diff --git a/Documentation/images/gwt-user-review-ui-change-screen-change-info-cannot-merge.png b/Documentation/images/gwt-user-review-ui-change-screen-change-info-cannot-merge.png
deleted file mode 100644
index 69a28ec..0000000
--- a/Documentation/images/gwt-user-review-ui-change-screen-change-info-cannot-merge.png
+++ /dev/null
Binary files differ
diff --git a/Documentation/images/gwt-user-review-ui-change-screen-change-info.png b/Documentation/images/gwt-user-review-ui-change-screen-change-info.png
deleted file mode 100644
index e92b49d..0000000
--- a/Documentation/images/gwt-user-review-ui-change-screen-change-info.png
+++ /dev/null
Binary files differ
diff --git a/Documentation/images/gwt-user-review-ui-change-screen-commit-info-merge-commit.png b/Documentation/images/gwt-user-review-ui-change-screen-commit-info-merge-commit.png
deleted file mode 100644
index 097637e..0000000
--- a/Documentation/images/gwt-user-review-ui-change-screen-commit-info-merge-commit.png
+++ /dev/null
Binary files differ
diff --git a/Documentation/images/gwt-user-review-ui-change-screen-commit-info.png b/Documentation/images/gwt-user-review-ui-change-screen-commit-info.png
deleted file mode 100644
index fe0c1d1..0000000
--- a/Documentation/images/gwt-user-review-ui-change-screen-commit-info.png
+++ /dev/null
Binary files differ
diff --git a/Documentation/images/gwt-user-review-ui-change-screen-included-in-list.png b/Documentation/images/gwt-user-review-ui-change-screen-included-in-list.png
deleted file mode 100644
index ad30fe2..0000000
--- a/Documentation/images/gwt-user-review-ui-change-screen-included-in-list.png
+++ /dev/null
Binary files differ
diff --git a/Documentation/images/gwt-user-review-ui-change-screen-not-current.png b/Documentation/images/gwt-user-review-ui-change-screen-not-current.png
deleted file mode 100644
index 9a87c67..0000000
--- a/Documentation/images/gwt-user-review-ui-change-screen-not-current.png
+++ /dev/null
Binary files differ
diff --git a/Documentation/images/gwt-user-review-ui-change-screen-permalink.png b/Documentation/images/gwt-user-review-ui-change-screen-permalink.png
deleted file mode 100644
index a1aede9..0000000
--- a/Documentation/images/gwt-user-review-ui-change-screen-permalink.png
+++ /dev/null
Binary files differ
diff --git a/Documentation/images/gwt-user-review-ui-change-screen-plugin-extensions.png b/Documentation/images/gwt-user-review-ui-change-screen-plugin-extensions.png
deleted file mode 100644
index 120b99c..0000000
--- a/Documentation/images/gwt-user-review-ui-change-screen-plugin-extensions.png
+++ /dev/null
Binary files differ
diff --git a/Documentation/images/gwt-user-review-ui-side-by-side-diff-screen-comment.png b/Documentation/images/gwt-user-review-ui-side-by-side-diff-screen-comment.png
deleted file mode 100644
index 2ecc47e..0000000
--- a/Documentation/images/gwt-user-review-ui-side-by-side-diff-screen-comment.png
+++ /dev/null
Binary files differ
diff --git a/Documentation/images/gwt-user-review-ui-side-by-side-diff-screen-keyboard-shortcuts.png b/Documentation/images/gwt-user-review-ui-side-by-side-diff-screen-keyboard-shortcuts.png
deleted file mode 100644
index 6f63f0e4..0000000
--- a/Documentation/images/gwt-user-review-ui-side-by-side-diff-screen-keyboard-shortcuts.png
+++ /dev/null
Binary files differ
diff --git a/Documentation/images/user-review-ui-change-screen-plugin-extensions.png b/Documentation/images/user-review-ui-change-screen-plugin-extensions.png
new file mode 100644
index 0000000..5d6fee7
--- /dev/null
+++ b/Documentation/images/user-review-ui-change-screen-plugin-extensions.png
Binary files differ
diff --git a/Documentation/js_licenses.txt b/Documentation/js_licenses.txt
index 0d8da89..813ff44 100644
--- a/Documentation/js_licenses.txt
+++ b/Documentation/js_licenses.txt
@@ -1077,6 +1077,38 @@
 ----
 
 
+[[immer]]
+immer
+
+* immer
+
+[[immer_license]]
+----
+MIT License
+
+Copyright (c) 2017 Michel Weststrate
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+
+----
+
+
 [[isarray]]
 isarray
 
diff --git a/Documentation/licenses.txt b/Documentation/licenses.txt
index ed1a336..11f9ff3 100644
--- a/Documentation/licenses.txt
+++ b/Documentation/licenses.txt
@@ -4036,6 +4036,38 @@
 ----
 
 
+[[immer]]
+immer
+
+* immer
+
+[[immer_license]]
+----
+MIT License
+
+Copyright (c) 2017 Michel Weststrate
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+
+----
+
+
 [[isarray]]
 isarray
 
diff --git a/Documentation/user-review-ui.txt b/Documentation/user-review-ui.txt
index 367908e..6f5f7297 100644
--- a/Documentation/user-review-ui.txt
+++ b/Documentation/user-review-ui.txt
@@ -218,7 +218,7 @@
 ** [[plugin-actions]]Further actions may be available if plugins are installed.
 
 +
-image::images/user-review-ui-change-screen-change-info-actions.png[width=600, link="images/user-review-ui-change-screen-change-info-actions.png"]
+image::images/user-review-ui-change-screen-change-info-actions.png[width=400, link="images/user-review-ui-change-screen-change-info-actions.png"]
 
 - [[labels]]Labels & Votes:
 +
@@ -259,7 +259,7 @@
 set is currently viewed can be seen from the `Patch Sets` drop-down
 panel in the change header.
 
-image::images/user-review-ui-change-screen-patch-sets.png[width=487, link="images/user-review-ui-change-screen-patch-sets.png"]
+image::images/user-review-ui-change-screen-patch-sets.png[width=300, link="images/user-review-ui-change-screen-patch-sets.png"]
 
 
 [[download]]
@@ -458,7 +458,7 @@
 comments; a summary comment is only added if the reply popup panel is
 open when the quick approve button is clicked.
 
-image::images/user-review-ui-change-screen-quick-approve.png[width=800, link="images/gwt-user-review-ui-change-screen-quick-approve.png"]
+image::images/user-review-ui-change-screen-quick-approve.png[width=800, link="images/user-review-ui-change-screen-quick-approve.png"]
 
 [[history]]
 === History
@@ -485,11 +485,11 @@
 [[plugin-extensions]]
 === Plugin Extensions
 
-Gerrit plugins may extend the change screen; they can add buttons for
-additional actions to the change info block and display arbitrary UI
-controls below the change info block.
+Gerrit plugins may extend the change screen. Java plugins in the
+backend can add additional actions to the triple-dot menu block.
+Frontend plugins can change the UI controls in arbitrary ways.
 
-image::images/gwt-user-review-ui-change-screen-plugin-extensions.png[width=800, link="images/gwt-user-review-ui-change-screen-plugin-extensions.png"]
+image::images/user-review-ui-change-screen-plugin-extensions.png[width=300, link="images/user-review-ui-change-screen-plugin-extensions.png"]
 
 [[side-by-side]]
 == Side-by-Side Diff Screen
@@ -509,7 +509,7 @@
 diff preference allows to control whether the files should be
 automatically marked as reviewed when they are viewed.
 
-image::images/user-review-ui-side-by-side-diff-screen-reviewed.png[width=800, link="images/gwt-user-review-ui-side-by-side-diff-screen-reviewed.png"]
+image::images/user-review-ui-side-by-side-diff-screen-reviewed.png[width=800, link="images/user-review-ui-side-by-side-diff-screen-reviewed.png"]
 
 [[patch-set-selection]]
 In the header, on each side, the list of patch sets is shown. Clicking
@@ -616,7 +616,7 @@
 File level comments are added by clicking the 'File' header at the top
 of the file.
 
-image::images/user-review-ui-side-by-side-diff-screen-file-level-comment.png[width=800, link="images/gwt-user-review-ui-side-by-side-diff-screen-file-level-comment.png"]
+image::images/user-review-ui-side-by-side-diff-screen-file-level-comment.png[width=400, link="images/user-review-ui-side-by-side-diff-screen-file-level-comment.png"]
 
 [[diff-preferences]]
 === Diff Preferences
@@ -626,7 +626,7 @@
 preferences. The diff preferences can be accessed by clicking on the
 settings icon in the screen header.
 
-image::images/user-review-ui-side-by-side-diff-screen-preferences.png[width=800, link="images/gwt-user-review-ui-side-by-side-diff-screen-preferences.png"]
+image::images/user-review-ui-side-by-side-diff-screen-preferences.png[width=800, link="images/user-review-ui-side-by-side-diff-screen-preferences.png"]
 
 The following diff preferences can be configured:
 
@@ -673,7 +673,7 @@
 If many lines are skipped there are additional links to expand the
 context by ten lines before and after the skipped block.
 +
-image::images/user-review-ui-side-by-side-diff-screen-expand-skipped-lines.png[width=800, link="images/gwt-user-review-ui-side-by-side-diff-screen-expand-skipped-lines.png"]
+image::images/user-review-ui-side-by-side-diff-screen-expand-skipped-lines.png[width=800, link="images/user-review-ui-side-by-side-diff-screen-expand-skipped-lines.png"]
 
 - [[syntax-highlighting]]`Syntax Highlighting`:
 +
@@ -703,7 +703,7 @@
 a popup that shows a list of available keyboard shortcuts.
 
 
-image::images/user-review-ui-change-screen-keyboard-shortcuts.png[width=800, link="images/gwt-user-review-ui-change-screen-keyboard-shortcuts.png"]
+image::images/user-review-ui-change-screen-keyboard-shortcuts.png[width=800, link="images/user-review-ui-change-screen-keyboard-shortcuts.png"]
 
 
 In addition, Vim-like commands can be used to link:#key-navigation[
diff --git a/java/com/google/gerrit/server/restapi/change/ReplyAttentionSetUpdates.java b/java/com/google/gerrit/server/restapi/change/ReplyAttentionSetUpdates.java
index 0356cdd..53d0f18 100644
--- a/java/com/google/gerrit/server/restapi/change/ReplyAttentionSetUpdates.java
+++ b/java/com/google/gerrit/server/restapi/change/ReplyAttentionSetUpdates.java
@@ -19,7 +19,9 @@
 import com.google.common.collect.ImmutableSet;
 import com.google.common.collect.Sets;
 import com.google.common.collect.Sets.SetView;
+import com.google.common.flogger.FluentLogger;
 import com.google.gerrit.entities.Account;
+import com.google.gerrit.entities.AttentionSetUpdate;
 import com.google.gerrit.entities.HumanComment;
 import com.google.gerrit.entities.PatchSet;
 import com.google.gerrit.extensions.api.changes.AttentionSetInput;
@@ -60,6 +62,7 @@
  * This class is used to update the attention set when performing a review or replying on a change.
  */
 public class ReplyAttentionSetUpdates {
+  private static final FluentLogger logger = FluentLogger.forEnclosingClass();
 
   private final PermissionBackend permissionBackend;
   private final AddToAttentionSetOp.Factory addToAttentionSetOpFactory;
@@ -316,11 +319,15 @@
     AttentionSetUtil.validateInput(add);
     try {
       Account.Id attentionUserId =
-          getAccountIdAndValidateUser(changeNotes, add.user, accountsChangedInCommit);
+          getAccountIdAndValidateUser(
+              changeNotes, add.user, accountsChangedInCommit, AttentionSetUpdate.Operation.ADD);
       addToAttentionSet(bu, changeNotes, attentionUserId, add.reason, false);
     } catch (AccountResolver.UnresolvableAccountException ex) {
       // This happens only when the account doesn't exist. Silently ignore it. If we threw an error
       // message here, then it would be possible to probe whether an account exists.
+    } catch (AuthException ex) {
+      // adding users without permission to the attention set should fail silently.
+      logger.atFine().log(ex.getMessage());
     }
   }
 
@@ -334,17 +341,25 @@
     AttentionSetUtil.validateInput(remove);
     try {
       Account.Id attentionUserId =
-          getAccountIdAndValidateUser(changeNotes, remove.user, accountsChangedInCommit);
+          getAccountIdAndValidateUser(
+              changeNotes,
+              remove.user,
+              accountsChangedInCommit,
+              AttentionSetUpdate.Operation.REMOVE);
       removeFromAttentionSet(bu, changeNotes, attentionUserId, remove.reason, false);
     } catch (AccountResolver.UnresolvableAccountException ex) {
       // This happens only when the account doesn't exist. Silently ignore it. If we threw an error
       // message here, then it would be possible to probe whether an account exists.
+    } catch (AuthException ex) {
+      // this should never happen since removing users with permissions should work.
+      logger.atSevere().log(ex.getMessage());
     }
   }
 
-  private Account.Id getAccountId(ChangeNotes changeNotes, String user)
+  private Account.Id getAccountId(
+      ChangeNotes changeNotes, String user, AttentionSetUpdate.Operation operation)
       throws ConfigInvalidException, IOException, UnprocessableEntityException,
-          PermissionBackendException {
+          PermissionBackendException, AuthException {
     Account.Id attentionUserId = accountResolver.resolve(user).asUnique().account().id();
     try {
       permissionBackend
@@ -352,22 +367,29 @@
           .change(changeNotes)
           .check(ChangePermission.READ);
     } catch (AuthException e) {
+      // If the change is private, it is okay to add the user to the attention set since that
+      // person will be granted visibility when a reviewer.
       if (!changeNotes.getChange().isPrivate()) {
-        // If the change is private, it is okay to add the user to the attention set since that
-        // person will be granted visibility when a reviewer.
-        throw new UnprocessableEntityException(
-            "Can't add to attention set: Read not permitted for " + attentionUserId, e);
+
+        // Removing users without access is allowed, adding is not allowed
+        if (operation == AttentionSetUpdate.Operation.ADD) {
+          throw new AuthException(
+              "Can't modify attention set: Read not permitted for " + attentionUserId, e);
+        }
       }
     }
     return attentionUserId;
   }
 
   private Account.Id getAccountIdAndValidateUser(
-      ChangeNotes changeNotes, String user, Set<Account.Id> accountsChangedInCommit)
+      ChangeNotes changeNotes,
+      String user,
+      Set<Account.Id> accountsChangedInCommit,
+      AttentionSetUpdate.Operation operation)
       throws ConfigInvalidException, IOException, PermissionBackendException,
-          UnprocessableEntityException, BadRequestException {
+          UnprocessableEntityException, BadRequestException, AuthException {
     try {
-      Account.Id attentionUserId = getAccountId(changeNotes, user);
+      Account.Id attentionUserId = getAccountId(changeNotes, user, operation);
       if (accountsChangedInCommit.contains(attentionUserId)) {
         throw new BadRequestException(
             String.format(
diff --git a/java/com/google/gerrit/truth/NullAwareCorrespondence.java b/java/com/google/gerrit/truth/NullAwareCorrespondence.java
index 687ad94..5b107a6 100644
--- a/java/com/google/gerrit/truth/NullAwareCorrespondence.java
+++ b/java/com/google/gerrit/truth/NullAwareCorrespondence.java
@@ -7,15 +7,6 @@
 // http://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing, software
-// 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
diff --git a/javatests/com/google/gerrit/acceptance/api/revision/RevisionIT.java b/javatests/com/google/gerrit/acceptance/api/revision/RevisionIT.java
index af41556..4590d34 100644
--- a/javatests/com/google/gerrit/acceptance/api/revision/RevisionIT.java
+++ b/javatests/com/google/gerrit/acceptance/api/revision/RevisionIT.java
@@ -1421,22 +1421,12 @@
     BadRequestException thrown =
         assertThrows(
             BadRequestException.class,
-            () ->
-                gApi.changes()
-                    .id(r.getChangeId())
-                    .revision(r.getCommit().name())
-                    .files(3)
-                    .keySet());
+            () -> gApi.changes().id(r.getChangeId()).revision(r.getCommit().name()).files(3));
     assertThat(thrown).hasMessageThat().isEqualTo("invalid parent number: 3");
     thrown =
         assertThrows(
             BadRequestException.class,
-            () ->
-                gApi.changes()
-                    .id(r.getChangeId())
-                    .revision(r.getCommit().name())
-                    .files(-1)
-                    .keySet());
+            () -> gApi.changes().id(r.getChangeId()).revision(r.getCommit().name()).files(-1));
     assertThat(thrown).hasMessageThat().isEqualTo("invalid parent number: -1");
   }
 
@@ -1449,14 +1439,13 @@
 
     BadRequestException thrown =
         assertThrows(
-            BadRequestException.class,
-            () -> gApi.changes().id(changeId).revision(revId2).files(2).keySet());
+            BadRequestException.class, () -> gApi.changes().id(changeId).revision(revId2).files(2));
     assertThat(thrown).hasMessageThat().isEqualTo("invalid parent number: 2");
 
     thrown =
         assertThrows(
             BadRequestException.class,
-            () -> gApi.changes().id(changeId).revision(revId2).files(-1).keySet());
+            () -> gApi.changes().id(changeId).revision(revId2).files(-1));
     assertThat(thrown).hasMessageThat().isEqualTo("invalid parent number: -1");
   }
 
diff --git a/javatests/com/google/gerrit/acceptance/rest/change/AttentionSetIT.java b/javatests/com/google/gerrit/acceptance/rest/change/AttentionSetIT.java
index 800ee42..a4f9fc5 100644
--- a/javatests/com/google/gerrit/acceptance/rest/change/AttentionSetIT.java
+++ b/javatests/com/google/gerrit/acceptance/rest/change/AttentionSetIT.java
@@ -15,6 +15,7 @@
 package com.google.gerrit.acceptance.rest.change;
 
 import static com.google.common.truth.Truth.assertThat;
+import static com.google.gerrit.acceptance.testsuite.project.TestProjectUpdate.block;
 import static com.google.gerrit.extensions.restapi.testing.AttentionSetUpdateSubject.assertThat;
 import static com.google.gerrit.testing.GerritJUnit.assertThrows;
 
@@ -32,23 +33,29 @@
 import com.google.gerrit.acceptance.config.GerritConfig;
 import com.google.gerrit.acceptance.testsuite.account.AccountOperations;
 import com.google.gerrit.acceptance.testsuite.change.ChangeOperations;
+import com.google.gerrit.acceptance.testsuite.project.ProjectOperations;
 import com.google.gerrit.acceptance.testsuite.request.RequestScopeOperations;
 import com.google.gerrit.common.Nullable;
 import com.google.gerrit.entities.Account;
+import com.google.gerrit.entities.AccountGroup;
 import com.google.gerrit.entities.AttentionSetUpdate;
 import com.google.gerrit.entities.AttentionSetUpdate.Operation;
 import com.google.gerrit.entities.Change;
 import com.google.gerrit.entities.LabelId;
 import com.google.gerrit.entities.Patch;
+import com.google.gerrit.entities.Permission;
 import com.google.gerrit.extensions.api.changes.AttentionSetInput;
 import com.google.gerrit.extensions.api.changes.DeleteReviewerInput;
 import com.google.gerrit.extensions.api.changes.HashtagsInput;
 import com.google.gerrit.extensions.api.changes.ReviewInput;
 import com.google.gerrit.extensions.api.changes.ReviewerInput;
+import com.google.gerrit.extensions.api.groups.GroupInput;
 import com.google.gerrit.extensions.client.GeneralPreferencesInfo;
 import com.google.gerrit.extensions.client.GeneralPreferencesInfo.EmailStrategy;
 import com.google.gerrit.extensions.client.ReviewerState;
 import com.google.gerrit.extensions.client.Side;
+import com.google.gerrit.extensions.common.GroupInfo;
+import com.google.gerrit.extensions.restapi.AuthException;
 import com.google.gerrit.extensions.restapi.BadRequestException;
 import com.google.gerrit.server.account.ServiceUserClassifier;
 import com.google.gerrit.server.query.change.ChangeData;
@@ -82,6 +89,7 @@
   @Inject private FakeEmailSender email;
   @Inject private TestCommentHelper testCommentHelper;
   @Inject private Provider<InternalChangeQuery> changeQueryProvider;
+  @Inject private ProjectOperations projectOperations;
 
   /** Simulates a fake clock. Uses second granularity. */
   private static class FakeClock implements LongSupplier {
@@ -1834,6 +1842,44 @@
     assertThat(attentionSet).hasReasonThat().isEqualTo("Their vote was deleted");
   }
 
+  @Test
+  public void accountsWithNoReadPermissionIgnoredOnReply() throws Exception {
+    // Create a group with user.
+    GroupInput groupInput = new GroupInput();
+    groupInput.name = name("User");
+    groupInput.members = ImmutableList.of(String.valueOf(user.id()));
+    GroupInfo group = gApi.groups().create(groupInput).get();
+
+    PushOneCommit.Result r = createChange();
+    gApi.changes().id(r.getChangeId()).addReviewer(user.email());
+
+    // remove read permission for user.
+    projectOperations
+        .project(project)
+        .forUpdate()
+        .add(block(Permission.READ).ref("refs/*").group(AccountGroup.uuid(group.id)))
+        .update();
+
+    // removing user without permissions from attention set is allowed on reply.
+    gApi.changes()
+        .id(r.getChangeId())
+        .current()
+        .review(new ReviewInput().removeUserFromAttentionSet(user.email(), "reason"));
+
+    // Add user to attention throws an exception.
+    assertThrows(
+        AuthException.class,
+        () -> change(r).addToAttentionSet(new AttentionSetInput(user.email(), "reason")));
+
+    // Add user to attention set is ignored on reply.
+    gApi.changes()
+        .id(r.getChangeId())
+        .current()
+        .review(new ReviewInput().addUserToAttentionSet(user.email(), "reason"));
+    assertThat(Iterables.getOnlyElement(getAttentionSetUpdatesForUser(r, user)).operation())
+        .isEqualTo(Operation.REMOVE);
+  }
+
   private List<AttentionSetUpdate> getAttentionSetUpdatesForUser(
       PushOneCommit.Result r, TestAccount account) {
     return getAttentionSetUpdates(r.getChange().getId()).stream()
diff --git a/polygerrit-ui/app/elements/change/gr-file-list/gr-file-list.ts b/polygerrit-ui/app/elements/change/gr-file-list/gr-file-list.ts
index 23c0e14..9dcb67e 100644
--- a/polygerrit-ui/app/elements/change/gr-file-list/gr-file-list.ts
+++ b/polygerrit-ui/app/elements/change/gr-file-list/gr-file-list.ts
@@ -677,7 +677,8 @@
     patchRange?: PatchRange,
     file?: NormalizedFileInfo
   ) {
-    const draftCount = changeComments?.computeDraftCountForFile(
+    if (changeComments === undefined) return '';
+    const draftCount = changeComments.computeDraftCountForFile(
       patchRange,
       file
     );
@@ -693,7 +694,8 @@
     patchRange?: PatchRange,
     file?: NormalizedFileInfo
   ) {
-    const draftCount = changeComments?.computeDraftCountForFile(
+    if (changeComments === undefined) return '';
+    const draftCount = changeComments.computeDraftCountForFile(
       patchRange,
       file
     );
diff --git a/polygerrit-ui/app/elements/change/gr-messages-list/gr-messages-list.ts b/polygerrit-ui/app/elements/change/gr-messages-list/gr-messages-list.ts
index d341083..fae624e 100644
--- a/polygerrit-ui/app/elements/change/gr-messages-list/gr-messages-list.ts
+++ b/polygerrit-ui/app/elements/change/gr-messages-list/gr-messages-list.ts
@@ -90,9 +90,9 @@
  */
 function computeThreads(
   message: CombinedMessage,
-  changeComments: ChangeComments
+  changeComments?: ChangeComments
 ): CommentThread[] {
-  if (message._index === undefined) {
+  if (message._index === undefined || changeComments === undefined) {
     return [];
   }
   const messageId = getMessageId(message);
@@ -369,7 +369,7 @@
     return combinedMessages;
   }
 
-  getCommentThreads(message: CombinedMessage, changeComments: ChangeComments) {
+  getCommentThreads(message: CombinedMessage, changeComments?: ChangeComments) {
     return computeThreads(message, changeComments);
   }
 
diff --git a/polygerrit-ui/app/elements/settings/gr-watched-projects-editor/gr-watched-projects-editor.ts b/polygerrit-ui/app/elements/settings/gr-watched-projects-editor/gr-watched-projects-editor.ts
index 6178e7a..4381a59 100644
--- a/polygerrit-ui/app/elements/settings/gr-watched-projects-editor/gr-watched-projects-editor.ts
+++ b/polygerrit-ui/app/elements/settings/gr-watched-projects-editor/gr-watched-projects-editor.ts
@@ -31,6 +31,7 @@
 import {hasOwnProperty} from '../../../utils/common-util';
 import {ProjectWatchInfo} from '../../../types/common';
 import {appContext} from '../../../services/app-context';
+import {IronInputElement} from '@polymer/iron-input';
 
 const NOTIFICATION_TYPES = [
   {name: 'Changes', key: 'notify_new_changes'},
@@ -43,9 +44,11 @@
 export interface GrWatchedProjectsEditor {
   $: {
     newFilter: HTMLInputElement;
+    newFilterInput: IronInputElement;
     newProject: GrAutocomplete;
   };
 }
+
 @customElement('gr-watched-projects-editor')
 export class GrWatchedProjectsEditor extends PolymerElement {
   static get template() {
@@ -62,7 +65,7 @@
   _projectsToRemove: ProjectWatchInfo[] = [];
 
   @property({type: Object})
-  _query?: AutocompleteQuery;
+  _query: AutocompleteQuery;
 
   private readonly restApiService = appContext.restApiService;
 
diff --git a/polygerrit-ui/app/elements/settings/gr-watched-projects-editor/gr-watched-projects-editor_html.ts b/polygerrit-ui/app/elements/settings/gr-watched-projects-editor/gr-watched-projects-editor_html.ts
index edc8fb2..fb65a03 100644
--- a/polygerrit-ui/app/elements/settings/gr-watched-projects-editor/gr-watched-projects-editor_html.ts
+++ b/polygerrit-ui/app/elements/settings/gr-watched-projects-editor/gr-watched-projects-editor_html.ts
@@ -102,13 +102,13 @@
           </th>
           <th colspan$="[[_getTypeCount()]]">
             <iron-input
+              id="newFilterInput"
               class="newFilterInput"
               placeholder="branch:name, or other search expression"
             >
               <input
                 id="newFilter"
                 class="newFilterInput"
-                is="iron-input"
                 placeholder="branch:name, or other search expression"
               />
             </iron-input>
diff --git a/polygerrit-ui/app/elements/settings/gr-watched-projects-editor/gr-watched-projects-editor_test.js b/polygerrit-ui/app/elements/settings/gr-watched-projects-editor/gr-watched-projects-editor_test.ts
similarity index 76%
rename from polygerrit-ui/app/elements/settings/gr-watched-projects-editor/gr-watched-projects-editor_test.js
rename to polygerrit-ui/app/elements/settings/gr-watched-projects-editor/gr-watched-projects-editor_test.ts
index aac8995..cb4b86d 100644
--- a/polygerrit-ui/app/elements/settings/gr-watched-projects-editor/gr-watched-projects-editor_test.js
+++ b/polygerrit-ui/app/elements/settings/gr-watched-projects-editor/gr-watched-projects-editor_test.ts
@@ -15,14 +15,18 @@
  * limitations under the License.
  */
 
-import '../../../test/common-test-setup-karma.js';
-import './gr-watched-projects-editor.js';
-import {stubRestApi} from '../../../test/test-utils.js';
+import '../../../test/common-test-setup-karma';
+import './gr-watched-projects-editor';
+import {GrWatchedProjectsEditor} from './gr-watched-projects-editor';
+import {stubRestApi} from '../../../test/test-utils';
+import {ProjectWatchInfo} from '../../../types/common';
+import {queryAll, queryAndAssert} from '../../../test/test-utils';
+import * as MockInteractions from '@polymer/iron-test-helpers/mock-interactions';
 
 const basicFixture = fixtureFromElement('gr-watched-projects-editor');
 
 suite('gr-watched-projects-editor tests', () => {
-  let element;
+  let element: GrWatchedProjectsEditor;
 
   setup(done => {
     const projects = [
@@ -30,29 +34,34 @@
         project: 'project a',
         notify_submitted_changes: true,
         notify_abandoned_changes: true,
-      }, {
+      },
+      {
         project: 'project b',
         filter: 'filter 1',
         notify_new_changes: true,
-      }, {
+      },
+      {
         project: 'project b',
         filter: 'filter 2',
-      }, {
+      },
+      {
         project: 'project c',
         notify_new_changes: true,
         notify_new_patch_sets: true,
         notify_all_comments: true,
       },
-    ];
+    ] as ProjectWatchInfo[];
 
     stubRestApi('getWatchedProjects').returns(Promise.resolve(projects));
     stubRestApi('getSuggestedProjects').callsFake(input => {
       if (input.startsWith('th')) {
-        return Promise.resolve({'the project': {
-          id: 'the project',
-          state: 'ACTIVE',
-          web_links: [],
-        }});
+        return Promise.resolve({
+          'the project': {
+            id: 'the project',
+            state: 'ACTIVE',
+            web_links: [],
+          },
+        });
       } else {
         return Promise.resolve({});
       }
@@ -60,18 +69,18 @@
 
     element = basicFixture.instantiate();
 
-    element.loadData().then(() => { flush(done); });
+    element.loadData().then(() => {
+      flush(done);
+    });
   });
 
   test('renders', () => {
-    const rows = element.shadowRoot
-        .querySelector('table').querySelectorAll('tbody tr');
+    const rows = queryAndAssert(element, 'table').querySelectorAll('tbody tr');
     assert.equal(rows.length, 4);
 
-    function getKeysOfRow(row) {
-      const boxes = rows[row].querySelectorAll('input[checked]');
-      return Array.prototype.map.call(boxes,
-          e => e.getAttribute('data-key'));
+    function getKeysOfRow(row: number) {
+      const boxes = queryAll(rows[row], 'input[checked]');
+      return Array.prototype.map.call(boxes, e => e.getAttribute('data-key'));
     }
 
     let checkedKeys = getKeysOfRow(0);
@@ -157,41 +166,44 @@
   test('_handleAddProject', () => {
     element.$.newProject.value = 'project d';
     element.$.newProject.setText('project d');
-    element.$.newFilter.bindValue = '';
+    element.$.newFilterInput.bindValue = '';
 
     element._handleAddProject();
 
-    assert.equal(element._projects.length, 5);
-    assert.equal(element._projects[4].project, 'project d');
-    assert.isNotOk(element._projects[4].filter);
-    assert.isTrue(element._projects[4]._is_local);
+    const projects = element._projects!;
+    assert.equal(projects.length, 5);
+    assert.equal(projects[4].project, 'project d');
+    assert.isNotOk(projects[4].filter);
+    assert.isTrue(projects[4]._is_local);
   });
 
   test('_handleAddProject with invalid inputs', () => {
     element.$.newProject.value = 'project b';
     element.$.newProject.setText('project b');
-    element.$.newFilter.bindValue = 'filter 1';
+    element.$.newFilterInput.bindValue = 'filter 1';
     element.$.newFilter.value = 'filter 1';
 
     element._handleAddProject();
 
-    assert.equal(element._projects.length, 4);
+    assert.equal(element._projects!.length, 4);
   });
 
   test('_handleRemoveProject', () => {
-    assert.equal(element._projectsToRemove, 0);
-    const button = element.shadowRoot
-        .querySelector('table tbody tr:nth-child(2) gr-button');
+    assert.deepEqual(element._projectsToRemove, []);
+
+    const button = queryAndAssert(
+      element,
+      'table tbody tr:nth-child(2) gr-button'
+    );
     MockInteractions.tap(button);
 
     flush();
 
-    const rows = element.shadowRoot
-        .querySelector('table tbody').querySelectorAll('tr');
+    const rows = queryAndAssert(element, 'table tbody').querySelectorAll('tr');
+
     assert.equal(rows.length, 3);
 
     assert.equal(element._projectsToRemove.length, 1);
     assert.equal(element._projectsToRemove[0].project, 'project b');
   });
 });
-
diff --git a/polygerrit-ui/app/node_modules_licenses/licenses.ts b/polygerrit-ui/app/node_modules_licenses/licenses.ts
index f04e224..bcdab0e 100644
--- a/polygerrit-ui/app/node_modules_licenses/licenses.ts
+++ b/polygerrit-ui/app/node_modules_licenses/licenses.ts
@@ -405,6 +405,14 @@
       packageLicenseFile: "LICENSE",
     }
   },
+  {
+    name: "immer",
+    license: {
+      name: "immer",
+      type: LicenseTypes.Mit,
+      packageLicenseFile: "LICENSE",
+    }
+  }
 ];
 
 export default packages;
diff --git a/polygerrit-ui/app/package.json b/polygerrit-ui/app/package.json
index 4e18e47..d26dc97 100644
--- a/polygerrit-ui/app/package.json
+++ b/polygerrit-ui/app/package.json
@@ -37,6 +37,7 @@
     "@webcomponents/webcomponentsjs": "^1.3.3",
     "ba-linkify": "file:../../lib/ba-linkify/src/",
     "codemirror-minified": "^5.62.0",
+    "immer": "^9.0.5",
     "lit-element": "^2.5.1",
     "page": "^1.11.6",
     "polymer-bridges": "file:../../polymer-bridges/",
diff --git a/polygerrit-ui/app/services/comments/comments-model.ts b/polygerrit-ui/app/services/comments/comments-model.ts
index 87f42c1..b26ec9b 100644
--- a/polygerrit-ui/app/services/comments/comments-model.ts
+++ b/polygerrit-ui/app/services/comments/comments-model.ts
@@ -130,6 +130,7 @@
     d => d.__draftID === draft.__draftID || d.id === draft.id
   );
   if (index === -1) return;
-  drafts[draft.path] = [...drafts[draft.path]].splice(index, 1);
+  drafts[draft.path] = [...drafts[draft.path]];
+  drafts[draft.path].splice(index, 1);
   privateState$.next(nextState);
 }
diff --git a/polygerrit-ui/app/services/gr-reporting/gr-reporting_impl.ts b/polygerrit-ui/app/services/gr-reporting/gr-reporting_impl.ts
index 2cc6f41..0df7d12 100644
--- a/polygerrit-ui/app/services/gr-reporting/gr-reporting_impl.ts
+++ b/polygerrit-ui/app/services/gr-reporting/gr-reporting_impl.ts
@@ -419,7 +419,10 @@
       eventInfo.inBackgroundTab = isInBackgroundTab;
     }
 
-    if (this._flagsService.enabledExperiments.length) {
+    if (
+      name === Timing.APP_STARTED &&
+      this._flagsService.enabledExperiments.length
+    ) {
       eventInfo.enabledExperiments = JSON.stringify(
         this._flagsService.enabledExperiments
       );
diff --git a/polygerrit-ui/app/types/common.ts b/polygerrit-ui/app/types/common.ts
index 826794e..0f2608e 100644
--- a/polygerrit-ui/app/types/common.ts
+++ b/polygerrit-ui/app/types/common.ts
@@ -984,6 +984,7 @@
   notify_all_comments?: boolean;
   notify_submitted_changes?: boolean;
   notify_abandoned_changes?: boolean;
+  _is_local?: boolean; // Added manually
 }
 /**
  * The DeleteDraftCommentsInput entity contains information specifying a set of draft comments that should be deleted
diff --git a/polygerrit-ui/app/yarn.lock b/polygerrit-ui/app/yarn.lock
index d8657f7..4fb98dd 100644
--- a/polygerrit-ui/app/yarn.lock
+++ b/polygerrit-ui/app/yarn.lock
@@ -600,6 +600,11 @@
     agent-base "6"
     debug "4"
 
+immer@^9.0.5:
+  version "9.0.5"
+  resolved "https://registry.yarnpkg.com/immer/-/immer-9.0.5.tgz#a7154f34fe7064f15f00554cc94c66cc0bf453ec"
+  integrity sha512-2WuIehr2y4lmYz9gaQzetPR2ECniCifk4ORaQbU3g5EalLt+0IVTosEPJ5BoYl/75ky2mivzdRzV8wWgQGOSYQ==
+
 inflight@^1.0.4:
   version "1.0.6"
   resolved "https://registry.yarnpkg.com/inflight/-/inflight-1.0.6.tgz#49bd6331d7d02d0c09bc910a1075ba8165b56df9"