diff --git a/Documentation/config-gerrit.txt b/Documentation/config-gerrit.txt
index 234389e..be6e140 100644
--- a/Documentation/config-gerrit.txt
+++ b/Documentation/config-gerrit.txt
@@ -2543,6 +2543,26 @@
 by the target version of the upgrade. Refer to the release notes and check whether
 the rolling upgrade is possible or not and the associated constraints.
 
+[[gerrit.importedServerId]]gerrit.importedServerId::
++
+ServerId of the repositories imported from other Gerrit servers. Changes coming
+associated with the imported serverIds are indexed and displayed in the UI.
++
+Specify multiple `gerrit.importedServerId` for allowing the import from multiple
+Gerrit servers with different serverIds.
++
+[NOTE]
+The account-ids referenced in the imported changes are used for looking up the
+associated account-id locally, using the `imported:` external-id.
+Example: the account-id 1000 from the imported server-id 59a4964e-6376-4ed9-beef
+will be looked up in the local accounts using the `imported:1000@59a4964e-6376-4ed9-beef`
+external-id.
++
+If this value is not set, all changes imported from other Gerrit servers will be
+ignored.
++
+By default empty.
+
 [[gerrit.serverId]]gerrit.serverId::
 +
 Used by NoteDb to, amongst other things, identify author identities from
diff --git a/java/com/google/gerrit/entities/Account.java b/java/com/google/gerrit/entities/Account.java
index 303e79f..85dbdeb 100644
--- a/java/com/google/gerrit/entities/Account.java
+++ b/java/com/google/gerrit/entities/Account.java
@@ -46,6 +46,10 @@
  */
 @AutoValue
 public abstract class Account {
+
+  /** Placeholder for indicating an account-id that does not correspond to any local account */
+  public static final Id UNKNOWN_ACCOUNT_ID = id(0);
+
   public static Id id(int id) {
     return new AutoValue_Account_Id(id);
   }
diff --git a/java/com/google/gerrit/server/account/externalids/ExternalId.java b/java/com/google/gerrit/server/account/externalids/ExternalId.java
index 0a51171..1616198 100644
--- a/java/com/google/gerrit/server/account/externalids/ExternalId.java
+++ b/java/com/google/gerrit/server/account/externalids/ExternalId.java
@@ -135,6 +135,9 @@
   /** Scheme used for GPG public keys. */
   public static final String SCHEME_GPGKEY = "gpgkey";
 
+  /** Scheme for imported accounts from other servers with different GerritServerId */
+  public static final String SCHEME_IMPORTED = "imported";
+
   /** Scheme for external auth used during authentication, e.g. OAuth Token */
   public static final String SCHEME_EXTERNAL = "external";
 
diff --git a/java/com/google/gerrit/server/account/externalids/ExternalIdCache.java b/java/com/google/gerrit/server/account/externalids/ExternalIdCache.java
index 9f766d0..fe8feac 100644
--- a/java/com/google/gerrit/server/account/externalids/ExternalIdCache.java
+++ b/java/com/google/gerrit/server/account/externalids/ExternalIdCache.java
@@ -30,7 +30,7 @@
  *
  * <p>All returned collections are unmodifiable.
  */
-interface ExternalIdCache {
+public interface ExternalIdCache {
   Optional<ExternalId> byKey(ExternalId.Key key) throws IOException;
 
   ImmutableSet<ExternalId> byAccount(Account.Id accountId) throws IOException;
diff --git a/java/com/google/gerrit/server/config/GerritImportedServerIds.java b/java/com/google/gerrit/server/config/GerritImportedServerIds.java
new file mode 100644
index 0000000..c47d3be
--- /dev/null
+++ b/java/com/google/gerrit/server/config/GerritImportedServerIds.java
@@ -0,0 +1,29 @@
+// Copyright (C) 2022 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.
+
+package com.google.gerrit.server.config;
+
+import static java.lang.annotation.RetentionPolicy.RUNTIME;
+
+import com.google.inject.BindingAnnotation;
+import java.lang.annotation.Retention;
+
+/**
+ * List of ServerIds of the Gerrit data imported from other servers.
+ *
+ * <p>This values correspond to the {@code GerritServerId} of other servers.
+ */
+@Retention(RUNTIME)
+@BindingAnnotation
+public @interface GerritImportedServerIds {}
diff --git a/java/com/google/gerrit/server/config/GerritImportedServerIdsProvider.java b/java/com/google/gerrit/server/config/GerritImportedServerIdsProvider.java
new file mode 100644
index 0000000..f3f7645
--- /dev/null
+++ b/java/com/google/gerrit/server/config/GerritImportedServerIdsProvider.java
@@ -0,0 +1,37 @@
+// Copyright (C) 2022 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.
+
+package com.google.gerrit.server.config;
+
+import com.google.common.collect.ImmutableSet;
+import com.google.inject.Inject;
+import com.google.inject.Provider;
+import org.eclipse.jgit.lib.Config;
+
+public class GerritImportedServerIdsProvider implements Provider<ImmutableSet<String>> {
+  public static final String SECTION = "gerrit";
+  public static final String KEY = "importedServerId";
+
+  private final ImmutableSet<String> importedIds;
+
+  @Inject
+  public GerritImportedServerIdsProvider(@GerritServerConfig Config cfg) {
+    importedIds = ImmutableSet.copyOf(cfg.getStringList(SECTION, null, KEY));
+  }
+
+  @Override
+  public ImmutableSet<String> get() {
+    return importedIds;
+  }
+}
diff --git a/java/com/google/gerrit/server/notedb/AbstractChangeNotes.java b/java/com/google/gerrit/server/notedb/AbstractChangeNotes.java
index 158972f..3757244 100644
--- a/java/com/google/gerrit/server/notedb/AbstractChangeNotes.java
+++ b/java/com/google/gerrit/server/notedb/AbstractChangeNotes.java
@@ -17,6 +17,7 @@
 import static java.util.Objects.requireNonNull;
 
 import com.google.common.annotations.VisibleForTesting;
+import com.google.common.collect.ImmutableSet;
 import com.google.gerrit.common.Nullable;
 import com.google.gerrit.common.UsedAt;
 import com.google.gerrit.entities.Change;
@@ -24,6 +25,7 @@
 import com.google.gerrit.exceptions.StorageException;
 import com.google.gerrit.metrics.Timer0;
 import com.google.gerrit.server.config.AllUsersName;
+import com.google.gerrit.server.config.GerritImportedServerIds;
 import com.google.gerrit.server.config.GerritServerId;
 import com.google.gerrit.server.git.GitRepositoryManager;
 import com.google.gerrit.server.notedb.ChangeNotesCommit.ChangeNotesRevWalk;
@@ -51,6 +53,7 @@
     public final AllUsersName allUsers;
     public final NoteDbMetrics metrics;
     public final String serverId;
+    public final ImmutableSet<String> importedServerIds;
 
     // Providers required to avoid dependency cycles.
 
@@ -64,7 +67,8 @@
         ChangeNoteJson changeNoteJson,
         NoteDbMetrics metrics,
         Provider<ChangeNotesCache> cache,
-        @GerritServerId String serverId) {
+        @GerritServerId String serverId,
+        @GerritImportedServerIds ImmutableSet<String> importedServerIds) {
       this.failOnLoadForTest = new AtomicBoolean();
       this.repoManager = repoManager;
       this.allUsers = allUsers;
@@ -72,6 +76,7 @@
       this.metrics = metrics;
       this.cache = cache;
       this.serverId = serverId;
+      this.importedServerIds = importedServerIds;
     }
   }
 
diff --git a/java/com/google/gerrit/server/notedb/ChangeNotes.java b/java/com/google/gerrit/server/notedb/ChangeNotes.java
index 26d5933..31934d5 100644
--- a/java/com/google/gerrit/server/notedb/ChangeNotes.java
+++ b/java/com/google/gerrit/server/notedb/ChangeNotes.java
@@ -406,6 +406,10 @@
     return state.metaId();
   }
 
+  public String getServerId() {
+    return state.serverId();
+  }
+
   public ImmutableSortedMap<PatchSet.Id, PatchSet> getPatchSets() {
     if (patchSets == null) {
       ImmutableSortedMap.Builder<PatchSet.Id, PatchSet> b =
@@ -655,7 +659,9 @@
      * be to bump the cache version, but that would invalidate all persistent cache entries, what we
      * rather try to avoid.
      */
-    if (!Strings.isNullOrEmpty(stateServerId) && !args.serverId.equals(stateServerId)) {
+    if (!Strings.isNullOrEmpty(stateServerId)
+        && !args.serverId.equals(stateServerId)
+        && !args.importedServerIds.contains(stateServerId)) {
       throw new InvalidServerIdException(args.serverId, stateServerId);
     }
 
diff --git a/java/com/google/gerrit/server/notedb/ChangeNotesCache.java b/java/com/google/gerrit/server/notedb/ChangeNotesCache.java
index 19044e6..0f2c877 100644
--- a/java/com/google/gerrit/server/notedb/ChangeNotesCache.java
+++ b/java/com/google/gerrit/server/notedb/ChangeNotesCache.java
@@ -26,6 +26,7 @@
 import com.google.gerrit.proto.Protos;
 import com.google.gerrit.server.ReviewerByEmailSet;
 import com.google.gerrit.server.ReviewerSet;
+import com.google.gerrit.server.account.externalids.ExternalIdCache;
 import com.google.gerrit.server.cache.CacheModule;
 import com.google.gerrit.server.cache.proto.Cache.ChangeNotesKeyProto;
 import com.google.gerrit.server.cache.serialize.CacheSerializer;
@@ -366,7 +367,13 @@
           "Load change notes for change %s of project %s", key.changeId(), key.project());
       ChangeNotesParser parser =
           new ChangeNotesParser(
-              key.changeId(), key.id(), walkSupplier.get(), args.changeNoteJson, args.metrics);
+              key.changeId(),
+              key.id(),
+              walkSupplier.get(),
+              args.changeNoteJson,
+              args.metrics,
+              args.serverId,
+              externalIdCache);
       ChangeNotesState result = parser.parseAll();
       // This assignment only happens if call() was actually called, which only
       // happens when Cache#get(K, Callable<V>) incurs a cache miss.
@@ -377,11 +384,16 @@
 
   private final Cache<Key, ChangeNotesState> cache;
   private final Args args;
+  private final ExternalIdCache externalIdCache;
 
   @Inject
-  ChangeNotesCache(@Named(CACHE_NAME) Cache<Key, ChangeNotesState> cache, Args args) {
+  ChangeNotesCache(
+      @Named(CACHE_NAME) Cache<Key, ChangeNotesState> cache,
+      Args args,
+      ExternalIdCache externalIdCache) {
     this.cache = cache;
     this.args = args;
+    this.externalIdCache = externalIdCache;
   }
 
   Value get(
diff --git a/java/com/google/gerrit/server/notedb/ChangeNotesParser.java b/java/com/google/gerrit/server/notedb/ChangeNotesParser.java
index 6e5e19c..f2a659d 100644
--- a/java/com/google/gerrit/server/notedb/ChangeNotesParser.java
+++ b/java/com/google/gerrit/server/notedb/ChangeNotesParser.java
@@ -79,6 +79,7 @@
 import com.google.gerrit.server.ReviewerByEmailSet;
 import com.google.gerrit.server.ReviewerSet;
 import com.google.gerrit.server.ReviewerStatusUpdate;
+import com.google.gerrit.server.account.externalids.ExternalIdCache;
 import com.google.gerrit.server.notedb.ChangeNoteUtil.ParsedPatchSetApproval;
 import com.google.gerrit.server.notedb.ChangeNotesCommit.ChangeNotesRevWalk;
 import com.google.gerrit.server.util.LabelVote;
@@ -199,18 +200,24 @@
   // the latest record unsets the field).
   private Optional<PatchSet.Id> cherryPickOf;
   private Instant mergedOn;
+  private final ExternalIdCache externalIdCache;
+  private final String gerritServerId;
 
   ChangeNotesParser(
       Change.Id changeId,
       ObjectId tip,
       ChangeNotesRevWalk walk,
       ChangeNoteJson changeNoteJson,
-      NoteDbMetrics metrics) {
+      NoteDbMetrics metrics,
+      String gerritServerId,
+      ExternalIdCache externalIdCache) {
     this.id = changeId;
     this.tip = tip;
     this.walk = walk;
     this.changeNoteJson = changeNoteJson;
     this.metrics = metrics;
+    this.externalIdCache = externalIdCache;
+    this.gerritServerId = gerritServerId;
     approvals = new LinkedHashMap<>();
     bufferedApprovals = new ArrayList<>();
     reviewers = HashBasedTable.create();
@@ -1406,7 +1413,7 @@
   }
 
   private Account.Id parseIdent(PersonIdent ident) throws ConfigInvalidException {
-    return NoteDbUtil.parseIdent(ident)
+    return NoteDbUtil.parseIdent(ident, gerritServerId, externalIdCache)
         .orElseThrow(
             () -> parseException("cannot retrieve account id: %s", ident.getEmailAddress()));
   }
diff --git a/java/com/google/gerrit/server/notedb/NoteDbUtil.java b/java/com/google/gerrit/server/notedb/NoteDbUtil.java
index 396e29b..64bf430 100644
--- a/java/com/google/gerrit/server/notedb/NoteDbUtil.java
+++ b/java/com/google/gerrit/server/notedb/NoteDbUtil.java
@@ -20,8 +20,12 @@
 import com.google.common.primitives.Ints;
 import com.google.gerrit.entities.Account;
 import com.google.gerrit.extensions.restapi.RestModifyView;
+import com.google.gerrit.server.account.externalids.ExternalId;
+import com.google.gerrit.server.account.externalids.ExternalIdCache;
+import java.io.IOException;
 import java.sql.Timestamp;
 import java.util.Optional;
+import org.eclipse.jgit.errors.ConfigInvalidException;
 import org.eclipse.jgit.lib.PersonIdent;
 import org.eclipse.jgit.util.GitDateFormatter;
 import org.eclipse.jgit.util.GitDateFormatter.Format;
@@ -48,6 +52,45 @@
     return Optional.empty();
   }
 
+  /**
+   * Returns an AccountId for the given email address and the current serverId. Reverse lookup the
+   * AccountId using the ExternalIdCache if the account has a foreign serverId.
+   *
+   * @param ident the accountId@serverId identity
+   * @param serverId the Gerrit's serverId
+   * @param externalIdCache reference to the cache for looking up the external ids
+   * @return a defined accountId if the account was found, {@link Account#UNKNOWN_ACCOUNT_ID} if the
+   *     lookup via external-id did not return any account, or an empty value if the identity was
+   *     malformed.
+   * @throws ConfigInvalidException when the lookup of the external-id failed
+   */
+  public static Optional<Account.Id> parseIdent(
+      PersonIdent ident, String serverId, ExternalIdCache externalIdCache)
+      throws ConfigInvalidException {
+    String email = ident.getEmailAddress();
+    int at = email.indexOf('@');
+    if (at >= 0) {
+      Integer id = Ints.tryParse(email.substring(0, at));
+      String accountServerId = email.substring(at + 1);
+      if (id != null) {
+        if (accountServerId.equals(serverId)) {
+          return Optional.of(Account.id(id));
+        }
+
+        ExternalId.Key extIdKey = ExternalId.Key.create(ExternalId.SCHEME_IMPORTED, email, false);
+        try {
+          return externalIdCache
+              .byKey(extIdKey)
+              .map(ExternalId::accountId)
+              .or(() -> Optional.of(Account.UNKNOWN_ACCOUNT_ID));
+        } catch (IOException e) {
+          throw new ConfigInvalidException("Unable to lookup external id from cache", e);
+        }
+      }
+    }
+    return Optional.empty();
+  }
+
   public static String extractHostPartFromPersonIdent(PersonIdent ident) {
     String email = ident.getEmailAddress();
     int at = email.indexOf('@');
diff --git a/java/com/google/gerrit/server/schema/SchemaModule.java b/java/com/google/gerrit/server/schema/SchemaModule.java
index ff2073d..e0e64a3 100644
--- a/java/com/google/gerrit/server/schema/SchemaModule.java
+++ b/java/com/google/gerrit/server/schema/SchemaModule.java
@@ -16,6 +16,7 @@
 
 import static com.google.inject.Scopes.SINGLETON;
 
+import com.google.common.collect.ImmutableSet;
 import com.google.gerrit.extensions.config.FactoryModule;
 import com.google.gerrit.server.GerritPersonIdent;
 import com.google.gerrit.server.GerritPersonIdentProvider;
@@ -25,9 +26,12 @@
 import com.google.gerrit.server.config.AllUsersNameProvider;
 import com.google.gerrit.server.config.AnonymousCowardName;
 import com.google.gerrit.server.config.AnonymousCowardNameProvider;
+import com.google.gerrit.server.config.GerritImportedServerIds;
+import com.google.gerrit.server.config.GerritImportedServerIdsProvider;
 import com.google.gerrit.server.config.GerritServerId;
 import com.google.gerrit.server.config.GerritServerIdProvider;
 import com.google.gerrit.server.index.group.GroupIndexCollection;
+import com.google.inject.TypeLiteral;
 import org.eclipse.jgit.lib.PersonIdent;
 
 /** Bindings for low-level Gerrit schema data. */
@@ -51,6 +55,11 @@
         .toProvider(GerritServerIdProvider.class)
         .in(SINGLETON);
 
+    bind(new TypeLiteral<ImmutableSet<String>>() {})
+        .annotatedWith(GerritImportedServerIds.class)
+        .toProvider(GerritImportedServerIdsProvider.class)
+        .in(SINGLETON);
+
     // It feels wrong to have this binding in a seemingly unrelated module, but it's a dependency of
     // SchemaCreatorImpl, so it's needed.
     // TODO(dborowitz): Is there any way to untangle this?
diff --git a/java/com/google/gerrit/testing/InMemoryModule.java b/java/com/google/gerrit/testing/InMemoryModule.java
index b00cadb..b1ab6b1 100644
--- a/java/com/google/gerrit/testing/InMemoryModule.java
+++ b/java/com/google/gerrit/testing/InMemoryModule.java
@@ -19,6 +19,7 @@
 import static com.google.inject.Scopes.SINGLETON;
 
 import com.google.common.base.Strings;
+import com.google.common.collect.ImmutableSet;
 import com.google.common.util.concurrent.ListeningExecutorService;
 import com.google.gerrit.acceptance.testsuite.project.ProjectOperations;
 import com.google.gerrit.acceptance.testsuite.project.ProjectOperationsImpl;
@@ -61,6 +62,8 @@
 import com.google.gerrit.server.config.FileBasedAllProjectsConfigProvider;
 import com.google.gerrit.server.config.FileBasedGlobalPluginConfigProvider;
 import com.google.gerrit.server.config.GerritGlobalModule;
+import com.google.gerrit.server.config.GerritImportedServerIds;
+import com.google.gerrit.server.config.GerritImportedServerIdsProvider;
 import com.google.gerrit.server.config.GerritInstanceIdModule;
 import com.google.gerrit.server.config.GerritInstanceNameModule;
 import com.google.gerrit.server.config.GerritOptions;
@@ -311,6 +314,17 @@
 
   @Provides
   @Singleton
+  @GerritImportedServerIds
+  public ImmutableSet<String> createImportedServerIds() {
+    ImmutableSet<String> serverIds =
+        ImmutableSet.copyOf(
+            cfg.getStringList(
+                GerritServerIdProvider.SECTION, null, GerritImportedServerIdsProvider.KEY));
+    return serverIds;
+  }
+
+  @Provides
+  @Singleton
   @SendEmailExecutor
   public ExecutorService createSendEmailExecutor() {
     return newDirectExecutorService();
diff --git a/javatests/com/google/gerrit/server/notedb/AbstractChangeNotesTest.java b/javatests/com/google/gerrit/server/notedb/AbstractChangeNotesTest.java
index d7c779e..1b286d1 100644
--- a/javatests/com/google/gerrit/server/notedb/AbstractChangeNotesTest.java
+++ b/javatests/com/google/gerrit/server/notedb/AbstractChangeNotesTest.java
@@ -18,6 +18,7 @@
 import static java.util.concurrent.TimeUnit.SECONDS;
 
 import com.google.common.collect.ImmutableList;
+import com.google.common.collect.ImmutableSet;
 import com.google.gerrit.entities.Account;
 import com.google.gerrit.entities.Change;
 import com.google.gerrit.entities.Comment;
@@ -39,6 +40,8 @@
 import com.google.gerrit.server.account.GroupBackend;
 import com.google.gerrit.server.account.Realm;
 import com.google.gerrit.server.account.ServiceUserClassifier;
+import com.google.gerrit.server.account.externalids.DisabledExternalIdCache;
+import com.google.gerrit.server.account.externalids.ExternalIdCache;
 import com.google.gerrit.server.approval.PatchSetApprovalUuidGenerator;
 import com.google.gerrit.server.approval.testing.TestPatchSetApprovalUuidGenerator;
 import com.google.gerrit.server.config.AllUsersName;
@@ -48,11 +51,13 @@
 import com.google.gerrit.server.config.CanonicalWebUrl;
 import com.google.gerrit.server.config.DefaultUrlFormatter.DefaultUrlFormatterModule;
 import com.google.gerrit.server.config.EnablePeerIPInReflogRecord;
+import com.google.gerrit.server.config.GerritImportedServerIds;
 import com.google.gerrit.server.config.GerritServerConfig;
 import com.google.gerrit.server.config.GerritServerId;
 import com.google.gerrit.server.extensions.events.GitReferenceUpdated;
 import com.google.gerrit.server.git.GitModule;
 import com.google.gerrit.server.git.GitRepositoryManager;
+import com.google.gerrit.server.git.RepositoryCaseMismatchException;
 import com.google.gerrit.server.group.SystemGroupBackend;
 import com.google.gerrit.server.project.NullProjectCache;
 import com.google.gerrit.server.project.ProjectCache;
@@ -67,9 +72,12 @@
 import com.google.inject.Guice;
 import com.google.inject.Inject;
 import com.google.inject.Injector;
+import com.google.inject.Module;
+import com.google.inject.TypeLiteral;
 import java.time.Instant;
 import java.time.ZoneId;
 import java.util.concurrent.ExecutorService;
+import org.eclipse.jgit.errors.RepositoryNotFoundException;
 import org.eclipse.jgit.internal.storage.dfs.InMemoryRepository;
 import org.eclipse.jgit.junit.TestRepository;
 import org.eclipse.jgit.lib.Config;
@@ -84,10 +92,13 @@
 @Ignore
 @RunWith(ConfigSuite.class)
 public abstract class AbstractChangeNotesTest {
+  protected static final String LOCAL_SERVER_ID = "gerrit";
+
   private static final ZoneId ZONE_ID = ZoneId.of("America/Los_Angeles");
 
   @ConfigSuite.Parameter public Config testConfig;
 
+  protected Account.Id changeOwnerId;
   protected Account.Id otherUserId;
   protected FakeAccountCache accountCache;
   protected IdentifiedUser changeOwner;
@@ -111,11 +122,21 @@
 
   @Inject @GerritServerId protected String serverId;
 
+  @Inject protected ExternalIdCache externalIdCache;
+
   protected Injector injector;
   private String systemTimeZone;
 
   @Before
   public void setUpTestEnvironment() throws Exception {
+    setupTestPrerequisites();
+
+    injector = createTestInjector(LOCAL_SERVER_ID);
+    createAllUsers(injector);
+    injector.injectMembers(this);
+  }
+
+  protected void setupTestPrerequisites() throws Exception {
     setTimeForTesting();
 
     serverIdent = new PersonIdent("Gerrit Server", "noreply@gerrit.com", TimeUtil.now(), ZONE_ID);
@@ -134,60 +155,77 @@
     ou.setPreferredEmail("other@account.com");
     accountCache.put(ou.build());
     assertableFanOutExecutor = new AssertableExecutorService();
-
-    injector =
-        Guice.createInjector(
-            new FactoryModule() {
-              @Override
-              public void configure() {
-                install(new GitModule());
-
-                install(new DefaultUrlFormatterModule());
-                install(NoteDbModule.forTest());
-                bind(AllUsersName.class).toProvider(AllUsersNameProvider.class);
-                bind(String.class).annotatedWith(GerritServerId.class).toInstance("gerrit");
-                bind(GitRepositoryManager.class).toInstance(repoManager);
-                bind(ProjectCache.class).to(NullProjectCache.class);
-                bind(Config.class).annotatedWith(GerritServerConfig.class).toInstance(testConfig);
-                bind(String.class)
-                    .annotatedWith(AnonymousCowardName.class)
-                    .toProvider(AnonymousCowardNameProvider.class);
-                bind(String.class)
-                    .annotatedWith(CanonicalWebUrl.class)
-                    .toInstance("http://localhost:8080/");
-                bind(Boolean.class)
-                    .annotatedWith(EnablePeerIPInReflogRecord.class)
-                    .toInstance(Boolean.FALSE);
-                bind(Realm.class).to(FakeRealm.class);
-                bind(GroupBackend.class).to(SystemGroupBackend.class).in(SINGLETON);
-                bind(AccountCache.class).toInstance(accountCache);
-                bind(PersonIdent.class)
-                    .annotatedWith(GerritPersonIdent.class)
-                    .toInstance(serverIdent);
-                bind(GitReferenceUpdated.class).toInstance(GitReferenceUpdated.DISABLED);
-                bind(MetricMaker.class).to(DisabledMetricMaker.class);
-                bind(ExecutorService.class)
-                    .annotatedWith(FanOutExecutor.class)
-                    .toInstance(assertableFanOutExecutor);
-                bind(ServiceUserClassifier.class).to(ServiceUserClassifier.NoOp.class);
-                bind(InternalChangeQuery.class)
-                    .toProvider(
-                        () -> {
-                          throw new UnsupportedOperationException();
-                        });
-                bind(PatchSetApprovalUuidGenerator.class)
-                    .to(TestPatchSetApprovalUuidGenerator.class);
-              }
-            });
-
-    injector.injectMembers(this);
-    repoManager.createRepository(allUsers);
-    changeOwner = userFactory.create(co.id());
-    otherUser = userFactory.create(ou.id());
-    otherUserId = otherUser.getAccountId();
+    changeOwnerId = co.id();
+    otherUserId = ou.id();
     internalUser = new InternalUser();
   }
 
+  protected Injector createTestInjector(String serverId, String... importedServerIds)
+      throws Exception {
+    return createTestInjector(DisabledExternalIdCache.module(), serverId, importedServerIds);
+  }
+
+  protected Injector createTestInjector(
+      Module extraGuiceModule, String serverId, String... importedServerIds) throws Exception {
+
+    return Guice.createInjector(
+        new FactoryModule() {
+          @Override
+          public void configure() {
+            install(extraGuiceModule);
+            install(new GitModule());
+
+            install(new DefaultUrlFormatterModule());
+            install(NoteDbModule.forTest());
+            bind(AllUsersName.class).toProvider(AllUsersNameProvider.class);
+            bind(String.class).annotatedWith(GerritServerId.class).toInstance(serverId);
+            bind(new TypeLiteral<ImmutableSet<String>>() {})
+                .annotatedWith(GerritImportedServerIds.class)
+                .toInstance(new ImmutableSet.Builder<String>().add(importedServerIds).build());
+            bind(GitRepositoryManager.class).toInstance(repoManager);
+            bind(ProjectCache.class).to(NullProjectCache.class);
+            bind(Config.class).annotatedWith(GerritServerConfig.class).toInstance(testConfig);
+            bind(String.class)
+                .annotatedWith(AnonymousCowardName.class)
+                .toProvider(AnonymousCowardNameProvider.class);
+            bind(String.class)
+                .annotatedWith(CanonicalWebUrl.class)
+                .toInstance("http://localhost:8080/");
+            bind(Boolean.class)
+                .annotatedWith(EnablePeerIPInReflogRecord.class)
+                .toInstance(Boolean.FALSE);
+            bind(Realm.class).to(FakeRealm.class);
+            bind(GroupBackend.class).to(SystemGroupBackend.class).in(SINGLETON);
+            bind(AccountCache.class).toInstance(accountCache);
+            bind(PersonIdent.class).annotatedWith(GerritPersonIdent.class).toInstance(serverIdent);
+            bind(GitReferenceUpdated.class).toInstance(GitReferenceUpdated.DISABLED);
+            bind(MetricMaker.class).to(DisabledMetricMaker.class);
+            bind(ExecutorService.class)
+                .annotatedWith(FanOutExecutor.class)
+                .toInstance(assertableFanOutExecutor);
+            bind(ServiceUserClassifier.class).to(ServiceUserClassifier.NoOp.class);
+            bind(InternalChangeQuery.class)
+                .toProvider(
+                    () -> {
+                      throw new UnsupportedOperationException();
+                    });
+            bind(PatchSetApprovalUuidGenerator.class).to(TestPatchSetApprovalUuidGenerator.class);
+          }
+        });
+  }
+
+  protected void createAllUsers(Injector injector)
+      throws RepositoryCaseMismatchException, RepositoryNotFoundException {
+    AllUsersName allUsersName = injector.getInstance(AllUsersName.class);
+
+    repoManager.createRepository(allUsersName);
+
+    IdentifiedUser.GenericFactory identifiedUserFactory =
+        injector.getInstance(IdentifiedUser.GenericFactory.class);
+    changeOwner = identifiedUserFactory.create(changeOwnerId);
+    otherUser = identifiedUserFactory.create(otherUserId);
+  }
+
   private void setTimeForTesting() {
     systemTimeZone = System.setProperty("user.timezone", "US/Eastern");
     TestTimeUtil.resetWithClockStep(1, SECONDS);
@@ -200,8 +238,12 @@
   }
 
   protected Change newChange(boolean workInProgress) throws Exception {
+    return newChange(injector, workInProgress);
+  }
+
+  protected Change newChange(Injector injector, boolean workInProgress) throws Exception {
     Change c = TestChanges.newChange(project, changeOwner.getAccountId());
-    ChangeUpdate u = newUpdateForNewChange(c, changeOwner);
+    ChangeUpdate u = newUpdate(injector, c, changeOwner, false);
     u.setChangeId(c.getKey().get());
     u.setBranch(c.getDest().branch());
     u.setWorkInProgress(workInProgress);
@@ -218,15 +260,20 @@
   }
 
   protected ChangeUpdate newUpdateForNewChange(Change c, CurrentUser user) throws Exception {
-    return newUpdate(c, user, false);
+    return newUpdate(injector, c, user, false);
   }
 
   protected ChangeUpdate newUpdate(Change c, CurrentUser user) throws Exception {
-    return newUpdate(c, user, true);
+    return newUpdate(injector, c, user, true);
   }
 
   protected ChangeUpdate newUpdate(Change c, CurrentUser user, boolean shouldExist)
       throws Exception {
+    return newUpdate(injector, c, user, shouldExist);
+  }
+
+  protected ChangeUpdate newUpdate(
+      Injector injector, Change c, CurrentUser user, boolean shouldExist) throws Exception {
     ChangeUpdate update = TestChanges.newUpdate(injector, c, user, shouldExist);
     update.setPatchSetId(c.currentPatchSetId());
     update.setAllowWriteToNewRef(true);
@@ -237,6 +284,10 @@
     return new ChangeNotes(args, c, true, null).load();
   }
 
+  protected ChangeNotes newNotes(AbstractChangeNotes.Args cArgs, Change c) {
+    return new ChangeNotes(cArgs, c, true, null).load();
+  }
+
   protected static SubmitRecord submitRecord(
       String status, String errorMessage, SubmitRecord.Label... labels) {
     SubmitRecord rec = new SubmitRecord();
diff --git a/javatests/com/google/gerrit/server/notedb/ChangeNotesCommitTest.java b/javatests/com/google/gerrit/server/notedb/ChangeNotesCommitTest.java
index 666b8fc..9445f4a 100644
--- a/javatests/com/google/gerrit/server/notedb/ChangeNotesCommitTest.java
+++ b/javatests/com/google/gerrit/server/notedb/ChangeNotesCommitTest.java
@@ -98,7 +98,8 @@
   private ChangeNotesParser newParser(ObjectId tip) throws Exception {
     walk.reset();
     ChangeNoteJson changeNoteJson = injector.getInstance(ChangeNoteJson.class);
-    return new ChangeNotesParser(newChange().getId(), tip, walk, changeNoteJson, args.metrics);
+    return new ChangeNotesParser(
+        newChange().getId(), tip, walk, changeNoteJson, args.metrics, serverId, externalIdCache);
   }
 
   private RevCommit writeCommit(String body) throws Exception {
diff --git a/javatests/com/google/gerrit/server/notedb/ChangeNotesParserTest.java b/javatests/com/google/gerrit/server/notedb/ChangeNotesParserTest.java
index 276f093..4543b50 100644
--- a/javatests/com/google/gerrit/server/notedb/ChangeNotesParserTest.java
+++ b/javatests/com/google/gerrit/server/notedb/ChangeNotesParserTest.java
@@ -201,11 +201,11 @@
             + "Branch: refs/heads/master\n"
             + "Change-id: I577fb248e474018276351785930358ec0450e9f7\n"
             + "Patch-set: 1\n"
-            + "Copied-Label: Label1=+1 Account <1@gerrit>,Other Account <2@Gerrit>\n"
+            + "Copied-Label: Label1=+1 Account <1@gerrit>,Other Account <2@gerrit>\n"
             + "Copied-Label: Label2=+1 Account <1@gerrit>\n"
-            + "Copied-Label: Label3=+1 Account <1@gerrit>,Other Account <2@Gerrit> :\"tag\"\n"
-            + "Copied-Label: Label4=+1 Account <1@Gerrit> :\"tag with characters %^#@^( *::!\"\n"
-            + "Copied-Label: -Label1 Account <1@gerrit>,Other Account <2@Gerrit>\\n"
+            + "Copied-Label: Label3=+1 Account <1@gerrit>,Other Account <2@gerrit> :\"tag\"\n"
+            + "Copied-Label: Label4=+1 Account <1@gerrit> :\"tag with characters %^#@^( *::!\"\n"
+            + "Copied-Label: -Label1 Account <1@gerrit>,Other Account <2@gerrit>\\n"
             + "Copied-Label: -Label1 Account <1@gerrit>\n"
             + "Subject: This is a test change\n");
 
@@ -782,6 +782,7 @@
   private ChangeNotesParser newParser(ObjectId tip) throws Exception {
     walk.reset();
     ChangeNoteJson changeNoteJson = injector.getInstance(ChangeNoteJson.class);
-    return new ChangeNotesParser(newChange().getId(), tip, walk, changeNoteJson, args.metrics);
+    return new ChangeNotesParser(
+        newChange().getId(), tip, walk, changeNoteJson, args.metrics, serverId, externalIdCache);
   }
 }
diff --git a/javatests/com/google/gerrit/server/notedb/ChangeNotesTest.java b/javatests/com/google/gerrit/server/notedb/ChangeNotesTest.java
index 8def660..4edfa8b4 100644
--- a/javatests/com/google/gerrit/server/notedb/ChangeNotesTest.java
+++ b/javatests/com/google/gerrit/server/notedb/ChangeNotesTest.java
@@ -2084,7 +2084,13 @@
     try (ChangeNotesRevWalk rw = ChangeNotesCommit.newRevWalk(repo)) {
       ChangeNotesParser notesWithComments =
           new ChangeNotesParser(
-              c.getId(), commitWithComments.copy(), rw, changeNoteJson, args.metrics);
+              c.getId(),
+              commitWithComments.copy(),
+              rw,
+              changeNoteJson,
+              args.metrics,
+              serverId,
+              externalIdCache);
       ChangeNotesState state = notesWithComments.parseAll();
       assertThat(state.approvals()).isEmpty();
       assertThat(state.publishedComments()).hasSize(1);
@@ -2093,7 +2099,13 @@
     try (ChangeNotesRevWalk rw = ChangeNotesCommit.newRevWalk(repo)) {
       ChangeNotesParser notesWithApprovals =
           new ChangeNotesParser(
-              c.getId(), commitWithApprovals.copy(), rw, changeNoteJson, args.metrics);
+              c.getId(),
+              commitWithApprovals.copy(),
+              rw,
+              changeNoteJson,
+              args.metrics,
+              serverId,
+              externalIdCache);
 
       ChangeNotesState state = notesWithApprovals.parseAll();
       assertThat(state.approvals()).hasSize(1);
diff --git a/javatests/com/google/gerrit/server/notedb/ImportedChangeNotesTest.java b/javatests/com/google/gerrit/server/notedb/ImportedChangeNotesTest.java
new file mode 100644
index 0000000..bb49a6d
--- /dev/null
+++ b/javatests/com/google/gerrit/server/notedb/ImportedChangeNotesTest.java
@@ -0,0 +1,114 @@
+// Copyright (C) 2022 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.
+
+package com.google.gerrit.server.notedb;
+
+import static com.google.common.truth.Truth.assertThat;
+import static com.google.gerrit.testing.GerritJUnit.assertThrows;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.ArgumentMatchers.eq;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+import com.google.gerrit.entities.Account;
+import com.google.gerrit.entities.Change;
+import com.google.gerrit.server.account.externalids.ExternalId;
+import com.google.gerrit.server.account.externalids.ExternalIdCache;
+import com.google.gerrit.server.git.RepositoryCaseMismatchException;
+import com.google.inject.AbstractModule;
+import java.util.Optional;
+import org.eclipse.jgit.errors.RepositoryNotFoundException;
+import org.junit.Before;
+import org.junit.Test;
+
+public class ImportedChangeNotesTest extends AbstractChangeNotesTest {
+
+  private static final String FOREIGN_SERVER_ID = "foreign-server-id";
+  private static final String IMPORTED_SERVER_ID = "gerrit-imported-1";
+
+  private ExternalIdCache externalIdCacheMock;
+
+  @Before
+  @Override
+  public void setUpTestEnvironment() throws Exception {
+    setupTestPrerequisites();
+  }
+
+  private void initServerIds(String serverId, String... importedServerIds)
+      throws Exception, RepositoryCaseMismatchException, RepositoryNotFoundException {
+    externalIdCacheMock = mock(ExternalIdCache.class);
+    injector =
+        createTestInjector(
+            new AbstractModule() {
+              @Override
+              protected void configure() {
+                bind(ExternalIdCache.class).toInstance(externalIdCacheMock);
+              }
+            },
+            serverId,
+            importedServerIds);
+    injector.injectMembers(this);
+    createAllUsers(injector);
+  }
+
+  @Test
+  public void allowChangeFromImportedServerId() throws Exception {
+    initServerIds(LOCAL_SERVER_ID, IMPORTED_SERVER_ID);
+
+    ExternalId.Key importedAccountIdKey =
+        ExternalId.Key.create(
+            ExternalId.SCHEME_IMPORTED,
+            changeOwner.getAccountId() + "@" + IMPORTED_SERVER_ID,
+            false);
+    ExternalId importedAccountId =
+        ExternalId.create(importedAccountIdKey, changeOwner.getAccountId(), null, null, null);
+
+    when(externalIdCacheMock.byKey(eq(importedAccountIdKey)))
+        .thenReturn(Optional.of(importedAccountId));
+
+    Change importedChange = newChange(createTestInjector(IMPORTED_SERVER_ID), false);
+    Change localChange = newChange();
+
+    assertThat(newNotes(importedChange).getServerId()).isEqualTo(IMPORTED_SERVER_ID);
+    assertThat(newNotes(localChange).getServerId()).isEqualTo(LOCAL_SERVER_ID);
+  }
+
+  @Test
+  public void rejectChangeWithForeignServerId() throws Exception {
+    initServerIds(LOCAL_SERVER_ID);
+    when(externalIdCacheMock.byKey(any())).thenReturn(Optional.empty());
+
+    Change foreignChange = newChange(createTestInjector(FOREIGN_SERVER_ID), false);
+
+    InvalidServerIdException invalidServerIdEx =
+        assertThrows(InvalidServerIdException.class, () -> newNotes(foreignChange));
+
+    String invalidServerIdMessage = invalidServerIdEx.getMessage();
+    assertThat(invalidServerIdMessage).contains("expected " + LOCAL_SERVER_ID);
+    assertThat(invalidServerIdMessage).contains("actual: " + FOREIGN_SERVER_ID);
+  }
+
+  @Test
+  public void changeFromImportedServerIdWithUnknownAccountId() throws Exception {
+    initServerIds(LOCAL_SERVER_ID, IMPORTED_SERVER_ID);
+
+    when(externalIdCacheMock.byKey(any())).thenReturn(Optional.empty());
+
+    Change importedChange = newChange(createTestInjector(IMPORTED_SERVER_ID), false);
+    assertThat(newNotes(importedChange).getServerId()).isEqualTo(IMPORTED_SERVER_ID);
+
+    assertThat(newNotes(importedChange).getChange().getOwner())
+        .isEqualTo(Account.UNKNOWN_ACCOUNT_ID);
+  }
+}
diff --git a/polygerrit-ui/app/constants/constants.ts b/polygerrit-ui/app/constants/constants.ts
index 99f7606..bb7b313 100644
--- a/polygerrit-ui/app/constants/constants.ts
+++ b/polygerrit-ui/app/constants/constants.ts
@@ -270,6 +270,7 @@
     change_table: [],
     email_strategy: EmailStrategy.ATTENTION_SET_ONLY,
     default_base_for_merges: DefaultBase.AUTO_MERGE,
+    allow_browser_notifications: false,
   };
 }
 
diff --git a/polygerrit-ui/app/elements/change-list/gr-create-change-help/gr-create-change-help.ts b/polygerrit-ui/app/elements/change-list/gr-create-change-help/gr-create-change-help.ts
index 0afb273..9c53fea 100644
--- a/polygerrit-ui/app/elements/change-list/gr-create-change-help/gr-create-change-help.ts
+++ b/polygerrit-ui/app/elements/change-list/gr-create-change-help/gr-create-change-help.ts
@@ -4,7 +4,6 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 import '../../shared/gr-button/gr-button';
-import '../../shared/gr-icons/gr-icons';
 import {fireEvent} from '../../../utils/event-util';
 import {sharedStyles} from '../../../styles/shared-styles';
 import {LitElement, css, html} from 'lit';
diff --git a/polygerrit-ui/app/elements/change/gr-change-actions/gr-change-actions.ts b/polygerrit-ui/app/elements/change/gr-change-actions/gr-change-actions.ts
index 77a0eb2..87e9576 100644
--- a/polygerrit-ui/app/elements/change/gr-change-actions/gr-change-actions.ts
+++ b/polygerrit-ui/app/elements/change/gr-change-actions/gr-change-actions.ts
@@ -8,7 +8,6 @@
 import '../../shared/gr-dialog/gr-dialog';
 import '../../shared/gr-dropdown/gr-dropdown';
 import '../../shared/gr-icon/gr-icon';
-import '../../shared/gr-icons/gr-icons';
 import '../../shared/gr-overlay/gr-overlay';
 import '../gr-confirm-abandon-dialog/gr-confirm-abandon-dialog';
 import '../gr-confirm-cherrypick-dialog/gr-confirm-cherrypick-dialog';
diff --git a/polygerrit-ui/app/elements/change/gr-change-view/gr-change-view.ts b/polygerrit-ui/app/elements/change/gr-change-view/gr-change-view.ts
index 8293daa..1000925 100644
--- a/polygerrit-ui/app/elements/change/gr-change-view/gr-change-view.ts
+++ b/polygerrit-ui/app/elements/change/gr-change-view/gr-change-view.ts
@@ -15,7 +15,7 @@
 import '../../shared/gr-change-star/gr-change-star';
 import '../../shared/gr-change-status/gr-change-status';
 import '../../shared/gr-editable-content/gr-editable-content';
-import '../../shared/gr-linked-text/gr-linked-text';
+import '../../shared/gr-formatted-text/gr-formatted-text';
 import '../../shared/gr-overlay/gr-overlay';
 import '../../shared/gr-tooltip-content/gr-tooltip-content';
 import '../gr-change-actions/gr-change-actions';
@@ -104,12 +104,7 @@
 import {GrIncludedInDialog} from '../gr-included-in-dialog/gr-included-in-dialog';
 import {GrDownloadDialog} from '../gr-download-dialog/gr-download-dialog';
 import {GrChangeMetadata} from '../gr-change-metadata/gr-change-metadata';
-import {
-  assertIsDefined,
-  assert,
-  query as queryEl,
-  queryAll,
-} from '../../../utils/common-util';
+import {assertIsDefined, assert, queryAll} from '../../../utils/common-util';
 import {GrEditControls} from '../../edit/gr-edit-controls/gr-edit-controls';
 import {
   CommentThread,
@@ -121,14 +116,12 @@
 import {GrFileList} from '../gr-file-list/gr-file-list';
 import {EditRevisionInfo, ParsedChangeInfo} from '../../../types/types';
 import {
-  ChecksTabState,
   CloseFixPreviewEvent,
   EditableContentSaveEvent,
   EventType,
   OpenFixPreviewEvent,
   ShowAlertEventDetail,
   SwitchTabEvent,
-  SwitchTabEventDetail,
   TabState,
   ValueChangedEvent,
 } from '../../../types/events';
@@ -486,9 +479,12 @@
   @state()
   private changeViewAriaHidden = false;
 
+  /**
+   * This can be a string only for plugin provided tabs.
+   */
   // visible for testing
   @state()
-  activeTab = Tab.FILES;
+  activeTab: Tab | string = Tab.FILES;
 
   @property({type: Boolean})
   unresolvedOnly = true;
@@ -702,6 +698,11 @@
     );
     subscribe(
       this,
+      () => this.getViewModel().tab$,
+      t => (this.activeTab = t ?? Tab.FILES)
+    );
+    subscribe(
+      this,
       () => this.getChecksModel().aPluginHasRegistered$,
       b => {
         this.showChecksTab = b;
@@ -959,7 +960,7 @@
           /* Account for border and padding and rounding errors. */
           max-width: calc(72ch + 2px + 2 * var(--spacing-m) + 0.4px);
         }
-        .commitMessage gr-linked-text {
+        .commitMessage gr-formatted-text {
           word-break: break-word;
         }
         #commitMessageEditor {
@@ -1460,12 +1461,10 @@
                 .commitCollapsible=${this.computeCommitCollapsible()}
                 remove-zero-width-space=""
               >
-                <gr-linked-text
-                  pre=""
-                  .content=${this.latestCommitMessage}
-                  .config=${this.projectConfig?.commentlinks}
-                  remove-zero-width-space=""
-                ></gr-linked-text>
+                <gr-formatted-text
+                  .content=${this.latestCommitMessage ?? ''}
+                  .markdown=${false}
+                ></gr-formatted-text>
               </gr-editable-content>
             </div>
             <h3 class="assistive-tech-only">Comments and Checks Summary</h3>
@@ -1496,7 +1495,10 @@
 
   private renderTabHeaders() {
     return html`
-      <paper-tabs id="tabs" @selected-changed=${this.setActiveTab}>
+      <paper-tabs
+        id="tabs"
+        @selected-changed=${this.onPaperTabSelectionChanged}
+      >
         <paper-tab @click=${this.onPaperTabClick} data-name=${Tab.FILES}
           ><span>Files</span></paper-tab
         >
@@ -1729,38 +1731,38 @@
     }
   }
 
-  setActiveTab(e: SwitchTabEvent) {
-    const paperTabs = queryEl<PaperTabsElement>(this, '#tabs');
-    if (!paperTabs) return;
-    const tabs = [...queryAll<HTMLElement>(paperTabs, 'paper-tab')];
+  onPaperTabSelectionChanged(e: ValueChangedEvent) {
+    if (!this.tabs) return;
+    const tabs = [...queryAll<HTMLElement>(this.tabs, 'paper-tab')];
     if (!tabs) return;
 
-    let tabName = e.detail.tab;
-    let tabIndex = e.detail.value;
+    const tabIndex = Number(e.detail.value);
+    assert(
+      Number.isInteger(tabIndex) && 0 <= tabIndex && tabIndex < tabs.length,
+      `${tabIndex} must be integer`
+    );
+    const tab = tabs[tabIndex].dataset['name'];
 
-    if (tabIndex === undefined) {
-      assert(tabName !== undefined, 'tabName or tabIndex must be defined');
-      tabIndex = tabs.findIndex(t => t.dataset['name'] === tabName);
-      assert(tabIndex !== -1, `tab ${tabName} not found`);
+    this.getViewModel().updateState({tab});
+  }
+
+  setActiveTab(e: SwitchTabEvent) {
+    if (!this.tabs) return;
+    const tabs = [...queryAll<HTMLElement>(this.tabs, 'paper-tab')];
+    if (!tabs) return;
+
+    const tab = e.detail.tab;
+    const tabIndex = tabs.findIndex(t => t.dataset['name'] === tab);
+    assert(tabIndex !== -1, `tab ${tab} not found`);
+
+    if (this.tabs.selected !== tabIndex) {
+      this.tabs.selected = tabIndex;
     }
 
-    if (tabName === undefined) {
-      tabName = tabs[tabIndex].dataset['name'];
-    }
-
-    if (paperTabs.selected !== tabIndex) {
-      // paperTabs.selected is undefined during rendering
-      if (paperTabs.selected !== undefined) {
-        const src = (e.composedPath()?.[0] as Element | undefined)?.tagName;
-        this.reporting.reportInteraction(Interaction.SHOW_TAB, {tabName, src});
-      }
-      paperTabs.selected = tabIndex;
-    }
-
-    this.activeTab = tabName as Tab;
+    this.getViewModel().updateState({tab});
 
     if (e.detail.tabState) this.tabState = e.detail.tabState;
-    if (e.detail.scrollIntoView) paperTabs.scrollIntoView({block: 'center'});
+    if (e.detail.scrollIntoView) this.tabs.scrollIntoView({block: 'center'});
   }
 
   /**
@@ -2246,19 +2248,7 @@
     } else if (this.viewState?.commentId) {
       tab = Tab.COMMENT_THREADS;
     }
-    const detail: SwitchTabEventDetail = {
-      tab,
-    };
-    if (tab === Tab.CHECKS) {
-      const state: ChecksTabState = {};
-      detail.tabState = {checksTab: state};
-    }
-
-    this.setActiveTab(
-      new CustomEvent(EventType.SHOW_TAB, {
-        detail,
-      })
-    );
+    this.setActiveTab(new CustomEvent(EventType.SHOW_TAB, {detail: {tab}}));
   }
 
   // Private but used in tests.
diff --git a/polygerrit-ui/app/elements/change/gr-change-view/gr-change-view_test.ts b/polygerrit-ui/app/elements/change/gr-change-view/gr-change-view_test.ts
index ad84fb0..f3017f8 100644
--- a/polygerrit-ui/app/elements/change/gr-change-view/gr-change-view_test.ts
+++ b/polygerrit-ui/app/elements/change/gr-change-view/gr-change-view_test.ts
@@ -433,9 +433,7 @@
                         id="commitMessageEditor"
                         remove-zero-width-space=""
                       >
-                        <gr-linked-text pre="" remove-zero-width-space="">
-                          <span id="output" slot="insert"></span>
-                        </gr-linked-text>
+                        <gr-formatted-text></gr-formatted-text>
                       </gr-editable-content>
                     </div>
                     <h3 class="assistive-tech-only">
diff --git a/polygerrit-ui/app/elements/change/gr-reply-dialog/gr-reply-dialog.ts b/polygerrit-ui/app/elements/change/gr-reply-dialog/gr-reply-dialog.ts
index b540c89..96a2aba 100644
--- a/polygerrit-ui/app/elements/change/gr-reply-dialog/gr-reply-dialog.ts
+++ b/polygerrit-ui/app/elements/change/gr-reply-dialog/gr-reply-dialog.ts
@@ -854,7 +854,6 @@
           .reviewerState=${ReviewerState.CC}
           @account-added=${this.handleAccountAdded}
           @accounts-changed=${this.handleCcsChanged}
-          .removableValues=${this.change?.removable_reviewers}
           .filter=${this.filterCCSuggestion}
           .pendingConfirmation=${this.ccPendingConfirmation}
           @pending-confirmation-changed=${this.handleCcsConfirmationChanged}
diff --git a/polygerrit-ui/app/elements/change/gr-submit-requirement-hovercard/gr-submit-requirement-hovercard.ts b/polygerrit-ui/app/elements/change/gr-submit-requirement-hovercard/gr-submit-requirement-hovercard.ts
index 7fe070c..66ad38c 100644
--- a/polygerrit-ui/app/elements/change/gr-submit-requirement-hovercard/gr-submit-requirement-hovercard.ts
+++ b/polygerrit-ui/app/elements/change/gr-submit-requirement-hovercard/gr-submit-requirement-hovercard.ts
@@ -30,7 +30,6 @@
 import {ReviewInput} from '../../../types/common';
 import {getAppContext} from '../../../services/app-context';
 import {assertIsDefined} from '../../../utils/common-util';
-import {CURRENT} from '../../../utils/patch-set-util';
 import {fireReload} from '../../../utils/event-util';
 import {submitRequirementsStyles} from '../../../styles/gr-submit-requirements-styles';
 import {
@@ -321,7 +320,11 @@
       },
     };
     return this.restApiService
-      .saveChangeReview(this.change._number, CURRENT, review)
+      .saveChangeReview(
+        this.change._number,
+        this.change.current_revision,
+        review
+      )
       .then(() => {
         fireReload(this, true);
       });
diff --git a/polygerrit-ui/app/elements/change/gr-submit-requirement-hovercard/gr-submit-requirement-hovercard_test.ts b/polygerrit-ui/app/elements/change/gr-submit-requirement-hovercard/gr-submit-requirement-hovercard_test.ts
index 2117ec5..4e78e8a 100644
--- a/polygerrit-ui/app/elements/change/gr-submit-requirement-hovercard/gr-submit-requirement-hovercard_test.ts
+++ b/polygerrit-ui/app/elements/change/gr-submit-requirement-hovercard/gr-submit-requirement-hovercard_test.ts
@@ -18,7 +18,7 @@
   createSubmitRequirementResultInfo,
 } from '../../../test/test-data-generators';
 import {ParsedChangeInfo} from '../../../types/types';
-import {query, queryAndAssert} from '../../../test/test-utils';
+import {query, queryAndAssert, stubRestApi} from '../../../test/test-utils';
 import {GrButton} from '../../shared/gr-button/gr-button';
 import {ChangeStatus, SubmitRequirementResultInfo} from '../../../api/rest-api';
 
@@ -321,6 +321,22 @@
       assert.isUndefined(query(element, '.quickApprove'));
     });
 
+    test('uses patchset from change', async () => {
+      const saveChangeReview = stubRestApi('saveChangeReview').resolves();
+      const element = await fixture<GrSubmitRequirementHovercard>(
+        html`<gr-submit-requirement-hovercard
+          .requirement=${submitRequirement}
+          .change=${change}
+          .account=${account}
+        ></gr-submit-requirement-hovercard>`
+      );
+
+      queryAndAssert<GrButton>(element, '.quickApprove > gr-button').click();
+
+      assert.equal(saveChangeReview.callCount, 1);
+      assert.equal(saveChangeReview.firstCall.args[1], change.current_revision);
+    });
+
     test('override button renders', async () => {
       const submitRequirement: SubmitRequirementResultInfo = {
         ...createSubmitRequirementResultInfo(),
diff --git a/polygerrit-ui/app/elements/checks/gr-checks-results.ts b/polygerrit-ui/app/elements/checks/gr-checks-results.ts
index a4e26fe..848948f 100644
--- a/polygerrit-ui/app/elements/checks/gr-checks-results.ts
+++ b/polygerrit-ui/app/elements/checks/gr-checks-results.ts
@@ -77,6 +77,7 @@
 import {DropdownItem} from '../shared/gr-dropdown-list/gr-dropdown-list';
 import './gr-checks-attempt';
 import {createDiffUrl} from '../../models/views/diff';
+import {changeViewModelToken} from '../../models/views/change';
 
 /**
  * Firing this event sets the regular expression of the results filter.
@@ -756,7 +757,7 @@
   filterInput?: HTMLInputElement;
 
   @state()
-  filterRegExp = new RegExp('');
+  filterRegExp = '';
 
   /** All runs. Shown should only the selected/filtered ones. */
   @property({attribute: false})
@@ -766,8 +767,8 @@
    * Check names of runs that are selected in the runs panel. When this array
    * is empty, then no run is selected and all runs should be shown.
    */
-  @property({attribute: false})
-  selectedRuns: string[] = [];
+  @state()
+  selectedRuns: Set<string> = new Set();
 
   @state()
   actions: Action[] = [];
@@ -808,6 +809,8 @@
    */
   private isSectionExpandedByUser = new Map<Category, boolean>();
 
+  private readonly getViewModel = resolve(this, changeViewModelToken);
+
   private readonly getChangeModel = resolve(this, changeModelToken);
 
   private readonly getChecksModel = resolve(this, checksModelToken);
@@ -853,6 +856,16 @@
       () => this.getChecksModel().someProvidersAreLoadingSelected$,
       x => (this.someProvidersAreLoading = x)
     );
+    subscribe(
+      this,
+      () => this.getViewModel().checksRunsSelected$,
+      x => (this.selectedRuns = x)
+    );
+    subscribe(
+      this,
+      () => this.getViewModel().checksResultsFilter$,
+      x => (this.filterRegExp = x)
+    );
   }
 
   static override get styles() {
@@ -1051,6 +1064,9 @@
 
   protected override updated(changedProperties: PropertyValues) {
     super.updated(changedProperties);
+    if (changedProperties.has('filterRegExp') && this.filterInput) {
+      this.filterInput.value = this.filterRegExp;
+    }
     if (changedProperties.has('tabState') && this.tabState) {
       const {statusOrCategory, checkName} = this.tabState;
       if (isCategory(statusOrCategory)) {
@@ -1224,11 +1240,10 @@
   }
 
   private handleFilter(e: ChecksResultsFilterEvent) {
-    if (!this.filterInput) return;
-    const oldValue = this.filterInput.value ?? '';
     const newValue = e.detail.filterRegExp ?? '';
-    this.filterInput.value = oldValue === newValue ? '' : newValue;
-    this.onFilterInputChange();
+    this.getViewModel().updateState({
+      checksResultsFilter: this.filterRegExp === newValue ? '' : newValue,
+    });
   }
 
   private renderAction(action?: Action) {
@@ -1289,10 +1304,7 @@
   }
 
   isRunSelected(run: {checkName: string}) {
-    return (
-      this.selectedRuns.length === 0 ||
-      this.selectedRuns.includes(run.checkName)
-    );
+    return this.selectedRuns.size === 0 || this.selectedRuns.has(run.checkName);
   }
 
   renderFilter() {
@@ -1300,10 +1312,11 @@
       run =>
         this.isRunSelected(run) && isAttemptSelected(this.selectedAttempt, run)
     );
-    if (this.selectedRuns.length === 0 && allResults(runs).length <= 3) {
-      if (this.filterRegExp.source.length > 0) {
-        this.filterRegExp = new RegExp('');
-      }
+    if (
+      this.selectedRuns.size === 0 &&
+      allResults(runs).length <= 3 &&
+      this.filterRegExp === ''
+    ) {
       return;
     }
     return html`
@@ -1325,7 +1338,9 @@
       {},
       {deduping: Deduping.EVENT_ONCE_PER_CHANGE}
     );
-    this.filterRegExp = new RegExp(this.filterInput.value, 'i');
+    this.getViewModel().updateState({
+      checksResultsFilter: this.filterInput.value,
+    });
   }
 
   renderSection(category: Category) {
@@ -1342,18 +1357,32 @@
       ],
       []
     );
-    const isSelection = this.selectedRuns.length > 0;
+    const isSelectionActive = this.selectedRuns.size > 0;
     const selected = all.filter(result => this.isRunSelected(result));
-    const filtered = selected.filter(result =>
-      matches(result, this.filterRegExp)
-    );
+    const re = new RegExp(this.filterRegExp, 'i');
+    const filtered = selected.filter(result => matches(result, re));
+    const isFilterActiveWithResults =
+      this.filterRegExp !== '' && filtered.length > 0;
+
+    // The logic for deciding whether to expand a section by default is a bit
+    // complicated, but we want to collapse empty and info/success sections by
+    // default for a clean and focused user experience. However, as soon as the
+    // user starts selecting or filtering we must take this into account and
+    // prefer to expand the sections.
     let expanded = this.isSectionExpanded.get(category);
     const expandedByUser = this.isSectionExpandedByUser.get(category) ?? false;
     if (!expandedByUser || expanded === undefined) {
-      expanded = selected.length > 0 && (isWarningOrError || isSelection);
+      // Note that we are using `selected` for `isEmpty` and not `filtered`,
+      // because if the filter is what makes a section empty, then we want to
+      // show an expanded section, which contains a message about this.
+      const isEmpty = selected.length === 0;
+      expanded =
+        !isEmpty &&
+        (isWarningOrError || isSelectionActive || isFilterActiveWithResults);
       this.isSectionExpanded.set(category, expanded);
     }
     const expandedClass = expanded ? 'expanded' : 'collapsed';
+
     const isShowAll = this.isShowAll.get(category) ?? false;
     const resultCount = filtered.length;
     const empty = resultCount === 0 ? 'empty' : '';
diff --git a/polygerrit-ui/app/elements/checks/gr-checks-runs.ts b/polygerrit-ui/app/elements/checks/gr-checks-runs.ts
index 09a2558..128a9b0a 100644
--- a/polygerrit-ui/app/elements/checks/gr-checks-runs.ts
+++ b/polygerrit-ui/app/elements/checks/gr-checks-runs.ts
@@ -44,7 +44,7 @@
 } from '../../models/checks/checks-fakes';
 import {assertIsDefined} from '../../utils/common-util';
 import {modifierPressed, whenVisible} from '../../utils/dom-util';
-import {fireRunSelected, fireRunSelectionReset} from './gr-checks-util';
+import {fireRunSelected, RunSelectedEvent} from './gr-checks-util';
 import {ChecksTabState} from '../../types/events';
 import {charsOnly} from '../../utils/string-util';
 import {getAppContext} from '../../services/app-context';
@@ -57,6 +57,7 @@
 import {Interaction} from '../../constants/reporting';
 import {Deduping} from '../../api/reporting';
 import {when} from 'lit/directives/when.js';
+import {changeViewModelToken} from '../../models/views/change';
 
 @customElement('gr-checks-run')
 export class GrChecksRun extends LitElement {
@@ -403,8 +404,8 @@
   @property({type: Boolean, reflect: true})
   collapsed = false;
 
-  @property({attribute: false})
-  selectedRuns: string[] = [];
+  @state()
+  selectedRuns: Set<string> = new Set();
 
   @state()
   selectedAttempt: AttemptChoice = LATEST_ATTEMPT;
@@ -424,6 +425,8 @@
 
   private getChecksModel = resolve(this, checksModelToken);
 
+  private readonly getViewModel = resolve(this, changeViewModelToken);
+
   private readonly reporting = getAppContext().reportingService;
 
   constructor() {
@@ -453,6 +456,11 @@
       () => this.getChecksModel().runFilterRegexp$,
       x => (this.filterRegExp = x)
     );
+    subscribe(
+      this,
+      () => this.getViewModel().checksRunsSelected$,
+      x => (this.selectedRuns = x)
+    );
     this.addEventListener('click', () => {
       if (this.collapsed) this.toggleCollapsed();
     });
@@ -660,8 +668,8 @@
 
   private renderTitleButtons() {
     if (this.collapsed) return;
-    if (this.selectedRuns.length < 2) return;
-    const actions = this.selectedRuns.map(selected => {
+    if (this.selectedRuns.size < 2) return;
+    const actions = [...this.selectedRuns].map(selected => {
       const run = this.runs.find(
         run => run.isLatestAttempt && run.checkName === selected
       );
@@ -676,7 +684,8 @@
       <gr-button
         class="font-normal"
         link
-        @click=${() => fireRunSelectionReset(this)}
+        @click=${() =>
+          this.getViewModel().updateState({checksRunsSelected: undefined})}
         >Unselect All</gr-button
       >
       <gr-tooltip-content
@@ -820,16 +829,23 @@
   }
 
   renderRun(run: CheckRun) {
-    const selectedRun = this.selectedRuns.includes(run.checkName);
-    const deselected = !selectedRun && this.selectedRuns.length > 0;
+    const selectedRun = this.selectedRuns.has(run.checkName);
+    const deselected = !selectedRun && this.selectedRuns.size > 0;
     return html`<gr-checks-run
       .run=${run}
       ?condensed=${this.collapsed}
       .selected=${selectedRun}
       .deselected=${deselected}
+      @run-selected=${this.handleRunSelected}
     ></gr-checks-run>`;
   }
 
+  handleRunSelected(e: RunSelectedEvent) {
+    if (e.detail.checkName) {
+      this.getViewModel().toggleSelectedCheckRun(e.detail.checkName);
+    }
+  }
+
   showFilter(): boolean {
     if (this.collapsed) return false;
     return this.runs.length > 10 || !!this.filterRegExp;
diff --git a/polygerrit-ui/app/elements/checks/gr-checks-tab.ts b/polygerrit-ui/app/elements/checks/gr-checks-tab.ts
index 82893bc..c1bcdc1 100644
--- a/polygerrit-ui/app/elements/checks/gr-checks-tab.ts
+++ b/polygerrit-ui/app/elements/checks/gr-checks-tab.ts
@@ -14,7 +14,6 @@
 import './gr-checks-runs';
 import './gr-checks-results';
 import {NumericChangeId, PatchSetNumber} from '../../types/common';
-import {RunSelectedEvent} from './gr-checks-util';
 import {TabState} from '../../types/events';
 import {getAppContext} from '../../services/app-context';
 import {subscribe} from '../lit/subscription-controller';
@@ -50,9 +49,6 @@
   @state()
   changeNum: NumericChangeId | undefined = undefined;
 
-  @state()
-  selectedRuns: string[] = [];
-
   private readonly getChangeModel = resolve(this, changeModelToken);
 
   private readonly getChecksModel = resolve(this, checksModelToken);
@@ -132,41 +128,16 @@
           class="runs"
           ?collapsed=${this.offsetWidth < 1000}
           .runs=${this.runs}
-          .selectedRuns=${this.selectedRuns}
           .tabState=${this.tabState?.checksTab}
-          @run-selected=${this.handleRunSelected}
         ></gr-checks-runs>
         <gr-checks-results
           class="results"
           .tabState=${this.tabState?.checksTab}
           .runs=${this.runs}
-          .selectedRuns=${this.selectedRuns}
         ></gr-checks-results>
       </div>
     `;
   }
-
-  handleRunSelected(e: RunSelectedEvent) {
-    this.reporting.reportInteraction(Interaction.CHECKS_RUN_SELECTED, {
-      checkName: e.detail.checkName,
-      reset: e.detail.reset,
-    });
-    if (e.detail.reset) {
-      this.selectedRuns = [];
-      return;
-    }
-    if (e.detail.checkName) {
-      this.toggleSelected(e.detail.checkName);
-    }
-  }
-
-  toggleSelected(checkName: string) {
-    if (this.selectedRuns.includes(checkName)) {
-      this.selectedRuns = this.selectedRuns.filter(r => r !== checkName);
-    } else {
-      this.selectedRuns = [...this.selectedRuns, checkName];
-    }
-  }
 }
 
 declare global {
diff --git a/polygerrit-ui/app/elements/checks/gr-checks-util.ts b/polygerrit-ui/app/elements/checks/gr-checks-util.ts
index 939a87e..c7477c4 100644
--- a/polygerrit-ui/app/elements/checks/gr-checks-util.ts
+++ b/polygerrit-ui/app/elements/checks/gr-checks-util.ts
@@ -11,7 +11,6 @@
 } from '../../models/checks/checks-util';
 
 export interface RunSelectedEventDetail {
-  reset: boolean;
   checkName?: string;
 }
 
@@ -33,16 +32,6 @@
   );
 }
 
-export function fireRunSelectionReset(target: EventTarget) {
-  target.dispatchEvent(
-    new CustomEvent('run-selected', {
-      detail: {reset: true},
-      composed: true,
-      bubbles: true,
-    })
-  );
-}
-
 export function isAttemptSelected(
   selectedAttempt: AttemptChoice,
   run: CheckRun
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 a35ca40..f829313 100644
--- a/polygerrit-ui/app/elements/core/gr-router/gr-router.ts
+++ b/polygerrit-ui/app/elements/core/gr-router/gr-router.ts
@@ -315,11 +315,12 @@
         // Note that router model view must be updated before view model state.
         // So this check is slightly fragile, but should work.
         if (this.view !== GerritView.CHANGE) return;
-        const browserUrl = window.location.toString();
-        const stateUrl = new URL(createChangeUrl(state), browserUrl).toString();
-        if (browserUrl !== stateUrl) {
+        const browserUrl = new URL(window.location.toString());
+        const stateUrl = new URL(createChangeUrl(state), browserUrl);
+        stateUrl.hash = browserUrl.hash;
+        if (browserUrl.toString() !== stateUrl.toString()) {
           page.replace(
-            stateUrl,
+            stateUrl.toString(),
             null,
             /* init: */ false,
             /* dispatch: */ false
@@ -1405,8 +1406,12 @@
     }
     const filter = queryMap.get('filter');
     if (filter) state.filter = filter;
+    const checksResultsFilter = queryMap.get('checksResultsFilter');
+    if (checksResultsFilter) state.checksResultsFilter = checksResultsFilter;
     const attempt = stringToAttemptChoice(queryMap.get('attempt'));
     if (attempt && attempt !== LATEST_ATTEMPT) state.attempt = attempt;
+    const selected = queryMap.get('checksRunsSelected');
+    if (selected) state.checksRunsSelected = new Set(selected.split(','));
 
     assertIsDefined(state.project, 'project');
     this.reporting.setRepoName(state.project);
diff --git a/polygerrit-ui/app/elements/core/gr-router/gr-router_test.ts b/polygerrit-ui/app/elements/core/gr-router/gr-router_test.ts
index ce3ed0d..119ba48 100644
--- a/polygerrit-ui/app/elements/core/gr-router/gr-router_test.ts
+++ b/polygerrit-ui/app/elements/core/gr-router/gr-router_test.ts
@@ -1149,6 +1149,8 @@
           queryMap.set('filter', 'fff');
           queryMap.set('select', 'sss');
           queryMap.set('attempt', '1');
+          queryMap.set('checksRunsSelected', 'asdf,qwer');
+          queryMap.set('checksResultsFilter', 'asdf.*qwer');
           ctx.querystring = queryMap.toString();
           assertctxToParams(ctx, 'handleChangeRoute', {
             view: GerritView.CHANGE,
@@ -1159,6 +1161,8 @@
             attempt: 1,
             filter: 'fff',
             tab: 'checks',
+            checksRunsSelected: new Set(['asdf', 'qwer']),
+            checksResultsFilter: 'asdf.*qwer',
           });
         });
       });
diff --git a/polygerrit-ui/app/elements/diff/gr-apply-fix-dialog/gr-apply-fix-dialog.ts b/polygerrit-ui/app/elements/diff/gr-apply-fix-dialog/gr-apply-fix-dialog.ts
index 262f1fd..17d7516 100644
--- a/polygerrit-ui/app/elements/diff/gr-apply-fix-dialog/gr-apply-fix-dialog.ts
+++ b/polygerrit-ui/app/elements/diff/gr-apply-fix-dialog/gr-apply-fix-dialog.ts
@@ -22,7 +22,7 @@
 import {PROVIDED_FIX_ID} from '../../../utils/comment-util';
 import {OpenFixPreviewEvent} from '../../../types/events';
 import {getAppContext} from '../../../services/app-context';
-import {fireCloseFixPreview, fireEvent} from '../../../utils/event-util';
+import {fireCloseFixPreview} from '../../../utils/event-util';
 import {DiffLayer, ParsedChangeInfo} from '../../../types/types';
 import {GrButton} from '../../shared/gr-button/gr-button';
 import {TokenHighlightLayer} from '../../../embed/diff/gr-diff-builder/token-highlight-layer';
@@ -33,6 +33,7 @@
 import {assert} from '../../../utils/common-util';
 import {resolve} from '../../../models/dependency';
 import {createChangeUrl} from '../../../models/views/change';
+import {GrDialog} from '../../shared/gr-dialog/gr-dialog';
 
 interface FilePreview {
   filepath: string;
@@ -44,6 +45,15 @@
   @query('#applyFixOverlay')
   applyFixOverlay?: GrOverlay;
 
+  @query('#applyFixDialog')
+  applyFixDialog?: GrDialog;
+
+  /** The currently observed dialog by `dialogOberserver`. */
+  observedDialog?: GrDialog;
+
+  /** The current observer observing the `observedDialog`. */
+  dialogObserver?: ResizeObserver;
+
   @query('#nextFix')
   nextFix?: GrButton;
 
@@ -102,9 +112,6 @@
         this.diffPrefs = diffPreferences;
       }
     );
-    this.addEventListener('diff-context-expanded', () => {
-      if (this.applyFixOverlay) fireEvent(this.applyFixOverlay, 'iron-resize');
-    });
   }
 
   static override styles = [
@@ -148,6 +155,39 @@
     `;
   }
 
+  override updated() {
+    this.updateDialogObserver();
+  }
+
+  override disconnectedCallback() {
+    this.removeDialogObserver();
+    super.disconnectedCallback();
+  }
+
+  private removeDialogObserver() {
+    this.dialogObserver?.disconnect();
+    this.dialogObserver = undefined;
+    this.observedDialog = undefined;
+  }
+
+  private updateDialogObserver() {
+    if (
+      this.applyFixDialog === this.observedDialog &&
+      this.dialogObserver !== undefined
+    ) {
+      return;
+    }
+
+    this.removeDialogObserver();
+    if (!this.applyFixDialog) return;
+
+    this.observedDialog = this.applyFixDialog;
+    this.dialogObserver = new ResizeObserver(() => {
+      this.applyFixOverlay?.refit();
+    });
+    this.dialogObserver.observe(this.observedDialog);
+  }
+
   private renderHeader() {
     return html`
       <div slot="header">${this.currentFix?.description ?? ''}</div>
@@ -202,7 +242,7 @@
    * Given event with fixSuggestions, fetch diffs associated with first
    * suggested fix and open dialog.
    */
-  async open(e: OpenFixPreviewEvent) {
+  open(e: OpenFixPreviewEvent) {
     this.patchNum = e.detail.patchNum;
     this.fixSuggestions = e.detail.fixSuggestions;
     assert(this.fixSuggestions.length > 0, 'no fix in the event');
@@ -212,9 +252,6 @@
       this.showSelectedFixSuggestion(this.fixSuggestions[0]),
       this.applyFixOverlay?.open()
     );
-    return Promise.all(promises).then(() => {
-      if (this.applyFixOverlay) fireEvent(this.applyFixOverlay, 'iron-resize');
-    });
   }
 
   private async showSelectedFixSuggestion(fixSuggestion: FixSuggestionInfo) {
diff --git a/polygerrit-ui/app/elements/diff/gr-apply-fix-dialog/gr-apply-fix-dialog_test.ts b/polygerrit-ui/app/elements/diff/gr-apply-fix-dialog/gr-apply-fix-dialog_test.ts
index b6e4a95..4d2d454 100644
--- a/polygerrit-ui/app/elements/diff/gr-apply-fix-dialog/gr-apply-fix-dialog_test.ts
+++ b/polygerrit-ui/app/elements/diff/gr-apply-fix-dialog/gr-apply-fix-dialog_test.ts
@@ -52,7 +52,7 @@
   }
 
   async function open(detail: OpenFixPreviewEventDetail) {
-    await element.open(
+    element.open(
       new CustomEvent<OpenFixPreviewEventDetail>(EventType.OPEN_FIX_PREVIEW, {
         detail,
       })
diff --git a/polygerrit-ui/app/elements/gr-app.ts b/polygerrit-ui/app/elements/gr-app.ts
index 33ba1e4..0cec8dd 100644
--- a/polygerrit-ui/app/elements/gr-app.ts
+++ b/polygerrit-ui/app/elements/gr-app.ts
@@ -70,7 +70,6 @@
         appContext.flagsService,
         appContext.userModel
       );
-      this.serviceWorkerInstaller.init();
     }
   }
 
diff --git a/polygerrit-ui/app/elements/lit/fit-controller.ts b/polygerrit-ui/app/elements/lit/fit-controller.ts
new file mode 100644
index 0000000..423a4f0
--- /dev/null
+++ b/polygerrit-ui/app/elements/lit/fit-controller.ts
@@ -0,0 +1,213 @@
+/**
+ * @license
+ * Copyright 2022 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import {ReactiveController, ReactiveControllerHost} from 'lit';
+
+export interface FitControllerHost {
+  /**
+   * This offset will increase or decrease the distance to the left side
+   * of the screen, a negative offset will move the dropdown to the left
+   * a positive one, to the right.
+   *
+   */
+  horizontalOffset: number;
+
+  /**
+   * This offset will increase or decrease the distance to the top
+   * side of the screen: a negative offset will move the dropdown upwards
+   * , a positive one, downwards.
+   *
+   */
+  verticalOffset: number;
+}
+
+export interface PositionStyles {
+  top: string;
+  left: string;
+  position: string;
+  maxWidth: string;
+  maxHeight: string;
+  boxSizing: string;
+}
+
+/**
+ * `FitController` fits an element in another element using `max-height`
+ * and `max-width`.
+ *
+ * FitController overrides all properties defined in PositionStyles for the
+ * host.
+ * The element will only be sized and/or positioned if it has not already been
+ * sized and/or positioned by CSS.
+ *  CSS properties            | Action
+ * --------------------------|-------------------------------------------
+ * `position` set            | Element is not centered horizontally/vertically
+ * `top` or `bottom` set     | Element is not vertically centered
+ * `left` or `right` set     | Element is not horizontally centered
+ * `max-height` set          | Element respects `max-height`
+ * `max-width` set           | Element respects `max-width`
+ *
+ * `FitController` positions an element into another element and gives it
+ * a horizontalAlignment = left and verticalAlignment = top.
+ * This will override the element's css position.
+ *
+ * Use `horizontalOffset, verticalOffset` to offset the element from its
+ * `positionTarget`; `FitController` will collapse these in order to
+ * keep the element within `window` boundaries, while preserving the element's
+ * CSS margin values.
+ *
+ */
+export class FitController implements ReactiveController {
+  host: ReactiveControllerHost & HTMLElement & FitControllerHost;
+
+  private originalStyles?: PositionStyles;
+
+  private positionTarget?: HTMLElement;
+
+  constructor(host: ReactiveControllerHost & HTMLElement & FitControllerHost) {
+    (this.host = host).addController(this);
+  }
+
+  hostConnected() {
+    this.positionTarget = this.getPositionTarget();
+  }
+
+  hostDisconnected() {}
+
+  // private but used in tests
+  getPositionTarget() {
+    let parent = this.host.parentNode;
+
+    if (parent && parent.nodeType === Node.DOCUMENT_FRAGMENT_NODE) {
+      parent = (parent as ShadowRoot).host;
+    }
+
+    return parent as HTMLElement;
+  }
+
+  private saveOriginalStyles() {
+    // These properties are changed in position() hence keep the original
+    // values to reset the host styles later.
+    this.originalStyles = {
+      top: this.host.style.top || '',
+      left: this.host.style.left || '',
+      position: this.host.style.position || '',
+      maxWidth: this.host.style.maxWidth || '',
+      maxHeight: this.host.style.maxHeight || '',
+      boxSizing: this.host.style.boxSizing || '',
+    };
+  }
+
+  /**
+   * Reset the host style, and clear the memoized data.
+   */
+  private resetStyles() {
+    // It is necessary to clear the max-width:0px and max-height:0px.
+    // A component may call refit() multiple times, in which case we don't
+    // want the values assigned from the first call which may not be precisely
+    // correct to influence the second call.
+    // Hence we reset the styles here.
+    if (this.originalStyles !== undefined) {
+      Object.assign(this.host.style, this.originalStyles);
+    }
+    this.originalStyles = undefined;
+  }
+
+  setPositionTarget(target: HTMLElement) {
+    this.positionTarget = target;
+  }
+
+  /**
+   * Equivalent to calling `resetStyles()` and `position()`.
+   * Useful to call this after the element or the `window` element has
+   * been resized, or if any of the positioning properties
+   * (e.g. `horizontalOffset, verticalOffset`) are updated.
+   * It preserves the scroll position of the host.
+   */
+  refit() {
+    const scrollLeft = this.host.scrollLeft;
+    const scrollTop = this.host.scrollTop;
+    this.resetStyles();
+    this.position();
+    this.host.scrollLeft = scrollLeft;
+    this.host.scrollTop = scrollTop;
+  }
+
+  private position() {
+    this.saveOriginalStyles();
+
+    this.host.style.position = 'fixed';
+    // Need border-box for margin/padding.
+    this.host.style.boxSizing = 'border-box';
+
+    const hostRect = this.host.getBoundingClientRect();
+    const positionRect = this.getNormalizedRect(this.positionTarget!);
+    const windowRect = this.getNormalizedRect(window);
+
+    this.calculateAndSetPositions(hostRect, positionRect, windowRect);
+  }
+
+  // private but used in tests
+  calculateAndSetPositions(
+    hostRect: DOMRect,
+    positionRect: DOMRect,
+    windowRect: DOMRect
+  ) {
+    const hostStyles = (window as Window).getComputedStyle(this.host);
+    const hostMinWidth = parseInt(hostStyles.minWidth) || 0;
+    const hostMinHeight = parseInt(hostStyles.minHeight) || 0;
+
+    const hostMargin = {
+      top: parseInt(hostStyles.marginTop) || 0,
+      right: parseInt(hostStyles.marginRight) || 0,
+      bottom: parseInt(hostStyles.marginBottom) || 0,
+      left: parseInt(hostStyles.marginLeft) || 0,
+    };
+
+    let leftPosition =
+      positionRect.left + this.host.horizontalOffset + hostMargin.left;
+    let topPosition =
+      positionRect.top + this.host.verticalOffset + hostMargin.top;
+
+    // Limit right/bottom within window respecting the margin.
+    const rightPosition = Math.min(
+      windowRect.right - hostMargin.right,
+      leftPosition + hostRect.width
+    );
+    const bottomPosition = Math.min(
+      windowRect.bottom - hostMargin.bottom,
+      topPosition + hostRect.height
+    );
+
+    // Respect hostMinWidth and hostMinHeight
+    // Current width is rightPosition - leftPosition or hostRect.width
+    //    rightPosition - leftPosition >= hostMinWidth
+    // => leftPosition <= rightPosition - hostMinWidth
+    leftPosition = Math.min(leftPosition, rightPosition - hostMinWidth);
+    topPosition = Math.min(topPosition, bottomPosition - hostMinHeight);
+
+    // Limit left/top within window respecting the margin.
+    leftPosition = Math.max(windowRect.left + hostMargin.left, leftPosition);
+    topPosition = Math.max(windowRect.top + hostMargin.top, topPosition);
+
+    // Use right/bottom to set maxWidth/maxHeight and respect
+    // minWidth/minHeight.
+    const maxWidth = Math.max(rightPosition - leftPosition, hostMinWidth);
+    const maxHeight = Math.max(bottomPosition - topPosition, hostMinHeight);
+
+    this.host.style.maxWidth = `${maxWidth}px`;
+    this.host.style.maxHeight = `${maxHeight}px`;
+
+    this.host.style.left = `${leftPosition}px`;
+    this.host.style.top = `${topPosition}px`;
+  }
+
+  private getNormalizedRect(target: Window | HTMLElement): DOMRect {
+    if (target === document.documentElement || target === window) {
+      return new DOMRect(0, 0, window.innerWidth, window.innerHeight);
+    }
+    return (target as HTMLElement).getBoundingClientRect();
+  }
+}
diff --git a/polygerrit-ui/app/elements/lit/fit-controller_test.ts b/polygerrit-ui/app/elements/lit/fit-controller_test.ts
new file mode 100644
index 0000000..2a60b83
--- /dev/null
+++ b/polygerrit-ui/app/elements/lit/fit-controller_test.ts
@@ -0,0 +1,143 @@
+/**
+ * @license
+ * Copyright 2022 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import '../../test/common-test-setup';
+import {fixture, html, assert} from '@open-wc/testing';
+import {FitController} from './fit-controller';
+import {LitElement} from 'lit';
+import {customElement} from 'lit/decorators.js';
+
+@customElement('fit-element')
+class FitElement extends LitElement {
+  fitController = new FitController(this);
+
+  horizontalOffset = 0;
+
+  verticalOffset = 0;
+
+  override render() {
+    return html`<div></div>`;
+  }
+}
+
+suite('fit controller', () => {
+  let element: FitElement;
+  setup(async () => {
+    element = await fixture(html`<fit-element></fit-element>`);
+  });
+
+  test('refit positioning', async () => {
+    const hostRect = new DOMRect(0, 0, 50, 50);
+
+    const positionRect = new DOMRect(37, 37, 300, 60);
+
+    const windowRect = new DOMRect(0, 0, 600, 600);
+
+    element.fitController.calculateAndSetPositions(
+      hostRect,
+      positionRect,
+      windowRect
+    );
+
+    assert.equal(element.style.top, '37px');
+    assert.equal(element.style.left, '37px');
+  });
+
+  test('refit positioning with offset', async () => {
+    const elementWithOffset: FitElement = await fixture(
+      html`<fit-element></fit-element>`
+    );
+    elementWithOffset.verticalOffset = 10;
+    elementWithOffset.horizontalOffset = 20;
+
+    const hostRect = new DOMRect(0, 0, 50, 50);
+
+    const positionRect = new DOMRect(37, 37, 300, 60);
+
+    const windowRect = new DOMRect(0, 0, 600, 600);
+
+    elementWithOffset.fitController.calculateAndSetPositions(
+      hostRect,
+      positionRect,
+      windowRect
+    );
+
+    assert.equal(elementWithOffset.style.top, '47px');
+    assert.equal(elementWithOffset.style.left, '57px');
+  });
+
+  test('host margin updates positioning', async () => {
+    const hostRect = new DOMRect(0, 0, 50, 50);
+
+    const positionRect = new DOMRect(37, 37, 300, 60);
+
+    const windowRect = new DOMRect(0, 0, 600, 600);
+
+    element.style.marginLeft = '10px';
+    element.style.marginTop = '10px';
+    element.fitController.calculateAndSetPositions(
+      hostRect,
+      positionRect,
+      windowRect
+    );
+
+    // is 10px extra from the previous test due to host margin
+    assert.equal(element.style.top, '47px');
+    assert.equal(element.style.left, '47px');
+  });
+
+  test('host minWidth, minHeight overrides positioning', async () => {
+    const hostRect = new DOMRect(0, 0, 50, 50);
+
+    const positionRect = new DOMRect(37, 37, 300, 60);
+
+    const windowRect = new DOMRect(0, 0, 600, 600);
+
+    element.style.marginLeft = '10px';
+    element.style.marginTop = '10px';
+
+    element.style.minHeight = '50px';
+    element.style.minWidth = '60px';
+
+    element.fitController.calculateAndSetPositions(
+      hostRect,
+      positionRect,
+      windowRect
+    );
+
+    assert.equal(element.style.top, '47px');
+
+    // Should be 47 like the previous test but that would make it overall
+    // smaller in width than the minWidth defined
+    assert.equal(element.style.left, '37px');
+    assert.equal(element.style.maxWidth, '60px');
+  });
+
+  test('positioning happens within window size ', async () => {
+    const hostRect = new DOMRect(0, 0, 50, 50);
+
+    const positionRect = new DOMRect(37, 37, 300, 60);
+
+    // window size is small hence limits the position
+    const windowRect = new DOMRect(0, 0, 50, 50);
+
+    element.style.marginLeft = '10px';
+    element.style.marginTop = '10px';
+
+    element.fitController.calculateAndSetPositions(
+      hostRect,
+      positionRect,
+      windowRect
+    );
+
+    assert.equal(element.style.top, '47px');
+    assert.equal(element.style.left, '47px');
+    // With the window size being 50, the element is styled with width 3px
+    // width = windowSize - leftPosition = 50 - 47 = 3px
+    // Without the window width restriction, in previous test maxWidth is 60px
+    assert.equal(element.style.maxWidth, '3px');
+  });
+});
diff --git a/polygerrit-ui/app/elements/settings/gr-settings-view/gr-settings-view.ts b/polygerrit-ui/app/elements/settings/gr-settings-view/gr-settings-view.ts
index c4ca51e..ff2904a 100644
--- a/polygerrit-ui/app/elements/settings/gr-settings-view/gr-settings-view.ts
+++ b/polygerrit-ui/app/elements/settings/gr-settings-view/gr-settings-view.ts
@@ -28,7 +28,11 @@
 import {GrGroupList} from '../gr-group-list/gr-group-list';
 import {GrIdentities} from '../gr-identities/gr-identities';
 import {GrDiffPreferences} from '../../shared/gr-diff-preferences/gr-diff-preferences';
-import {PreferencesInput, ServerInfo} from '../../../types/common';
+import {
+  AccountDetailInfo,
+  PreferencesInput,
+  ServerInfo,
+} from '../../../types/common';
 import {GrSshEditor} from '../gr-ssh-editor/gr-ssh-editor';
 import {GrGpgEditor} from '../gr-gpg-editor/gr-gpg-editor';
 import {GrEmailEditor} from '../gr-email-editor/gr-email-editor';
@@ -58,6 +62,7 @@
 import {subscribe} from '../../lit/subscription-controller';
 import {resolve} from '../../../models/dependency';
 import {settingsViewModelToken} from '../../../models/views/settings';
+import {areNotificationsEnabled} from '../../../utils/worker-util';
 
 const GERRIT_DOCS_BASE_URL =
   'https://gerrit-review.googlesource.com/' + 'Documentation';
@@ -111,6 +116,9 @@
 
   @query('#publishCommentsOnPush') publishCommentsOnPush!: HTMLInputElement;
 
+  @query('#allowBrowserNotifications')
+  allowBrowserNotifications?: HTMLInputElement;
+
   @query('#disableKeyboardShortcuts')
   disableKeyboardShortcuts!: HTMLInputElement;
 
@@ -186,6 +194,8 @@
   // private but used in test
   @state() showNumber?: boolean;
 
+  @state() account?: AccountDetailInfo;
+
   // private but used in test
   public _testOnly_loadingPromise?: Promise<void>;
 
@@ -193,7 +203,8 @@
 
   private readonly userModel = getAppContext().userModel;
 
-  private readonly flagsService = getAppContext().flagsService;
+  // private but used in test
+  readonly flagsService = getAppContext().flagsService;
 
   private readonly getViewModel = resolve(this, settingsViewModelToken);
 
@@ -209,6 +220,13 @@
     );
     subscribe(
       this,
+      () => this.userModel.account$,
+      acc => {
+        this.account = acc;
+      }
+    );
+    subscribe(
+      this,
       () => this.userModel.preferences$,
       prefs => {
         if (!prefs) {
@@ -399,7 +417,8 @@
           <fieldset id="preferences">
             ${this.renderTheme()} ${this.renderChangesPerPages()}
             ${this.renderDateTimeFormat()} ${this.renderEmailNotification()}
-            ${this.renderEmailFormat()} ${this.renderDefaultBaseForMerges()}
+            ${this.renderEmailFormat()} ${this.renderBrowserNotifications()}
+            ${this.renderDefaultBaseForMerges()}
             ${this.renderRelativeDateInChangeTable()} ${this.renderDiffView()}
             ${this.renderShowSizeBarsInFileList()}
             ${this.renderPublishCommentsOnPush()}
@@ -869,6 +888,31 @@
     `;
   }
 
+  private renderBrowserNotifications() {
+    if (!this.flagsService.isEnabled(KnownExperimentId.PUSH_NOTIFICATIONS))
+      return nothing;
+    if (!areNotificationsEnabled(this.account)) return nothing;
+    return html`
+      <section id="allowBrowserNotificationsSection">
+        <label class="title" for="allowBrowserNotifications"
+          >Allow browser notifications</label
+        >
+        <span class="value">
+          <input
+            id="allowBrowserNotifications"
+            type="checkbox"
+            ?checked=${this.localPrefs.allow_browser_notifications}
+            @change=${() => {
+              this.localPrefs.allow_browser_notifications =
+                this.allowBrowserNotifications!.checked;
+              this.prefsChanged = true;
+            }}
+          />
+        </span>
+      </section>
+    `;
+  }
+
   private renderDefaultBaseForMerges() {
     if (!this.localPrefs.default_base_for_merges) return nothing;
     return nothing;
diff --git a/polygerrit-ui/app/elements/settings/gr-settings-view/gr-settings-view_test.ts b/polygerrit-ui/app/elements/settings/gr-settings-view/gr-settings-view_test.ts
index 72c19b4..0798991 100644
--- a/polygerrit-ui/app/elements/settings/gr-settings-view/gr-settings-view_test.ts
+++ b/polygerrit-ui/app/elements/settings/gr-settings-view/gr-settings-view_test.ts
@@ -6,7 +6,13 @@
 import '../../../test/common-test-setup';
 import './gr-settings-view';
 import {GrSettingsView} from './gr-settings-view';
-import {queryAll, stubRestApi, waitEventLoop} from '../../../test/test-utils';
+import {
+  queryAll,
+  queryAndAssert,
+  stubFlags,
+  stubRestApi,
+  waitEventLoop,
+} from '../../../test/test-utils';
 import {
   AuthInfo,
   AccountDetailInfo,
@@ -510,6 +516,24 @@
     );
   });
 
+  test('allow browser notifications', async () => {
+    stubFlags('isEnabled').returns(true);
+    element = await fixture(html`<gr-settings-view></gr-settings-view>`);
+    element.account = createAccountDetailWithId();
+    await element.updateComplete;
+    assert.dom.equal(
+      queryAndAssert(element, '#allowBrowserNotificationsSection'),
+      /* HTML */ `<section id="allowBrowserNotificationsSection">
+        <label class="title" for="allowBrowserNotifications">
+          Allow browser notifications
+        </label>
+        <span class="value">
+          <input checked="" id="allowBrowserNotifications" type="checkbox" />
+        </span>
+      </section>`
+    );
+  });
+
   test('calls the title-change event', async () => {
     const titleChangedStub = sinon.stub();
 
diff --git a/polygerrit-ui/app/elements/shared/gr-comment-thread/gr-comment-thread.ts b/polygerrit-ui/app/elements/shared/gr-comment-thread/gr-comment-thread.ts
index 78a1509..9dfbc04 100644
--- a/polygerrit-ui/app/elements/shared/gr-comment-thread/gr-comment-thread.ts
+++ b/polygerrit-ui/app/elements/shared/gr-comment-thread/gr-comment-thread.ts
@@ -73,6 +73,7 @@
 import {Interaction} from '../../../constants/reporting';
 import {HtmlPatched} from '../../../utils/lit-util';
 import {createDiffUrl} from '../../../models/views/diff';
+import {createChangeUrl} from '../../../models/views/change';
 
 declare global {
   interface HTMLElementEventMap {
@@ -779,13 +780,20 @@
     if (!comment) return;
     assertIsDefined(this.changeNum, 'changeNum');
     assertIsDefined(this.repoName, 'repoName');
-    const url = generateAbsoluteUrl(
-      createDiffUrl({
+    let url: string;
+    if (this.isPatchsetLevel()) {
+      url = createChangeUrl({
         changeNum: this.changeNum,
         project: this.repoName,
         commentId: comment.id,
-      })
-    );
+      });
+    } else {
+      url = createDiffUrl({
+        changeNum: this.changeNum,
+        project: this.repoName,
+        commentId: comment.id,
+      });
+    }
     assertIsDefined(url, 'url for comment');
     copyToClipbard(generateAbsoluteUrl(url), 'Link');
   }
diff --git a/polygerrit-ui/app/elements/shared/gr-comment-thread/gr-comment-thread_test.ts b/polygerrit-ui/app/elements/shared/gr-comment-thread/gr-comment-thread_test.ts
index b767a32..10e54c7 100644
--- a/polygerrit-ui/app/elements/shared/gr-comment-thread/gr-comment-thread_test.ts
+++ b/polygerrit-ui/app/elements/shared/gr-comment-thread/gr-comment-thread_test.ts
@@ -28,6 +28,8 @@
 import {SinonStub} from 'sinon';
 import {fixture, html, waitUntil, assert} from '@open-wc/testing';
 import {GrButton} from '../gr-button/gr-button';
+import {SpecialFilePath} from '../../../constants/constants';
+import {GrIcon} from '../gr-icon/gr-icon';
 
 const c1 = {
   author: {name: 'Kermit'},
@@ -447,4 +449,35 @@
       },
     ]);
   });
+
+  test('patchset comments link to /comments URL', async () => {
+    const clipboardStub = sinon.stub(navigator.clipboard, 'writeText');
+    element.thread = {
+      ...createThread(c1),
+      path: SpecialFilePath.PATCHSET_LEVEL_COMMENTS,
+    };
+    await element.updateComplete;
+
+    queryAndAssert<GrIcon>(element, 'gr-icon.copy').click();
+
+    assert.equal(1, clipboardStub.callCount);
+    assert.equal(
+      clipboardStub.firstCall.args[0],
+      'http://localhost:9876/c/test-repo-name/+/1/comments/the-root'
+    );
+  });
+
+  test('file comments link to /comment URL', async () => {
+    const clipboardStub = sinon.stub(navigator.clipboard, 'writeText');
+    element.thread = createThread(c1);
+    await element.updateComplete;
+
+    queryAndAssert<GrIcon>(element, 'gr-icon.copy').click();
+
+    assert.equal(1, clipboardStub.callCount);
+    assert.equal(
+      clipboardStub.firstCall.args[0],
+      'http://localhost:9876/c/test-repo-name/+/1/comment/the-root/'
+    );
+  });
 });
diff --git a/polygerrit-ui/app/elements/shared/gr-formatted-text/gr-formatted-text.ts b/polygerrit-ui/app/elements/shared/gr-formatted-text/gr-formatted-text.ts
index 6ab0ec4..5a1db30 100644
--- a/polygerrit-ui/app/elements/shared/gr-formatted-text/gr-formatted-text.ts
+++ b/polygerrit-ui/app/elements/shared/gr-formatted-text/gr-formatted-text.ts
@@ -16,11 +16,7 @@
 import {subscribe} from '../../lit/subscription-controller';
 import {configModelToken} from '../../../models/config/config-model';
 import {CommentLinks, EmailAddress} from '../../../api/rest-api';
-import {
-  applyHtmlRewritesFromConfig,
-  applyLinkRewritesFromConfig,
-  linkifyNormalUrls,
-} from '../../../utils/link-util';
+import {linkifyUrlsAndApplyRewrite} from '../../../utils/link-util';
 import '../gr-account-chip/gr-account-chip';
 import {KnownExperimentId} from '../../../services/flags/flags';
 import {getAppContext} from '../../../services/app-context';
@@ -125,7 +121,7 @@
   }
 
   private renderAsPlaintext() {
-    const linkedText = this.rewriteText(
+    const linkedText = linkifyUrlsAndApplyRewrite(
       htmlEscape(this.content).toString(),
       this.repoCommentLinks
     );
@@ -140,7 +136,7 @@
     // renderer so we wrap 'this.rewriteText' so that 'this' is preserved via
     // closure.
     const boundRewriteText = (text: string) =>
-      this.rewriteText(text, this.repoCommentLinks);
+      linkifyUrlsAndApplyRewrite(text, this.repoCommentLinks);
 
     // We are overriding some marked-element renderers for a few reasons:
     // 1. Disable inline images as a design/policy choice.
@@ -201,24 +197,6 @@
     return text;
   }
 
-  private rewriteText(text: string, repoCommentLinks: CommentLinks) {
-    // Turn universally identifiable URLs into links. Ex: www.google.com. The
-    // markdown library inside marked-element does this too, but is more
-    // conservative and misses some URLs like "google.com" without "www" prefix.
-    text = linkifyNormalUrls(text);
-
-    // Apply the host's config-specific regex replacements to create links. Ex:
-    // link "Bug 12345" to "google.com/bug/12345"
-    text = applyLinkRewritesFromConfig(text, repoCommentLinks);
-
-    // Apply the host's config-specific regex replacements to write arbitrary
-    // html. Most examples seen in the wild are also used for linking but with
-    // finer control over the rendered text. Ex: "Bug 12345" => "#12345"
-    text = applyHtmlRewritesFromConfig(text, repoCommentLinks);
-
-    return text;
-  }
-
   override updated() {
     // Look for @mentions and replace them with an account-label chip.
     if (this.flagsService.isEnabled(KnownExperimentId.MENTION_USERS)) {
diff --git a/polygerrit-ui/app/elements/shared/gr-formatted-text/gr-formatted-text_test.ts b/polygerrit-ui/app/elements/shared/gr-formatted-text/gr-formatted-text_test.ts
index 6391347..ca498318 100644
--- a/polygerrit-ui/app/elements/shared/gr-formatted-text/gr-formatted-text_test.ts
+++ b/polygerrit-ui/app/elements/shared/gr-formatted-text/gr-formatted-text_test.ts
@@ -77,6 +77,76 @@
       await element.updateComplete;
     });
 
+    test('does not apply rewrites within links', async () => {
+      element.content = 'google.com/LinkRewriteMe';
+      await element.updateComplete;
+
+      assert.shadowDom.equal(
+        element,
+        /* HTML */ `
+          <pre class="plaintext">
+            <a
+              href="http://google.com/LinkRewriteMe"
+              rel="noopener"
+              target="_blank"
+            >
+              google.com/LinkRewriteMe
+            </a>
+          </pre>
+        `
+      );
+    });
+
+    test('does not apply rewrites on rewritten text', async () => {
+      await setCommentLinks({
+        capitalizeFoo: {
+          match: 'foo',
+          html: 'FOO',
+        },
+        lowercaseFoo: {
+          match: 'FOO',
+          html: 'foo',
+        },
+      });
+      element.content = 'foo';
+      await element.updateComplete;
+
+      assert.shadowDom.equal(
+        element,
+        /* HTML */ `
+          <pre class="plaintext">
+          FOO
+        </pre
+          >
+        `
+      );
+    });
+
+    test('supports overlapping rewrites', async () => {
+      await setCommentLinks({
+        bracketNum: {
+          match: '(Start:) ([0-9]+)',
+          html: '$1 [$2]',
+        },
+        bracketNum2: {
+          match: '(Start: [0-9]+) ([0-9]+)',
+          html: '$1 [$2]',
+        },
+      });
+      element.content = 'Start: 123 456';
+      await element.updateComplete;
+
+      assert.shadowDom.equal(
+        element,
+        /* HTML */ `
+          <pre class="plaintext">
+            Start: [123] [456]
+          </pre
+          >
+        `
+      );
+    });
+
     test('renders text with links and rewrites', async () => {
       element.content = `text with plain link: google.com
         \ntext with config link: LinkRewriteMe
diff --git a/polygerrit-ui/app/elements/shared/gr-linked-text/gr-linked-text.ts b/polygerrit-ui/app/elements/shared/gr-linked-text/gr-linked-text.ts
deleted file mode 100644
index 16a60e7..0000000
--- a/polygerrit-ui/app/elements/shared/gr-linked-text/gr-linked-text.ts
+++ /dev/null
@@ -1,178 +0,0 @@
-/**
- * @license
- * Copyright 2015 Google LLC
- * SPDX-License-Identifier: Apache-2.0
- */
-import '../../../styles/shared-styles';
-import {GrLinkTextParser, LinkTextParserConfig} from './link-text-parser';
-import {LitElement, css, html, PropertyValues} from 'lit';
-import {customElement, property} from 'lit/decorators.js';
-import {assertIsDefined} from '../../../utils/common-util';
-
-declare global {
-  interface HTMLElementTagNameMap {
-    'gr-linked-text': GrLinkedText;
-  }
-}
-
-@customElement('gr-linked-text')
-export class GrLinkedText extends LitElement {
-  private outputElement?: HTMLSpanElement;
-
-  @property({type: Boolean, attribute: 'remove-zero-width-space'})
-  removeZeroWidthSpace?: boolean;
-
-  @property({type: String})
-  content = '';
-
-  @property({type: Boolean, attribute: true})
-  pre = false;
-
-  @property({type: Boolean, attribute: true})
-  disabled = false;
-
-  @property({type: Boolean, attribute: true})
-  inline = false;
-
-  @property({type: Object})
-  config?: LinkTextParserConfig;
-
-  static override get styles() {
-    return css`
-      :host {
-        display: block;
-      }
-      :host([inline]) {
-        display: inline;
-      }
-      :host([pre]) ::slotted(span) {
-        white-space: var(--linked-text-white-space, pre-wrap);
-        word-wrap: var(--linked-text-word-wrap, break-word);
-      }
-    `;
-  }
-
-  override render() {
-    return html`<slot name="insert"></slot>`;
-  }
-
-  // NOTE: LinkTextParser dynamically creates HTML fragments based on backend
-  // configuration commentLinks. These commentLinks can contain arbitrary HTML
-  // fragments. This means that arbitrary HTML needs to be injected into the
-  // DOM-tree, where this HTML is is controlled on the server-side in the
-  // server-configuration rather than by arbitrary users.
-  // To enable this injection of 'unsafe' HTML, LinkTextParser generates
-  // HTML fragments. Lit does not support inserting html fragments directly
-  // into its DOM-tree as it controls the DOM-tree that it generates.
-  // Therefore, to get around this we create a single element that we slot into
-  // the Lit-owned DOM.  This element will not be part of this LitElement as
-  // it's slotted in and thus can be modified on the fly by handleParseResult.
-  override firstUpdated(_changedProperties: PropertyValues): void {
-    this.outputElement = document.createElement('span');
-    this.outputElement.id = 'output';
-    this.outputElement.slot = 'insert';
-    this.append(this.outputElement);
-  }
-
-  override updated(changedProperties: PropertyValues): void {
-    if (changedProperties.has('content') || changedProperties.has('config')) {
-      this._contentOrConfigChanged();
-    } else if (changedProperties.has('disabled')) {
-      this.styleLinks();
-    }
-  }
-
-  /**
-   * Because either the source text or the linkification config has changed,
-   * the content should be re-parsed.
-   * Private but used in tests.
-   *
-   * @param content The raw, un-linkified source string to parse.
-   * @param config The server config specifying commentLink patterns
-   */
-  _contentOrConfigChanged() {
-    if (!this.config) {
-      assertIsDefined(this.outputElement);
-      this.outputElement.textContent = this.content;
-      return;
-    }
-
-    assertIsDefined(this.outputElement);
-    this.outputElement.textContent = '';
-    const parser = new GrLinkTextParser(
-      this.config,
-      (text: string | null, href: string | null, fragment?: DocumentFragment) =>
-        this.handleParseResult(text, href, fragment),
-      this.removeZeroWidthSpace
-    );
-    parser.parse(this.content);
-
-    // Ensure that external links originating from HTML commentlink configs
-    // open in a new tab. @see Issue 5567
-    // Ensure links to the same host originating from commentlink configs
-    // open in the same tab. When target is not set - default is _self
-    // @see Issue 4616
-    this.outputElement.querySelectorAll('a').forEach(anchor => {
-      if (anchor.hostname === window.location.hostname) {
-        anchor.removeAttribute('target');
-      } else {
-        anchor.setAttribute('target', '_blank');
-      }
-      anchor.setAttribute('rel', 'noopener');
-    });
-
-    this.styleLinks();
-  }
-
-  /**
-   * Styles the links based on whether gr-linked-text is disabled or not
-   */
-  private styleLinks() {
-    assertIsDefined(this.outputElement);
-    this.outputElement.querySelectorAll('a').forEach(anchor => {
-      anchor.setAttribute('style', this.computeLinkStyle());
-    });
-  }
-
-  private computeLinkStyle() {
-    if (this.disabled) {
-      return `
-        color: inherit;
-        text-decoration: none;
-        pointer-events: none;
-      `;
-    } else {
-      return 'color: var(--link-color)';
-    }
-  }
-
-  /**
-   * This method is called when the GrLikTextParser emits a partial result
-   * (used as the "callback" parameter). It will be called in either of two
-   * ways:
-   * - To create a link: when called with `text` and `href` arguments, a link
-   *   element should be created and attached to the resulting DOM.
-   * - To attach an arbitrary fragment: when called with only the `fragment`
-   *   argument, the fragment should be attached to the resulting DOM as is.
-   */
-  private handleParseResult(
-    text: string | null,
-    href: string | null,
-    fragment?: DocumentFragment
-  ) {
-    assertIsDefined(this.outputElement);
-    const output = this.outputElement;
-    if (href) {
-      const a = document.createElement('a');
-      a.setAttribute('href', href);
-      // GrLinkTextParser either pass text and href together or
-      // only DocumentFragment - see LinkTextParserCallback
-      a.textContent = text!;
-      a.target = '_blank';
-      a.setAttribute('rel', 'noopener');
-      output.appendChild(a);
-    } else if (fragment) {
-      output.appendChild(fragment);
-    }
-  }
-}
diff --git a/polygerrit-ui/app/elements/shared/gr-linked-text/gr-linked-text_test.ts b/polygerrit-ui/app/elements/shared/gr-linked-text/gr-linked-text_test.ts
deleted file mode 100644
index 00e0313..0000000
--- a/polygerrit-ui/app/elements/shared/gr-linked-text/gr-linked-text_test.ts
+++ /dev/null
@@ -1,471 +0,0 @@
-/**
- * @license
- * Copyright 2015 Google LLC
- * SPDX-License-Identifier: Apache-2.0
- */
-import '../../../test/common-test-setup';
-import './gr-linked-text';
-import {fixture, html, assert} from '@open-wc/testing';
-import {GrLinkedText} from './gr-linked-text';
-import {queryAndAssert} from '../../../test/test-utils';
-
-suite('gr-linked-text tests', () => {
-  let element: GrLinkedText;
-
-  let originalCanonicalPath: string | undefined;
-
-  setup(async () => {
-    originalCanonicalPath = window.CANONICAL_PATH;
-    element = await fixture<GrLinkedText>(html`
-      <gr-linked-text>
-        <div id="output"></div>
-      </gr-linked-text>
-    `);
-
-    element.config = {
-      ph: {
-        match: '([Bb]ug|[Ii]ssue)\\s*#?(\\d+)',
-        link: 'https://bugs.chromium.org/p/gerrit/issues/detail?id=$2',
-      },
-      prefixsameinlinkandpattern: {
-        match: '([Hh][Tt][Tt][Pp]example)\\s*#?(\\d+)',
-        link: 'https://bugs.chromium.org/p/gerrit/issues/detail?id=$2',
-      },
-      changeid: {
-        match: '(I[0-9a-f]{8,40})',
-        link: '#/q/$1',
-      },
-      changeid2: {
-        match: 'Change-Id: +(I[0-9a-f]{8,40})',
-        link: '#/q/$1',
-      },
-      googlesearch: {
-        match: 'google:(.+)',
-        link: 'https://bing.com/search?q=$1', // html should supersede link.
-        html: '<a href="https://google.com/search?q=$1">$1</a>',
-      },
-      hashedhtml: {
-        match: 'hash:(.+)',
-        html: '<a href="#/awesomesauce">$1</a>',
-      },
-      baseurl: {
-        match: 'test (.+)',
-        html: '<a href="/r/awesomesauce">$1</a>',
-      },
-      anotatstartwithbaseurl: {
-        match: 'a test (.+)',
-        html: '[Lookup: <a href="/r/awesomesauce">$1</a>]',
-      },
-      disabledconfig: {
-        match: 'foo:(.+)',
-        link: 'https://google.com/search?q=$1',
-        enabled: false,
-      },
-    };
-  });
-
-  teardown(() => {
-    window.CANONICAL_PATH = originalCanonicalPath;
-  });
-
-  test('render', async () => {
-    element.content =
-      'https://bugs.chromium.org/p/gerrit/issues/detail?id=3650';
-    await element.updateComplete;
-    assert.lightDom.equal(
-      element,
-      /* HTML */ `
-        <div id="output"></div>
-        <span id="output" slot="insert">
-          <a
-            href="https://bugs.chromium.org/p/gerrit/issues/detail?id=3650"
-            rel="noopener"
-            style="color: var(--link-color)"
-            target="_blank"
-          >
-            https://bugs.chromium.org/p/gerrit/issues/detail?id=3650
-          </a>
-        </span>
-      `
-    );
-  });
-
-  test('URL pattern was parsed and linked.', async () => {
-    // Regular inline link.
-    const url = 'https://bugs.chromium.org/p/gerrit/issues/detail?id=3650';
-    element.content = url;
-    await element.updateComplete;
-
-    const linkEl = queryAndAssert(element, 'span#output')
-      .childNodes[0] as HTMLAnchorElement;
-    assert.equal(linkEl.target, '_blank');
-    assert.equal(linkEl.rel, 'noopener');
-    assert.equal(linkEl.href, url);
-    assert.equal(linkEl.textContent, url);
-  });
-
-  test('Bug pattern was parsed and linked', async () => {
-    // "Issue/Bug" pattern.
-    element.content = 'Issue 3650';
-    await element.updateComplete;
-
-    let linkEl = queryAndAssert(element, 'span#output')
-      .childNodes[0] as HTMLAnchorElement;
-    const url = 'https://bugs.chromium.org/p/gerrit/issues/detail?id=3650';
-    assert.equal(linkEl.target, '_blank');
-    assert.equal(linkEl.href, url);
-    assert.equal(linkEl.textContent, 'Issue 3650');
-
-    element.content = 'Bug 3650';
-    await element.updateComplete;
-
-    linkEl = queryAndAssert(element, 'span#output')
-      .childNodes[0] as HTMLAnchorElement;
-    assert.equal(linkEl.target, '_blank');
-    assert.equal(linkEl.rel, 'noopener');
-    assert.equal(linkEl.href, url);
-    assert.equal(linkEl.textContent, 'Bug 3650');
-  });
-
-  test('Pattern with same prefix as link was correctly parsed', async () => {
-    // Pattern starts with the same prefix (`http`) as the url.
-    element.content = 'httpexample 3650';
-    await element.updateComplete;
-
-    assert.equal(queryAndAssert(element, 'span#output').childNodes.length, 1);
-    const linkEl = queryAndAssert(element, 'span#output')
-      .childNodes[0] as HTMLAnchorElement;
-    const url = 'https://bugs.chromium.org/p/gerrit/issues/detail?id=3650';
-    assert.equal(linkEl.target, '_blank');
-    assert.equal(linkEl.href, url);
-    assert.equal(linkEl.textContent, 'httpexample 3650');
-  });
-
-  test('Change-Id pattern was parsed and linked', async () => {
-    // "Change-Id:" pattern.
-    const changeID = 'I11d6a37f5e9b5df0486f6c922d8836dfa780e03e';
-    const prefix = 'Change-Id: ';
-    element.content = prefix + changeID;
-    await element.updateComplete;
-
-    const textNode = queryAndAssert(element, 'span#output').childNodes[0];
-    const linkEl = queryAndAssert(element, 'span#output')
-      .childNodes[1] as HTMLAnchorElement;
-    assert.equal(textNode.textContent, prefix);
-    const url = '/q/' + changeID;
-    assert.isFalse(linkEl.hasAttribute('target'));
-    // Since url is a path, the host is added automatically.
-    assert.isTrue(linkEl.href.endsWith(url));
-    assert.equal(linkEl.textContent, changeID);
-  });
-
-  test('Change-Id pattern was parsed and linked with base url', async () => {
-    window.CANONICAL_PATH = '/r';
-
-    // "Change-Id:" pattern.
-    const changeID = 'I11d6a37f5e9b5df0486f6c922d8836dfa780e03e';
-    const prefix = 'Change-Id: ';
-    element.content = prefix + changeID;
-    await element.updateComplete;
-
-    const textNode = queryAndAssert(element, 'span#output').childNodes[0];
-    const linkEl = queryAndAssert(element, 'span#output')
-      .childNodes[1] as HTMLAnchorElement;
-    assert.equal(textNode.textContent, prefix);
-    const url = '/r/q/' + changeID;
-    assert.isFalse(linkEl.hasAttribute('target'));
-    // Since url is a path, the host is added automatically.
-    assert.isTrue(linkEl.href.endsWith(url));
-    assert.equal(linkEl.textContent, changeID);
-  });
-
-  test('Multiple matches', async () => {
-    element.content = 'Issue 3650\nIssue 3450';
-    await element.updateComplete;
-
-    const linkEl1 = queryAndAssert(element, 'span#output')
-      .childNodes[0] as HTMLAnchorElement;
-    const linkEl2 = queryAndAssert(element, 'span#output')
-      .childNodes[2] as HTMLAnchorElement;
-
-    assert.equal(linkEl1.target, '_blank');
-    assert.equal(
-      linkEl1.href,
-      'https://bugs.chromium.org/p/gerrit/issues/detail?id=3650'
-    );
-    assert.equal(linkEl1.textContent, 'Issue 3650');
-
-    assert.equal(linkEl2.target, '_blank');
-    assert.equal(
-      linkEl2.href,
-      'https://bugs.chromium.org/p/gerrit/issues/detail?id=3450'
-    );
-    assert.equal(linkEl2.textContent, 'Issue 3450');
-  });
-
-  test('Change-Id pattern parsed before bug pattern', async () => {
-    // "Change-Id:" pattern.
-    const changeID = 'I11d6a37f5e9b5df0486f6c922d8836dfa780e03e';
-    const prefix = 'Change-Id: ';
-
-    // "Issue/Bug" pattern.
-    const bug = 'Issue 3650';
-
-    const changeUrl = '/q/' + changeID;
-    const bugUrl = 'https://bugs.chromium.org/p/gerrit/issues/detail?id=3650';
-
-    element.content = prefix + changeID + bug;
-    await element.updateComplete;
-
-    const textNode = queryAndAssert(element, 'span#output').childNodes[0];
-    const changeLinkEl = queryAndAssert(element, 'span#output')
-      .childNodes[1] as HTMLAnchorElement;
-    const bugLinkEl = queryAndAssert(element, 'span#output')
-      .childNodes[2] as HTMLAnchorElement;
-
-    assert.equal(textNode.textContent, prefix);
-
-    assert.isFalse(changeLinkEl.hasAttribute('target'));
-    assert.isTrue(changeLinkEl.href.endsWith(changeUrl));
-    assert.equal(changeLinkEl.textContent, changeID);
-
-    assert.equal(bugLinkEl.target, '_blank');
-    assert.equal(bugLinkEl.href, bugUrl);
-    assert.equal(bugLinkEl.textContent, 'Issue 3650');
-  });
-
-  test('html field in link config', async () => {
-    element.content = 'google:do a barrel roll';
-    await element.updateComplete;
-
-    const linkEl = queryAndAssert(element, 'span#output')
-      .childNodes[0] as HTMLAnchorElement;
-    assert.equal(
-      linkEl.getAttribute('href'),
-      'https://google.com/search?q=do a barrel roll'
-    );
-    assert.equal(linkEl.textContent, 'do a barrel roll');
-  });
-
-  test('removing hash from links', async () => {
-    element.content = 'hash:foo';
-    await element.updateComplete;
-
-    const linkEl = queryAndAssert(element, 'span#output')
-      .childNodes[0] as HTMLAnchorElement;
-    assert.isTrue(linkEl.href.endsWith('/awesomesauce'));
-    assert.equal(linkEl.textContent, 'foo');
-  });
-
-  test('html with base url', async () => {
-    window.CANONICAL_PATH = '/r';
-
-    element.content = 'test foo';
-    await element.updateComplete;
-
-    const linkEl = queryAndAssert(element, 'span#output')
-      .childNodes[0] as HTMLAnchorElement;
-    assert.isTrue(linkEl.href.endsWith('/r/awesomesauce'));
-    assert.equal(linkEl.textContent, 'foo');
-  });
-
-  test('a is not at start', async () => {
-    window.CANONICAL_PATH = '/r';
-
-    element.content = 'a test foo';
-    await element.updateComplete;
-
-    const linkEl = queryAndAssert(element, 'span#output')
-      .childNodes[1] as HTMLAnchorElement;
-    assert.isTrue(linkEl.href.endsWith('/r/awesomesauce'));
-    assert.equal(linkEl.textContent, 'foo');
-  });
-
-  test('hash html with base url', async () => {
-    window.CANONICAL_PATH = '/r';
-
-    element.content = 'hash:foo';
-    await element.updateComplete;
-
-    const linkEl = queryAndAssert(element, 'span#output')
-      .childNodes[0] as HTMLAnchorElement;
-    assert.isTrue(linkEl.href.endsWith('/r/awesomesauce'));
-    assert.equal(linkEl.textContent, 'foo');
-  });
-
-  test('disabled config', async () => {
-    element.content = 'foo:baz';
-    await element.updateComplete;
-
-    assert.equal(queryAndAssert(element, 'span#output').innerHTML, 'foo:baz');
-  });
-
-  test('R=email labels link correctly', async () => {
-    element.removeZeroWidthSpace = true;
-    element.content = 'R=\u200Btest@google.com';
-    await element.updateComplete;
-
-    assert.equal(
-      queryAndAssert(element, 'span#output').textContent,
-      'R=test@google.com'
-    );
-    assert.equal(
-      queryAndAssert(element, 'span#output').innerHTML.match(/(R=<a)/g)!.length,
-      1
-    );
-  });
-
-  test('CC=email labels link correctly', async () => {
-    element.removeZeroWidthSpace = true;
-    element.content = 'CC=\u200Btest@google.com';
-    await element.updateComplete;
-
-    assert.equal(
-      queryAndAssert(element, 'span#output').textContent,
-      'CC=test@google.com'
-    );
-    assert.equal(
-      queryAndAssert(element, 'span#output').innerHTML.match(/(CC=<a)/g)!
-        .length,
-      1
-    );
-  });
-
-  test('only {http,https,mailto} protocols are linkified', async () => {
-    element.content = 'xx mailto:test@google.com yy';
-    await element.updateComplete;
-
-    let links = queryAndAssert(element, 'span#output').querySelectorAll('a');
-    assert.equal(links.length, 1);
-    assert.equal(links[0].getAttribute('href'), 'mailto:test@google.com');
-    assert.equal(links[0].innerHTML, 'mailto:test@google.com');
-
-    element.content = 'xx http://google.com yy';
-    await element.updateComplete;
-
-    links = queryAndAssert(element, 'span#output').querySelectorAll('a');
-    assert.equal(links.length, 1);
-    assert.equal(links[0].getAttribute('href'), 'http://google.com');
-    assert.equal(links[0].innerHTML, 'http://google.com');
-
-    element.content = 'xx https://google.com yy';
-    await element.updateComplete;
-
-    links = queryAndAssert(element, 'span#output').querySelectorAll('a');
-    assert.equal(links.length, 1);
-    assert.equal(links[0].getAttribute('href'), 'https://google.com');
-    assert.equal(links[0].innerHTML, 'https://google.com');
-
-    element.content = 'xx ssh://google.com yy';
-    await element.updateComplete;
-
-    links = queryAndAssert(element, 'span#output').querySelectorAll('a');
-    assert.equal(links.length, 0);
-
-    element.content = 'xx ftp://google.com yy';
-    await element.updateComplete;
-
-    links = queryAndAssert(element, 'span#output').querySelectorAll('a');
-    assert.equal(links.length, 0);
-  });
-
-  test('links without leading whitespace are linkified', async () => {
-    element.content = 'xx abcmailto:test@google.com yy';
-    await element.updateComplete;
-
-    assert.equal(
-      queryAndAssert(element, 'span#output').innerHTML.substr(0, 6),
-      'xx abc'
-    );
-    let links = queryAndAssert(element, 'span#output').querySelectorAll('a');
-    assert.equal(links.length, 1);
-    assert.equal(links[0].getAttribute('href'), 'mailto:test@google.com');
-    assert.equal(links[0].innerHTML, 'mailto:test@google.com');
-
-    element.content = 'xx defhttp://google.com yy';
-    await element.updateComplete;
-
-    assert.equal(
-      queryAndAssert(element, 'span#output').innerHTML.substr(0, 6),
-      'xx def'
-    );
-    links = queryAndAssert(element, 'span#output').querySelectorAll('a');
-    assert.equal(links.length, 1);
-    assert.equal(links[0].getAttribute('href'), 'http://google.com');
-    assert.equal(links[0].innerHTML, 'http://google.com');
-
-    element.content = 'xx qwehttps://google.com yy';
-    await element.updateComplete;
-
-    assert.equal(
-      queryAndAssert(element, 'span#output').innerHTML.substr(0, 6),
-      'xx qwe'
-    );
-    links = queryAndAssert(element, 'span#output').querySelectorAll('a');
-    assert.equal(links.length, 1);
-    assert.equal(links[0].getAttribute('href'), 'https://google.com');
-    assert.equal(links[0].innerHTML, 'https://google.com');
-
-    // Non-latin character
-    element.content = 'xx абвhttps://google.com yy';
-    await element.updateComplete;
-
-    assert.equal(
-      queryAndAssert(element, 'span#output').innerHTML.substr(0, 6),
-      'xx абв'
-    );
-    links = queryAndAssert(element, 'span#output').querySelectorAll('a');
-    assert.equal(links.length, 1);
-    assert.equal(links[0].getAttribute('href'), 'https://google.com');
-    assert.equal(links[0].innerHTML, 'https://google.com');
-
-    element.content = 'xx ssh://google.com yy';
-    await element.updateComplete;
-
-    links = queryAndAssert(element, 'span#output').querySelectorAll('a');
-    assert.equal(links.length, 0);
-
-    element.content = 'xx ftp://google.com yy';
-    await element.updateComplete;
-
-    links = queryAndAssert(element, 'span#output').querySelectorAll('a');
-    assert.equal(links.length, 0);
-  });
-
-  test('overlapping links', async () => {
-    element.config = {
-      b1: {
-        match: '(B:\\s*)(\\d+)',
-        html: '$1<a href="ftp://foo/$2">$2</a>',
-      },
-      b2: {
-        match: '(B:\\s*\\d+\\s*,\\s*)(\\d+)',
-        html: '$1<a href="ftp://foo/$2">$2</a>',
-      },
-    };
-    element.content = '- B: 123, 45';
-    await element.updateComplete;
-
-    const links = element.querySelectorAll('a');
-
-    assert.equal(links.length, 2);
-    assert.equal(
-      queryAndAssert<HTMLSpanElement>(element, 'span').textContent,
-      '- B: 123, 45'
-    );
-
-    assert.equal(links[0].href, 'ftp://foo/123');
-    assert.equal(links[0].textContent, '123');
-
-    assert.equal(links[1].href, 'ftp://foo/45');
-    assert.equal(links[1].textContent, '45');
-  });
-
-  test('_contentOrConfigChanged called with config', async () => {
-    const contentConfigStub = sinon.stub(element, '_contentOrConfigChanged');
-    element.content = 'some text';
-    await element.updateComplete;
-
-    assert.isTrue(contentConfigStub.called);
-  });
-});
diff --git a/polygerrit-ui/app/elements/shared/gr-linked-text/link-text-parser.ts b/polygerrit-ui/app/elements/shared/gr-linked-text/link-text-parser.ts
deleted file mode 100644
index 73cf58b..0000000
--- a/polygerrit-ui/app/elements/shared/gr-linked-text/link-text-parser.ts
+++ /dev/null
@@ -1,415 +0,0 @@
-/**
- * @license
- * Copyright 2015 Google LLC
- * SPDX-License-Identifier: Apache-2.0
- */
-import 'ba-linkify/ba-linkify';
-import {getBaseUrl} from '../../../utils/url-util';
-import {CommentLinkInfo} from '../../../types/common';
-
-/**
- * Pattern describing URLs with supported protocols.
- */
-const URL_PROTOCOL_PATTERN = /^(.*)(https?:\/\/|mailto:)/;
-
-export type LinkTextParserCallback = ((text: string, href: string) => void) &
-  ((text: null, href: null, fragment: DocumentFragment) => void);
-
-export interface CommentLinkItem {
-  position: number;
-  length: number;
-  html: HTMLAnchorElement | DocumentFragment;
-}
-
-export type LinkTextParserConfig = {[name: string]: CommentLinkInfo};
-
-export class GrLinkTextParser {
-  private readonly baseUrl = getBaseUrl();
-
-  /**
-   * Construct a parser for linkifying text. Will linkify plain URLs that appear
-   * in the text as well as custom links if any are specified in the linkConfig
-   * parameter.
-   *
-   * @param linkConfig Comment links as specified by the commentlinks field on a
-   *     project config.
-   * @param callback The callback to be fired when an intermediate parse result
-   *     is emitted. The callback is passed text and href strings if a link is to
-   *     be created, or a document fragment otherwise.
-   * @param removeZeroWidthSpace If true, zero-width spaces will be removed from
-   *     R=<email> and CC=<email> expressions.
-   */
-  constructor(
-    private readonly linkConfig: LinkTextParserConfig,
-    private readonly callback: LinkTextParserCallback,
-    private readonly removeZeroWidthSpace?: boolean
-  ) {
-    Object.preventExtensions(this);
-  }
-
-  /**
-   * Emit a callback to create a link element.
-   *
-   * @param text The text of the link.
-   * @param href The URL to use as the href of the link.
-   */
-  addText(text: string, href: string) {
-    if (!text) {
-      return;
-    }
-    this.callback(text, href);
-  }
-
-  /**
-   * Given the source text and a list of CommentLinkItem objects that were
-   * generated by the commentlinks config, emit parsing callbacks.
-   *
-   * @param text The chuml of source text over which the outputArray items range.
-   * @param outputArray The list of items to add resulting from commentlink
-   *     matches.
-   */
-  processLinks(text: string, outputArray: CommentLinkItem[]) {
-    this.sortArrayReverse(outputArray);
-    const fragment = document.createDocumentFragment();
-    let cursor = text.length;
-
-    // Start inserting linkified URLs from the end of the String. That way, the
-    // string positions of the items don't change as we iterate through.
-    outputArray.forEach(item => {
-      // Add any text between the current linkified item and the item added
-      // before if it exists.
-      if (item.position + item.length !== cursor) {
-        fragment.insertBefore(
-          document.createTextNode(
-            text.slice(item.position + item.length, cursor)
-          ),
-          fragment.firstChild
-        );
-      }
-      fragment.insertBefore(item.html, fragment.firstChild);
-      cursor = item.position;
-    });
-
-    // Add the beginning portion at the end.
-    if (cursor !== 0) {
-      fragment.insertBefore(
-        document.createTextNode(text.slice(0, cursor)),
-        fragment.firstChild
-      );
-    }
-
-    this.callback(null, null, fragment);
-  }
-
-  /**
-   * Sort the given array of CommentLinkItems such that the positions are in
-   * reverse order.
-   */
-  sortArrayReverse(outputArray: CommentLinkItem[]) {
-    outputArray.sort((a, b) => b.position - a.position);
-  }
-
-  addItem(
-    text: string,
-    href: string,
-    html: null,
-    position: number,
-    length: number,
-    outputArray: CommentLinkItem[]
-  ): void;
-
-  addItem(
-    text: null,
-    href: null,
-    html: string,
-    position: number,
-    length: number,
-    outputArray: CommentLinkItem[]
-  ): void;
-
-  /**
-   * Create a CommentLinkItem and append it to the given output array. This
-   * method can be called in either of two ways:
-   * - With `text` and `href` parameters provided, and the `html` parameter
-   *   passed as `null`. In this case, the new CommentLinkItem will be a link
-   *   element with the given text and href value.
-   * - With the `html` paremeter provided, and the `text` and `href` parameters
-   *   passed as `null`. In this case, the string of HTML will be parsed and the
-   *   first resulting node will be used as the resulting content.
-   *
-   * @param text The text to use if creating a link.
-   * @param href The href to use as the URL if creating a link.
-   * @param html The html to parse and use as the result.
-   * @param  position The position inside the source text where the item
-   *     starts.
-   * @param length The number of characters in the source text
-   *     represented by the item.
-   * @param outputArray The array to which the
-   *     new item is to be appended.
-   */
-  addItem(
-    text: string | null,
-    href: string | null,
-    html: string | null,
-    position: number,
-    length: number,
-    outputArray: CommentLinkItem[]
-  ): void {
-    if (href) {
-      const a = document.createElement('a');
-      a.setAttribute('href', href);
-      a.textContent = text;
-      a.target = '_blank';
-      a.rel = 'noopener';
-      outputArray.push({
-        html: a,
-        position,
-        length,
-      });
-    } else if (html) {
-      // addItem has 2 overloads. If href is null, then html
-      // can't be null.
-      // TODO(TS): remove if(html) and keep else block without condition
-      const fragment = document.createDocumentFragment();
-      // Create temporary div to hold the nodes in.
-      const div = document.createElement('div');
-      div.innerHTML = html;
-      while (div.firstChild) {
-        fragment.appendChild(div.firstChild);
-      }
-      outputArray.push({
-        html: fragment,
-        position,
-        length,
-      });
-    }
-  }
-
-  /**
-   * Create a CommentLinkItem for a link and append it to the given output
-   * array.
-   *
-   * @param text The text for the link.
-   * @param href The href to use as the URL of the link.
-   * @param position The position inside the source text where the link
-   *     starts.
-   * @param length The number of characters in the source text
-   *     represented by the link.
-   * @param outputArray The array to which the
-   *     new item is to be appended.
-   */
-  addLink(
-    text: string,
-    href: string,
-    position: number,
-    length: number,
-    outputArray: CommentLinkItem[]
-  ) {
-    // TODO(TS): remove !test condition
-    if (!text || this.hasOverlap(position, length, outputArray)) {
-      return;
-    }
-    if (
-      !!this.baseUrl &&
-      href.startsWith('/') &&
-      !href.startsWith(this.baseUrl)
-    ) {
-      href = this.baseUrl + href;
-    }
-    this.addItem(text, href, null, position, length, outputArray);
-  }
-
-  /**
-   * Create a CommentLinkItem specified by an HTMl string and append it to the
-   * given output array.
-   *
-   * @param html The html to parse and use as the result.
-   * @param position The position inside the source text where the item
-   *     starts.
-   * @param length The number of characters in the source text
-   *     represented by the item.
-   * @param outputArray The array to which the
-   *     new item is to be appended.
-   */
-  addHTML(
-    html: string,
-    position: number,
-    length: number,
-    outputArray: CommentLinkItem[]
-  ) {
-    if (this.hasOverlap(position, length, outputArray)) {
-      return;
-    }
-    if (
-      !!this.baseUrl &&
-      html.match(/<a href="\//g) &&
-      !new RegExp(`<a href="${this.baseUrl}`, 'g').test(html)
-    ) {
-      html = html.replace(/<a href="\//g, `<a href="${this.baseUrl}/`);
-    }
-    this.addItem(null, null, html, position, length, outputArray);
-  }
-
-  /**
-   * Does the given range overlap with anything already in the item list.
-   */
-  hasOverlap(position: number, length: number, outputArray: CommentLinkItem[]) {
-    const endPosition = position + length;
-    for (let i = 0; i < outputArray.length; i++) {
-      const arrayItemStart = outputArray[i].position;
-      const arrayItemEnd = outputArray[i].position + outputArray[i].length;
-      if (
-        (position >= arrayItemStart && position < arrayItemEnd) ||
-        (endPosition > arrayItemStart && endPosition <= arrayItemEnd) ||
-        (position === arrayItemStart && position === arrayItemEnd)
-      ) {
-        return true;
-      }
-    }
-    return false;
-  }
-
-  /**
-   * Parse the given source text and emit callbacks for the items that are
-   * parsed.
-   */
-  parse(text?: string | null) {
-    if (text) {
-      window.linkify(text, {
-        callback: (text: string, href?: string) => this.parseChunk(text, href),
-      });
-    }
-  }
-
-  /**
-   * Callback that is pased into the linkify function. ba-linkify will call this
-   * method in either of two ways:
-   * - With both a `text` and `href` parameter provided: this indicates that
-   *   ba-linkify has found a plain URL and wants it linkified.
-   * - With only a `text` parameter provided: this represents the non-link
-   *   content that lies between the links the library has found.
-   *
-   */
-  parseChunk(text: string, href?: string) {
-    // TODO(wyatta) switch linkify sequence, see issue 5526.
-    if (this.removeZeroWidthSpace) {
-      // Remove the zero-width space added in gr-change-view.
-      text = text.replace(/^(CC|R)=\u200B/gm, '$1=');
-    }
-
-    // If the href is provided then ba-linkify has recognized it as a URL. If
-    // the source text does not include a protocol, the protocol will be added
-    // by ba-linkify. Create the link if the href is provided and its protocol
-    // matches the expected pattern.
-    if (href) {
-      const result = URL_PROTOCOL_PATTERN.exec(href);
-      if (result) {
-        const prefixText = result[1];
-        if (prefixText.length > 0) {
-          // Fix for simple cases from
-          // https://bugs.chromium.org/p/gerrit/issues/detail?id=11697
-          // When leading whitespace is missed before link,
-          // linkify add this text before link as a schema name to href.
-          // We suppose, that prefixText just a single word
-          // before link and add this word as is, without processing
-          // any patterns in it.
-          this.parseLinks(prefixText, {});
-          text = text.substring(prefixText.length);
-          href = href.substring(prefixText.length);
-        }
-        this.addText(text, href);
-        return;
-      }
-    }
-    // For the sections of text that lie between the links found by
-    // ba-linkify, we search for the project-config-specified link patterns.
-    this.parseLinks(text, this.linkConfig);
-  }
-
-  /**
-   * Walk over the given source text to find matches for comemntlink patterns
-   * and emit parse result callbacks.
-   *
-   * @param text The raw source text.
-   * @param config A comment links specification object.
-   */
-  parseLinks(text: string, config: LinkTextParserConfig) {
-    // The outputArray is used to store all of the matches found for all
-    // patterns.
-    const outputArray: CommentLinkItem[] = [];
-    for (const [configName, linkInfo] of Object.entries(config)) {
-      // TODO(TS): it seems, the following line can be rewritten as:
-      // if(enabled === false || enabled === 0 || enabled === '')
-      // Should be double-checked before update
-      // eslint-disable-next-line eqeqeq
-      if (linkInfo.enabled != null && linkInfo.enabled == false) {
-        continue;
-      }
-      // PolyGerrit doesn't use hash-based navigation like the GWT UI.
-      // Account for this.
-      const html = linkInfo.html;
-      const link = linkInfo.link;
-      if (html) {
-        linkInfo.html = html.replace(/<a href="#\//g, '<a href="/');
-      } else if (link) {
-        if (link[0] === '#') {
-          linkInfo.link = link.substr(1);
-        }
-      }
-
-      const pattern = new RegExp(linkInfo.match, 'g');
-
-      let match;
-      let textToCheck = text;
-      let susbtrIndex = 0;
-
-      while ((match = pattern.exec(textToCheck))) {
-        textToCheck = textToCheck.substr(match.index + match[0].length);
-        let result = match[0].replace(
-          pattern,
-          // Either html or link has a value. Otherwise an exception is thrown
-          // in the code below.
-          (linkInfo.html || linkInfo.link)!
-        );
-
-        if (linkInfo.html) {
-          let i;
-          // Skip portion of replacement string that is equal to original to
-          // allow overlapping patterns.
-          for (i = 0; i < result.length; i++) {
-            if (result[i] !== match[0][i]) {
-              break;
-            }
-          }
-          result = result.slice(i);
-
-          this.addHTML(
-            result,
-            susbtrIndex + match.index + i,
-            match[0].length - i,
-            outputArray
-          );
-        } else if (linkInfo.link) {
-          this.addLink(
-            match[0],
-            result,
-            susbtrIndex + match.index,
-            match[0].length,
-            outputArray
-          );
-        } else {
-          throw Error(
-            'linkconfig entry ' +
-              configName +
-              ' doesn’t contain a link or html attribute.'
-          );
-        }
-
-        // Update the substring location so we know where we are in relation to
-        // the initial full text string.
-        susbtrIndex = susbtrIndex + match.index + match[0].length;
-      }
-    }
-    this.processLinks(text, outputArray);
-  }
-}
diff --git a/polygerrit-ui/app/embed/diff/gr-diff-image-viewer/gr-image-viewer.ts b/polygerrit-ui/app/embed/diff/gr-diff-image-viewer/gr-image-viewer.ts
index fe4632b..8a92bcc 100644
--- a/polygerrit-ui/app/embed/diff/gr-diff-image-viewer/gr-image-viewer.ts
+++ b/polygerrit-ui/app/embed/diff/gr-diff-image-viewer/gr-image-viewer.ts
@@ -13,6 +13,7 @@
 import '@polymer/paper-listbox/paper-listbox';
 import './gr-overview-image';
 import './gr-zoomed-image';
+import '../../../elements/shared/gr-icons/gr-icons';
 
 import {GrLibLoader} from '../../../elements/shared/gr-lib-loader/gr-lib-loader';
 import {RESEMBLEJS_LIBRARY_CONFIG} from '../../../elements/shared/gr-lib-loader/resemblejs_config';
diff --git a/polygerrit-ui/app/embed/diff/gr-diff/gr-diff.ts b/polygerrit-ui/app/embed/diff/gr-diff/gr-diff.ts
index f0697df..53c2780 100644
--- a/polygerrit-ui/app/embed/diff/gr-diff/gr-diff.ts
+++ b/polygerrit-ui/app/embed/diff/gr-diff/gr-diff.ts
@@ -5,7 +5,6 @@
  */
 import '../../../styles/shared-styles';
 import '../../../elements/shared/gr-button/gr-button';
-import '../../../elements/shared/gr-icons/gr-icons';
 import '../../../elements/shared/gr-icon/gr-icon';
 import '../gr-diff-builder/gr-diff-builder-element';
 import '../gr-diff-highlight/gr-diff-highlight';
diff --git a/polygerrit-ui/app/models/browser/browser-model.ts b/polygerrit-ui/app/models/browser/browser-model.ts
index 9b69b24..1592cd8 100644
--- a/polygerrit-ui/app/models/browser/browser-model.ts
+++ b/polygerrit-ui/app/models/browser/browser-model.ts
@@ -4,12 +4,12 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 import {Observable, combineLatest} from 'rxjs';
-import {distinctUntilChanged, map} from 'rxjs/operators';
 import {Finalizable} from '../../services/registry';
 import {define} from '../dependency';
 import {DiffViewMode} from '../../api/diff';
 import {UserModel} from '../user/user-model';
 import {Model} from '../model';
+import {select} from '../../utils/observable-util';
 
 // This value is somewhat arbitrary and not based on research or calculations.
 const MAX_UNIFIED_DEFAULT_WINDOW_WIDTH_PX = 850;
@@ -27,30 +27,24 @@
 export const browserModelToken = define<BrowserModel>('browser-model');
 
 export class BrowserModel extends Model<BrowserState> implements Finalizable {
-  readonly diffViewMode$: Observable<DiffViewMode>;
+  private readonly isScreenTooSmall$ = select(
+    this.state$,
+    state =>
+      !!state.screenWidth &&
+      state.screenWidth < MAX_UNIFIED_DEFAULT_WINDOW_WIDTH_PX
+  );
+
+  readonly diffViewMode$: Observable<DiffViewMode> = select(
+    combineLatest([
+      this.isScreenTooSmall$,
+      this.userModel.preferenceDiffViewMode$,
+    ]),
+    ([isScreenTooSmall, preferenceDiffViewMode]) =>
+      isScreenTooSmall ? DiffViewMode.UNIFIED : preferenceDiffViewMode
+  );
 
   constructor(readonly userModel: UserModel) {
     super(initialState);
-    const screenWidth$ = this.state$.pipe(
-      map(
-        state =>
-          !!state.screenWidth &&
-          state.screenWidth < MAX_UNIFIED_DEFAULT_WINDOW_WIDTH_PX
-      ),
-      distinctUntilChanged()
-    );
-    // TODO; Inject the UserModel once preferenceDiffViewMode$ has moved to
-    // the user model.
-    this.diffViewMode$ = combineLatest([
-      screenWidth$,
-      userModel.preferenceDiffViewMode$,
-    ]).pipe(
-      map(([isScreenTooSmall, preferenceDiffViewMode]) => {
-        if (isScreenTooSmall) return DiffViewMode.UNIFIED;
-        else return preferenceDiffViewMode;
-      }),
-      distinctUntilChanged()
-    );
   }
 
   /* Observe the screen width so that the app can react to changes to it */
diff --git a/polygerrit-ui/app/models/change/change-model.ts b/polygerrit-ui/app/models/change/change-model.ts
index 5cfe670..35a08c6 100644
--- a/polygerrit-ui/app/models/change/change-model.ts
+++ b/polygerrit-ui/app/models/change/change-model.ts
@@ -14,20 +14,11 @@
   RevisionPatchSetNum,
 } from '../../types/common';
 import {DefaultBase} from '../../constants/constants';
-import {
-  combineLatest,
-  from,
-  fromEvent,
-  Observable,
-  Subscription,
-  forkJoin,
-  of,
-} from 'rxjs';
+import {combineLatest, from, fromEvent, Observable, forkJoin, of} from 'rxjs';
 import {
   map,
   filter,
   withLatestFrom,
-  distinctUntilChanged,
   startWith,
   switchMap,
 } from 'rxjs/operators';
@@ -234,35 +225,33 @@
      * out inconsistent state, e.g. router changeNum already updated, change not
      * yet reset to undefined.
      */
-    combineLatest([this.routerModel.state$, this.state$, this.userModel.state$])
-      .pipe(
+    select(
+      combineLatest([
+        this.routerModel.state$,
+        this.state$,
+        this.userModel.state$,
+      ]).pipe(
         filter(([routerState, changeState, _]) => {
           const changeNum = changeState.change?._number;
           const routerChangeNum = routerState.changeNum;
           return changeNum === undefined || changeNum === routerChangeNum;
         }),
-        distinctUntilChanged()
-      )
-      .pipe(
         withLatestFrom(
           this.routerModel.routerBasePatchNum$,
           this.patchNum$,
           this.change$,
           this.userModel.preferences$
-        ),
-        map(([_, routerBasePatchNum, patchNum, change, preferences]) =>
-          computeBase(routerBasePatchNum, patchNum, change, preferences)
-        ),
-        distinctUntilChanged()
-      );
+        )
+      ),
+      ([_, routerBasePatchNum, patchNum, change, preferences]) =>
+        computeBase(routerBasePatchNum, patchNum, change, preferences)
+    );
 
   public readonly isOwner$: Observable<boolean> = select(
     combineLatest([this.change$, this.userModel.account$]),
     ([change, account]) => isOwner(change, account)
   );
 
-  private subscriptions: Subscription[] = [];
-
   // For usage in `combineLatest` we need `startWith` such that reload$ has an
   // initial value.
   readonly reload$: Observable<unknown> = fromEvent(document, 'reload').pipe(
@@ -316,13 +305,6 @@
     ];
   }
 
-  override finalize() {
-    for (const s of this.subscriptions) {
-      s.unsubscribe();
-    }
-    this.subscriptions = [];
-  }
-
   // Temporary workaround until path is derived in the model itself.
   updatePath(diffPath?: string) {
     this.updateState({diffPath});
diff --git a/polygerrit-ui/app/models/change/change-model_test.ts b/polygerrit-ui/app/models/change/change-model_test.ts
index 0ee508a..fdf9e04 100644
--- a/polygerrit-ui/app/models/change/change-model_test.ts
+++ b/polygerrit-ui/app/models/change/change-model_test.ts
@@ -22,6 +22,7 @@
   CommitId,
   EDIT,
   NumericChangeId,
+  PARENT,
   PatchSetNum,
   PatchSetNumber,
 } from '../../types/common';
@@ -63,7 +64,7 @@
   });
 });
 
-suite('change service tests', () => {
+suite('change model tests', () => {
   let changeModel: ChangeModel;
   let knownChange: ParsedChangeInfo;
   const testCompleted = new Subject<void>();
@@ -279,4 +280,25 @@
       message: 'blah blah',
     });
   });
+
+  // At some point we had forgotten the `select()` wrapper for this selector.
+  // And the missing `replay` led to a bug that was hard to find. That is why
+  // we are testing this explicitly here.
+  test('basePatchNum$ selector', async () => {
+    const spy = sinon.spy();
+    changeModel.basePatchNum$.subscribe(spy);
+
+    // test replay
+    assert.equal(spy.callCount, 1);
+    assert.equal(spy.lastCall.firstArg, PARENT);
+
+    // test update
+    changeModel.routerModel.updateState({basePatchNum: 1 as PatchSetNumber});
+    assert.equal(spy.callCount, 2);
+    assert.equal(spy.lastCall.firstArg, 1 as PatchSetNumber);
+
+    // test distinctUntilChanged
+    changeModel.updateStateChange(createParsedChange());
+    assert.equal(spy.callCount, 2);
+  });
 });
diff --git a/polygerrit-ui/app/models/change/files-model.ts b/polygerrit-ui/app/models/change/files-model.ts
index 31e42a6..6922f6d 100644
--- a/polygerrit-ui/app/models/change/files-model.ts
+++ b/polygerrit-ui/app/models/change/files-model.ts
@@ -12,7 +12,7 @@
   PatchSetNumber,
   RevisionPatchSetNum,
 } from '../../types/common';
-import {combineLatest, Subscription, of, from} from 'rxjs';
+import {combineLatest, of, from} from 'rxjs';
 import {switchMap, map} from 'rxjs/operators';
 import {RestApiService} from '../../services/gr-rest-api/gr-rest-api';
 import {Finalizable} from '../../services/registry';
@@ -131,8 +131,6 @@
     state => state.filesRightBase
   );
 
-  private subscriptions: Subscription[] = [];
-
   constructor(
     readonly changeModel: ChangeModel,
     readonly commentsModel: CommentsModel,
@@ -198,11 +196,4 @@
         this.updateState(state);
       });
   }
-
-  override finalize() {
-    for (const s of this.subscriptions) {
-      s.unsubscribe();
-    }
-    this.subscriptions = [];
-  }
 }
diff --git a/polygerrit-ui/app/models/checks/checks-model.ts b/polygerrit-ui/app/models/checks/checks-model.ts
index 2b92529..9c4c45c 100644
--- a/polygerrit-ui/app/models/checks/checks-model.ts
+++ b/polygerrit-ui/app/models/checks/checks-model.ts
@@ -20,7 +20,6 @@
   Observable,
   of,
   Subject,
-  Subscription,
   timer,
 } from 'rxjs';
 import {
@@ -151,7 +150,12 @@
   };
 }
 
-const FETCH_RESULT_TIMEOUT_MS = 10000;
+/**
+ * Android's Checks Plugin has a 15s timeout internally. So we are using
+ * something slightly larger, so that we get a proper error from the plugin,
+ * if they run into timeout issues.
+ */
+const FETCH_RESULT_TIMEOUT_MS = 16000;
 
 /**
  * Can be used in `reduce()` to collect all results from all runs from all
@@ -185,9 +189,11 @@
 
   private checkToPluginMap = new Map<string, string>();
 
-  private changeNum?: NumericChangeId;
+  // visible for testing
+  changeNum?: NumericChangeId;
 
-  private latestPatchNum?: PatchSetNumber;
+  // visible for testing
+  latestPatchNum?: PatchSetNumber;
 
   private readonly documentVisibilityChange$ = new BehaviorSubject(undefined);
 
@@ -195,9 +201,6 @@
 
   private readonly visibilityChangeListener: () => void;
 
-  private subscriptions: Subscription[] = [];
-
-  // TODO: Maybe consider migrating usages to `changeViewModel` directly.
   public checksSelectedPatchsetNumber$ = select(
     this.changeViewModel.checksPatchset$,
     ps => ps
@@ -384,6 +387,9 @@
     this.reporting.time(Timing.CHECKS_LOAD);
     this.subscriptions = [
       this.changeModel.changeNum$.subscribe(x => (this.changeNum = x)),
+      this.changeModel.latestPatchNum$.subscribe(
+        x => (this.latestPatchNum = x)
+      ),
       this.pluginsModel.checksPlugins$.subscribe(plugins => {
         for (const plugin of plugins) {
           this.register(plugin);
@@ -461,10 +467,7 @@
       'visibilitychange',
       this.visibilityChangeListener
     );
-    for (const s of this.subscriptions) {
-      s.unsubscribe();
-    }
-    this.subscriptions = [];
+    super.finalize();
   }
 
   // Must only be used by the checks service or whatever is in control of this
@@ -750,8 +753,10 @@
         patchset === ChecksPatchset.LATEST
           ? this.changeModel.latestPatchNum$
           : this.checksSelectedPatchsetNumber$,
-        this.reloadSubjects[pluginName].pipe(throttleTime(1000)),
-        timer(0, pollIntervalMs),
+        this.reloadSubjects[pluginName].pipe(
+          throttleTime(1000, undefined, {trailing: true, leading: true})
+        ),
+        pollIntervalMs === 0 ? from([0]) : timer(0, pollIntervalMs),
         this.documentVisibilityChange$,
       ])
         .pipe(
diff --git a/polygerrit-ui/app/models/checks/checks-model_test.ts b/polygerrit-ui/app/models/checks/checks-model_test.ts
index 83ed464..3489c5a 100644
--- a/polygerrit-ui/app/models/checks/checks-model_test.ts
+++ b/polygerrit-ui/app/models/checks/checks-model_test.ts
@@ -7,6 +7,7 @@
 import './checks-model';
 import {ChecksModel, ChecksPatchset, ChecksProviderState} from './checks-model';
 import {
+  Action,
   Category,
   CheckRun,
   ChecksApiConfig,
@@ -22,6 +23,7 @@
 import {assert} from '@open-wc/testing';
 import {testResolver} from '../../test/common-test-setup';
 import {changeViewModelToken} from '../views/change';
+import {NumericChangeId, PatchSetNumber} from '../../api/rest-api';
 
 const PLUGIN_NAME = 'test-plugin';
 
@@ -42,8 +44,12 @@
   },
 ];
 
-const CONFIG: ChecksApiConfig = {
-  fetchPollingIntervalSeconds: 1000,
+const CONFIG_POLLING_5S: ChecksApiConfig = {
+  fetchPollingIntervalSeconds: 5,
+};
+
+const CONFIG_POLLING_NONE: ChecksApiConfig = {
+  fetchPollingIntervalSeconds: 0,
 };
 
 function createProvider(): ChecksProvider {
@@ -82,13 +88,67 @@
     const provider = createProvider();
     const fetchSpy = sinon.spy(provider, 'fetch');
 
-    model.register({pluginName: 'test-plugin', provider, config: CONFIG});
+    model.register({
+      pluginName: 'test-plugin',
+      provider,
+      config: CONFIG_POLLING_NONE,
+    });
     await waitUntil(() => change === undefined);
 
     const testChange = createParsedChange();
     model.changeModel.updateStateChange(testChange);
     await waitUntil(() => change === testChange);
     await waitUntilCalled(fetchSpy, 'fetch');
+
+    assert.equal(
+      model.latestPatchNum,
+      testChange.revisions[testChange.current_revision]
+        ._number as PatchSetNumber
+    );
+    assert.equal(model.changeNum, testChange._number);
+  });
+
+  test('reload throttle', async () => {
+    const clock = sinon.useFakeTimers();
+    let change: ParsedChangeInfo | undefined = undefined;
+    model.changeModel.change$.subscribe(c => (change = c));
+    const provider = createProvider();
+    const fetchSpy = sinon.spy(provider, 'fetch');
+
+    model.register({
+      pluginName: 'test-plugin',
+      provider,
+      config: CONFIG_POLLING_NONE,
+    });
+    await waitUntil(() => change === undefined);
+
+    const testChange = createParsedChange();
+    model.changeModel.updateStateChange(testChange);
+    await waitUntil(() => change === testChange);
+    clock.tick(1);
+    assert.equal(fetchSpy.callCount, 1);
+
+    // The second reload call will be processed, but only after a 1s throttle.
+    model.reload('test-plugin');
+    clock.tick(100);
+    assert.equal(fetchSpy.callCount, 1);
+    // 2000 ms is greater than the 1000 ms throttle time.
+    clock.tick(2000);
+    assert.equal(fetchSpy.callCount, 2);
+  });
+
+  test('triggerAction', async () => {
+    model.changeNum = 314 as NumericChangeId;
+    model.latestPatchNum = 13 as PatchSetNumber;
+    const action: Action = {
+      name: 'test action',
+      callback: () => undefined,
+    };
+    const spy = sinon.spy(action, 'callback');
+    model.triggerAction(action, undefined, 'none');
+    assert.isTrue(spy.calledOnce);
+    assert.equal(spy.lastCall.args[0], 314);
+    assert.equal(spy.lastCall.args[1], 13);
   });
 
   test('model.updateStateSetProvider', () => {
@@ -204,4 +264,58 @@
     assert.lengthOf(current.runs[0].results!, 1);
     assert.equal(current.runs[0].results![0].summary, 'new');
   });
+
+  test('polls for changes', async () => {
+    const clock = sinon.useFakeTimers();
+    let change: ParsedChangeInfo | undefined = undefined;
+    model.changeModel.change$.subscribe(c => (change = c));
+    const provider = createProvider();
+    const fetchSpy = sinon.spy(provider, 'fetch');
+
+    model.register({
+      pluginName: 'test-plugin',
+      provider,
+      config: CONFIG_POLLING_5S,
+    });
+    await waitUntil(() => change === undefined);
+    clock.tick(1);
+    const testChange = createParsedChange();
+    model.changeModel.updateStateChange(testChange);
+    await waitUntil(() => change === testChange);
+    await waitUntilCalled(fetchSpy, 'fetch');
+    clock.tick(1);
+    const pollCount = fetchSpy.callCount;
+
+    // polling should continue while we wait
+    clock.tick(CONFIG_POLLING_5S.fetchPollingIntervalSeconds * 1000 * 2);
+
+    assert.isTrue(fetchSpy.callCount > pollCount);
+  });
+
+  test('does not poll when config specifies 0 seconds', async () => {
+    const clock = sinon.useFakeTimers();
+    let change: ParsedChangeInfo | undefined = undefined;
+    model.changeModel.change$.subscribe(c => (change = c));
+    const provider = createProvider();
+    const fetchSpy = sinon.spy(provider, 'fetch');
+
+    model.register({
+      pluginName: 'test-plugin',
+      provider,
+      config: CONFIG_POLLING_NONE,
+    });
+    await waitUntil(() => change === undefined);
+    clock.tick(1);
+    const testChange = createParsedChange();
+    model.changeModel.updateStateChange(testChange);
+    await waitUntil(() => change === testChange);
+    await waitUntilCalled(fetchSpy, 'fetch');
+    clock.tick(1);
+    const pollCount = fetchSpy.callCount;
+
+    // polling should not happen
+    clock.tick(60 * 1000);
+
+    assert.equal(fetchSpy.callCount, pollCount);
+  });
 });
diff --git a/polygerrit-ui/app/models/checks/checks-util.ts b/polygerrit-ui/app/models/checks/checks-util.ts
index 09c9273..7ccdf91 100644
--- a/polygerrit-ui/app/models/checks/checks-util.ts
+++ b/polygerrit-ui/app/models/checks/checks-util.ts
@@ -8,12 +8,16 @@
   Category,
   CheckResult as CheckResultApi,
   CheckRun as CheckRunApi,
+  Fix,
   Link,
   LinkIcon,
+  Replacement,
   RunStatus,
 } from '../../api/checks';
 import {PatchSetNumber} from '../../api/rest-api';
+import {FixSuggestionInfo, FixReplacementInfo} from '../../types/common';
 import {OpenFixPreviewEventDetail} from '../../types/events';
+import {notUndefined} from '../../types/types';
 import {PROVIDED_FIX_ID} from '../../utils/comment-util';
 import {assert, assertNever} from '../../utils/common-util';
 import {fire} from '../../utils/event-util';
@@ -86,17 +90,15 @@
   target: EventTarget,
   result?: RunResult
 ): Action | undefined {
-  const fixes = result?.fixes;
-  if (!fixes || fixes?.length === 0 || !result?.patchset) return;
+  if (!result?.patchset) return;
+  if (!result?.fixes) return;
+  const fixSuggestions = result.fixes
+    .map(f => rectifyFix(f, result?.checkName))
+    .filter(notUndefined);
+  if (fixSuggestions.length === 0) return;
   const eventDetail: OpenFixPreviewEventDetail = {
-    patchNum: result?.patchset as PatchSetNumber,
-    fixSuggestions: fixes.map(fix => {
-      return {
-        description: `Fix provided by ${result?.checkName}`,
-        fix_id: PROVIDED_FIX_ID,
-        ...fix,
-      };
-    }),
+    patchNum: result.patchset as PatchSetNumber,
+    fixSuggestions,
   };
   return {
     name: 'Show Fix',
@@ -107,6 +109,36 @@
   };
 }
 
+export function rectifyFix(
+  fix: Fix | undefined,
+  checkName: string
+): FixSuggestionInfo | undefined {
+  if (!fix?.replacements) return undefined;
+  const replacements = fix.replacements
+    .map(rectifyReplacement)
+    .filter(notUndefined);
+  if (replacements.length === 0) return undefined;
+
+  return {
+    description: fix.description ?? `Fix provided by ${checkName}`,
+    fix_id: PROVIDED_FIX_ID,
+    replacements,
+  };
+}
+
+export function rectifyReplacement(
+  r: Replacement | undefined
+): FixReplacementInfo | undefined {
+  if (!r?.path) return undefined;
+  if (!r?.range) return undefined;
+  if (r?.replacement === undefined) return undefined;
+  if (!Number.isInteger(r.range.start_line)) return undefined;
+  if (!Number.isInteger(r.range.end_line)) return undefined;
+  if (!Number.isInteger(r.range.start_character)) return undefined;
+  if (!Number.isInteger(r.range.end_character)) return undefined;
+  return r;
+}
+
 export function worstCategory(run: CheckRun) {
   if (hasResultsOf(run, Category.ERROR)) return Category.ERROR;
   if (hasResultsOf(run, Category.WARNING)) return Category.WARNING;
diff --git a/polygerrit-ui/app/models/checks/checks-util_test.ts b/polygerrit-ui/app/models/checks/checks-util_test.ts
index 5a7bd75..c237c59 100644
--- a/polygerrit-ui/app/models/checks/checks-util_test.ts
+++ b/polygerrit-ui/app/models/checks/checks-util_test.ts
@@ -10,9 +10,13 @@
   ALL_ATTEMPTS,
   AttemptChoice,
   LATEST_ATTEMPT,
+  rectifyFix,
   sortAttemptChoices,
   stringToAttemptChoice,
 } from './checks-util';
+import {Fix, Replacement} from '../../api/checks';
+import {CommentRange} from '../../api/core';
+import {PROVIDED_FIX_ID} from '../../utils/comment-util';
 
 suite('checks-util tests', () => {
   setup(() => {});
@@ -33,6 +37,55 @@
     assert.equal(stringToAttemptChoice('1x'), undefined);
   });
 
+  test('rectifyFix', () => {
+    assert.isUndefined(rectifyFix(undefined, 'name'));
+    assert.isUndefined(rectifyFix({} as Fix, 'name'));
+    assert.isUndefined(
+      rectifyFix({description: 'asdf', replacements: []}, 'name')
+    );
+    assert.isUndefined(
+      rectifyFix(
+        {description: 'asdf', replacements: [{} as Replacement]},
+        'test-check-name'
+      )
+    );
+    assert.isUndefined(
+      rectifyFix(
+        {
+          description: 'asdf',
+          replacements: [
+            {
+              path: 'test-path',
+              range: {} as CommentRange,
+              replacement: 'test-replacement-string',
+            },
+          ],
+        },
+        'test-check-name'
+      )
+    );
+    const rectified = rectifyFix(
+      {
+        replacements: [
+          {
+            path: 'test-path',
+            range: {
+              start_line: 1,
+              end_line: 1,
+              start_character: 0,
+              end_character: 1,
+            } as CommentRange,
+            replacement: 'test-replacement-string',
+          },
+        ],
+      },
+      'test-check-name'
+    );
+    assert.isDefined(rectified);
+    assert.equal(rectified?.description, 'Fix provided by test-check-name');
+    assert.equal(rectified?.fix_id, PROVIDED_FIX_ID);
+  });
+
   test('sortAttemptChoices', () => {
     const unsorted: (AttemptChoice | undefined)[] = [
       3,
diff --git a/polygerrit-ui/app/models/comments/comments-model.ts b/polygerrit-ui/app/models/comments/comments-model.ts
index 39d9eaa..8ed4b69 100644
--- a/polygerrit-ui/app/models/comments/comments-model.ts
+++ b/polygerrit-ui/app/models/comments/comments-model.ts
@@ -30,7 +30,7 @@
 import {RouterModel} from '../../services/router/router-model';
 import {Finalizable} from '../../services/registry';
 import {define} from '../dependency';
-import {combineLatest, forkJoin, from, Observable, Subscription} from 'rxjs';
+import {combineLatest, forkJoin, from, Observable} from 'rxjs';
 import {fire, fireAlert, fireEvent} from '../../utils/event-util';
 import {CURRENT} from '../../utils/patch-set-util';
 import {RestApiService} from '../../services/gr-rest-api/gr-rest-api';
@@ -370,8 +370,6 @@
 
   private readonly reloadListener: () => void;
 
-  private readonly subscriptions: Subscription[] = [];
-
   private drafts: {[path: string]: DraftInfo[]} = {};
 
   private draftToastTask?: DelayedTask;
@@ -421,10 +419,7 @@
 
   override finalize() {
     document.removeEventListener('reload', this.reloadListener);
-    for (const s of this.subscriptions) {
-      s.unsubscribe();
-    }
-    this.subscriptions.splice(0, this.subscriptions.length);
+    super.finalize();
   }
 
   // Note that this does *not* reload ported comments.
diff --git a/polygerrit-ui/app/models/config/config-model.ts b/polygerrit-ui/app/models/config/config-model.ts
index c4bd637..6e374d1 100644
--- a/polygerrit-ui/app/models/config/config-model.ts
+++ b/polygerrit-ui/app/models/config/config-model.ts
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 import {ConfigInfo, RepoName, ServerInfo} from '../../types/common';
-import {from, of, Subscription} from 'rxjs';
+import {from, of} from 'rxjs';
 import {switchMap} from 'rxjs/operators';
 import {Finalizable} from '../../services/registry';
 import {RestApiService} from '../../services/gr-rest-api/gr-rest-api';
@@ -50,8 +50,6 @@
     url => url
   );
 
-  private subscriptions: Subscription[];
-
   constructor(
     readonly changeModel: ChangeModel,
     readonly restApiService: RestApiService
@@ -83,11 +81,4 @@
   updateServerConfig(serverConfig?: ServerInfo) {
     this.updateState({serverConfig});
   }
-
-  override finalize() {
-    for (const s of this.subscriptions) {
-      s.unsubscribe();
-    }
-    this.subscriptions = [];
-  }
 }
diff --git a/polygerrit-ui/app/models/model.ts b/polygerrit-ui/app/models/model.ts
index 2e90a5e..19b52fc 100644
--- a/polygerrit-ui/app/models/model.ts
+++ b/polygerrit-ui/app/models/model.ts
@@ -3,7 +3,7 @@
  * Copyright 2021 Google LLC
  * SPDX-License-Identifier: Apache-2.0
  */
-import {BehaviorSubject, Observable} from 'rxjs';
+import {BehaviorSubject, Observable, Subscription} from 'rxjs';
 import {Finalizable} from '../services/registry';
 import {deepEqual} from '../utils/deep-util';
 
@@ -22,10 +22,19 @@
  *  Any new subscriber will immediately receive the current value.
  */
 export abstract class Model<T> implements Finalizable {
+  /**
+   * rxjs does not like `next()` being called on a subject during processing of
+   * another `next()` call. So make sure that state updates complete before
+   * starting another one.
+   */
+  private stateUpdateInProgress = false;
+
   private subject$: BehaviorSubject<T>;
 
   public state$: Observable<T>;
 
+  protected subscriptions: Subscription[] = [];
+
   constructor(initialState: T) {
     this.subject$ = new BehaviorSubject(initialState);
     this.state$ = this.subject$.asObservable();
@@ -36,15 +45,32 @@
   }
 
   setState(state: T) {
+    if (this.stateUpdateInProgress) {
+      setTimeout(() => this.setState(state));
+      return;
+    }
     if (deepEqual(state, this.getState())) return;
-    this.subject$.next(state);
+    try {
+      this.stateUpdateInProgress = true;
+      this.subject$.next(state);
+    } finally {
+      this.stateUpdateInProgress = false;
+    }
   }
 
   updateState(state: Partial<T>) {
+    if (this.stateUpdateInProgress) {
+      setTimeout(() => this.updateState(state));
+      return;
+    }
     this.setState({...this.getState(), ...state});
   }
 
   finalize() {
     this.subject$.complete();
+    for (const s of this.subscriptions) {
+      s.unsubscribe();
+    }
+    this.subscriptions = [];
   }
 }
diff --git a/polygerrit-ui/app/models/model_test.ts b/polygerrit-ui/app/models/model_test.ts
new file mode 100644
index 0000000..3fa88e7
--- /dev/null
+++ b/polygerrit-ui/app/models/model_test.ts
@@ -0,0 +1,65 @@
+/**
+ * @license
+ * Copyright 2022 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+import {assert, waitUntil} from '@open-wc/testing';
+import '../test/common-test-setup';
+import {Model} from './model';
+
+interface TestModelState {
+  prop1?: string;
+  prop2?: string;
+  prop3?: string;
+}
+
+export class TestModel extends Model<TestModelState> {
+  constructor() {
+    super({});
+  }
+}
+
+suite('model tests', () => {
+  test('setState update in progress', async () => {
+    const model = new TestModel();
+    let firstUpdateCompleted = false;
+    let secondUpdateCompleted = false;
+    model.state$.subscribe(s => {
+      if (s.prop2 === 'set') {
+        // Otherwise this would be a clear indication of a nested `setState()`
+        // call, which `stateUpdateInProgress` is supposed to avoid.
+        assert.isTrue(firstUpdateCompleted);
+        secondUpdateCompleted = true;
+      }
+      if (s.prop1 === 'set' && s.prop2 !== 'set')
+        model.setState({prop2: 'set'});
+    });
+
+    // This call should return before the subscriber calls `setState()` again.
+    model.setState({prop1: 'set'});
+    firstUpdateCompleted = true;
+
+    await waitUntil(() => secondUpdateCompleted);
+  });
+
+  test('updateState update in progress', async () => {
+    const model = new TestModel();
+    let completed = false;
+    model.state$.subscribe(s => {
+      if (s.prop1 !== 'go') return;
+      if (s.prop2 !== 'set' && s.prop3 !== 'set')
+        model.updateState({prop2: 'set'});
+      if (s.prop2 === 'set' && s.prop3 === 'set') completed = true;
+    });
+    model.state$.subscribe(s => {
+      if (s.prop1 !== 'go') return;
+      if (s.prop2 !== 'set' && s.prop3 !== 'set')
+        model.updateState({prop3: 'set'});
+      if (s.prop2 === 'set' && s.prop3 === 'set') completed = true;
+    });
+
+    model.updateState({prop1: 'go'});
+
+    await waitUntil(() => completed);
+  });
+});
diff --git a/polygerrit-ui/app/models/user/user-model.ts b/polygerrit-ui/app/models/user/user-model.ts
index b69c715..fa00a0b 100644
--- a/polygerrit-ui/app/models/user/user-model.ts
+++ b/polygerrit-ui/app/models/user/user-model.ts
@@ -3,7 +3,7 @@
  * Copyright 2021 Google LLC
  * SPDX-License-Identifier: Apache-2.0
  */
-import {from, of, Observable, Subscription} from 'rxjs';
+import {from, of, Observable} from 'rxjs';
 import {switchMap} from 'rxjs/operators';
 import {
   DiffPreferencesInfo as DiffPreferencesInfoAPI,
@@ -83,8 +83,6 @@
     preference => preference.theme
   );
 
-  private subscriptions: Subscription[] = [];
-
   constructor(readonly restApiService: RestApiService) {
     super({
       preferences: createDefaultPreferences(),
@@ -140,13 +138,6 @@
     ];
   }
 
-  override finalize() {
-    for (const s of this.subscriptions) {
-      s.unsubscribe();
-    }
-    this.subscriptions = [];
-  }
-
   updatePreferences(prefs: Partial<PreferencesInfo>) {
     return this.restApiService
       .savePreferences(prefs)
diff --git a/polygerrit-ui/app/models/views/change.ts b/polygerrit-ui/app/models/views/change.ts
index 826ec66..100c46b 100644
--- a/polygerrit-ui/app/models/views/change.ts
+++ b/polygerrit-ui/app/models/views/change.ts
@@ -11,8 +11,10 @@
   ChangeInfo,
   PatchSetNumber,
 } from '../../api/rest-api';
+import {Tab} from '../../constants/constants';
 import {GerritView} from '../../services/router/router-model';
 import {UrlEncodedCommentId} from '../../types/common';
+import {toggleSet} from '../../utils/common-util';
 import {select} from '../../utils/observable-util';
 import {
   encodeURL,
@@ -33,7 +35,8 @@
   patchNum?: RevisionPatchSetNum;
   basePatchNum?: BasePatchSetNum;
   commentId?: UrlEncodedCommentId;
-  tab?: string;
+  /** This can be a string only for plugin provided tabs. */
+  tab?: Tab | string;
 
   /** Checks related view state */
 
@@ -43,6 +46,10 @@
   filter?: string;
   /** selected attempt for check runs (undefined=latest) */
   attempt?: AttemptChoice;
+  /** selected check runs identified by `checkName` */
+  checksRunsSelected?: Set<string>;
+  /** regular expression for filtering check results */
+  checksResultsFilter?: string;
 
   /** State properties that trigger one-time actions */
 
@@ -107,6 +114,15 @@
   if (state.filter) {
     queries.push(`filter=${state.filter}`);
   }
+  if (state.checksResultsFilter) {
+    queries.push(`checksResultsFilter=${state.checksResultsFilter}`);
+  }
+  if (state.checksRunsSelected && state.checksRunsSelected.size > 0) {
+    queries.push(`checksRunsSelected=${[...state.checksRunsSelected].sort()}`);
+  }
+  if (state.tab && state.tab !== Tab.FILES) {
+    queries.push(`tab=${state.tab}`);
+  }
   if (state.forceReload) {
     queries.push('forceReload=true');
   }
@@ -130,9 +146,9 @@
   }
   if (state.project) {
     const encodedProject = encodeURL(state.project, true);
-    return getBaseUrl() + `/c/${encodedProject}/+/${state.changeNum}${suffix}`;
+    return `${getBaseUrl()}/c/${encodedProject}/+/${state.changeNum}${suffix}`;
   } else {
-    return getBaseUrl() + `/c/${state.changeNum}${suffix}`;
+    return `${getBaseUrl()}/c/${state.changeNum}${suffix}`;
   }
 }
 
@@ -151,6 +167,16 @@
 
   public readonly filter$ = select(this.state$, state => state?.filter);
 
+  public readonly checksResultsFilter$ = select(
+    this.state$,
+    state => state?.checksResultsFilter ?? ''
+  );
+
+  public readonly checksRunsSelected$ = select(
+    this.state$,
+    state => state?.checksRunsSelected ?? new Set<string>()
+  );
+
   constructor() {
     super(undefined);
     this.state$.subscribe(s => {
@@ -163,4 +189,11 @@
       }
     });
   }
+
+  toggleSelectedCheckRun(checkName: string) {
+    const current = this.getState()?.checksRunsSelected ?? new Set();
+    const next = new Set(current);
+    toggleSet(next, checkName);
+    this.updateState({checksRunsSelected: next});
+  }
 }
diff --git a/polygerrit-ui/app/models/views/change_test.ts b/polygerrit-ui/app/models/views/change_test.ts
index 2f05e9f..24ced82 100644
--- a/polygerrit-ui/app/models/views/change_test.ts
+++ b/polygerrit-ui/app/models/views/change_test.ts
@@ -14,13 +14,15 @@
 import '../../test/common-test-setup';
 import {createChangeUrl, ChangeViewState} from './change';
 
+const STATE: ChangeViewState = {
+  view: GerritView.CHANGE,
+  changeNum: 1234 as NumericChangeId,
+  project: 'test' as RepoName,
+};
+
 suite('change view state tests', () => {
   test('createChangeUrl()', () => {
-    const state: ChangeViewState = {
-      view: GerritView.CHANGE,
-      changeNum: 1234 as NumericChangeId,
-      project: 'test' as RepoName,
-    };
+    const state: ChangeViewState = {...STATE};
 
     assert.equal(createChangeUrl(state), '/c/test/+/1234');
 
@@ -34,6 +36,37 @@
     assert.equal(createChangeUrl(state), '/c/test/+/1234/5..10#123');
   });
 
+  test('createChangeUrl() baseUrl', () => {
+    window.CANONICAL_PATH = '/base';
+    const state: ChangeViewState = {...STATE};
+    assert.equal(createChangeUrl(state).substring(0, 5), '/base');
+    window.CANONICAL_PATH = undefined;
+  });
+
+  test('createChangeUrl() checksRunsSelected', () => {
+    const state: ChangeViewState = {
+      ...STATE,
+      checksRunsSelected: new Set(['asdf']),
+    };
+
+    assert.equal(
+      createChangeUrl(state),
+      '/c/test/+/1234?checksRunsSelected=asdf'
+    );
+  });
+
+  test('createChangeUrl() checksResultsFilter', () => {
+    const state: ChangeViewState = {
+      ...STATE,
+      checksResultsFilter: 'asdf.*qwer',
+    };
+
+    assert.equal(
+      createChangeUrl(state),
+      '/c/test/+/1234?checksResultsFilter=asdf.*qwer'
+    );
+  });
+
   test('createChangeUrl() with repo name encoding', () => {
     const state: ChangeViewState = {
       view: GerritView.CHANGE,
diff --git a/polygerrit-ui/app/models/views/dashboard.ts b/polygerrit-ui/app/models/views/dashboard.ts
index 7141637..d9ff2d2 100644
--- a/polygerrit-ui/app/models/views/dashboard.ts
+++ b/polygerrit-ui/app/models/views/dashboard.ts
@@ -7,7 +7,7 @@
 import {GerritView} from '../../services/router/router-model';
 import {DashboardId} from '../../types/common';
 import {DashboardSection} from '../../utils/dashboard-util';
-import {encodeURL} from '../../utils/url-util';
+import {encodeURL, getBaseUrl} from '../../utils/url-util';
 import {define} from '../dependency';
 import {Model} from '../model';
 import {ViewState} from './base';
@@ -46,14 +46,14 @@
       queryParams.push('title=' + encodeURIComponent(state.title));
     }
     const user = state.user ? state.user : '';
-    return `/dashboard/${user}?${queryParams.join('&')}`;
+    return `${getBaseUrl()}/dashboard/${user}?${queryParams.join('&')}`;
   } else if (repoName) {
     // Project dashboard.
     const encodedRepo = encodeURL(repoName, true);
-    return `/p/${encodedRepo}/+/dashboard/${state.dashboard}`;
+    return `${getBaseUrl()}/p/${encodedRepo}/+/dashboard/${state.dashboard}`;
   } else {
     // User dashboard.
-    return `/dashboard/${state.user || 'self'}`;
+    return `${getBaseUrl()}/dashboard/${state.user || 'self'}`;
   }
 }
 
diff --git a/polygerrit-ui/app/models/views/dashboard_test.ts b/polygerrit-ui/app/models/views/dashboard_test.ts
index 9deed72..86bb5c0 100644
--- a/polygerrit-ui/app/models/views/dashboard_test.ts
+++ b/polygerrit-ui/app/models/views/dashboard_test.ts
@@ -15,6 +15,12 @@
       assert.equal(createDashboardUrl({}), '/dashboard/self');
     });
 
+    test('baseUrl', () => {
+      window.CANONICAL_PATH = '/base';
+      assert.equal(createDashboardUrl({}).substring(0, 5), '/base');
+      window.CANONICAL_PATH = undefined;
+    });
+
     test('user dashboard', () => {
       assert.equal(createDashboardUrl({user: 'user'}), '/dashboard/user');
     });
diff --git a/polygerrit-ui/app/models/views/diff.ts b/polygerrit-ui/app/models/views/diff.ts
index 63df521..3cc107a 100644
--- a/polygerrit-ui/app/models/views/diff.ts
+++ b/polygerrit-ui/app/models/views/diff.ts
@@ -12,7 +12,11 @@
 } from '../../api/rest-api';
 import {GerritView} from '../../services/router/router-model';
 import {UrlEncodedCommentId} from '../../types/common';
-import {encodeURL, getPatchRangeExpression} from '../../utils/url-util';
+import {
+  encodeURL,
+  getBaseUrl,
+  getPatchRangeExpression,
+} from '../../utils/url-util';
 import {define} from '../dependency';
 import {Model} from '../model';
 import {ViewState} from './base';
@@ -85,9 +89,9 @@
 
   if (state.project) {
     const encodedProject = encodeURL(state.project, true);
-    return `/c/${encodedProject}/+/${state.changeNum}${suffix}`;
+    return `${getBaseUrl()}/c/${encodedProject}/+/${state.changeNum}${suffix}`;
   } else {
-    return `/c/${state.changeNum}${suffix}`;
+    return `${getBaseUrl()}/c/${state.changeNum}${suffix}`;
   }
 }
 
diff --git a/polygerrit-ui/app/models/views/diff_test.ts b/polygerrit-ui/app/models/views/diff_test.ts
index ec20037..b0f91bb 100644
--- a/polygerrit-ui/app/models/views/diff_test.ts
+++ b/polygerrit-ui/app/models/views/diff_test.ts
@@ -25,6 +25,10 @@
     };
     assert.equal(createDiffUrl(params), '/c/42/12/x%252By/path.cpp');
 
+    window.CANONICAL_PATH = '/base';
+    assert.equal(createDiffUrl(params).substring(0, 5), '/base');
+    window.CANONICAL_PATH = undefined;
+
     params.project = 'test' as RepoName;
     assert.equal(createDiffUrl(params), '/c/test/+/42/12/x%252By/path.cpp');
 
diff --git a/polygerrit-ui/app/models/views/edit.ts b/polygerrit-ui/app/models/views/edit.ts
index d8f4770..c63c8ce 100644
--- a/polygerrit-ui/app/models/views/edit.ts
+++ b/polygerrit-ui/app/models/views/edit.ts
@@ -10,7 +10,11 @@
   RevisionPatchSetNum,
 } from '../../api/rest-api';
 import {GerritView} from '../../services/router/router-model';
-import {encodeURL, getPatchRangeExpression} from '../../utils/url-util';
+import {
+  encodeURL,
+  getBaseUrl,
+  getPatchRangeExpression,
+} from '../../utils/url-util';
 import {define} from '../dependency';
 import {Model} from '../model';
 import {ViewState} from './base';
@@ -41,9 +45,9 @@
 
   if (state.project) {
     const encodedProject = encodeURL(state.project, true);
-    return `/c/${encodedProject}/+/${state.changeNum}${suffix}`;
+    return `${getBaseUrl()}/c/${encodedProject}/+/${state.changeNum}${suffix}`;
   } else {
-    return `/c/${state.changeNum}${suffix}`;
+    return `${getBaseUrl()}/c/${state.changeNum}${suffix}`;
   }
 }
 
diff --git a/polygerrit-ui/app/models/views/edit_test.ts b/polygerrit-ui/app/models/views/edit_test.ts
index e1a05c7..2912063 100644
--- a/polygerrit-ui/app/models/views/edit_test.ts
+++ b/polygerrit-ui/app/models/views/edit_test.ts
@@ -27,5 +27,9 @@
       createEditUrl(params),
       '/c/test-project/+/42/12/x%252By/path.cpp,edit#31'
     );
+
+    window.CANONICAL_PATH = '/base';
+    assert.equal(createEditUrl(params).substring(0, 5), '/base');
+    window.CANONICAL_PATH = undefined;
   });
 });
diff --git a/polygerrit-ui/app/models/views/search.ts b/polygerrit-ui/app/models/views/search.ts
index 58cb8f7..13de8f3 100644
--- a/polygerrit-ui/app/models/views/search.ts
+++ b/polygerrit-ui/app/models/views/search.ts
@@ -6,7 +6,7 @@
 import {RepoName, BranchName, TopicName} from '../../api/rest-api';
 import {GerritView} from '../../services/router/router-model';
 import {addQuotesWhen} from '../../utils/string-util';
-import {encodeURL} from '../../utils/url-util';
+import {encodeURL, getBaseUrl} from '../../utils/url-util';
 import {define} from '../dependency';
 import {Model} from '../model';
 import {ViewState} from './base';
@@ -35,7 +35,7 @@
   }
 
   if (params.query) {
-    return '/q/' + encodeURL(params.query, true) + offsetExpr;
+    return `${getBaseUrl()}/q/${encodeURL(params.query, true)}${offsetExpr}`;
   }
 
   const operators: string[] = [];
@@ -80,7 +80,7 @@
     }
   }
 
-  return '/q/' + operators.join('+') + offsetExpr;
+  return `${getBaseUrl()}/q/${operators.join('+')}${offsetExpr}`;
 }
 
 export const searchViewModelToken =
diff --git a/polygerrit-ui/app/models/views/search_test.ts b/polygerrit-ui/app/models/views/search_test.ts
index 138ce1e..d48667b 100644
--- a/polygerrit-ui/app/models/views/search_test.ts
+++ b/polygerrit-ui/app/models/views/search_test.ts
@@ -23,6 +23,10 @@
         'topic:g%2525h+status:op%2525en'
     );
 
+    window.CANONICAL_PATH = '/base';
+    assert.equal(createSearchUrl(options).substring(0, 5), '/base');
+    window.CANONICAL_PATH = undefined;
+
     options.offset = 100;
     assert.equal(
       createSearchUrl(options),
diff --git a/polygerrit-ui/app/rollup.config.js b/polygerrit-ui/app/rollup.config.js
index 47492a3..be60a63 100644
--- a/polygerrit-ui/app/rollup.config.js
+++ b/polygerrit-ui/app/rollup.config.js
@@ -30,6 +30,7 @@
 
 const resolve = requirePlugin('rollup-plugin-node-resolve');
 const {terser} = requirePlugin('rollup-plugin-terser');
+const define = requirePlugin('rollup-plugin-define');
 
 // @polymer/font-roboto-local uses import.meta.url value
 // as a base path to fonts. We should substitute a correct javascript
@@ -75,5 +76,11 @@
       extensions: ['.js'],
       moduleDirectory: 'external/ui_npm/node_modules',
     },
-  }), importLocalFontMetaUrlResolver()],
+  }),
+  define({
+     replacements: {
+       'process.env.NODE_ENV': JSON.stringify('production'),
+     },
+  }),
+  importLocalFontMetaUrlResolver()],
 };
diff --git a/polygerrit-ui/app/rules.bzl b/polygerrit-ui/app/rules.bzl
index 1d5e577..9ab0f64 100644
--- a/polygerrit-ui/app/rules.bzl
+++ b/polygerrit-ui/app/rules.bzl
@@ -29,6 +29,7 @@
         silent = True,
         sourcemap = "hidden",
         deps = [
+            "@tools_npm//rollup-plugin-define",
             "@tools_npm//rollup-plugin-node-resolve",
         ],
     )
@@ -42,6 +43,7 @@
         silent = True,
         sourcemap = "hidden",
         deps = [
+            "@tools_npm//rollup-plugin-define",
             "@tools_npm//rollup-plugin-node-resolve",
         ],
     )
@@ -55,6 +57,7 @@
         silent = True,
         sourcemap = "hidden",
         deps = [
+            "@tools_npm//rollup-plugin-define",
             "@tools_npm//rollup-plugin-node-resolve",
         ],
     )
diff --git a/polygerrit-ui/app/services/router/router-model.ts b/polygerrit-ui/app/services/router/router-model.ts
index 99b9870..f8bc778 100644
--- a/polygerrit-ui/app/services/router/router-model.ts
+++ b/polygerrit-ui/app/services/router/router-model.ts
@@ -4,7 +4,6 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 import {Observable} from 'rxjs';
-import {distinctUntilChanged, map} from 'rxjs/operators';
 import {Finalizable} from '../registry';
 import {
   NumericChangeId,
@@ -12,6 +11,7 @@
   BasePatchSetNum,
 } from '../../types/common';
 import {Model} from '../../models/model';
+import {select} from '../../utils/observable-util';
 
 export enum GerritView {
   ADMIN = 'admin',
@@ -37,31 +37,23 @@
 }
 
 export class RouterModel extends Model<RouterState> implements Finalizable {
-  readonly routerView$: Observable<GerritView | undefined>;
+  readonly routerView$: Observable<GerritView | undefined> = select(
+    this.state$,
+    state => state.view
+  );
 
-  readonly routerChangeNum$: Observable<NumericChangeId | undefined>;
+  readonly routerChangeNum$: Observable<NumericChangeId | undefined> = select(
+    this.state$,
+    state => state.changeNum
+  );
 
-  readonly routerPatchNum$: Observable<RevisionPatchSetNum | undefined>;
+  readonly routerPatchNum$: Observable<RevisionPatchSetNum | undefined> =
+    select(this.state$, state => state.patchNum);
 
-  readonly routerBasePatchNum$: Observable<BasePatchSetNum | undefined>;
+  readonly routerBasePatchNum$: Observable<BasePatchSetNum | undefined> =
+    select(this.state$, state => state.basePatchNum);
 
   constructor() {
     super({});
-    this.routerView$ = this.state$.pipe(
-      map(state => state.view),
-      distinctUntilChanged()
-    );
-    this.routerChangeNum$ = this.state$.pipe(
-      map(state => state.changeNum),
-      distinctUntilChanged()
-    );
-    this.routerPatchNum$ = this.state$.pipe(
-      map(state => state.patchNum),
-      distinctUntilChanged()
-    );
-    this.routerBasePatchNum$ = this.state$.pipe(
-      map(state => state.basePatchNum),
-      distinctUntilChanged()
-    );
   }
 }
diff --git a/polygerrit-ui/app/services/service-worker-installer.ts b/polygerrit-ui/app/services/service-worker-installer.ts
index 0eec23a..53cd325 100644
--- a/polygerrit-ui/app/services/service-worker-installer.ts
+++ b/polygerrit-ui/app/services/service-worker-installer.ts
@@ -16,6 +16,7 @@
 /** Type of incoming messages for ServiceWorker. */
 export enum ServiceWorkerMessageType {
   TRIGGER_NOTIFICATIONS = 'TRIGGER_NOTIFICATIONS',
+  USER_PREFERENCE_CHANGE = 'USER_PREFERENCE_CHANGE',
 }
 
 export const TRIGGER_NOTIFICATION_UPDATES_MS = 5 * 60 * 1000;
@@ -25,33 +26,48 @@
 
   account?: AccountDetailInfo;
 
+  allowBrowserNotificationsPreference?: boolean;
+
   constructor(
     private readonly flagsService: FlagsService,
     private readonly userModel: UserModel
   ) {
+    if (!this.flagsService.isEnabled(KnownExperimentId.PUSH_NOTIFICATIONS)) {
+      return;
+    }
     this.userModel.account$.subscribe(acc => (this.account = acc));
+    this.userModel.preferences$.subscribe(prefs => {
+      if (
+        this.allowBrowserNotificationsPreference !==
+        prefs.allow_browser_notifications
+      ) {
+        this.allowBrowserNotificationsPreference =
+          prefs.allow_browser_notifications;
+        navigator.serviceWorker.controller?.postMessage({
+          type: ServiceWorkerMessageType.USER_PREFERENCE_CHANGE,
+          allowBrowserNotificationsPreference:
+            this.allowBrowserNotificationsPreference,
+        });
+      }
+    });
+    Promise.all([
+      until(this.userModel.account$, account => !!account),
+      until(
+        this.userModel.preferences$,
+        prefs => !!prefs.allow_browser_notifications
+      ),
+    ]).then(() => {
+      this.init();
+    });
   }
 
-  async init() {
+  private async init() {
     if (this.initialized) return;
-    if (
-      !this.flagsService.isEnabled(
-        KnownExperimentId.PUSH_NOTIFICATIONS_DEVELOPER
-      )
-    ) {
-      if (!this.flagsService.isEnabled(KnownExperimentId.PUSH_NOTIFICATIONS)) {
-        return;
-      }
-      const timeout1s = new Promise(resolve => {
-        setTimeout(resolve, 1000);
-      });
-      // We wait for account to be defined, if its not defined in 1s, it's guest
-      await Promise.race([
-        timeout1s,
-        until(this.userModel.account$, account => !!account),
-      ]);
-      if (!areNotificationsEnabled(this.account)) return;
+    if (!this.flagsService.isEnabled(KnownExperimentId.PUSH_NOTIFICATIONS)) {
+      return;
     }
+    if (!this.areNotificationsEnabled()) return;
+
     if (!('serviceWorker' in navigator)) {
       console.error('Service worker API not available');
       return;
@@ -62,6 +78,21 @@
     this.initialized = true;
   }
 
+  areNotificationsEnabled() {
+    // Push Notification developer can have notification enabled even if they
+    // are disabled for this.account.
+    if (
+      !this.flagsService.isEnabled(
+        KnownExperimentId.PUSH_NOTIFICATIONS_DEVELOPER
+      ) &&
+      !areNotificationsEnabled(this.account)
+    ) {
+      return false;
+    }
+
+    return this.allowBrowserNotificationsPreference;
+  }
+
   /**
    * Every 5 minutes, we trigger service-worker to get
    * latest updates in attention set and service-worker will create
diff --git a/polygerrit-ui/app/services/service-worker-installer_test.ts b/polygerrit-ui/app/services/service-worker-installer_test.ts
index 77dd907d..e8fd233 100644
--- a/polygerrit-ui/app/services/service-worker-installer_test.ts
+++ b/polygerrit-ui/app/services/service-worker-installer_test.ts
@@ -7,23 +7,29 @@
 import '../test/common-test-setup';
 import {ServiceWorkerInstaller} from './service-worker-installer';
 import {assert} from '@open-wc/testing';
+import {createDefaultPreferences} from '../constants/constants';
+import {waitUntilObserved} from '../test/test-utils';
 
-suite('service woerker installler tests', () => {
-  let serviceWorkerInstaller: ServiceWorkerInstaller;
-
-  setup(() => {
+suite('service worker installer tests', () => {
+  test('init', async () => {
+    const registerStub = sinon.stub(window.navigator.serviceWorker, 'register');
     const flagsService = getAppContext().flagsService;
     const userModel = getAppContext().userModel;
     sinon.stub(flagsService, 'isEnabled').returns(true);
-    serviceWorkerInstaller = new ServiceWorkerInstaller(
-      flagsService,
-      userModel
+    new ServiceWorkerInstaller(flagsService, userModel);
+    const prefs = {
+      ...createDefaultPreferences(),
+      allow_browser_notifications: true,
+    };
+    userModel.setPreferences(prefs);
+    await waitUntilObserved(
+      userModel.preferences$,
+      pref => pref.allow_browser_notifications === true
     );
-  });
-
-  test('init', () => {
-    const registerStub = sinon.stub(window.navigator.serviceWorker, 'register');
-    serviceWorkerInstaller.init();
+    await waitUntilObserved(
+      userModel.preferences$,
+      pref => pref.allow_browser_notifications === true
+    );
     assert.isTrue(registerStub.called);
   });
 });
diff --git a/polygerrit-ui/app/styles/themes/app-theme.ts b/polygerrit-ui/app/styles/themes/app-theme.ts
index 117e7cc..e148da9 100644
--- a/polygerrit-ui/app/styles/themes/app-theme.ts
+++ b/polygerrit-ui/app/styles/themes/app-theme.ts
@@ -99,6 +99,8 @@
     --purple-100: #e9d2fd;
     --purple-50: #f3e8fd;
     --purple-tonal: #523272;
+    --deep-purple-800: #4527a0;
+    --deep-purple-600: #5e35b1;
     --pink-800: #b80672;
     --pink-500: #f538a0;
     --pink-50: #fde7f3;
diff --git a/polygerrit-ui/app/styles/themes/dark-theme.ts b/polygerrit-ui/app/styles/themes/dark-theme.ts
index d11e372..2330041 100644
--- a/polygerrit-ui/app/styles/themes/dark-theme.ts
+++ b/polygerrit-ui/app/styles/themes/dark-theme.ts
@@ -219,8 +219,8 @@
     --dark-remove-highlight-color: #62110f;
     --light-remove-highlight-color: #320404;
 
-    --dark-rebased-add-highlight-color: rgba(11, 255, 155, 0.15);
-    --light-rebased-add-highlight-color: #487165;
+    --dark-rebased-add-highlight-color: var(--deep-purple-800);
+    --light-rebased-add-highlight-color: var(--deep-purple-600);
     --dark-rebased-remove-highlight-color: rgba(255, 139, 6, 0.15);
     --light-rebased-remove-highlight-color: #2f3f2f;
 
diff --git a/polygerrit-ui/app/test/test-data-generators.ts b/polygerrit-ui/app/test/test-data-generators.ts
index 9337500..4e29f53 100644
--- a/polygerrit-ui/app/test/test-data-generators.ts
+++ b/polygerrit-ui/app/test/test-data-generators.ts
@@ -686,6 +686,7 @@
     change_table: [],
     email_strategy: EmailStrategy.ENABLED,
     default_base_for_merges: DefaultBase.AUTO_MERGE,
+    allow_browser_notifications: true,
   };
 }
 
diff --git a/polygerrit-ui/app/types/common.ts b/polygerrit-ui/app/types/common.ts
index 523dadb..008a8de 100644
--- a/polygerrit-ui/app/types/common.ts
+++ b/polygerrit-ui/app/types/common.ts
@@ -1122,6 +1122,7 @@
   work_in_progress_by_default?: boolean;
   // The email_format doesn't mentioned in doc, but exists in Java class GeneralPreferencesInfo
   email_format?: EmailFormat;
+  allow_browser_notifications?: boolean;
 }
 
 /**
diff --git a/polygerrit-ui/app/types/events.ts b/polygerrit-ui/app/types/events.ts
index 597bb6f..496513d 100644
--- a/polygerrit-ui/app/types/events.ts
+++ b/polygerrit-ui/app/types/events.ts
@@ -209,9 +209,7 @@
 // Type for the custom event to switch tab.
 export interface SwitchTabEventDetail {
   // name of the tab to set as active, from custom event
-  tab?: string;
-  // index of tab to set as active, from paper-tabs event
-  value?: number;
+  tab: string;
   // scroll into the tab afterwards, from custom event
   scrollIntoView?: boolean;
   // define state of tab after opening
diff --git a/polygerrit-ui/app/utils/change-util.ts b/polygerrit-ui/app/utils/change-util.ts
index 07b63d6..9062ac7 100644
--- a/polygerrit-ui/app/utils/change-util.ts
+++ b/polygerrit-ui/app/utils/change-util.ts
@@ -282,7 +282,9 @@
   change?: ChangeInfo,
   reviewer?: AccountInfo
 ): boolean {
-  if (!change?.removable_reviewers || !reviewer) return false;
+  if (!reviewer || !change) return false;
+  if (isCc(change, reviewer)) return true;
+  if (!change.removable_reviewers) return false;
   return change.removable_reviewers.some(
     account =>
       account._account_id === reviewer._account_id ||
diff --git a/polygerrit-ui/app/utils/common-util.ts b/polygerrit-ui/app/utils/common-util.ts
index 05c054b..183d167 100644
--- a/polygerrit-ui/app/utils/common-util.ts
+++ b/polygerrit-ui/app/utils/common-util.ts
@@ -117,7 +117,7 @@
 /**
  * Add value, if the set does not contain it. Otherwise remove it.
  */
-export function toggleSetMembership<T>(set: Set<T>, value: T): void {
+export function toggleSet<T>(set: Set<T>, value: T): void {
   if (set.has(value)) {
     set.delete(value);
   } else {
@@ -125,6 +125,14 @@
   }
 }
 
+export function toggle<T>(array: T[], item: T): T[] {
+  if (array.includes(item)) {
+    return array.filter(r => r !== item);
+  } else {
+    return array.concat([item]);
+  }
+}
+
 export function unique<T>(item: T, index: number, array: T[]) {
   return array.indexOf(item) === index;
 }
diff --git a/polygerrit-ui/app/utils/common-util_test.ts b/polygerrit-ui/app/utils/common-util_test.ts
index 0d85f34..76c8a6c 100644
--- a/polygerrit-ui/app/utils/common-util_test.ts
+++ b/polygerrit-ui/app/utils/common-util_test.ts
@@ -11,6 +11,7 @@
   containsAll,
   intersection,
   difference,
+  toggle,
 } from './common-util';
 
 suite('common-util tests', () => {
@@ -97,4 +98,11 @@
     assert.deepEqual(difference([1, 2, 3], [1, 2, 3]), []);
     assert.deepEqual(difference([1, 2, 3], [4, 5, 6]), [1, 2, 3]);
   });
+
+  test('toggle', () => {
+    assert.deepEqual(toggle([], 1), [1]);
+    assert.deepEqual(toggle([1], 1), []);
+    assert.deepEqual(toggle([1, 2, 3], 1), [2, 3]);
+    assert.deepEqual(toggle([2, 3], 1), [2, 3, 1]);
+  });
 });
diff --git a/polygerrit-ui/app/utils/link-util.ts b/polygerrit-ui/app/utils/link-util.ts
index 9079f4c..b5b9025 100644
--- a/polygerrit-ui/app/utils/link-util.ts
+++ b/polygerrit-ui/app/utils/link-util.ts
@@ -4,76 +4,164 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 import 'ba-linkify/ba-linkify';
-import {CommentLinks} from '../types/common';
+import {CommentLinkInfo, CommentLinks} from '../types/common';
 import {getBaseUrl} from './url-util';
 
-export function linkifyNormalUrls(base: string): string {
-  // Some tools are known to look for reviewers/CCs by finding lines such as
-  // "R=foo@gmail.com, bar@gmail.com". However, "=" is technically a valid email
-  // character, so ba-linkify interprets the entire string "R=foo@gmail.com" as
-  // an email address. To fix this, we insert a zero width space character
-  // \u200B before linking that prevents ba-linkify from associating the prefix
-  // with the email. After linking we remove the zero width space.
-  const baseWithZeroWidthSpace = base.replace(/^(R=|CC=)/g, '$&\u200B');
+/**
+ * Finds links within the base string and convert them to HTML. Config-based
+ * rewrites are only applied on text that is not linked by the default linking
+ * library.
+ */
+export function linkifyUrlsAndApplyRewrite(
+  base: string,
+  repoCommentLinks: CommentLinks
+): string {
   const parts: string[] = [];
-  window.linkify(baseWithZeroWidthSpace, {
+  window.linkify(insertZeroWidthSpace(base), {
     callback: (text, href) => {
-      const result = href ? createLinkTemplate(href, text) : text;
-      const resultWithoutZeroWidthSpace = result.replace(/\u200B/g, '');
-      parts.push(resultWithoutZeroWidthSpace);
+      if (href) {
+        parts.push(removeZeroWidthSpace(createLinkTemplate(href, text)));
+      } else {
+        const rewriteResults = getRewriteResultsFromConfig(
+          text,
+          repoCommentLinks
+        );
+        parts.push(removeZeroWidthSpace(applyRewrites(text, rewriteResults)));
+      }
     },
   });
   return parts.join('');
 }
 
-export function applyLinkRewritesFromConfig(
+/**
+ * Generates a list of rewrites that would be applied to a base string. They are
+ * not applied immediately to the base text because one rewrite may interfere or
+ * overlap with a later rewrite. Only after all rewrites are known they are
+ * carefully merged with `applyRewrites`.
+ */
+function getRewriteResultsFromConfig(
   base: string,
   repoCommentLinks: CommentLinks
-) {
-  const linkRewritesFromConfig = Object.values(repoCommentLinks).filter(
-    commentLinkInfo => commentLinkInfo.enabled !== false && commentLinkInfo.link
+): RewriteResult[] {
+  const enabledRewrites = Object.values(repoCommentLinks).filter(
+    commentLinkInfo =>
+      commentLinkInfo.enabled !== false &&
+      (commentLinkInfo.link !== undefined || commentLinkInfo.html !== undefined)
   );
-  const rewrites = linkRewritesFromConfig.map(rewrite => {
-    const replacementHref = rewrite.link!.startsWith('/')
-      ? `${getBaseUrl()}${rewrite.link!}`
-      : rewrite.link!;
-    return {
-      match: new RegExp(rewrite.match, 'g'),
-      replace: createLinkTemplate(
+  return enabledRewrites.flatMap(rewrite => {
+    const regexp = new RegExp(rewrite.match, 'g');
+    const partialResults: RewriteResult[] = [];
+    let match: RegExpExecArray | null;
+
+    while ((match = regexp.exec(base)) !== null) {
+      const fullReplacementText = getReplacementText(match[0], rewrite);
+      // The replacement may not be changing the entire matched substring so we
+      // "trim" the replacement position and text to the part that is actually
+      // different. This makes sure that unchanged portions are still eligible
+      // for other rewrites without being rejected as overlaps during
+      // `applyRewrites`. The new `replacementText` is not eligible for other
+      // rewrites since it would introduce unexpected interactions between
+      // rewrites depending on their order of definition/execution.
+      const sharedPrefixLength = getSharedPrefixLength(
+        match[0],
+        fullReplacementText
+      );
+      const sharedSuffixLength = getSharedSuffixLength(
+        match[0],
+        fullReplacementText
+      );
+      const prefixIndex = sharedPrefixLength;
+      const matchSuffixIndex = match[0].length - sharedSuffixLength;
+      const fullReplacementSuffixIndex =
+        fullReplacementText.length - sharedSuffixLength;
+      partialResults.push({
+        replacedTextStartPosition: match.index + prefixIndex,
+        replacedTextEndPosition: match.index + matchSuffixIndex,
+        replacementText: fullReplacementText.substring(
+          prefixIndex,
+          fullReplacementSuffixIndex
+        ),
+      });
+    }
+    return partialResults;
+  });
+}
+
+/**
+ * Applies all the rewrites to the given base string. To resolve cases where
+ * multiple rewrites target overlapping pieces of the base string, the rewrite
+ * that ends latest is kept and the rest are not applied and discarded.
+ */
+function applyRewrites(base: string, rewriteResults: RewriteResult[]): string {
+  const rewritesByEndPosition = [...rewriteResults].sort((a, b) => {
+    if (b.replacedTextEndPosition !== a.replacedTextEndPosition) {
+      return b.replacedTextEndPosition - a.replacedTextEndPosition;
+    }
+    return a.replacedTextStartPosition - b.replacedTextStartPosition;
+  });
+  const filteredSortedRewrites: RewriteResult[] = [];
+  let latestReplace = base.length;
+  for (const rewrite of rewritesByEndPosition) {
+    // Only accept rewrites that do not overlap with any previously accepted
+    // rewrites.
+    if (rewrite.replacedTextEndPosition <= latestReplace) {
+      filteredSortedRewrites.push(rewrite);
+      latestReplace = rewrite.replacedTextStartPosition;
+    }
+  }
+  return filteredSortedRewrites.reduce(
+    (text, rewrite) =>
+      text
+        .substring(0, rewrite.replacedTextStartPosition)
+        .concat(rewrite.replacementText)
+        .concat(text.substring(rewrite.replacedTextEndPosition)),
+    base
+  );
+}
+
+/**
+ * For a given regexp match, apply the rewrite based on the rewrite's type and
+ * return the resulting string.
+ */
+function getReplacementText(
+  matchedText: string,
+  rewrite: CommentLinkInfo
+): string {
+  if (rewrite.link !== undefined) {
+    const replacementHref = rewrite.link.startsWith('/')
+      ? `${getBaseUrl()}${rewrite.link}`
+      : rewrite.link;
+    const regexp = new RegExp(rewrite.match, 'g');
+    return matchedText.replace(
+      regexp,
+      createLinkTemplate(
         replacementHref,
         rewrite.text ?? '$&',
         rewrite.prefix,
         rewrite.suffix
-      ),
-    };
-  });
-  return applyRewrites(base, rewrites);
+      )
+    );
+  } else if (rewrite.html !== undefined) {
+    return matchedText.replace(new RegExp(rewrite.match, 'g'), rewrite.html);
+  } else {
+    throw new Error('commentLinkInfo is not a link or html rewrite');
+  }
 }
 
-export function applyHtmlRewritesFromConfig(
-  base: string,
-  repoCommentLinks: CommentLinks
-) {
-  const htmlRewritesFromConfig = Object.values(repoCommentLinks).filter(
-    commentLinkInfo => commentLinkInfo.enabled !== false && commentLinkInfo.html
-  );
-  const rewrites = htmlRewritesFromConfig.map(rewrite => {
-    return {
-      match: new RegExp(rewrite.match, 'g'),
-      replace: rewrite.html!,
-    };
-  });
-  return applyRewrites(base, rewrites);
+/**
+ * Some tools are known to look for reviewers/CCs by finding lines such as
+ * "R=foo@gmail.com, bar@gmail.com". However, "=" is technically a valid email
+ * character, so ba-linkify interprets the entire string "R=foo@gmail.com" as an
+ * email address. To fix this, we insert a zero width space character \u200B
+ * before linking that prevents ba-linkify from associating the prefix with the
+ * email. After linking we remove the zero width space.
+ */
+function insertZeroWidthSpace(base: string) {
+  return base.replace(/^(R=|CC=)/g, '$&\u200B');
 }
 
-function applyRewrites(
-  base: string,
-  rewrites: {match: RegExp | string; replace: string}[]
-) {
-  return rewrites.reduce(
-    (text, rewrite) => text.replace(rewrite.match, rewrite.replace),
-    base
-  );
+function removeZeroWidthSpace(base: string) {
+  return base.replace(/\u200B/g, '');
 }
 
 function createLinkTemplate(
@@ -88,3 +176,41 @@
     suffix ?? ''
   }`;
 }
+
+/**
+ * Returns the number of characters that are identical at the start of both
+ * strings.
+ *
+ * For example, `getSharedPrefixLength('12345678', '1234zz78')` would return 4
+ */
+function getSharedPrefixLength(a: string, b: string) {
+  let i = 0;
+  for (; i < a.length && i < b.length; ++i) {
+    if (a[i] !== b[i]) {
+      return i;
+    }
+  }
+  return i;
+}
+
+/**
+ * Returns the number of characters that are identical at the end of both
+ * strings.
+ *
+ * For example, `getSharedSuffixLength('12345678', '1234zz78')` would return 2
+ */
+function getSharedSuffixLength(a: string, b: string) {
+  let i = a.length;
+  for (let j = b.length; i !== 0 && j !== 0; --i, --j) {
+    if (a[i] !== b[j]) {
+      return a.length - 1 - i;
+    }
+  }
+  return a.length - i;
+}
+
+interface RewriteResult {
+  replacedTextStartPosition: number;
+  replacedTextEndPosition: number;
+  replacementText: string;
+}
diff --git a/polygerrit-ui/app/utils/link-util_test.ts b/polygerrit-ui/app/utils/link-util_test.ts
index a1ec2fa..61d6bff 100644
--- a/polygerrit-ui/app/utils/link-util_test.ts
+++ b/polygerrit-ui/app/utils/link-util_test.ts
@@ -3,11 +3,7 @@
  * Copyright 2022 Google LLC
  * SPDX-License-Identifier: Apache-2.0
  */
-import {
-  applyHtmlRewritesFromConfig,
-  applyLinkRewritesFromConfig,
-  linkifyNormalUrls,
-} from './link-util';
+import {linkifyUrlsAndApplyRewrite} from './link-util';
 import {assert} from '@open-wc/testing';
 
 suite('link-util tests', () => {
@@ -15,55 +11,220 @@
     return `<a href="${href}" rel="noopener" target="_blank">${text}</a>`;
   }
 
-  test('applyHtmlRewritesFromConfig', () => {
-    assert.equal(
-      applyHtmlRewritesFromConfig('#12345 foo', {
-        'number-emphasizer': {
-          match: '#(\\d+)',
-          html: '<h1>Change $1 is the best change</h1>',
-        },
-        'foo-capitalizer': {
-          match: 'foo',
-          html: '<div>FOO</div>',
-        },
-      }),
-      '<h1>Change 12345 is the best change</h1> <div>FOO</div>'
-    );
+  suite('link rewrites', () => {
+    test('without text', () => {
+      assert.equal(
+        linkifyUrlsAndApplyRewrite('foo', {
+          fooLinkWithoutText: {
+            match: 'foo',
+            link: 'foo.gov',
+          },
+        }),
+        link('foo', 'foo.gov')
+      );
+    });
+
+    test('with text', () => {
+      assert.equal(
+        linkifyUrlsAndApplyRewrite('foo', {
+          fooLinkWithText: {
+            match: 'foo',
+            link: 'foo.gov',
+            text: 'foo site',
+          },
+        }),
+        link('foo site', 'foo.gov')
+      );
+    });
+
+    test('with prefix and suffix', () => {
+      assert.equal(
+        linkifyUrlsAndApplyRewrite('there are 12 foos here', {
+          fooLinkWithText: {
+            match: '(.*)(bug|foo)s(.*)',
+            link: '$2.gov',
+            text: '$2 list',
+            prefix: '$1on the ',
+            suffix: '$3',
+          },
+        }),
+        `there are 12 on the ${link('foo list', 'foo.gov')} here`
+      );
+    });
+
+    test('multiple matches', () => {
+      assert.equal(
+        linkifyUrlsAndApplyRewrite('foo foo', {
+          foo: {
+            match: 'foo',
+            link: 'foo.gov',
+          },
+        }),
+        `${link('foo', 'foo.gov')} ${link('foo', 'foo.gov')}`
+      );
+    });
+
+    test('does not apply within normal links', () => {
+      assert.equal(
+        linkifyUrlsAndApplyRewrite('google.com', {
+          ogle: {
+            match: 'ogle',
+            link: 'gerritcodereview.com',
+          },
+        }),
+        link('google.com', 'http://google.com')
+      );
+    });
+  });
+  suite('html rewrites', () => {
+    test('basic case', () => {
+      assert.equal(
+        linkifyUrlsAndApplyRewrite('foo', {
+          foo: {
+            match: '(foo)',
+            html: '<div>$1</div>',
+          },
+        }),
+        '<div>foo</div>'
+      );
+    });
+
+    test('only inserts', () => {
+      assert.equal(
+        linkifyUrlsAndApplyRewrite('foo', {
+          foo: {
+            match: 'foo',
+            html: 'foo bar',
+          },
+        }),
+        'foo bar'
+      );
+    });
+
+    test('only deletes', () => {
+      assert.equal(
+        linkifyUrlsAndApplyRewrite('foo bar baz', {
+          bar: {
+            match: 'bar',
+            html: '',
+          },
+        }),
+        'foo  baz'
+      );
+    });
+
+    test('multiple matches', () => {
+      assert.equal(
+        linkifyUrlsAndApplyRewrite('foo foo', {
+          foo: {
+            match: '(foo)',
+            html: '<div>$1</div>',
+          },
+        }),
+        '<div>foo</div> <div>foo</div>'
+      );
+    });
+
+    test('does not apply within normal links', () => {
+      assert.equal(
+        linkifyUrlsAndApplyRewrite('google.com', {
+          ogle: {
+            match: 'ogle',
+            html: '<div>gerritcodereview.com<div>',
+          },
+        }),
+        link('google.com', 'http://google.com')
+      );
+    });
   });
 
-  test('applyLinkRewritesFromConfig', () => {
-    const linkedNumber = link('#12345', 'google.com/12345');
-    const linkedFoo = link('foo', 'foo.gov');
-    const linkedBar = link('Bar Page: 300', 'bar.com/page?id=300');
+  test('for overlapping rewrites prefer the latest ending', () => {
     assert.equal(
-      applyLinkRewritesFromConfig('#12345 foo crowbar:12 bar:300', {
-        'number-linker': {
-          match: '#(\\d+)',
-          link: 'google.com/$1',
-        },
-        'foo-linker': {
+      linkifyUrlsAndApplyRewrite('foobarbaz', {
+        foo: {
           match: 'foo',
           link: 'foo.gov',
         },
-        'advanced-link': {
-          match: '(^|\\s)bar:(\\d+)($|\\s)',
-          link: 'bar.com/page?id=$2',
-          text: 'Bar Page: $2',
-          prefix: '$1',
-          suffix: '$3',
+        foobarbaz: {
+          match: 'foobarbaz',
+          html: '<div>foobarbaz.gov</div>',
+        },
+        foobar: {
+          match: 'foobar',
+          link: 'foobar.gov',
         },
       }),
-      `${linkedNumber} ${linkedFoo} crowbar:12 ${linkedBar}`
+      '<div>foobarbaz.gov</div>'
     );
   });
 
-  suite('linkifyNormalUrls', () => {
+  test('overlapping rewrites with same ending prefers earliest start', () => {
+    assert.equal(
+      linkifyUrlsAndApplyRewrite('foobarbaz', {
+        foo: {
+          match: 'baz',
+          link: 'Baz.gov',
+        },
+        foobarbaz: {
+          match: 'foobarbaz',
+          html: '<div>FooBarBaz.gov</div>',
+        },
+        foobar: {
+          match: 'barbaz',
+          link: 'BarBaz.gov',
+        },
+      }),
+      '<div>FooBarBaz.gov</div>'
+    );
+  });
+
+  test('removed overlapping rewrites do not prevent other rewrites', () => {
+    assert.equal(
+      linkifyUrlsAndApplyRewrite('foobarbaz', {
+        foo: {
+          match: 'foo',
+          html: 'FOO',
+        },
+        oobarba: {
+          match: 'oobarba',
+          html: 'OOBARBA',
+        },
+        baz: {
+          match: 'baz',
+          html: 'BAZ',
+        },
+      }),
+      'FOObarBAZ'
+    );
+  });
+
+  test('rewrites do not interfere with each other matching', () => {
+    assert.equal(
+      linkifyUrlsAndApplyRewrite('bugs: 123 234 345', {
+        bug1: {
+          match: '(bugs:) (\\d+)',
+          html: '$1 <div>bug/$2</div>',
+        },
+        bug2: {
+          match: '(bugs:) (\\d+) (\\d+)',
+          html: '$1 $2 <div>bug/$3</div>',
+        },
+        bug3: {
+          match: '(bugs:) (\\d+) (\\d+) (\\d+)',
+          html: '$1 $2 $3 <div>bug/$4</div>',
+        },
+      }),
+      'bugs: <div>bug/123</div> <div>bug/234</div> <div>bug/345</div>'
+    );
+  });
+
+  suite('normal links', () => {
     test('links urls', () => {
       const googleLink = link('google.com', 'http://google.com');
       const mapsLink = link('maps.google.com', 'http://maps.google.com');
 
       assert.equal(
-        linkifyNormalUrls('google.com, maps.google.com'),
+        linkifyUrlsAndApplyRewrite('google.com, maps.google.com', {}),
         `${googleLink}, ${mapsLink}`
       );
     });
@@ -72,7 +233,7 @@
       const fooEmail = link('foo@gmail.com', 'mailto:foo@gmail.com');
       const barEmail = link('bar@gmail.com', 'mailto:bar@gmail.com');
       assert.equal(
-        linkifyNormalUrls('R=foo@gmail.com, bar@gmail.com'),
+        linkifyUrlsAndApplyRewrite('R=foo@gmail.com, bar@gmail.com', {}),
         `R=${fooEmail}, ${barEmail}`
       );
     });
@@ -81,7 +242,7 @@
       const fooEmail = link('foo@gmail.com', 'mailto:foo@gmail.com');
       const barEmail = link('bar@gmail.com', 'mailto:bar@gmail.com');
       assert.equal(
-        linkifyNormalUrls('CC=foo@gmail.com, bar@gmail.com'),
+        linkifyUrlsAndApplyRewrite('CC=foo@gmail.com, bar@gmail.com', {}),
         `CC=${fooEmail}, ${barEmail}`
       );
     });
@@ -92,7 +253,7 @@
         'mailto:fooR=barCC=baz@gmail.com'
       );
       assert.equal(
-        linkifyNormalUrls('fooR=barCC=baz@gmail.com'),
+        linkifyUrlsAndApplyRewrite('fooR=barCC=baz@gmail.com', {}),
         fooBarBazEmail
       );
     });
diff --git a/polygerrit-ui/app/utils/string-util_test.ts b/polygerrit-ui/app/utils/string-util_test.ts
index 0a7ee27..c6c65b1 100644
--- a/polygerrit-ui/app/utils/string-util_test.ts
+++ b/polygerrit-ui/app/utils/string-util_test.ts
@@ -12,7 +12,7 @@
   diffFilePaths,
 } from './string-util';
 
-suite('formatter util tests', () => {
+suite('string-util tests', () => {
   test('pluralize', () => {
     const noun = 'comment';
     assert.equal(pluralize(0, noun), '');
diff --git a/polygerrit-ui/app/workers/service-worker-class.ts b/polygerrit-ui/app/workers/service-worker-class.ts
index c257d8d..218744d 100644
--- a/polygerrit-ui/app/workers/service-worker-class.ts
+++ b/polygerrit-ui/app/workers/service-worker-class.ts
@@ -27,6 +27,8 @@
   // private but used in test
   latestUpdateTimestampMs = Date.now();
 
+  allowBrowserNotificationsPreference = false;
+
   /**
    * We cannot rely on a state in a service worker, because every time
    * service worker starts or stops, new instance is created. So every time
@@ -44,6 +46,8 @@
   saveState() {
     return putServiceWorkerState({
       latestUpdateTimestampMs: this.latestUpdateTimestampMs,
+      allowBrowserNotificationsPreference:
+        this.allowBrowserNotificationsPreference,
     });
   }
 
@@ -51,19 +55,27 @@
     const state = await getServiceWorkerState();
     if (state) {
       this.latestUpdateTimestampMs = state.latestUpdateTimestampMs;
+      this.allowBrowserNotificationsPreference =
+        state.allowBrowserNotificationsPreference;
     }
   }
 
   private onMessage(e: ExtendableMessageEvent) {
-    if (e.data?.type !== ServiceWorkerMessageType.TRIGGER_NOTIFICATIONS) {
-      // Only this notification message type exists, but we do not throw error.
-      return;
+    if (e.data?.type === ServiceWorkerMessageType.TRIGGER_NOTIFICATIONS) {
+      e.waitUntil(
+        this.showLatestAttentionChangeNotification(
+          e.data?.account as AccountDetailInfo | undefined
+        )
+      );
+    } else if (
+      e.data?.type === ServiceWorkerMessageType.USER_PREFERENCE_CHANGE
+    ) {
+      e.waitUntil(
+        this.allowBrowserNotificationsPreferenceChanged(
+          e.data?.allowBrowserNotificationsPreference as boolean
+        )
+      );
     }
-    e.waitUntil(
-      this.showLatestAttentionChangeNotification(
-        e.data?.account as AccountDetailInfo | undefined
-      )
-    );
   }
 
   private onNotificationClick(e: NotificationEvent) {
@@ -71,10 +83,16 @@
     e.waitUntil(this.openWindow(e.notification.data.url));
   }
 
+  async allowBrowserNotificationsPreferenceChanged(preference: boolean) {
+    this.allowBrowserNotificationsPreference = preference;
+    await this.saveState();
+  }
+
   // private but used in test
   async showLatestAttentionChangeNotification(account?: AccountDetailInfo) {
     // Message always contains account, but we do not throw error.
     if (!account?._account_id) return;
+    if (!this.allowBrowserNotificationsPreference) return;
     const latestAttentionChanges = await this.getChangesToNotify(account);
     const numOfChangesToNotifyAbout = latestAttentionChanges.length;
     if (numOfChangesToNotifyAbout === 1) {
diff --git a/polygerrit-ui/app/workers/service-worker-class_test.ts b/polygerrit-ui/app/workers/service-worker-class_test.ts
index 8b508e8..4cbd7bb 100644
--- a/polygerrit-ui/app/workers/service-worker-class_test.ts
+++ b/polygerrit-ui/app/workers/service-worker-class_test.ts
@@ -25,6 +25,7 @@
       },
     } as {} as ServiceWorkerGlobalScope;
     serviceWorker = new ServiceWorker(moctCtx);
+    serviceWorker.allowBrowserNotificationsPreference = true;
   });
 
   test('notify about attention in t2 when time is t3', async () => {
diff --git a/polygerrit-ui/app/workers/service-worker-indexdb.ts b/polygerrit-ui/app/workers/service-worker-indexdb.ts
index f540d59..6d5ab40 100644
--- a/polygerrit-ui/app/workers/service-worker-indexdb.ts
+++ b/polygerrit-ui/app/workers/service-worker-indexdb.ts
@@ -6,6 +6,7 @@
 
 export interface GerritServiceWorkerState {
   latestUpdateTimestampMs: number;
+  allowBrowserNotificationsPreference: boolean;
 }
 
 const SERVICE_WORKER_DB = 'service-worker-db-1';
diff --git a/tools/node_tools/package.json b/tools/node_tools/package.json
index fc00451..3765575 100644
--- a/tools/node_tools/package.json
+++ b/tools/node_tools/package.json
@@ -15,6 +15,7 @@
     "polymer-bundler": "^4.0.10",
     "rollup": "^2.3.4",
     "rollup-plugin-commonjs": "^10.1.0",
+    "rollup-plugin-define": "^1.0.1",
     "rollup-plugin-node-resolve": "^5.2.0",
     "rollup-plugin-terser": "^5.1.3",
     "typescript": "^4.7.2"
diff --git a/tools/node_tools/yarn.lock b/tools/node_tools/yarn.lock
index 3914e17..c6b3eab 100644
--- a/tools/node_tools/yarn.lock
+++ b/tools/node_tools/yarn.lock
@@ -216,6 +216,14 @@
   resolved "https://registry.yarnpkg.com/@protobufjs/utf8/-/utf8-1.1.0.tgz#a777360b5b39a1a2e5106f8e858f2fd2d060c570"
   integrity sha512-Vvn3zZrhQZkkBE8LSuW3em98c0FwgO4nxzv6OdSxPKJIEKY2bGbHn+mhGIPerzI4twdxaP8/0+06HBpwf345Lw==
 
+"@rollup/pluginutils@^4.0.0":
+  version "4.2.1"
+  resolved "https://registry.yarnpkg.com/@rollup/pluginutils/-/pluginutils-4.2.1.tgz#e6c6c3aba0744edce3fb2074922d3776c0af2a6d"
+  integrity sha512-iKnFXr7NkdZAIHiIWE+BX5ULi/ucVFYWD6TbAV+rZctiRTY2PL6tsIKhoIOaoskiWAkgu+VsbXgUVDNLHf+InQ==
+  dependencies:
+    estree-walker "^2.0.1"
+    picomatch "^2.2.2"
+
 "@sindresorhus/is@^4.0.0":
   version "4.6.0"
   resolved "https://registry.yarnpkg.com/@sindresorhus/is/-/is-4.6.0.tgz#3c7c9c46e678feefe7a2e5bb609d3dbd665ffb3f"
@@ -576,6 +584,11 @@
   resolved "https://registry.yarnpkg.com/array-back/-/array-back-3.1.0.tgz#b8859d7a508871c9a7b2cf42f99428f65e96bfb0"
   integrity sha512-TkuxA4UCOvxuDK6NZYXCalszEzj+TLszyASooky+i742l9TqsOdYCMJJupxRic61hwquNtppB3hgcuq9SVSH1Q==
 
+ast-matcher@^1.1.1:
+  version "1.1.1"
+  resolved "https://registry.yarnpkg.com/ast-matcher/-/ast-matcher-1.1.1.tgz#95a6dc72318319507024fff438b7839e4e280813"
+  integrity sha512-wQPAp09kPFRQsOijM2Blfg4lH6B9MIhIUrhFtDdhD/1JFhPmfg2/+WAjViVYl3N7EwleHI+q/enTHjaDrv+wEw==
+
 async@^2.0.1:
   version "2.6.4"
   resolved "https://registry.yarnpkg.com/async/-/async-2.6.4.tgz#706b7ff6084664cd7eae713f6f965433b5504221"
@@ -985,6 +998,11 @@
   resolved "https://registry.yarnpkg.com/escape-string-regexp/-/escape-string-regexp-1.0.5.tgz#1b61c0562190a8dff6ae3bb2cf0200ca130b86d4"
   integrity sha512-vbRorB5FUQWvla16U8R/qgaFIya2qGzwDrNmCZuYKrbdSUMG6I1ZCGQRefkRVhuOkIGVne7BQ35DSfo1qvJqFg==
 
+escape-string-regexp@^4.0.0:
+  version "4.0.0"
+  resolved "https://registry.yarnpkg.com/escape-string-regexp/-/escape-string-regexp-4.0.0.tgz#14ba83a5d373e3d311e5afca29cf5bfad965bf34"
+  integrity sha512-TtpcNJ3XAzx3Gq8sWRzJaVajRs0uVxA2YAkdb1jm2YkPz4G6egUFAyA3n5vtEIZefPk5Wa4UXbKuS5fKkJWdgA==
+
 espree@^3.5.2:
   version "3.5.4"
   resolved "https://registry.yarnpkg.com/espree/-/espree-3.5.4.tgz#b0f447187c8a8bed944b815a660bddf5deb5d1a7"
@@ -998,6 +1016,11 @@
   resolved "https://registry.yarnpkg.com/estree-walker/-/estree-walker-0.6.1.tgz#53049143f40c6eb918b23671d1fe3219f3a1b362"
   integrity sha512-SqmZANLWS0mnatqbSfRP5g8OXZC12Fgg1IwNtLsyHDzJizORW4khDfjPqJZsemPWBB2uqykUah5YpQ6epsqC/w==
 
+estree-walker@^2.0.1:
+  version "2.0.2"
+  resolved "https://registry.yarnpkg.com/estree-walker/-/estree-walker-2.0.2.tgz#52f010178c2a4c117a7757cfe942adb7d2da4cac"
+  integrity sha512-Rfkk/Mp/DL7JVje3u18FxFujQlTNR2q6QfMSMB7AvCBx91NGj/ba3kCfza0f6dVDbw7YlRf/nDrn7pQrCCyQ/w==
+
 esutils@^2.0.2:
   version "2.0.3"
   resolved "https://registry.yarnpkg.com/esutils/-/esutils-2.0.3.tgz#74d2eb4de0b8da1293711910d50775b9b710ef64"
@@ -1325,7 +1348,7 @@
   dependencies:
     vlq "^0.2.2"
 
-magic-string@^0.25.2:
+magic-string@^0.25.2, magic-string@^0.25.7:
   version "0.25.9"
   resolved "https://registry.yarnpkg.com/magic-string/-/magic-string-0.25.9.tgz#de7f9faf91ef8a1c91d02c2e5314c8277dbcdd1c"
   integrity sha512-RmF0AsMzgt25qzqqLc1+MbHmhdx0ojF2Fvs4XnOqz2ZOBXzzkEwc/dJQZCYHAn7v1jbVOjAZfK8msRn4BxO4VQ==
@@ -1458,6 +1481,11 @@
   resolved "https://registry.yarnpkg.com/pend/-/pend-1.2.0.tgz#7a57eb550a6783f9115331fcf4663d5c8e007a50"
   integrity sha512-F3asv42UuXchdzt+xXqfW1OGlVBe+mxa2mqI0pg5yAHZPvFmY3Y6drSf/GQ1A86WgWEN9Kzh/WrgKa6iGcHXLg==
 
+picomatch@^2.2.2:
+  version "2.3.1"
+  resolved "https://registry.yarnpkg.com/picomatch/-/picomatch-2.3.1.tgz#3ba3833733646d9d3e4995946c1365a67fb07a42"
+  integrity sha512-JU3teHTNjmE2VCGFzuY8EXzCDVwEqB2a8fsIvwaStHhAWJEeVd1o1QD80CU6+ZdEXXSLbSsuLwJjkCBWqRQUVA==
+
 plist@^2.0.1:
   version "2.1.0"
   resolved "https://registry.yarnpkg.com/plist/-/plist-2.1.0.tgz#57ccdb7a0821df21831217a3cad54e3e146a1025"
@@ -1652,6 +1680,16 @@
     resolve "^1.11.0"
     rollup-pluginutils "^2.8.1"
 
+rollup-plugin-define@^1.0.1:
+  version "1.0.1"
+  resolved "https://registry.yarnpkg.com/rollup-plugin-define/-/rollup-plugin-define-1.0.1.tgz#45b027cec9d2e30df71118efa156170e3846fd3d"
+  integrity sha512-SM/CKFpLvWq5xBEf84ff/ooT3KodXPVITCkRliyNccuq8SZMpzthN/Bp7JkWScbGTX5lo1SF3cjxKKDjnnFCuA==
+  dependencies:
+    "@rollup/pluginutils" "^4.0.0"
+    ast-matcher "^1.1.1"
+    escape-string-regexp "^4.0.0"
+    magic-string "^0.25.7"
+
 rollup-plugin-node-resolve@^5.2.0:
   version "5.2.0"
   resolved "https://registry.yarnpkg.com/rollup-plugin-node-resolve/-/rollup-plugin-node-resolve-5.2.0.tgz#730f93d10ed202473b1fb54a5997a7db8c6d8523"