diff --git a/src/repository/api/ArcanistGitAPI.php b/src/repository/api/ArcanistGitAPI.php
--- a/src/repository/api/ArcanistGitAPI.php
+++ b/src/repository/api/ArcanistGitAPI.php
@@ -189,6 +189,28 @@
       list($commit, $tree, $parents, $time, $author, $author_email,
         $title, $message) = explode("\1", trim($line), 8);
       $message = rtrim($message);
+      $co_authors = array();
+
+      foreach (explode("\n", $message) as $message_line) {
+        if (strncasecmp($message_line, 'Co-authored-by:', 15) !== 0) {
+          continue;
+        }
+
+        $matches = array();
+        $status = preg_match(
+          '/^co-authored-by:\s*(.*)<(.*)>/i',
+          $message_line,
+          $matches);
+
+        if ($status !== 1) {
+          continue;
+        }
+
+        $co_authors[] = array(
+          'name' => trim($matches[1]),
+          'email' => trim($matches[2]),
+        );
+      }
 
       $commits[$commit] = array(
         'commit'  => $commit,
@@ -199,6 +221,7 @@
         'summary' => $title,
         'message' => $message,
         'authorEmail' => $author_email,
+        'coAuthors' => $co_authors,
       );
     }
 
diff --git a/src/repository/api/ArcanistMercurialAPI.php b/src/repository/api/ArcanistMercurialAPI.php
--- a/src/repository/api/ArcanistMercurialAPI.php
+++ b/src/repository/api/ArcanistMercurialAPI.php
@@ -202,6 +202,7 @@
           $parents, $desc) = explode("\1", $log, 9);
 
         list($author, $author_email) = $this->parseFullAuthor($full_author);
+        $co_authors = array();
 
         // NOTE: If a commit has only one parent, {parents} returns empty.
         // If it has two parents, {parents} returns revs and short hashes, not
@@ -223,6 +224,28 @@
             $node);
         }
 
+
+        foreach (explode("\n", $desc) as $line) {
+          if (strncasecmp($line, 'Co-authored-by:', 15) !== 0) {
+            continue;
+          }
+
+          $matches = array();
+          $status = preg_match(
+            '/^co-authored-by:\s*(.*)<(.*)>/i',
+            $line,
+            $matches);
+
+          if ($status !== 1) {
+            continue;
+          }
+
+          $co_authors[] = array(
+            'name' => $matches[1],
+            'email' => $matches[2],
+          );
+        }
+
         $commits[$node] = array(
           'author'  => $author,
           'time'    => strtotime($date),
@@ -235,6 +258,7 @@
           'summary' => head(explode("\n", $desc)),
           'message' => $desc,
           'authorEmail' => $author_email,
+          'coAuthors' => $co_authors,
         );
 
         $last_node = $node;
diff --git a/src/workflow/ArcanistWorkflow.php b/src/workflow/ArcanistWorkflow.php
--- a/src/workflow/ArcanistWorkflow.php
+++ b/src/workflow/ArcanistWorkflow.php
@@ -968,6 +968,11 @@
     return $working_copy;
   }
 
+  /**
+   * @param ArcanistRepositoryAPI<mixed> $api
+   *
+   * @return self<mixed>
+   */
   final public function setRepositoryAPI($api) {
     $this->repositoryAPI = $api;
     return $this;
@@ -981,6 +986,9 @@
     }
   }
 
+  /**
+   * @return ArcanistRepositoryAPI<mixed>
+   */
   final public function getRepositoryAPI() {
     $configuration_engine = $this->getConfigurationEngine();
     if ($configuration_engine) {