diff --git a/resources/celerity/map.php b/resources/celerity/map.php
--- a/resources/celerity/map.php
+++ b/resources/celerity/map.php
@@ -13,7 +13,7 @@
     'core.pkg.js' => 'ab3502fe',
     'dark-console.pkg.js' => '187792c2',
     'differential.pkg.css' => 'ffb69e3d',
-    'differential.pkg.js' => '5080baf4',
+    'differential.pkg.js' => '5986f349',
     'diffusion.pkg.css' => '42c75c37',
     'diffusion.pkg.js' => '78c9885d',
     'maniphest.pkg.css' => '35995d6d',
@@ -437,7 +437,7 @@
     'rsrc/js/application/releeph/releeph-preview-branch.js' => '75184d68',
     'rsrc/js/application/releeph/releeph-request-state-change.js' => '9f081f05',
     'rsrc/js/application/releeph/releeph-request-typeahead.js' => 'aa3a100c',
-    'rsrc/js/application/repository/repository-crossreference.js' => '6337cf26',
+    'rsrc/js/application/repository/repository-crossreference.js' => '44d48cd1',
     'rsrc/js/application/search/behavior-reorder-profile-menu-items.js' => 'e5bdb730',
     'rsrc/js/application/search/behavior-reorder-queries.js' => 'b86f297f',
     'rsrc/js/application/transactions/behavior-comment-actions.js' => '4dffaeb2',
@@ -693,7 +693,7 @@
     'javelin-behavior-reorder-applications' => 'aa371860',
     'javelin-behavior-reorder-columns' => '8ac32fd9',
     'javelin-behavior-reorder-profile-menu-items' => 'e5bdb730',
-    'javelin-behavior-repository-crossreference' => '6337cf26',
+    'javelin-behavior-repository-crossreference' => '44d48cd1',
     'javelin-behavior-scrollbar' => '92388bae',
     'javelin-behavior-search-reorder-queries' => 'b86f297f',
     'javelin-behavior-select-content' => 'e8240b50',
@@ -1309,6 +1309,12 @@
     '43bc9360' => array(
       'javelin-install',
     ),
+    '44d48cd1' => array(
+      'javelin-behavior',
+      'javelin-dom',
+      'javelin-stratcom',
+      'javelin-uri',
+    ),
     '457f4d16' => array(
       'javelin-behavior',
       'javelin-stratcom',
@@ -1536,12 +1542,6 @@
       'javelin-request',
       'javelin-uri',
     ),
-    '6337cf26' => array(
-      'javelin-behavior',
-      'javelin-dom',
-      'javelin-stratcom',
-      'javelin-uri',
-    ),
     '65bb0011' => array(
       'javelin-behavior',
       'javelin-dom',
diff --git a/src/applications/differential/view/DifferentialChangesetDetailView.php b/src/applications/differential/view/DifferentialChangesetDetailView.php
--- a/src/applications/differential/view/DifferentialChangesetDetailView.php
+++ b/src/applications/differential/view/DifferentialChangesetDetailView.php
@@ -246,6 +246,7 @@
           'displayPath' => hsprintf('%s', $display_parts),
           'icon' => $display_icon,
           'pathParts' => $path_parts,
+          'symbolPath' => $display_filename,
 
           'pathIconIcon' => $changeset->getPathIconIcon(),
           'pathIconColor' => $changeset->getPathIconColor(),
diff --git a/src/applications/diffusion/controller/DiffusionSymbolController.php b/src/applications/diffusion/controller/DiffusionSymbolController.php
--- a/src/applications/diffusion/controller/DiffusionSymbolController.php
+++ b/src/applications/diffusion/controller/DiffusionSymbolController.php
@@ -4,7 +4,10 @@
 
   public function handleRequest(AphrontRequest $request) {
     $viewer = $this->getViewer();
+
+    // See T13638 for discussion of escaping.
     $name = $request->getURIData('name');
+    $name = phutil_unescape_uri_path_component($name);
 
     $query = id(new DiffusionSymbolQuery())
       ->setViewer($viewer)
diff --git a/src/applications/diffusion/engineextension/DiffusionDatasourceEngineExtension.php b/src/applications/diffusion/engineextension/DiffusionDatasourceEngineExtension.php
--- a/src/applications/diffusion/engineextension/DiffusionDatasourceEngineExtension.php
+++ b/src/applications/diffusion/engineextension/DiffusionDatasourceEngineExtension.php
@@ -66,12 +66,12 @@
       $parts = null;
       if (preg_match('/(.*)(?:\\.|::|->)(.*)/', $symbol, $parts)) {
         return urisprintf(
-          '/diffusion/symbol/%s/?jump=true&context=%s',
+          '/diffusion/symbol/%p/?jump=true&context=%s',
           $parts[2],
           $parts[1]);
       } else {
         return urisprintf(
-          '/diffusion/symbol/%s/?jump=true',
+          '/diffusion/symbol/%p/?jump=true',
           $symbol);
       }
     }
diff --git a/webroot/rsrc/js/application/repository/repository-crossreference.js b/webroot/rsrc/js/application/repository/repository-crossreference.js
--- a/webroot/rsrc/js/application/repository/repository-crossreference.js
+++ b/webroot/rsrc/js/application/repository/repository-crossreference.js
@@ -66,13 +66,8 @@
 
         var target = e.getTarget();
 
-        try {
-          // If we're in an inline comment, don't link symbols.
-          if (JX.DOM.findAbove(target, 'div', 'differential-inline-comment')) {
-            return;
-          }
-        } catch (ex) {
-          // Continue if we're not inside an inline comment.
+        if (!canLinkNode(target)) {
+          return;
         }
 
         // If only part of the symbol was edited, the symbol name itself will
@@ -97,6 +92,29 @@
         }
       });
   }
+
+  function canLinkNode(node) {
+    try {
+      // If we're in an inline comment, don't link symbols.
+      if (JX.DOM.findAbove(node, 'div', 'differential-inline-comment')) {
+        return false;
+      }
+    } catch (ex) {
+      // Continue if we're not inside an inline comment.
+    }
+
+    // See T13644. Don't open symbols if we're inside a changeset header.
+    try {
+      if (JX.DOM.findAbove(node, 'h1')) {
+        return false;
+      }
+    } catch (ex) {
+      // Continue if not inside a header.
+    }
+
+    return true;
+  }
+
   function unhighlight() {
     highlighted && JX.DOM.alterClass(highlighted, classHighlight, false);
     highlighted = null;
@@ -159,6 +177,9 @@
     uri_symbol = uri_symbol.trim();
 
     // See T13437. Symbols like "#define" need to be encoded.
+    // See T13644. Symbols like "a/b" must be double-encoded to survive
+    // one layer of decoding by the webserver.
+    uri_symbol = encodeURIComponent(uri_symbol);
     uri_symbol = encodeURIComponent(uri_symbol);
 
     var uri = JX.$U('/diffusion/symbol/' + uri_symbol + '/');
@@ -223,7 +244,7 @@
     var changeset;
     try {
       changeset = JX.DOM.findAbove(target, 'div', 'differential-changeset');
-      return JX.Stratcom.getData(changeset).path;
+      return JX.Stratcom.getData(changeset).symbolPath || null;
     } catch (ex) {
       // Ignore.
     }
@@ -315,13 +336,8 @@
 
       var target = e.getTarget();
 
-      try {
-        // If we're in an inline comment, don't link symbols.
-        if (JX.DOM.findAbove(target, 'div', 'differential-inline-comment')) {
-          return;
-        }
-      } catch (ex) {
-        // Continue if we're not inside an inline comment.
+      if (!canLinkNode(target)) {
+        return;
       }
 
       // If only part of the symbol was edited, the symbol name itself will