Index: src/applications/differential/customfield/DifferentialJIRAIssuesField.php
===================================================================
--- src/applications/differential/customfield/DifferentialJIRAIssuesField.php
+++ src/applications/differential/customfield/DifferentialJIRAIssuesField.php
@@ -3,6 +3,8 @@
 final class DifferentialJIRAIssuesField
   extends DifferentialStoredCustomField {
 
+  private $error;
+
   public function getFieldKey() {
     return 'phabricator:jira-issues';
   }
@@ -12,7 +14,7 @@
   }
 
   public function setValueFromStorage($value) {
-    $this->setValue(json_decode($value, true));
+    $this->setValue(phutil_json_decode($value));
     return $this;
   }
 
@@ -33,7 +35,7 @@
   }
 
   public function renderPropertyViewValue(array $handles) {
-    $xobjs = $this->loadDoorkeeperExternalObjects();
+    $xobjs = $this->loadDoorkeeperExternalObjects($this->getValue());
     if (!$xobjs) {
       return null;
     }
@@ -47,12 +49,12 @@
     return phutil_implode_html(phutil_tag('br'), $links);
   }
 
-  private function buildDoorkeeperRefs() {
+  private function buildDoorkeeperRefs($value) {
     $provider = PhabricatorAuthProviderOAuth1JIRA::getJIRAProvider();
 
     $refs = array();
-    if ($this->getValue()) {
-      foreach ($this->getValue() as $jira_key) {
+    if ($value) {
+      foreach ($value as $jira_key) {
         $refs[] = id(new DoorkeeperObjectRef())
           ->setApplicationType(DoorkeeperBridgeJIRA::APPTYPE_JIRA)
           ->setApplicationDomain($provider->getProviderDomain())
@@ -64,8 +66,8 @@
     return $refs;
   }
 
-  private function loadDoorkeeperExternalObjects() {
-    $refs = $this->buildDoorkeeperRefs();
+  private function loadDoorkeeperExternalObjects($value) {
+    $refs = $this->buildDoorkeeperRefs($value);
     if (!$refs) {
       return array();
     }
@@ -78,6 +80,156 @@
     return $xobjs;
   }
 
-  // TODO: Implement edit; this field is readonly for now.
+  public function shouldAppearInEditView() {
+    return PhabricatorAuthProviderOAuth1JIRA::getJIRAProvider();
+  }
+
+  public function shouldAppearInApplicationTransactions() {
+    return PhabricatorAuthProviderOAuth1JIRA::getJIRAProvider();
+  }
+
+  public function readValueFromRequest(AphrontRequest $request) {
+    $this->setValue($request->getStrList($this->getFieldKey()));
+    return $this;
+  }
+
+  public function renderEditControl(array $handles) {
+    return id(new AphrontFormTextControl())
+      ->setLabel(pht('JIRA Issues'))
+      ->setCaption(
+        pht('Example: %s', phutil_tag('tt', array(), 'JIS-3, JIS-9')))
+      ->setName($this->getFieldKey())
+      ->setValue(implode(', ', nonempty($this->getValue(), array())))
+      ->setError($this->error);
+  }
+
+  public function getOldValueForApplicationTransactions() {
+    return nonempty($this->getValue(), array());
+  }
+
+  public function getNewValueForApplicationTransactions() {
+    return nonempty($this->getValue(), array());
+  }
+
+  public function validateApplicationTransactions(
+    PhabricatorApplicationTransactionEditor $editor,
+    $type,
+    array $xactions) {
+
+    $this->error = null;
+
+    $errors = parent::validateApplicationTransactions(
+      $editor,
+      $type,
+      $xactions);
+
+    $transaction = null;
+    foreach ($xactions as $xaction) {
+      $value = $xaction->getNewValue();
+
+      $refs = id(new DoorkeeperImportEngine())
+        ->setViewer($this->getViewer())
+        ->setRefs($this->buildDoorkeeperRefs($value))
+        ->execute();
+
+      $bad = array();
+      foreach ($refs as $ref) {
+        if (!$ref->getIsVisible()) {
+          $bad[] = $ref->getObjectID();
+        }
+      }
+
+      if ($bad) {
+        $bad = implode(', ', $bad);
+        $this->error = pht('Invalid');
+
+        $error = new PhabricatorApplicationTransactionValidationError(
+          $type,
+          pht('Invalid'),
+          pht(
+            "Some JIRA issues could not be loaded. They may not exist, or ".
+            "you may not have permission to view them: %s",
+            $bad),
+          $xaction);
+        $errors[] = $error;
+      }
+    }
+
+    return $errors;
+  }
+
+  public function getApplicationTransactionTitle(
+    PhabricatorApplicationTransaction $xaction) {
+
+    $old = $xaction->getOldValue();
+    if (!is_array($old)) {
+      $old = array();
+    }
+
+    $new = $xaction->getNewValue();
+    if (!is_array($new)) {
+      $new = array();
+    }
+
+    $add = array_diff($new, $old);
+    $rem = array_diff($old, $new);
+
+    $author_phid = $xaction->getAuthorPHID();
+    if ($add && $rem) {
+      return pht(
+        '%s updated JIRA issue(s): added %d %s; removed %d %s.',
+        $xaction->renderHandleLink($author_phid),
+        new PhutilNumber(count($add)),
+        implode(', ', $add),
+        new PhutilNumber(count($rem)),
+        implode(', ', $rem));
+    } else if ($add) {
+      return pht(
+        '%s added %d JIRA issue(s): %s.',
+        $xaction->renderHandleLink($author_phid),
+        new PhutilNumber(count($add)),
+        implode(', ', $add));
+    } else if ($rem) {
+      return pht(
+        '%s removed %d JIRA issue(s): %s.',
+        $xaction->renderHandleLink($author_phid),
+        new PhutilNumber(count($rem)),
+        implode(', ', $rem));
+    }
+
+    return parent::getApplicationTransactionTitle($xaction);
+  }
+
+  public function applyApplicationTransactionExternalEffects(
+    PhabricatorApplicationTransaction $xaction) {
+
+    // Update the CustomField storage.
+    parent::applyApplicationTransactionExternalEffects($xaction);
+
+    // Now, synchronize the Doorkeeper edges.
+    $revision = $this->getObject();
+    $revision_phid = $revision->getPHID();
+
+    $edge_type = PhabricatorEdgeConfig::TYPE_PHOB_HAS_JIRAISSUE;
+    $xobjs = $this->loadDoorkeeperExternalObjects($xaction->getNewValue());
+    $edge_dsts = mpull($xobjs, 'getPHID');
+
+    $edges = PhabricatorEdgeQuery::loadDestinationPHIDs(
+      $revision_phid,
+      $edge_type);
+
+    $editor = id(new PhabricatorEdgeEditor())
+      ->setActor($this->getViewer());
+
+    foreach (array_diff($edges, $edge_dsts) as $rem_edge) {
+      $editor->removeEdge($revision_phid, $edge_type, $rem_edge);
+    }
+
+    foreach (array_diff($edge_dsts, $edges) as $add_edge) {
+      $editor->addEdge($revision_phid, $edge_type, $add_edge);
+    }
+
+    $editor->save();
+  }
 
 }
Index: src/applications/transactions/editor/PhabricatorApplicationTransactionEditor.php
===================================================================
--- src/applications/transactions/editor/PhabricatorApplicationTransactionEditor.php
+++ src/applications/transactions/editor/PhabricatorApplicationTransactionEditor.php
@@ -1806,6 +1806,8 @@
         "integration for ApplicationTransactions.");
     }
 
+    $field->setViewer($this->getActor());
+
     return $field;
   }