     'PhabricatorDocumentEngineBlocks' => 'applications/files/diff/PhabricatorDocumentEngineBlocks.php',
     'PhabricatorDocumentRef' => 'applications/files/document/PhabricatorDocumentRef.php',
     'PhabricatorDocumentRenderingEngine' => 'applications/files/document/render/PhabricatorDocumentRenderingEngine.php',
@@ -9481,6 +9482,7 @@ phutil_register_library_map(array(
     'PhabricatorDivinerApplication' => 'PhabricatorApplication',
     'PhabricatorDocumentEngine' => 'Phobject',
     'PhabricatorDocumentEngineBlock' => 'Phobject',
+    'PhabricatorDocumentEngineBlockDiff' => 'Phobject',
     'PhabricatorDocumentEngineBlocks' => 'Phobject',
     'PhabricatorDocumentRef' => 'Phobject',
     'PhabricatorDocumentRenderingEngine' => 'Phobject',
diff --git a/src/aphront/response/Aphront403Response.php b/src/aphront/response/Aphront403Response.php
index 3f7f6d73ca..3d3d5c9457 100644
--- a/src/aphront/response/Aphront403Response.php
+++ b/src/aphront/response/Aphront403Response.php
@@ -28,7 +28,7 @@ final class Aphront403Response extends AphrontHTMLResponse {
     $dialog = id(new AphrontDialogView())
       ->setUser($user)
       ->setTitle(pht('403 Forbidden'))
-      ->addCancelButton('/', pht('Peace Out'))
+      ->addCancelButton('/', pht('Yikes!'))
       ->appendParagraph($forbidden_text);
 
     $view = id(new PhabricatorStandardPageView())
diff --git a/src/applications/differential/parser/DifferentialChangesetParser.php b/src/applications/differential/parser/DifferentialChangesetParser.php
index 408988ed1f..a485a787cb 100644
--- a/src/applications/differential/parser/DifferentialChangesetParser.php
+++ b/src/applications/differential/parser/DifferentialChangesetParser.php
@@ -247,7 +247,7 @@ final class DifferentialChangesetParser extends Phobject {
     return $this->depthOnlyLines;
   }
 
-  public function setVisibileLinesMask(array $mask) {
+  public function setVisibleLinesMask(array $mask) {
     $this->visible = $mask;
     return $this;
   }
@@ -699,13 +699,13 @@ final class DifferentialChangesetParser extends Phobject {
     $lines_context = $this->getLinesOfContext();
 
     $hunk_parser->generateIntraLineDiffs();
-    $hunk_parser->generateVisibileLinesMask($lines_context);
+    $hunk_parser->generateVisibleLinesMask($lines_context);
 
     $this->setOldLines($hunk_parser->getOldLines());
     $this->setNewLines($hunk_parser->getNewLines());
     $this->setIntraLineDiffs($hunk_parser->getIntraLineDiffs());
     $this->setDepthOnlyLines($hunk_parser->getDepthOnlyLines());
-    $this->setVisibileLinesMask($hunk_parser->getVisibleLinesMask());
+    $this->setVisibleLinesMask($hunk_parser->getVisibleLinesMask());
     $this->hunkStartLines = $hunk_parser->getHunkStartLines(
       $changeset->getHunks());
 
@@ -868,8 +868,19 @@ final class DifferentialChangesetParser extends Phobject {
       ->setHighlightingDisabled($this->highlightingDisabled)
       ->setDepthOnlyLines($this->getDepthOnlyLines());
 
+    list($engine, $old_ref, $new_ref) = $this->newDocumentEngine();
+    if ($engine) {
+      $engine_blocks = $engine->newEngineBlocks(
+        $old_ref,
+        $new_ref);
+    } else {
+      $engine_blocks = null;
+    }
+
+    $has_document_engine = ($engine_blocks !== null);
+
     $shield = null;
-    if ($this->isTopLevel && !$this->comments) {
+    if ($this->isTopLevel && !$this->comments && !$has_document_engine) {
       if ($this->isGenerated()) {
         $shield = $renderer->renderShield(
           pht(
@@ -1024,7 +1035,6 @@ final class DifferentialChangesetParser extends Phobject {
       ->setOldComments($old_comments)
       ->setNewComments($new_comments);
 
-    $engine_blocks = $this->newDocumentEngineChangesetView();
     if ($engine_blocks !== null) {
       $reference = $this->getRenderingReference();
       $parts = explode('/', $reference);
@@ -1041,6 +1051,10 @@ final class DifferentialChangesetParser extends Phobject {
         $vs = $id;
       }
 
+      $renderer
+        ->setDocumentEngine($engine)
+        ->setDocumentEngineBlocks($engine_blocks);
+
       return $renderer->renderDocumentEngineBlocks(
         $engine_blocks,
         (string)$id,
@@ -1653,7 +1667,7 @@ final class DifferentialChangesetParser extends Phobject {
     return $prefix.$line;
   }
 
-  private function newDocumentEngineChangesetView() {
+  private function newDocumentEngine() {
     $changeset = $this->changeset;
     $viewer = $this->getViewer();
 
@@ -1724,7 +1738,8 @@ final class DifferentialChangesetParser extends Phobject {
     }
 
     if ($document_engine) {
-      return $document_engine->newDiffView(
+      return array(
+        $document_engine,
         $old_ref,
         $new_ref);
     }
diff --git a/src/applications/differential/parser/DifferentialHunkParser.php b/src/applications/differential/parser/DifferentialHunkParser.php
index 84f466adcd..6cdadf69e7 100644
--- a/src/applications/differential/parser/DifferentialHunkParser.php
+++ b/src/applications/differential/parser/DifferentialHunkParser.php
@@ -36,7 +36,7 @@ final class DifferentialHunkParser extends Phobject {
   }
   public function getVisibleLinesMask() {
     if ($this->visibleLinesMask === null) {
-      throw new PhutilInvalidStateException('generateVisibileLinesMask');
+      throw new PhutilInvalidStateException('generateVisibleLinesMask');
     }
     return $this->visibleLinesMask;
   }
@@ -354,7 +354,7 @@ final class DifferentialHunkParser extends Phobject {
     return $this;
   }
 
-  public function generateVisibileLinesMask($lines_context) {
+  public function generateVisibleLinesMask($lines_context) {
     $old = $this->getOldLines();
     $new = $this->getNewLines();
     $max_length = max(count($old), count($new));
diff --git a/src/applications/differential/render/DifferentialChangesetHTMLRenderer.php b/src/applications/differential/render/DifferentialChangesetHTMLRenderer.php
index ae8db861b6..c856b9b14d 100644
--- a/src/applications/differential/render/DifferentialChangesetHTMLRenderer.php
+++ b/src/applications/differential/render/DifferentialChangesetHTMLRenderer.php
@@ -270,11 +270,20 @@ abstract class DifferentialChangesetHTMLRenderer
       }
     }
 
-    if ($this->getHighlightingDisabled()) {
-      $messages[] = pht(
-        'This file is larger than %s, so syntax highlighting is '.
-        'disabled by default.',
-        phutil_format_bytes(DifferentialChangesetParser::HIGHLIGHT_BYTE_LIMIT));
+    $blocks = $this->getDocumentEngineBlocks();
+    if ($blocks) {
+      foreach ($blocks->getMessages() as $message) {
+        $messages[] = $message;
+      }
+    } else {
+      if ($this->getHighlightingDisabled()) {
+        $byte_limit = DifferentialChangesetParser::HIGHLIGHT_BYTE_LIMIT;
+        $byte_limit = phutil_format_bytes($byte_limit);
+        $messages[] = pht(
+          'This file is larger than %s, so syntax highlighting is '.
+          'disabled by default.',
+          $byte_limit);
+      }
     }
 
     return $this->formatHeaderMessages($messages);
diff --git a/src/applications/differential/render/DifferentialChangesetOneUpRenderer.php b/src/applications/differential/render/DifferentialChangesetOneUpRenderer.php
index e628a5a2f8..fc50b0d605 100644
--- a/src/applications/differential/render/DifferentialChangesetOneUpRenderer.php
+++ b/src/applications/differential/render/DifferentialChangesetOneUpRenderer.php
@@ -233,42 +233,233 @@ final class DifferentialChangesetOneUpRenderer
     $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.
+    $engine = $this->getDocumentEngine();
+    $layout = $block_list->newTwoUpLayout();
 
-    $primitives = array();
-    foreach ($block_list->newOneUpLayout() as $block) {
-      $primitives[] = array(
-        'type' => 'old-file',
-        'htype' => '',
-        'line' => $block->getBlockKey(),
-        'render' => $block->newContentView(),
-      );
+    $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];
+
+        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.'));
+      }
     }
 
-    foreach ($this->getNewComments() as $line => $group) {
-      foreach ($group as $comment) {
-        $primitives[] = array(
-          'type' => 'inline',
-          'comment' => $comment,
-          'right' => true,
-        );
+    $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);
   }
 
diff --git a/src/applications/differential/render/DifferentialChangesetRenderer.php b/src/applications/differential/render/DifferentialChangesetRenderer.php
index e6c6f01fb7..6b1ed8fa27 100644
--- a/src/applications/differential/render/DifferentialChangesetRenderer.php
+++ b/src/applications/differential/render/DifferentialChangesetRenderer.php
@@ -36,6 +36,9 @@ abstract class DifferentialChangesetRenderer extends Phobject {
   private $scopeEngine = false;
   private $depthOnlyLines;
 
+  private $documentEngine;
+  private $documentEngineBlocks;
+
   private $oldFile = false;
   private $newFile = false;
 
@@ -239,6 +242,25 @@ abstract class DifferentialChangesetRenderer extends Phobject {
     return $this->oldChangesetID;
   }
 
+  public function setDocumentEngine(PhabricatorDocumentEngine $engine) {
+    $this->documentEngine = $engine;
+    return $this;
+  }
+
+  public function getDocumentEngine() {
+    return $this->documentEngine;
+  }
+
+  public function setDocumentEngineBlocks(
+    PhabricatorDocumentEngineBlocks $blocks) {
+    $this->documentEngineBlocks = $blocks;
+    return $this;
+  }
+
+  public function getDocumentEngineBlocks() {
+    return $this->documentEngineBlocks;
+  }
+
   public function setNewComments(array $new_comments) {
     foreach ($new_comments as $line_number => $comments) {
       assert_instances_of($comments, 'PhabricatorInlineCommentInterface');
@@ -355,6 +377,16 @@ abstract class DifferentialChangesetRenderer extends Phobject {
     $notice = null;
     if ($this->getIsTopLevel()) {
       $force = (!$content && !$props);
+
+      // If we have DocumentEngine messages about the blocks, assume they
+      // explain why there's no content.
+      $blocks = $this->getDocumentEngineBlocks();
+      if ($blocks) {
+        if ($blocks->getMessages()) {
+          $force = false;
+        }
+      }
+
       $notice = $this->renderChangeTypeHeader($force);
     }
 
diff --git a/src/applications/differential/render/DifferentialChangesetTwoUpRenderer.php b/src/applications/differential/render/DifferentialChangesetTwoUpRenderer.php
index 8285baa0ad..a7af9333ff 100644
--- a/src/applications/differential/render/DifferentialChangesetTwoUpRenderer.php
+++ b/src/applications/differential/render/DifferentialChangesetTwoUpRenderer.php
@@ -369,52 +369,123 @@ final class DifferentialChangesetTwoUpRenderer
     $old_changeset_key,
     $new_changeset_key) {
 
+    $engine = $this->getDocumentEngine();
+
+    $old_ref = null;
+    $new_ref = null;
+    $refs = $block_list->getDocumentRefs();
+    if ($refs) {
+      list($old_ref, $new_ref) = $refs;
+    }
+
     $old_comments = $this->getOldComments();
     $new_comments = $this->getNewComments();
 
+    $gap_view = javelin_tag(
+      'tr',
+      array(
+        'sigil' => 'context-target',
+      ),
+      phutil_tag(
+        'td',
+        array(
+          'colspan' => 6,
+          'class' => 'show-more',
+        ),
+        pht("\xE2\x80\xA2 \xE2\x80\xA2 \xE2\x80\xA2")));
+
     $rows = array();
+    $in_gap = false;
     foreach ($block_list->newTwoUpLayout() as $row) {
       list($old, $new) = $row;
 
       if ($old) {
-        $old_content = $old->newContentView();
         $old_key = $old->getBlockKey();
-
-        $old_classes = $old->getClasses();
-
-        if ($old->getDifferenceType() === '-') {
-          $old_classes[] = 'old';
-          $old_classes[] = 'old-full';
-        }
-
-        $old_classes[] = 'diff-flush';
-
-        $old_classes = implode(' ', $old_classes);
+        $is_visible = $old->getIsVisible();
       } else {
-        $old_content = null;
         $old_key = null;
-        $old_classes = null;
       }
 
       if ($new) {
-        $new_content = $new->newContentView();
         $new_key = $new->getBlockKey();
-        $new_classes = $new->getClasses();
+        $is_visible = $new->getIsVisible();
+      } else {
+        $new_key = null;
+      }
 
-        if ($new->getDifferenceType() === '+') {
-          $new_classes[] = 'new';
-          $new_classes[] = 'new-full';
+      if (!$is_visible) {
+        if (!$in_gap) {
+          $in_gap = true;
+          $rows[] = $gap_view;
+        }
+        continue;
+      }
+
+      if ($in_gap) {
+        $in_gap = false;
+      }
+
+      if ($old) {
+        $is_rem = ($old->getDifferenceType() === '-');
+      } else {
+        $is_rem = false;
+      }
+
+      if ($new) {
+        $is_add = ($new->getDifferenceType() === '+');
+      } else {
+        $is_add = false;
+      }
+
+      if ($is_rem && $is_add) {
+        $block_diff = $engine->newBlockDiffViews(
+          $old_ref,
+          $old,
+          $new_ref,
+          $new);
+
+        $old_content = $block_diff->getOldContent();
+        $new_content = $block_diff->getNewContent();
+
+        $old_classes = $block_diff->getOldClasses();
+        $new_classes = $block_diff->getNewClasses();
+      } else {
+        $old_classes = array();
+        $new_classes = array();
+
+        if ($old) {
+          $old_content = $engine->newBlockContentView(
+            $old_ref,
+            $old);
+
+          if ($is_rem) {
+            $old_classes[] = 'old';
+            $old_classes[] = 'old-full';
+          }
+        } else {
+          $old_content = null;
         }
 
-        $new_classes[] = 'diff-flush';
+        if ($new) {
+          $new_content = $engine->newBlockContentView(
+            $new_ref,
+            $new);
 
-        $new_classes = implode(' ', $new_classes);
-      } else {
-        $new_content = null;
-        $new_key = null;
-        $new_classes = null;
+          if ($is_add) {
+            $new_classes[] = 'new';
+            $new_classes[] = 'new-full';
+          }
+        } else {
+          $new_content = null;
+        }
       }
 
+      $old_classes[] = 'diff-flush';
+      $old_classes = implode(' ', $old_classes);
+
+      $new_classes[] = 'diff-flush';
+      $new_classes = implode(' ', $new_classes);
+
       $old_inline_rows = array();
       if ($old_key !== null) {
         $old_inlines = idx($old_comments, $old_key, array());
diff --git a/src/applications/files/diff/PhabricatorDocumentEngineBlock.php b/src/applications/files/diff/PhabricatorDocumentEngineBlock.php
index 38e9b56454..e2d5af23b2 100644
--- a/src/applications/files/diff/PhabricatorDocumentEngineBlock.php
+++ b/src/applications/files/diff/PhabricatorDocumentEngineBlock.php
@@ -5,9 +5,9 @@ final class PhabricatorDocumentEngineBlock
 
   private $blockKey;
   private $content;
-  private $classes = array();
   private $differenceHash;
   private $differenceType;
+  private $isVisible;
 
   public function setContent($content) {
     $this->content = $content;
@@ -18,10 +18,6 @@ final class PhabricatorDocumentEngineBlock
     return $this->content;
   }
 
-  public function newContentView() {
-    return $this->getContent();
-  }
-
   public function setBlockKey($block_key) {
     $this->blockKey = $block_key;
     return $this;
@@ -31,15 +27,6 @@ final class PhabricatorDocumentEngineBlock
     return $this->blockKey;
   }
 
-  public function addClass($class) {
-    $this->classes[] = $class;
-    return $this;
-  }
-
-  public function getClasses() {
-    return $this->classes;
-  }
-
   public function setDifferenceHash($difference_hash) {
     $this->differenceHash = $difference_hash;
     return $this;
@@ -58,4 +45,13 @@ final class PhabricatorDocumentEngineBlock
     return $this->differenceType;
   }
 
+  public function setIsVisible($is_visible) {
+    $this->isVisible = $is_visible;
+    return $this;
+  }
+
+  public function getIsVisible() {
+    return $this->isVisible;
+  }
+
 }
diff --git a/src/applications/files/diff/PhabricatorDocumentEngineBlockDiff.php b/src/applications/files/diff/PhabricatorDocumentEngineBlockDiff.php
new file mode 100644
index 0000000000..b582d523c6
--- /dev/null
+++ b/src/applications/files/diff/PhabricatorDocumentEngineBlockDiff.php
@@ -0,0 +1,47 @@
+<?php
+
+final class PhabricatorDocumentEngineBlockDiff
+  extends Phobject {
+
+  private $oldContent;
+  private $newContent;
+  private $oldClasses = array();
+  private $newClasses = array();
+
+  public function setOldContent($old_content) {
+    $this->oldContent = $old_content;
+    return $this;
+  }
+
+  public function getOldContent() {
+    return $this->oldContent;
+  }
+
+  public function setNewContent($new_content) {
+    $this->newContent = $new_content;
+    return $this;
+  }
+
+  public function getNewContent() {
+    return $this->newContent;
+  }
+
+  public function addOldClass($class) {
+    $this->oldClasses[] = $class;
+    return $this;
+  }
+
+  public function getOldClasses() {
+    return $this->oldClasses;
+  }
+
+  public function addNewClass($class) {
+    $this->newClasses[] = $class;
+    return $this;
+  }
+
+  public function getNewClasses() {
+    return $this->newClasses;
+  }
+
+}
diff --git a/src/applications/files/diff/PhabricatorDocumentEngineBlocks.php b/src/applications/files/diff/PhabricatorDocumentEngineBlocks.php
index fc45c204a8..f8f3a414b1 100644
--- a/src/applications/files/diff/PhabricatorDocumentEngineBlocks.php
+++ b/src/applications/files/diff/PhabricatorDocumentEngineBlocks.php
@@ -4,6 +4,16 @@ final class PhabricatorDocumentEngineBlocks
   extends Phobject {
 
   private $lists = array();
+  private $messages = array();
+
+  public function addMessage($message) {
+    $this->messages[] = $message;
+    return $this;
+  }
+
+  public function getMessages() {
+    return $this->messages;
+  }
 
   public function addBlockList(PhabricatorDocumentRef $ref, array $blocks) {
     assert_instances_of($blocks, 'PhabricatorDocumentEngineBlock');
@@ -16,10 +26,18 @@ final class PhabricatorDocumentEngineBlocks
     return $this;
   }
 
+  public function getDocumentRefs() {
+    return ipull($this->lists, 'ref');
+  }
+
   public function newTwoUpLayout() {
     $rows = array();
     $lists = $this->lists;
 
+    if (count($lists) != 2) {
+      return array();
+    }
+
     $specs = array();
     foreach ($this->lists as $list) {
       $specs[] = $this->newDiffSpec($list['blocks']);
@@ -38,6 +56,9 @@ final class PhabricatorDocumentEngineBlocks
       ->parseHunksForLineData($changeset->getHunks())
       ->reparseHunksForSpecialAttributes();
 
+    $hunk_parser->generateVisibleLinesMask(2);
+    $mask = $hunk_parser->getVisibleLinesMask();
+
     $old_lines = $hunk_parser->getOldLines();
     $new_lines = $hunk_parser->getNewLines();
 
@@ -48,6 +69,15 @@ final class PhabricatorDocumentEngineBlocks
       $old_line = idx($old_lines, $ii);
       $new_line = idx($new_lines, $ii);
 
+      $is_visible = !empty($mask[$ii + 1]);
+
+      // TODO: There's currently a bug where one-line files get incorrectly
+      // masked. This causes images to completely fail to render. Just ignore
+      // the mask if it came back empty.
+      if (!$mask) {
+        $is_visible = true;
+      }
+
       if ($old_line) {
         $old_hash = rtrim($old_line['text'], "\n");
         if (!strlen($old_hash)) {
@@ -55,7 +85,9 @@ final class PhabricatorDocumentEngineBlocks
           $old_block = null;
         } else {
           $old_block = array_shift($old_map[$old_hash]);
-          $old_block->setDifferenceType($old_line['type']);
+          $old_block
+            ->setDifferenceType($old_line['type'])
+            ->setIsVisible($is_visible);
         }
       } else {
         $old_block = null;
@@ -67,7 +99,9 @@ final class PhabricatorDocumentEngineBlocks
           $new_block = null;
         } else {
           $new_block = array_shift($new_map[$new_hash]);
-          $new_block->setDifferenceType($new_line['type']);
+          $new_block
+            ->setDifferenceType($new_line['type'])
+            ->setIsVisible($is_visible);
         }
       } else {
         $new_block = null;
diff --git a/src/applications/files/document/PhabricatorDocumentEngine.php b/src/applications/files/document/PhabricatorDocumentEngine.php
index 7e2a0d3b34..bc7960b4ad 100644
--- a/src/applications/files/document/PhabricatorDocumentEngine.php
+++ b/src/applications/files/document/PhabricatorDocumentEngine.php
@@ -37,7 +37,31 @@ abstract class PhabricatorDocumentEngine
     return false;
   }
 
-  public function newDiffView(
+  public function newBlockDiffViews(
+    PhabricatorDocumentRef $uref,
+    PhabricatorDocumentEngineBlock $ublock,
+    PhabricatorDocumentRef $vref,
+    PhabricatorDocumentEngineBlock $vblock) {
+
+    $u_content = $this->newBlockContentView($uref, $ublock);
+    $v_content = $this->newBlockContentView($vref, $vblock);
+
+    return id(new PhabricatorDocumentEngineBlockDiff())
+      ->setOldContent($u_content)
+      ->addOldClass('old')
+      ->addOldClass('old-full')
+      ->setNewContent($v_content)
+      ->addNewClass('new')
+      ->addNewClass('new-full');
+  }
+
+  public function newBlockContentView(
+    PhabricatorDocumentRef $ref,
+    PhabricatorDocumentEngineBlock $block) {
+    return $block->getContent();
+  }
+
+  public function newEngineBlocks(
     PhabricatorDocumentRef $uref,
     PhabricatorDocumentRef $vref) {
     throw new PhutilMethodNotImplementedException();
diff --git a/src/applications/files/document/PhabricatorImageDocumentEngine.php b/src/applications/files/document/PhabricatorImageDocumentEngine.php
index 53dcb83965..fa678cc034 100644
--- a/src/applications/files/document/PhabricatorImageDocumentEngine.php
+++ b/src/applications/files/document/PhabricatorImageDocumentEngine.php
@@ -27,7 +27,7 @@ final class PhabricatorImageDocumentEngine
     return ($uref->getFile() && $vref->getFile());
   }
 
-  public function newDiffView(
+  public function newEngineBlocks(
     PhabricatorDocumentRef $uref,
     PhabricatorDocumentRef $vref) {
 
@@ -39,6 +39,23 @@ final class PhabricatorImageDocumentEngine
       ->addBlockList($vref, $v_blocks);
   }
 
+  public function newBlockDiffViews(
+    PhabricatorDocumentRef $uref,
+    PhabricatorDocumentEngineBlock $ublock,
+    PhabricatorDocumentRef $vref,
+    PhabricatorDocumentEngineBlock $vblock) {
+
+    $u_content = $this->newBlockContentView($uref, $ublock);
+    $v_content = $this->newBlockContentView($vref, $vblock);
+
+    return id(new PhabricatorDocumentEngineBlockDiff())
+      ->setOldContent($u_content)
+      ->addOldClass('diff-image-cell')
+      ->setNewContent($v_content)
+      ->addNewClass('diff-image-cell');
+  }
+
+
   private function newDiffBlocks(PhabricatorDocumentRef $ref) {
     $blocks = array();
 
@@ -59,7 +76,6 @@ final class PhabricatorImageDocumentEngine
 
     $blocks[] = id(new PhabricatorDocumentEngineBlock())
       ->setBlockKey('1')
-      ->addClass('diff-image-cell')
       ->setDifferenceHash($hash)
       ->setContent($image_view);
 
diff --git a/src/applications/files/document/PhabricatorJupyterDocumentEngine.php b/src/applications/files/document/PhabricatorJupyterDocumentEngine.php
index 9836797f84..b5c8b04b6d 100644
--- a/src/applications/files/document/PhabricatorJupyterDocumentEngine.php
+++ b/src/applications/files/document/PhabricatorJupyterDocumentEngine.php
@@ -41,16 +41,143 @@ final class PhabricatorJupyterDocumentEngine
     return true;
   }
 
-  public function newDiffView(
+  public function newEngineBlocks(
     PhabricatorDocumentRef $uref,
     PhabricatorDocumentRef $vref) {
 
-    $u_blocks = $this->newDiffBlocks($uref);
-    $v_blocks = $this->newDiffBlocks($vref);
+    $blocks = new PhabricatorDocumentEngineBlocks();
 
-    return id(new PhabricatorDocumentEngineBlocks())
-      ->addBlockList($uref, $u_blocks)
-      ->addBlockList($vref, $v_blocks);
+    try {
+      $u_blocks = $this->newDiffBlocks($uref);
+      $v_blocks = $this->newDiffBlocks($vref);
+
+      $blocks->addBlockList($uref, $u_blocks);
+      $blocks->addBlockList($vref, $v_blocks);
+    } catch (Exception $ex) {
+      $blocks->addMessage($ex->getMessage());
+    }
+
+    return $blocks;
+  }
+
+  public function newBlockDiffViews(
+    PhabricatorDocumentRef $uref,
+    PhabricatorDocumentEngineBlock $ublock,
+    PhabricatorDocumentRef $vref,
+    PhabricatorDocumentEngineBlock $vblock) {
+
+    $ucell = $ublock->getContent();
+    $vcell = $vblock->getContent();
+
+    $utype = idx($ucell, 'cell_type');
+    $vtype = idx($vcell, 'cell_type');
+
+    if ($utype === $vtype) {
+      switch ($utype) {
+        case 'markdown':
+          $usource = idx($ucell, 'source');
+          $usource = implode('', $usource);
+
+          $vsource = idx($vcell, 'source');
+          $vsource = implode('', $vsource);
+
+          $diff = id(new PhutilProseDifferenceEngine())
+            ->getDiff($usource, $vsource);
+
+          $u_content = $this->newProseDiffCell($diff, array('=', '-'));
+          $v_content = $this->newProseDiffCell($diff, array('=', '+'));
+
+          $u_content = $this->newJupyterCell(null, $u_content, null);
+          $v_content = $this->newJupyterCell(null, $v_content, null);
+
+          $u_content = $this->newCellContainer($u_content);
+          $v_content = $this->newCellContainer($v_content);
+
+          return id(new PhabricatorDocumentEngineBlockDiff())
+            ->setOldContent($u_content)
+            ->addOldClass('old')
+            ->setNewContent($v_content)
+            ->addNewClass('new');
+      }
+    }
+
+    return parent::newBlockDiffViews($uref, $ublock, $vref, $vblock);
+  }
+
+  public function newBlockContentView(
+    PhabricatorDocumentRef $ref,
+    PhabricatorDocumentEngineBlock $block) {
+
+    $viewer = $this->getViewer();
+    $cell = $block->getContent();
+
+    $cell_content = $this->renderJupyterCell($viewer, $cell);
+
+    return $this->newCellContainer($cell_content);
+  }
+
+  private function newCellContainer($cell_content) {
+    $notebook_table = phutil_tag(
+      'table',
+      array(
+        'class' => 'jupyter-notebook',
+      ),
+      $cell_content);
+
+    $container = phutil_tag(
+      'div',
+      array(
+        'class' => 'document-engine-jupyter document-engine-diff',
+      ),
+      $notebook_table);
+
+    return $container;
+  }
+
+  private function newProseDiffCell(PhutilProseDiff $diff, array $mask) {
+    $mask = array_fuse($mask);
+
+    $result = array();
+    foreach ($diff->getParts() as $part) {
+      $type = $part['type'];
+      $text = $part['text'];
+
+      if (!isset($mask[$type])) {
+        continue;
+      }
+
+      switch ($type) {
+        case '-':
+          $result[] = phutil_tag(
+            'span',
+            array(
+              'class' => 'bright',
+            ),
+            $text);
+          break;
+        case '+':
+          $result[] = phutil_tag(
+            'span',
+            array(
+              'class' => 'bright',
+            ),
+            $text);
+          break;
+        case '=':
+          $result[] = $text;
+          break;
+      }
+    }
+
+    return array(
+      null,
+      phutil_tag(
+        'div',
+        array(
+          'class' => 'jupyter-cell-markdown',
+        ),
+        $result),
+    );
   }
 
   private function newDiffBlocks(PhabricatorDocumentRef $ref) {
@@ -62,22 +189,6 @@ final class PhabricatorJupyterDocumentEngine
     $idx = 1;
     $blocks = array();
     foreach ($cells as $cell) {
-      $cell_content = $this->renderJupyterCell($viewer, $cell);
-
-      $notebook_table = phutil_tag(
-        'table',
-        array(
-          'class' => 'jupyter-notebook',
-        ),
-        $cell_content);
-
-      $container = phutil_tag(
-        'div',
-        array(
-          'class' => 'document-engine-jupyter document-engine-diff',
-        ),
-        $notebook_table);
-
       // When the cell is a source code line, we can hash just the raw
       // input rather than all the cell metadata.
 
@@ -85,6 +196,9 @@ final class PhabricatorJupyterDocumentEngine
         case 'code/line':
           $hash_input = $cell['raw'];
           break;
+        case 'markdown':
+          $hash_input = implode('', $cell['source']);
+          break;
         default:
           $hash_input = serialize($cell);
           break;
@@ -97,7 +211,7 @@ final class PhabricatorJupyterDocumentEngine
       $blocks[] = id(new PhabricatorDocumentEngineBlock())
         ->setBlockKey($idx)
         ->setDifferenceHash($hash)
-        ->setContent($container);
+        ->setContent($cell);
 
       $idx++;
     }
@@ -197,6 +311,26 @@ final class PhabricatorJupyterDocumentEngine
     foreach ($cells as $cell) {
       $cell_type = idx($cell, 'cell_type');
 
+      if ($cell_type === 'markdown') {
+        $source = $cell['source'];
+        $source = implode('', $source);
+
+        // Attempt to split contiguous blocks of markdown into smaller
+        // pieces.
+
+        $chunks = preg_split(
+          '/\n\n+/',
+          $source);
+
+        foreach ($chunks as $chunk) {
+          $result = $cell;
+          $result['source'] = array($chunk);
+          $results[] = $result;
+        }
+
+        continue;
+      }
+
       if ($cell_type !== 'code') {
         $results[] = $cell;
         continue;
@@ -254,13 +388,6 @@ final class PhabricatorJupyterDocumentEngine
 
     list($label, $content) = $this->renderJupyterCellContent($viewer, $cell);
 
-    $label_cell = phutil_tag(
-      'td',
-      array(
-        'class' => 'jupyter-label',
-      ),
-      $label);
-
     $classes = null;
     switch (idx($cell, 'cell_type')) {
       case 'code/line':
@@ -268,6 +395,20 @@ final class PhabricatorJupyterDocumentEngine
         break;
     }
 
+    return $this->newJupyterCell(
+      $label,
+      $content,
+      $classes);
+  }
+
+  private function newJupyterCell($label, $content, $classes) {
+    $label_cell = phutil_tag(
+      'td',
+      array(
+        'class' => 'jupyter-label',
+      ),
+      $label);
+
     $content_cell = phutil_tag(
       'td',
       array(
@@ -300,7 +441,8 @@ final class PhabricatorJupyterDocumentEngine
         return $this->newCodeOutputCell($cell);
     }
 
-    return $this->newRawCell(id(new PhutilJSON())->encodeFormatted($cell));
+    return $this->newRawCell(id(new PhutilJSON())
+      ->encodeFormatted($cell));
   }
 
   private function newRawCell($content) {
@@ -321,8 +463,9 @@ final class PhabricatorJupyterDocumentEngine
       $content = array();
     }
 
-    $content = implode('', $content);
-    $content = phutil_escape_html_newlines($content);
+    // TODO: This should ideally highlight as Markdown, but the "md"
+    // highlighter in Pygments is painfully slow and not terribly useful.
+    $content = $this->highlightLines($content, 'txt');
 
     return array(
       null,
@@ -507,15 +650,20 @@ final class PhabricatorJupyterDocumentEngine
     return $label;
   }
 
-  private function highlightLines(array $lines) {
-    $head = head($lines);
-    $matches = null;
-    if (preg_match('/^%%(.*)$/', $head, $matches)) {
-      $restore = array_shift($lines);
-      $lang = $matches[1];
+  private function highlightLines(array $lines, $force_language = null) {
+    if ($force_language === null) {
+      $head = head($lines);
+      $matches = null;
+      if (preg_match('/^%%(.*)$/', $head, $matches)) {
+        $restore = array_shift($lines);
+        $lang = $matches[1];
+      } else {
+        $restore = null;
+        $lang = 'py';
+      }
     } else {
       $restore = null;
-      $lang = 'py';
+      $lang = $force_language;
     }
 
     $content = PhabricatorSyntaxHighlighter::highlightWithLanguage(
diff --git a/src/applications/paste/query/PhabricatorPasteQuery.php b/src/applications/paste/query/PhabricatorPasteQuery.php
index 54b53ceb4a..693c82780f 100644
--- a/src/applications/paste/query/PhabricatorPasteQuery.php
+++ b/src/applications/paste/query/PhabricatorPasteQuery.php
@@ -378,15 +378,15 @@ final class PhabricatorPasteQuery
   }
 
   private function highlightSource($source, $title, $language) {
-      if (empty($language)) {
-        return PhabricatorSyntaxHighlighter::highlightWithFilename(
-          $title,
-          $source);
-      } else {
-        return PhabricatorSyntaxHighlighter::highlightWithLanguage(
-          $language,
-          $source);
-      }
+    if (empty($language)) {
+      return PhabricatorSyntaxHighlighter::highlightWithFilename(
+        $title,
+        $source);
+    } else {
+      return PhabricatorSyntaxHighlighter::highlightWithLanguage(
+        $language,
+        $source);
+    }
   }
 
   public function getQueryApplicationClass() {
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
@@ -17,7 +17,7 @@ final class PHUIDiffOneUpInlineCommentRowScaffold
     $inline = head($inlines);
 
     $attrs = array(
-      'colspan' => 3,
+      'colspan' => 2,
       'id' => $inline->getScaffoldCellID(),
     );
 
@@ -32,6 +32,7 @@ final class PHUIDiffOneUpInlineCommentRowScaffold
     $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),
     );
 
diff --git a/webroot/rsrc/css/phui/phui-property-list-view.css b/webroot/rsrc/css/phui/phui-property-list-view.css
index 61be658feb..98cb0db820 100644
--- a/webroot/rsrc/css/phui/phui-property-list-view.css
+++ b/webroot/rsrc/css/phui/phui-property-list-view.css
@@ -315,6 +315,16 @@ div.phui-property-list-stacked .phui-property-list-properties
   border-width: 0 1px;
 }
 
+td.new .jupyter-cell-code-line {
+  background: {$new-background};
+  border-color: {$new-bright};
+}
+
+td.old .jupyter-cell-code-line {
+  background: {$old-background};
+  border-color: {$old-bright};
+}
+
 .jupyter-cell-code-head {
   border-top-width: 1px;
   margin-top: 4px;
@@ -364,3 +374,7 @@ div.phui-property-list-stacked .phui-property-list-properties
 .jupyter-output-html {
   background: {$sh-indigobackground};
 }
+
+.jupyter-cell-markdown {
+  white-space: pre-wrap;
+}