diff --git a/java/com/google/gerrit/acceptance/ExtensionRegistry.java b/java/com/google/gerrit/acceptance/ExtensionRegistry.java
index 85c4c13..1e5598e 100644
--- a/java/com/google/gerrit/acceptance/ExtensionRegistry.java
+++ b/java/com/google/gerrit/acceptance/ExtensionRegistry.java
@@ -25,6 +25,8 @@
 import com.google.gerrit.extensions.events.GitReferenceUpdatedListener;
 import com.google.gerrit.extensions.events.GroupIndexedListener;
 import com.google.gerrit.extensions.events.ProjectIndexedListener;
+import com.google.gerrit.extensions.events.ReviewerAddedListener;
+import com.google.gerrit.extensions.events.ReviewerDeletedListener;
 import com.google.gerrit.extensions.events.RevisionCreatedListener;
 import com.google.gerrit.extensions.events.TopicEditedListener;
 import com.google.gerrit.extensions.events.WorkInProgressStateChangedListener;
@@ -91,6 +93,8 @@
   private final DynamicMap<ProjectConfigEntry> pluginConfigEntries;
   private final DynamicSet<PluginPushOption> pluginPushOptions;
   private final DynamicSet<OnPostReview> onPostReviews;
+  private final DynamicSet<ReviewerAddedListener> reviewerAddedListeners;
+  private final DynamicSet<ReviewerDeletedListener> reviewerDeletedListeners;
 
   @Inject
   ExtensionRegistry(
@@ -125,7 +129,9 @@
       DynamicMap<PluginProjectPermissionDefinition> pluginProjectPermissionDefinitions,
       DynamicMap<ProjectConfigEntry> pluginConfigEntries,
       DynamicSet<PluginPushOption> pluginPushOption,
-      DynamicSet<OnPostReview> onPostReviews) {
+      DynamicSet<OnPostReview> onPostReviews,
+      DynamicSet<ReviewerAddedListener> reviewerAddedListeners,
+      DynamicSet<ReviewerDeletedListener> reviewerDeletedListeners) {
     this.accountIndexedListeners = accountIndexedListeners;
     this.changeIndexedListeners = changeIndexedListeners;
     this.groupIndexedListeners = groupIndexedListeners;
@@ -158,6 +164,8 @@
     this.pluginConfigEntries = pluginConfigEntries;
     this.pluginPushOptions = pluginPushOption;
     this.onPostReviews = onPostReviews;
+    this.reviewerAddedListeners = reviewerAddedListeners;
+    this.reviewerDeletedListeners = reviewerDeletedListeners;
   }
 
   public Registration newRegistration() {
@@ -302,6 +310,14 @@
       return add(onPostReviews, onPostReview);
     }
 
+    public Registration add(ReviewerAddedListener reviewerAddedListener) {
+      return add(reviewerAddedListeners, reviewerAddedListener);
+    }
+
+    public Registration add(ReviewerDeletedListener reviewerDeletedListener) {
+      return add(reviewerDeletedListeners, reviewerDeletedListener);
+    }
+
     private <T> Registration add(DynamicSet<T> dynamicSet, T extension) {
       return add(dynamicSet, extension, "gerrit");
     }
diff --git a/java/com/google/gerrit/server/change/AddReviewersOp.java b/java/com/google/gerrit/server/change/AddReviewersOp.java
index a333ce5..cbbd01a 100644
--- a/java/com/google/gerrit/server/change/AddReviewersOp.java
+++ b/java/com/google/gerrit/server/change/AddReviewersOp.java
@@ -219,8 +219,13 @@
               .map(r -> accountCache.get(r.accountId()))
               .flatMap(Streams::stream)
               .collect(toList());
-      reviewerAdded.fire(
-          ctx.getChangeData(change), patchSet, reviewers, ctx.getAccount(), ctx.getWhen());
+      eventSender =
+          () ->
+              reviewerAdded.fire(
+                  ctx.getChangeData(change), patchSet, reviewers, ctx.getAccount(), ctx.getWhen());
+      if (sendEvent) {
+        sendEvent();
+      }
     }
   }
 }
diff --git a/java/com/google/gerrit/server/change/DeleteReviewerOp.java b/java/com/google/gerrit/server/change/DeleteReviewerOp.java
index a26f107..1e40429 100644
--- a/java/com/google/gerrit/server/change/DeleteReviewerOp.java
+++ b/java/com/google/gerrit/server/change/DeleteReviewerOp.java
@@ -202,16 +202,23 @@
             "Cannot email update for change %s", currChange.getId());
       }
     }
-    reviewerDeleted.fire(
-        ctx.getChangeData(currChange),
-        patchSet,
-        accountCache.get(reviewer.id()).orElse(AccountState.forAccount(reviewer)),
-        ctx.getAccount(),
-        mailMessage,
-        newApprovals,
-        oldApprovals,
-        notify.handling(),
-        ctx.getWhen());
+
+    NotifyHandling notifyHandling = notify.handling();
+    eventSender =
+        () ->
+            reviewerDeleted.fire(
+                ctx.getChangeData(currChange),
+                patchSet,
+                accountCache.get(reviewer.id()).orElse(AccountState.forAccount(reviewer)),
+                ctx.getAccount(),
+                mailMessage,
+                newApprovals,
+                oldApprovals,
+                notifyHandling,
+                ctx.getWhen());
+    if (sendEvent) {
+      sendEvent();
+    }
   }
 
   private Iterable<PatchSetApproval> approvals(ChangeContext ctx, Account.Id accountId) {
diff --git a/java/com/google/gerrit/server/change/ReviewerOp.java b/java/com/google/gerrit/server/change/ReviewerOp.java
index 716ac5e..12227c2 100644
--- a/java/com/google/gerrit/server/change/ReviewerOp.java
+++ b/java/com/google/gerrit/server/change/ReviewerOp.java
@@ -32,6 +32,8 @@
 
 public class ReviewerOp implements BatchUpdateOp {
   protected boolean sendEmail = true;
+  protected boolean sendEvent = true;
+  protected Runnable eventSender = () -> {};
   protected PatchSet patchSet;
   protected Result opResult;
 
@@ -42,6 +44,14 @@
     this.sendEmail = false;
   }
 
+  public void suppressEvent() {
+    this.sendEvent = false;
+  }
+
+  public void sendEvent() {
+    eventSender.run();
+  }
+
   void setPatchSet(PatchSet patchSet) {
     this.patchSet = requireNonNull(patchSet);
   }
diff --git a/java/com/google/gerrit/server/notedb/CommitRewriter.java b/java/com/google/gerrit/server/notedb/CommitRewriter.java
index 7f13731..3cbe546 100644
--- a/java/com/google/gerrit/server/notedb/CommitRewriter.java
+++ b/java/com/google/gerrit/server/notedb/CommitRewriter.java
@@ -20,6 +20,7 @@
 import static com.google.gerrit.server.notedb.ChangeNoteUtil.FOOTER_LABEL;
 import static com.google.gerrit.server.notedb.ChangeNoteUtil.FOOTER_REAL_USER;
 import static com.google.gerrit.server.notedb.ChangeNoteUtil.FOOTER_SUBMITTED_WITH;
+import static com.google.gerrit.server.notedb.ChangeNoteUtil.FOOTER_TAG;
 import static com.google.gerrit.server.util.AccountTemplateUtil.ACCOUNT_TEMPLATE_PATTERN;
 import static com.google.gerrit.server.util.AccountTemplateUtil.ACCOUNT_TEMPLATE_REGEX;
 
@@ -39,6 +40,7 @@
 import com.google.gerrit.entities.SubmitRecord;
 import com.google.gerrit.git.RefUpdateUtil;
 import com.google.gerrit.json.OutputFormat;
+import com.google.gerrit.server.ChangeMessagesUtil;
 import com.google.gerrit.server.account.AccountCache;
 import com.google.gerrit.server.account.AccountState;
 import com.google.gerrit.server.account.externalids.ExternalId;
@@ -169,7 +171,8 @@
       Pattern.compile("Assignee changed from: (.*) to: (.*)");
 
   private static final Pattern REMOVED_REVIEWER_PATTERN =
-      Pattern.compile("Removed (cc|reviewer) (.*)(\\.| with the following votes)");
+      Pattern.compile(
+          "Removed (cc|reviewer) (.*)(\\.| with the following votes:\n.*)", Pattern.DOTALL);
 
   private static final Pattern REMOVED_VOTE_PATTERN = Pattern.compile("Removed (.*) by (.*)");
 
@@ -185,12 +188,18 @@
 
   private static final Pattern ON_CODE_OWNER_ADD_REVIEWER_PATTERN =
       Pattern.compile("(.*) who was added as reviewer owns the following files");
+
+  private static final String CODE_OWNER_ADD_REVIEWER_TAG =
+      ChangeMessagesUtil.AUTOGENERATED_BY_GERRIT_TAG_PREFIX + "code-owners:addReviewer";
+
   private static final String ON_CODE_OWNER_APPROVAL_REGEX = "code-owner approved by (.*):";
   private static final String ON_CODE_OWNER_OVERRIDE_REGEX =
       "code-owners submit requirement .* overridden by (.*)";
 
   private static final Pattern ON_CODE_OWNER_REVIEW_PATTERN =
       Pattern.compile(ON_CODE_OWNER_APPROVAL_REGEX + "|" + ON_CODE_OWNER_OVERRIDE_REGEX);
+  private static final Pattern ON_CODE_OWNER_POST_REVIEW_PATTERN =
+      Pattern.compile("Patch Set [0-9]+:[\\s\\S]*By (voting|removing)[\\s\\S]*");
 
   private static final Pattern REPLY_BY_REASON_PATTERN =
       Pattern.compile("(.*) replied on the change");
@@ -583,7 +592,7 @@
     }
     Matcher matcher = REMOVED_REVIEWER_PATTERN.matcher(originalChangeMessage);
 
-    if (matcher.find() && !ACCOUNT_TEMPLATE_PATTERN.matcher(matcher.group(2)).matches()) {
+    if (matcher.matches() && !ACCOUNT_TEMPLATE_PATTERN.matcher(matcher.group(2)).matches()) {
       // Since we do not use change messages for reviewer updates on UI, it does not matter what we
       // rewrite it to.
       return Optional.of(originalChangeMessage.substring(0, matcher.end(1)));
@@ -731,7 +740,11 @@
     if (Strings.isNullOrEmpty(originalMessage)) {
       return Optional.empty();
     }
-
+    Matcher onCodeOwnerPostReviewMatcher =
+        ON_CODE_OWNER_POST_REVIEW_PATTERN.matcher(originalMessage);
+    if (!onCodeOwnerPostReviewMatcher.matches()) {
+      return Optional.empty();
+    }
     Matcher onCodeOwnerReviewMatcher = ON_CODE_OWNER_REVIEW_PATTERN.matcher(originalMessage);
     while (onCodeOwnerReviewMatcher.find()) {
       String accountName =
@@ -823,7 +836,9 @@
     for (FooterLine fl : footerLines) {
       String footerKey = fl.getKey();
       String footerValue = fl.getValue();
-      if (footerKey.equalsIgnoreCase(FOOTER_ASSIGNEE.getName())) {
+      if (footerKey.equalsIgnoreCase(FOOTER_TAG.getName())) {
+        fixProgress.tag = footerValue;
+      } else if (footerKey.equalsIgnoreCase(FOOTER_ASSIGNEE.getName())) {
         Account.Id oldAssignee = fixProgress.assigneeId;
         FixIdentResult fixedAssignee = null;
         if (footerValue.equals("")) {
@@ -954,7 +969,8 @@
       fixedChangeMessage =
           fixCodeOwnersOnReviewChangeMessage(fixProgress.updateAuthorId, originalChangeMessage);
     }
-    if (!fixedChangeMessage.isPresent()) {
+    if (!fixedChangeMessage.isPresent()
+        && Objects.equals(fixProgress.tag, CODE_OWNER_ADD_REVIEWER_TAG)) {
       fixedChangeMessage =
           fixCodeOwnersOnAddReviewerChangeMessage(fixProgress, originalChangeMessage);
     }
@@ -1194,6 +1210,9 @@
     /** {@link RefNames#changeMetaRef} of the change that is being fixed. */
     final String changeMetaRef;
 
+    /** Tag at current commit update. */
+    String tag = null;
+
     /** Assignee at current commit update. */
     Account.Id assigneeId = null;
 
diff --git a/java/com/google/gerrit/server/restapi/change/PostReview.java b/java/com/google/gerrit/server/restapi/change/PostReview.java
index 5002a82..5c252f4 100644
--- a/java/com/google/gerrit/server/restapi/change/PostReview.java
+++ b/java/com/google/gerrit/server/restapi/change/PostReview.java
@@ -92,7 +92,9 @@
 import com.google.gerrit.server.PatchSetUtil;
 import com.google.gerrit.server.PublishCommentUtil;
 import com.google.gerrit.server.ReviewerSet;
+import com.google.gerrit.server.account.AccountCache;
 import com.google.gerrit.server.account.AccountResolver;
+import com.google.gerrit.server.account.AccountState;
 import com.google.gerrit.server.approval.ApprovalsUtil;
 import com.google.gerrit.server.change.ChangeResource;
 import com.google.gerrit.server.change.EmailReviewComments;
@@ -105,6 +107,7 @@
 import com.google.gerrit.server.change.WorkInProgressOp;
 import com.google.gerrit.server.config.GerritServerConfig;
 import com.google.gerrit.server.extensions.events.CommentAdded;
+import com.google.gerrit.server.extensions.events.ReviewerAdded;
 import com.google.gerrit.server.logging.Metadata;
 import com.google.gerrit.server.logging.TraceContext;
 import com.google.gerrit.server.notedb.ChangeNotes;
@@ -187,6 +190,7 @@
   private final BatchUpdate.Factory updateFactory;
   private final ChangeResource.Factory changeResourceFactory;
   private final ChangeData.Factory changeDataFactory;
+  private final AccountCache accountCache;
   private final ApprovalsUtil approvalsUtil;
   private final ChangeMessagesUtil cmUtil;
   private final CommentsUtil commentsUtil;
@@ -206,6 +210,7 @@
   private final PluginSetContext<CommentValidator> commentValidators;
   private final PluginSetContext<OnPostReview> onPostReviews;
   private final ReplyAttentionSetUpdates replyAttentionSetUpdates;
+  private final ReviewerAdded reviewerAdded;
   private final boolean strictLabels;
   private final boolean publishPatchSetLevelComment;
 
@@ -214,6 +219,7 @@
       BatchUpdate.Factory updateFactory,
       ChangeResource.Factory changeResourceFactory,
       ChangeData.Factory changeDataFactory,
+      AccountCache accountCache,
       ApprovalsUtil approvalsUtil,
       ChangeMessagesUtil cmUtil,
       CommentsUtil commentsUtil,
@@ -233,10 +239,12 @@
       PermissionBackend permissionBackend,
       PluginSetContext<CommentValidator> commentValidators,
       PluginSetContext<OnPostReview> onPostReviews,
-      ReplyAttentionSetUpdates replyAttentionSetUpdates) {
+      ReplyAttentionSetUpdates replyAttentionSetUpdates,
+      ReviewerAdded reviewerAdded) {
     this.updateFactory = updateFactory;
     this.changeResourceFactory = changeResourceFactory;
     this.changeDataFactory = changeDataFactory;
+    this.accountCache = accountCache;
     this.commentsUtil = commentsUtil;
     this.publishCommentUtil = publishCommentUtil;
     this.psUtil = psUtil;
@@ -256,6 +264,7 @@
     this.commentValidators = commentValidators;
     this.onPostReviews = onPostReviews;
     this.replyAttentionSetUpdates = replyAttentionSetUpdates;
+    this.reviewerAdded = reviewerAdded;
     this.strictLabels = gerritConfig.getBoolean("change", "strictLabels", false);
     this.publishPatchSetLevelComment =
         gerritConfig.getBoolean("event", "comment-added", "publishPatchSetLevelComment", true);
@@ -371,6 +380,7 @@
       logger.atFine().log("adding reviewer additions");
       for (ReviewerModification reviewerResult : reviewerResults) {
         reviewerResult.op.suppressEmail(); // Send a single batch email below.
+        reviewerResult.op.suppressEvent(); // Send events below, if possible as batch.
         bu.addOp(revision.getChange().getId(), reviewerResult.op);
         if (!ccOrReviewer && reviewerResult.reviewers.contains(account)) {
           logger.atFine().log("calling user is explicitly added as reviewer or CC");
@@ -386,6 +396,7 @@
         ReviewerModification selfAddition =
             reviewerModifier.ccCurrentUser(revision.getUser(), revision);
         selfAddition.op.suppressEmail();
+        selfAddition.op.suppressEvent();
         bu.addOp(revision.getChange().getId(), selfAddition.op);
       }
 
@@ -433,8 +444,10 @@
         reviewerResult.gatherResults(cd);
       }
 
-      // Sending from AddReviewersOp was suppressed so we can send a single batch email here.
+      // Sending emails and events from ReviewersOps was suppressed so we can send a single batch
+      // email/event here.
       batchEmailReviewers(revision.getUser(), revision.getChange(), reviewerResults, notify);
+      batchReviewerEvents(revision.getUser(), cd, revision.getPatchSet(), reviewerResults, ts);
     }
 
     return Response.ok(output);
@@ -512,6 +525,35 @@
     }
   }
 
+  private void batchReviewerEvents(
+      CurrentUser user,
+      ChangeData cd,
+      PatchSet patchSet,
+      List<ReviewerModification> reviewerModifications,
+      Timestamp when) {
+    List<AccountState> newlyAddedReviewers = new ArrayList<>();
+
+    // There are no events for CCs and reviewers added/deleted by email.
+    for (ReviewerModification modification : reviewerModifications) {
+      Result reviewerAdditionResult = modification.op.getResult();
+      if (modification.state() == ReviewerState.REVIEWER) {
+        newlyAddedReviewers.addAll(
+            reviewerAdditionResult.addedReviewers().stream()
+                .map(psa -> psa.accountId())
+                .map(accountId -> accountCache.get(accountId))
+                .flatMap(Streams::stream)
+                .collect(toList()));
+      } else if (modification.state() == ReviewerState.REMOVED) {
+        // There is no batch event for reviewer removals, hence fire the event for each
+        // modification that deleted a reviewer immediately.
+        modification.op.sendEvent();
+      }
+    }
+
+    // Fire a batch event for all newly added reviewers.
+    reviewerAdded.fire(cd, patchSet, newlyAddedReviewers, user.asIdentifiedUser().state(), when);
+  }
+
   private RevisionResource onBehalfOf(RevisionResource rev, LabelTypes labelTypes, ReviewInput in)
       throws BadRequestException, AuthException, UnprocessableEntityException,
           PermissionBackendException, IOException, ConfigInvalidException {
diff --git a/javatests/com/google/gerrit/acceptance/api/change/PostReviewIT.java b/javatests/com/google/gerrit/acceptance/api/change/PostReviewIT.java
index b79be80..96bc65d 100644
--- a/javatests/com/google/gerrit/acceptance/api/change/PostReviewIT.java
+++ b/javatests/com/google/gerrit/acceptance/api/change/PostReviewIT.java
@@ -27,6 +27,7 @@
 
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableMap;
+import com.google.common.collect.ImmutableSet;
 import com.google.common.collect.Iterables;
 import com.google.common.truth.Correspondence;
 import com.google.gerrit.acceptance.AbstractDaemonTest;
@@ -56,6 +57,8 @@
 import com.google.gerrit.extensions.common.RobotCommentInfo;
 import com.google.gerrit.extensions.config.FactoryModule;
 import com.google.gerrit.extensions.events.CommentAddedListener;
+import com.google.gerrit.extensions.events.ReviewerAddedListener;
+import com.google.gerrit.extensions.events.ReviewerDeletedListener;
 import com.google.gerrit.extensions.restapi.BadRequestException;
 import com.google.gerrit.extensions.restapi.ResourceNotFoundException;
 import com.google.gerrit.extensions.restapi.RestApiException;
@@ -74,6 +77,7 @@
 import com.google.inject.Inject;
 import com.google.inject.Module;
 import java.sql.Timestamp;
+import java.util.ArrayList;
 import java.util.Collection;
 import java.util.List;
 import java.util.Map;
@@ -699,6 +703,61 @@
   }
 
   @Test
+  public void addingReviewers() throws Exception {
+    PushOneCommit.Result r = createChange();
+
+    TestAccount user2 = accountCreator.user2();
+
+    TestReviewerAddedListener testReviewerAddedListener = new TestReviewerAddedListener();
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(testReviewerAddedListener)) {
+      // add user and user2
+      ReviewResult reviewResult =
+          gApi.changes()
+              .id(r.getChangeId())
+              .current()
+              .review(ReviewInput.create().reviewer(user.email()).reviewer(user2.email()));
+
+      assertThat(
+              reviewResult.reviewers.values().stream()
+                  .filter(a -> a.reviewers != null)
+                  .map(a -> Iterables.getOnlyElement(a.reviewers).name)
+                  .collect(toImmutableSet()))
+          .containsExactly(user.fullName(), user2.fullName());
+    }
+
+    assertThat(
+            gApi.changes().id(r.getChangeId()).reviewers().stream()
+                .map(a -> a.name)
+                .collect(toImmutableSet()))
+        .containsExactly(user.fullName(), user2.fullName());
+
+    // Ensure only one batch email was sent for this operation
+    FakeEmailSender.Message message = Iterables.getOnlyElement(sender.getMessages());
+    assertThat(message.body())
+        .containsMatch(
+            Pattern.quote("Hello ")
+                + "("
+                + Pattern.quote(String.format("%s, %s", user.fullName(), user2.fullName()))
+                + "|"
+                + Pattern.quote(String.format("%s, %s", user2.fullName(), user.fullName()))
+                + ")");
+    assertThat(message.htmlBody())
+        .containsMatch(
+            "("
+                + Pattern.quote(String.format("%s and %s", user.fullName(), user2.fullName()))
+                + "|"
+                + Pattern.quote(String.format("%s and %s", user2.fullName(), user.fullName()))
+                + ")"
+                + Pattern.quote(" to <strong>review</strong> this change"));
+
+    // Ensure that a batch event has been sent:
+    // * 1 batch event for adding user and user2 as reviewers
+    assertThat(testReviewerAddedListener.receivedEvents).hasSize(1);
+    assertThat(testReviewerAddedListener.getReviewerIds()).containsExactly(user.id(), user2.id());
+  }
+
+  @Test
   public void deletingReviewers() throws Exception {
     PushOneCommit.Result r = createChange();
 
@@ -712,21 +771,25 @@
 
     sender.clear();
 
-    // remove user and user2
-    ReviewResult reviewResult =
-        gApi.changes()
-            .id(r.getChangeId())
-            .current()
-            .review(
-                ReviewInput.create()
-                    .reviewer(user.email(), ReviewerState.REMOVED, /* confirmed= */ true)
-                    .reviewer(user2.email(), ReviewerState.REMOVED, /* confirmed= */ true));
+    TestReviewerDeletedListener testReviewerDeletedListener = new TestReviewerDeletedListener();
+    try (Registration registration =
+        extensionRegistry.newRegistration().add(testReviewerDeletedListener)) {
+      // remove user and user2
+      ReviewResult reviewResult =
+          gApi.changes()
+              .id(r.getChangeId())
+              .current()
+              .review(
+                  ReviewInput.create()
+                      .reviewer(user.email(), ReviewerState.REMOVED, /* confirmed= */ true)
+                      .reviewer(user2.email(), ReviewerState.REMOVED, /* confirmed= */ true));
 
-    assertThat(
-            reviewResult.reviewers.values().stream()
-                .map(a -> a.removed.name)
-                .collect(toImmutableSet()))
-        .containsExactly(user.fullName(), user2.fullName());
+      assertThat(
+              reviewResult.reviewers.values().stream()
+                  .map(a -> a.removed.name)
+                  .collect(toImmutableSet()))
+          .containsExactly(user.fullName(), user2.fullName());
+    }
 
     assertThat(gApi.changes().id(r.getChangeId()).reviewers()).isEmpty();
 
@@ -748,6 +811,12 @@
                 + "|"
                 + Pattern.quote(String.format("%s and %s", user2.fullName(), user.fullName()))
                 + ")");
+
+    // Ensure that events have been sent:
+    // * 2 events for removing user and user2 as reviewers (one event per removed reviewer, batch
+    //   event not available for reviewer removal)
+    assertThat(testReviewerDeletedListener.receivedEvents).hasSize(2);
+    assertThat(testReviewerDeletedListener.getReviewerIds()).containsExactly(user.id(), user2.id());
   }
 
   @Test
@@ -766,30 +835,38 @@
 
     sender.clear();
 
-    // remove user and user2 while adding user3 and user4
-    ReviewResult reviewResult =
-        gApi.changes()
-            .id(r.getChangeId())
-            .current()
-            .review(
-                ReviewInput.create()
-                    .reviewer(user.email(), ReviewerState.REMOVED, /* confirmed= */ true)
-                    .reviewer(user2.email(), ReviewerState.REMOVED, /* confirmed= */ true)
-                    .reviewer(user3.email())
-                    .reviewer(user4.email()));
+    TestReviewerAddedListener testReviewerAddedListener = new TestReviewerAddedListener();
+    TestReviewerDeletedListener testReviewerDeletedListener = new TestReviewerDeletedListener();
+    try (Registration registration =
+        extensionRegistry
+            .newRegistration()
+            .add(testReviewerAddedListener)
+            .add(testReviewerDeletedListener)) {
+      // remove user and user2 while adding user3 and user4
+      ReviewResult reviewResult =
+          gApi.changes()
+              .id(r.getChangeId())
+              .current()
+              .review(
+                  ReviewInput.create()
+                      .reviewer(user.email(), ReviewerState.REMOVED, /* confirmed= */ true)
+                      .reviewer(user2.email(), ReviewerState.REMOVED, /* confirmed= */ true)
+                      .reviewer(user3.email())
+                      .reviewer(user4.email()));
 
-    assertThat(
-            reviewResult.reviewers.values().stream()
-                .filter(a -> a.removed != null)
-                .map(a -> a.removed.name)
-                .collect(toImmutableSet()))
-        .containsExactly(user.fullName(), user2.fullName());
-    assertThat(
-            reviewResult.reviewers.values().stream()
-                .filter(a -> a.reviewers != null)
-                .map(a -> Iterables.getOnlyElement(a.reviewers).name)
-                .collect(toImmutableSet()))
-        .containsExactly(user3.fullName(), user4.fullName());
+      assertThat(
+              reviewResult.reviewers.values().stream()
+                  .filter(a -> a.removed != null)
+                  .map(a -> a.removed.name)
+                  .collect(toImmutableSet()))
+          .containsExactly(user.fullName(), user2.fullName());
+      assertThat(
+              reviewResult.reviewers.values().stream()
+                  .filter(a -> a.reviewers != null)
+                  .map(a -> Iterables.getOnlyElement(a.reviewers).name)
+                  .collect(toImmutableSet()))
+          .containsExactly(user3.fullName(), user4.fullName());
+    }
 
     assertThat(
             gApi.changes().id(r.getChangeId()).reviewers().stream()
@@ -832,6 +909,15 @@
                 + "|"
                 + Pattern.quote(String.format("%s and %s", user2.fullName(), user.fullName()))
                 + ")");
+
+    // Ensure that events have been sent:
+    // * 1 batch event for adding user3 and user4 as reviewers
+    // * 2 events for removing user and user2 as reviewers (one event per removed reviewer, batch
+    //   event not available for reviewer removal)
+    assertThat(testReviewerAddedListener.receivedEvents).hasSize(1);
+    assertThat(testReviewerAddedListener.getReviewerIds()).containsExactly(user3.id(), user4.id());
+    assertThat(testReviewerDeletedListener.receivedEvents).hasSize(2);
+    assertThat(testReviewerDeletedListener.getReviewerIds()).containsExactly(user.id(), user2.id());
   }
 
   @Test
@@ -964,4 +1050,36 @@
       return Optional.empty();
     }
   }
+
+  private static class TestReviewerAddedListener implements ReviewerAddedListener {
+    List<ReviewerAddedListener.Event> receivedEvents = new ArrayList<>();
+
+    @Override
+    public void onReviewersAdded(ReviewerAddedListener.Event event) {
+      receivedEvents.add(event);
+    }
+
+    public ImmutableSet<Account.Id> getReviewerIds() {
+      return receivedEvents.stream()
+          .flatMap(e -> e.getReviewers().stream())
+          .map(accountInfo -> Account.id(accountInfo._accountId))
+          .collect(toImmutableSet());
+    }
+  }
+
+  private static class TestReviewerDeletedListener implements ReviewerDeletedListener {
+    List<ReviewerDeletedListener.Event> receivedEvents = new ArrayList<>();
+
+    @Override
+    public void onReviewerDeleted(ReviewerDeletedListener.Event event) {
+      receivedEvents.add(event);
+    }
+
+    public ImmutableSet<Account.Id> getReviewerIds() {
+      return receivedEvents.stream()
+          .map(ReviewerDeletedListener.Event::getReviewer)
+          .map(accountInfo -> Account.id(accountInfo._accountId))
+          .collect(toImmutableSet());
+    }
+  }
 }
diff --git a/javatests/com/google/gerrit/server/notedb/CommitRewriterTest.java b/javatests/com/google/gerrit/server/notedb/CommitRewriterTest.java
index f316660..19c2bcf 100644
--- a/javatests/com/google/gerrit/server/notedb/CommitRewriterTest.java
+++ b/javatests/com/google/gerrit/server/notedb/CommitRewriterTest.java
@@ -34,6 +34,7 @@
 import com.google.gerrit.entities.RefNames;
 import com.google.gerrit.entities.SubmitRecord;
 import com.google.gerrit.json.OutputFormat;
+import com.google.gerrit.server.CurrentUser;
 import com.google.gerrit.server.IdentifiedUser;
 import com.google.gerrit.server.ReviewerStatusUpdate;
 import com.google.gerrit.server.notedb.ChangeNoteUtil.AttentionStatusInNoteDb;
@@ -1603,19 +1604,20 @@
     accountCache.put(duplicateReviewer);
     Change c = newChange();
     ImmutableList.Builder<ObjectId> commitsToFix = new ImmutableList.Builder<>();
-    ChangeUpdate addReviewerUpdate = newUpdate(c, changeOwner);
+    ChangeUpdate addReviewerUpdate = newCodeOwnerAddReviewerUpdate(c, changeOwner);
     addReviewerUpdate.putReviewer(reviewer.id(), REVIEWER);
     addReviewerUpdate.commit();
-    ChangeUpdate invalidOnAddReviewerUpdate = newUpdate(c, changeOwner);
+    ChangeUpdate invalidOnAddReviewerUpdate = newCodeOwnerAddReviewerUpdate(c, changeOwner);
     invalidOnAddReviewerUpdate.setChangeMessage(
         "Reviewer User who was added as reviewer owns the following files:\n"
             + "   * file1.java\n"
             + "   * file2.ts\n");
     commitsToFix.add(invalidOnAddReviewerUpdate.commit());
-    ChangeUpdate addOtherReviewerUpdate = newUpdate(c, changeOwner);
+    ChangeUpdate addOtherReviewerUpdate = newCodeOwnerAddReviewerUpdate(c, changeOwner);
     addOtherReviewerUpdate.putReviewer(otherUserId, REVIEWER);
     addOtherReviewerUpdate.commit();
-    ChangeUpdate invalidOnAddReviewerMultipleReviewerUpdate = newUpdate(c, changeOwner);
+    ChangeUpdate invalidOnAddReviewerMultipleReviewerUpdate =
+        newCodeOwnerAddReviewerUpdate(c, changeOwner);
     invalidOnAddReviewerMultipleReviewerUpdate.setChangeMessage(
         "Reviewer User who was added as reviewer owns the following files:\n"
             + "   * file1.java\n"
@@ -1624,17 +1626,17 @@
             + "\nMissing Reviewer who was added as reviewer owns the following files:\n"
             + "   * file4.java\n");
     commitsToFix.add(invalidOnAddReviewerMultipleReviewerUpdate.commit());
-    ChangeUpdate addDuplicateReviewerUpdate = newUpdate(c, changeOwner);
+    ChangeUpdate addDuplicateReviewerUpdate = newCodeOwnerAddReviewerUpdate(c, changeOwner);
     addDuplicateReviewerUpdate.putReviewer(duplicateReviewer.id(), REVIEWER);
     addDuplicateReviewerUpdate.commit();
     // Reviewer name resolves to multiple accounts in the same change
-    ChangeUpdate onAddReviewerUpdateWithDuplicate = newUpdate(c, changeOwner);
+    ChangeUpdate onAddReviewerUpdateWithDuplicate = newCodeOwnerAddReviewerUpdate(c, changeOwner);
     onAddReviewerUpdateWithDuplicate.setChangeMessage(
         "Reviewer User who was added as reviewer owns the following files:\n"
             + "   * file6.java\n");
     commitsToFix.add(onAddReviewerUpdateWithDuplicate.commit());
 
-    ChangeUpdate validOnAddReviewerUpdate = newUpdate(c, changeOwner);
+    ChangeUpdate validOnAddReviewerUpdate = newCodeOwnerAddReviewerUpdate(c, changeOwner);
     validOnAddReviewerUpdate.setChangeMessage(
         "Gerrit Account who was added as reviewer owns the following files:\n"
             + "   * file1.java\n"
@@ -2249,6 +2251,13 @@
         .collect(toImmutableList());
   }
 
+  protected ChangeUpdate newCodeOwnerAddReviewerUpdate(Change c, CurrentUser user)
+      throws Exception {
+    ChangeUpdate update = newUpdate(c, user, true);
+    update.setTag("autogenerated:gerrit:code-owners:addReviewer");
+    return update;
+  }
+
   private ImmutableList<String> commitHistoryDiff(BackfillResult result, Change.Id changeId) {
     return result.fixedRefDiff.get(RefNames.changeMetaRef(changeId)).stream()
         .map(CommitDiff::diff)
diff --git a/polygerrit-ui/app/elements/change/gr-submit-requirement-hovercard/gr-submit-requirement-hovercard_html.ts b/polygerrit-ui/app/elements/change/gr-submit-requirement-hovercard/gr-submit-requirement-hovercard_html.ts
index 192a812..b7b4d9c 100644
--- a/polygerrit-ui/app/elements/change/gr-submit-requirement-hovercard/gr-submit-requirement-hovercard_html.ts
+++ b/polygerrit-ui/app/elements/change/gr-submit-requirement-hovercard/gr-submit-requirement-hovercard_html.ts
@@ -51,13 +51,13 @@
     div.section {
       margin: 0 var(--spacing-xl) var(--spacing-m) var(--spacing-xl);
       display: flex;
+      align-items: center;
     }
     div.sectionIcon {
       flex: 0 0 30px;
     }
     div.sectionIcon iron-icon {
       position: relative;
-      top: 2px;
       width: 20px;
       height: 20px;
     }
diff --git a/polygerrit-ui/app/elements/core/gr-router/gr-router.ts b/polygerrit-ui/app/elements/core/gr-router/gr-router.ts
index 8e70eb9..f0cff85 100644
--- a/polygerrit-ui/app/elements/core/gr-router/gr-router.ts
+++ b/polygerrit-ui/app/elements/core/gr-router/gr-router.ts
@@ -178,7 +178,7 @@
   CHANGE_ID_QUERY: /^\/id\/(I[0-9a-f]{40})$/,
 
   // Matches /c/<changeNum>/[*][/].
-  CHANGE_LEGACY: /^\/c\/(\d+)\/(.*)$/,
+  CHANGE_LEGACY: /^\/c\/(\d+)\/?(.*)$/,
   CHANGE_NUMBER_LEGACY: /^\/(\d+)\/?/,
 
   // Matches
diff --git a/polygerrit-ui/app/elements/shared/gr-label-info/gr-label-info.ts b/polygerrit-ui/app/elements/shared/gr-label-info/gr-label-info.ts
index dba36a4..67f84a5 100644
--- a/polygerrit-ui/app/elements/shared/gr-label-info/gr-label-info.ts
+++ b/polygerrit-ui/app/elements/shared/gr-label-info/gr-label-info.ts
@@ -24,23 +24,26 @@
 import '../gr-label/gr-label';
 import '../gr-tooltip-content/gr-tooltip-content';
 import {dom, EventApi} from '@polymer/polymer/lib/legacy/polymer.dom';
-import {PolymerElement} from '@polymer/polymer/polymer-element';
-import {htmlTemplate} from './gr-label-info_html';
 import {GerritNav} from '../../core/gr-navigation/gr-navigation';
-import {customElement, property} from '@polymer/decorators';
 import {
-  ChangeInfo,
   AccountInfo,
   LabelInfo,
   ApprovalInfo,
   AccountId,
   isQuickLabelInfo,
   isDetailedLabelInfo,
+  LabelNameToInfoMap,
 } from '../../../types/common';
+import {LitElement, css, html} from 'lit';
+import {customElement, property} from 'lit/decorators';
 import {GrButton} from '../gr-button/gr-button';
 import {getVotingRangeOrDefault} from '../../../utils/label-util';
 import {appContext} from '../../../services/app-context';
 import {ParsedChangeInfo} from '../../../types/types';
+import {fontStyles} from '../../../styles/gr-font-styles';
+import {sharedStyles} from '../../../styles/shared-styles';
+import {votingStyles} from '../../../styles/gr-voting-styles';
+import {ifDefined} from 'lit/directives/if-defined';
 
 declare global {
   interface HTMLElementTagNameMap {
@@ -57,16 +60,12 @@
 
 interface FormattedLabel {
   className?: LabelClassName;
-  account: ApprovalInfo;
+  account: ApprovalInfo | AccountInfo;
   value: string;
 }
 
 @customElement('gr-label-info')
-export class GrLabelInfo extends PolymerElement {
-  static get template() {
-    return htmlTemplate;
-  }
-
+export class GrLabelInfo extends LitElement {
   @property({type: Object})
   labelInfo?: LabelInfo;
 
@@ -89,11 +88,148 @@
   // TODO(TS): not used, remove later
   _xhrPromise?: Promise<void>;
 
+  static override get styles() {
+    return [
+      sharedStyles,
+      fontStyles,
+      votingStyles,
+      css`
+        .placeholder {
+          color: var(--deemphasized-text-color);
+        }
+        .hidden {
+          display: none;
+        }
+        /* Note that most of the .voteChip styles are coming from the
+         gr-voting-styles include. */
+        .voteChip {
+          display: flex;
+          justify-content: center;
+          margin-right: var(--spacing-s);
+          padding: 1px;
+        }
+        .max {
+          background-color: var(--vote-color-approved);
+        }
+        .min {
+          background-color: var(--vote-color-rejected);
+        }
+        .positive {
+          background-color: var(--vote-color-recommended);
+          border-radius: 12px;
+          border: 1px solid var(--vote-outline-recommended);
+          color: var(--chip-color);
+        }
+        .negative {
+          background-color: var(--vote-color-disliked);
+          border-radius: 12px;
+          border: 1px solid var(--vote-outline-disliked);
+          color: var(--chip-color);
+        }
+        .hidden {
+          display: none;
+        }
+        td {
+          vertical-align: top;
+        }
+        tr {
+          min-height: var(--line-height-normal);
+        }
+        gr-tooltip-content {
+          display: block;
+        }
+        gr-button {
+          vertical-align: top;
+        }
+        gr-button::part(paper-button) {
+          height: var(--line-height-normal);
+          width: var(--line-height-normal);
+          padding: 0;
+        }
+        gr-button[disabled] iron-icon {
+          color: var(--border-color);
+        }
+        gr-account-link {
+          --account-max-length: 100px;
+          margin-right: var(--spacing-xs);
+        }
+        iron-icon {
+          height: calc(var(--line-height-normal) - 2px);
+          width: calc(var(--line-height-normal) - 2px);
+        }
+        .labelValueContainer:not(:first-of-type) td {
+          padding-top: var(--spacing-s);
+        }
+      `,
+    ];
+  }
+
+  override render() {
+    return html` <p
+        class="placeholder ${this.computeShowPlaceholder(
+          this.labelInfo,
+          this.change?.labels
+        )}"
+      >
+        No votes
+      </p>
+      <table>
+        ${this.mapLabelInfo(
+          this.labelInfo,
+          this.account,
+          this.change?.labels
+        ).map(mappedLabel => this.renderLabel(mappedLabel))}
+      </table>`;
+  }
+
+  renderLabel(mappedLabel: FormattedLabel) {
+    const {labelInfo, change} = this;
+    return html` <tr class="labelValueContainer">
+      <td>
+        <gr-tooltip-content
+          has-tooltip
+          title="${this._computeValueTooltip(labelInfo, mappedLabel.value)}"
+        >
+          <gr-label class="${mappedLabel.className} voteChip font-small">
+            ${mappedLabel.value}
+          </gr-label>
+        </gr-tooltip-content>
+      </td>
+      <td>
+        <gr-account-link
+          .account="${mappedLabel.account}"
+          .change="${change}"
+        ></gr-account-link>
+      </td>
+      <td>
+        <gr-tooltip-content has-tooltip title="Remove vote">
+          <gr-button
+            link
+            aria-label="Remove vote"
+            @click="${this.onDeleteVote}"
+            data-account-id="${ifDefined(mappedLabel.account._account_id)}"
+            class="deleteBtn ${this.computeDeleteClass(
+              mappedLabel.account,
+              this.mutable,
+              change
+            )}"
+          >
+            <iron-icon icon="gr-icons:delete"></iron-icon>
+          </gr-button>
+        </gr-tooltip-content>
+      </td>
+    </tr>`;
+  }
+
   /**
    * This method also listens on change.labels.*,
    * to trigger computation when a label is removed from the change.
    */
-  _mapLabelInfo(labelInfo?: LabelInfo, account?: AccountInfo) {
+  private mapLabelInfo(
+    labelInfo?: LabelInfo,
+    account?: AccountInfo,
+    _?: LabelNameToInfoMap
+  ): FormattedLabel[] {
     const result: FormattedLabel[] = [];
     if (!labelInfo) {
       return result;
@@ -108,7 +244,8 @@
           {
             value: ok ? '👍️' : '👎️',
             className: ok ? LabelClassName.POSITIVE : LabelClassName.NEGATIVE,
-            account: ok ? labelInfo.approved : labelInfo.rejected,
+            // executed only if approved or rejected is not undefined
+            account: ok ? labelInfo.approved! : labelInfo.rejected!,
           },
         ];
       }
@@ -143,7 +280,7 @@
             labelClassName = LabelClassName.NEGATIVE;
           }
         }
-        const formattedLabel = {
+        const formattedLabel: FormattedLabel = {
           value: `${labelValPrefix}${label.value}`,
           className: labelClassName,
           account: label,
@@ -167,10 +304,10 @@
    * @param reviewer An object describing the reviewer that left the
    *     vote.
    */
-  _computeDeleteClass(
+  private computeDeleteClass(
     reviewer: ApprovalInfo,
     mutable: boolean,
-    change: ChangeInfo
+    change?: ParsedChangeInfo
   ) {
     if (!mutable || !change || !change.removable_reviewers) {
       return 'hidden';
@@ -186,7 +323,7 @@
    * Closure annotation for Polymer.prototype.splice is off.
    * For now, suppressing annotations.
    */
-  _onDeleteVote(e: MouseEvent) {
+  private onDeleteVote(e: MouseEvent) {
     if (!this.change) return;
 
     e.preventDefault();
@@ -220,7 +357,7 @@
       });
   }
 
-  _computeValueTooltip(labelInfo: LabelInfo, score: string) {
+  _computeValueTooltip(labelInfo: LabelInfo | undefined, score: string) {
     if (
       !labelInfo ||
       !isDetailedLabelInfo(labelInfo) ||
@@ -235,7 +372,10 @@
    * This method also listens change.labels.* in
    * order to trigger computation when a label is removed from the change.
    */
-  _computeShowPlaceholder(labelInfo?: LabelInfo) {
+  private computeShowPlaceholder(
+    labelInfo?: LabelInfo,
+    _?: LabelNameToInfoMap
+  ) {
     if (!labelInfo) {
       return '';
     }
diff --git a/polygerrit-ui/app/elements/shared/gr-label-info/gr-label-info_html.ts b/polygerrit-ui/app/elements/shared/gr-label-info/gr-label-info_html.ts
deleted file mode 100644
index 1186ee1..0000000
--- a/polygerrit-ui/app/elements/shared/gr-label-info/gr-label-info_html.ts
+++ /dev/null
@@ -1,135 +0,0 @@
-/**
- * @license
- * Copyright (C) 2020 The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-import {html} from '@polymer/polymer/lib/utils/html-tag';
-
-export const htmlTemplate = html`
-  <style include="gr-font-styles">
-    /* Workaround for empty style block - see https://github.com/Polymer/tools/issues/408 */
-  </style>
-  <style include="gr-voting-styles">
-    /* Workaround for empty style block - see https://github.com/Polymer/tools/issues/408 */
-  </style>
-  <style include="shared-styles">
-    .placeholder {
-      color: var(--deemphasized-text-color);
-    }
-    .hidden {
-      display: none;
-    }
-    /* Note that most of the .voteChip styles are coming from the
-       gr-voting-styles include. */
-    .voteChip {
-      display: flex;
-      justify-content: center;
-      margin-right: var(--spacing-s);
-      padding: 1px;
-    }
-    .max {
-      background-color: var(--vote-color-approved);
-    }
-    .min {
-      background-color: var(--vote-color-rejected);
-    }
-    .positive {
-      background-color: var(--vote-color-recommended);
-      border-radius: 12px;
-      border: 1px solid var(--vote-outline-recommended);
-      color: var(--chip-color);
-    }
-    .negative {
-      background-color: var(--vote-color-disliked);
-      border-radius: 12px;
-      border: 1px solid var(--vote-outline-disliked);
-      color: var(--chip-color);
-    }
-    .hidden {
-      display: none;
-    }
-    td {
-      vertical-align: top;
-    }
-    tr {
-      min-height: var(--line-height-normal);
-    }
-    gr-tooltip-content {
-      display: block;
-    }
-    gr-button {
-      display: block;
-      vertical-align: top;
-      --gr-button-padding: 1px;
-    }
-    gr-button[disabled] iron-icon {
-      color: var(--border-color);
-    }
-    gr-account-link {
-      --account-max-length: 100px;
-      margin-right: var(--spacing-xs);
-    }
-    iron-icon {
-      height: calc(var(--line-height-normal) - 2px);
-      width: calc(var(--line-height-normal) - 2px);
-    }
-    .labelValueContainer:not(:first-of-type) td {
-      padding-top: var(--spacing-s);
-    }
-  </style>
-  <p
-    class$="placeholder [[_computeShowPlaceholder(labelInfo, change.labels.*)]]"
-  >
-    No votes
-  </p>
-  <table>
-    <template
-      is="dom-repeat"
-      items="[[_mapLabelInfo(labelInfo, account, change.labels.*)]]"
-      as="mappedLabel"
-    >
-      <tr class="labelValueContainer">
-        <td>
-          <gr-tooltip-content
-            has-tooltip
-            title="[[_computeValueTooltip(labelInfo, mappedLabel.value)]]"
-          >
-            <gr-label class$="[[mappedLabel.className]] voteChip font-small">
-              [[mappedLabel.value]]
-            </gr-label>
-          </gr-tooltip-content>
-        </td>
-        <td>
-          <gr-account-link
-            account="[[mappedLabel.account]]"
-            change="[[change]]"
-          ></gr-account-link>
-        </td>
-        <td>
-          <gr-tooltip-content has-tooltip title="Remove vote">
-            <gr-button
-              link=""
-              aria-label="Remove vote"
-              on-click="_onDeleteVote"
-              data-account-id$="[[mappedLabel.account._account_id]]"
-              class$="deleteBtn [[_computeDeleteClass(mappedLabel.account, mutable, change)]]"
-            >
-              <iron-icon icon="gr-icons:delete"></iron-icon>
-            </gr-button>
-          </gr-tooltip-content>
-        </td>
-      </tr>
-    </template>
-  </table>
-`;
diff --git a/polygerrit-ui/app/elements/shared/gr-label-info/gr-label-info_test.ts b/polygerrit-ui/app/elements/shared/gr-label-info/gr-label-info_test.ts
index b1bd6fa..cad1f69 100644
--- a/polygerrit-ui/app/elements/shared/gr-label-info/gr-label-info_test.ts
+++ b/polygerrit-ui/app/elements/shared/gr-label-info/gr-label-info_test.ts
@@ -66,15 +66,17 @@
       element.labelInfo = label;
       element.label = 'Code-Review';
 
-      await flush();
+      await element.updateComplete;
     });
 
-    test('_computeCanDeleteVote', () => {
+    test('_computeCanDeleteVote', async () => {
       element.mutable = false;
+      await element.updateComplete;
       const removeButton = queryAndAssert<GrButton>(element, 'gr-button');
       assert.isTrue(isHidden(removeButton));
       element.change!.removable_reviewers = [account];
       element.mutable = true;
+      await element.updateComplete;
       assert.isFalse(isHidden(removeButton));
     });
 
@@ -109,14 +111,14 @@
   suite('label color and order', () => {
     test('valueless label rejected', async () => {
       element.labelInfo = {rejected: {name: 'someone'}};
-      await flush();
+      await element.updateComplete;
       const labels = queryAll<GrLabel>(element, 'gr-label');
       assert.isTrue(labels[0].classList.contains('negative'));
     });
 
     test('valueless label approved', async () => {
       element.labelInfo = {approved: {name: 'someone'}};
-      await flush();
+      await element.updateComplete;
       const labels = queryAll<GrLabel>(element, 'gr-label');
       assert.isTrue(labels[0].classList.contains('positive'));
     });
@@ -137,7 +139,7 @@
           '+2': 'Ready to submit',
         },
       };
-      await flush();
+      await element.updateComplete;
       const labels = queryAll<GrLabel>(element, 'gr-label');
       assert.isTrue(labels[0].classList.contains('max'));
       assert.isTrue(labels[1].classList.contains('positive'));
@@ -157,7 +159,7 @@
           '+1': 'Looks good to me',
         },
       };
-      await flush();
+      await element.updateComplete;
       const labels = queryAll<GrLabel>(element, 'gr-label');
       assert.isTrue(labels[0].classList.contains('max'));
       assert.isTrue(labels[1].classList.contains('min'));
@@ -175,7 +177,7 @@
           '+2': 'Looks good to me',
         },
       };
-      await flush();
+      await element.updateComplete;
       const labels = queryAll<GrLabel>(element, 'gr-label');
       assert.isTrue(labels[0].classList.contains('max'));
       assert.isTrue(labels[1].classList.contains('positive'));
@@ -195,7 +197,7 @@
           '+1': 'Looks good to me',
         },
       };
-      await flush();
+      await element.updateComplete;
       const chips = queryAll<GrAccountLink>(element, 'gr-account-link');
       assert.equal(chips[0].account!._account_id, element.account._account_id);
     });
@@ -217,7 +219,7 @@
     assert.equal(element._computeValueTooltip(labelInfo, score), '');
   });
 
-  test('placeholder', () => {
+  test('placeholder', async () => {
     const values = {
       '0': 'No score',
       '+1': 'good',
@@ -226,30 +228,37 @@
       '-2': 'terrible',
     };
     element.labelInfo = {};
+    await element.updateComplete;
     assert.isFalse(
       isHidden(queryAndAssert<HTMLParagraphElement>(element, '.placeholder'))
     );
     element.labelInfo = {all: [], values};
+    await element.updateComplete;
     assert.isFalse(
       isHidden(queryAndAssert<HTMLParagraphElement>(element, '.placeholder'))
     );
     element.labelInfo = {all: [{value: 1}], values};
+    await element.updateComplete;
     assert.isTrue(
       isHidden(queryAndAssert<HTMLParagraphElement>(element, '.placeholder'))
     );
     element.labelInfo = {rejected: account};
+    await element.updateComplete;
     assert.isTrue(
       isHidden(queryAndAssert<HTMLParagraphElement>(element, '.placeholder'))
     );
     element.labelInfo = {rejected: account, all: [{value: 1}], values};
+    await element.updateComplete;
     assert.isTrue(
       isHidden(queryAndAssert<HTMLParagraphElement>(element, '.placeholder'))
     );
     element.labelInfo = {approved: account};
+    await element.updateComplete;
     assert.isTrue(
       isHidden(queryAndAssert<HTMLParagraphElement>(element, '.placeholder'))
     );
     element.labelInfo = {approved: account, all: [{value: 1}], values};
+    await element.updateComplete;
     assert.isTrue(
       isHidden(queryAndAssert<HTMLParagraphElement>(element, '.placeholder'))
     );