diff --git a/java/com/google/gerrit/server/approval/ApprovalInference.java b/java/com/google/gerrit/server/approval/ApprovalInference.java
index 2466b4f..1efbd37 100644
--- a/java/com/google/gerrit/server/approval/ApprovalInference.java
+++ b/java/com/google/gerrit/server/approval/ApprovalInference.java
@@ -30,7 +30,6 @@
 import com.google.gerrit.entities.PatchSetApproval;
 import com.google.gerrit.exceptions.StorageException;
 import com.google.gerrit.extensions.client.ChangeKind;
-import com.google.gerrit.extensions.client.DiffPreferencesInfo;
 import com.google.gerrit.index.query.QueryParseException;
 import com.google.gerrit.server.change.ChangeKindCache;
 import com.google.gerrit.server.change.LabelNormalizer;
@@ -40,7 +39,6 @@
 import com.google.gerrit.server.notedb.ChangeNotes;
 import com.google.gerrit.server.patch.DiffNotAvailableException;
 import com.google.gerrit.server.patch.DiffOperations;
-import com.google.gerrit.server.patch.PatchListKey;
 import com.google.gerrit.server.patch.filediff.FileDiffOutput;
 import com.google.gerrit.server.project.ProjectCache;
 import com.google.gerrit.server.project.ProjectState;
@@ -433,11 +431,6 @@
    */
   private Map<String, FileDiffOutput> listModifiedFiles(
       ProjectState project, PatchSet ps, Map.Entry<PatchSet.Id, PatchSet> priorPatchSet) {
-    PatchListKey key =
-        PatchListKey.againstCommit(
-            priorPatchSet.getValue().commitId(),
-            ps.commitId(),
-            DiffPreferencesInfo.Whitespace.IGNORE_NONE);
     try {
       return diffOperations.listModifiedFiles(
           project.getNameKey(), priorPatchSet.getValue().commitId(), ps.commitId());
diff --git a/java/com/google/gerrit/server/change/FileInfoJsonModule.java b/java/com/google/gerrit/server/change/FileInfoJsonModule.java
index f90bd14..de116bb 100644
--- a/java/com/google/gerrit/server/change/FileInfoJsonModule.java
+++ b/java/com/google/gerrit/server/change/FileInfoJsonModule.java
@@ -14,12 +14,31 @@
 
 package com.google.gerrit.server.change;
 
+import com.google.gerrit.server.config.GerritServerConfig;
 import com.google.inject.AbstractModule;
+import org.eclipse.jgit.lib.Config;
 
 public class FileInfoJsonModule extends AbstractModule {
+  /** Use the new diff cache implementation {@link FileInfoJsonNewImpl}. */
+  private final boolean useNewDiffCache;
+
+  /** Used to dark launch the new diff cache with the list files endpoint. */
+  private final boolean runNewDiffCacheAsync;
+
+  public FileInfoJsonModule(@GerritServerConfig Config cfg) {
+    this.useNewDiffCache =
+        cfg.getBoolean("cache", "diff_cache", "runNewDiffCache_ListFiles", false);
+    this.runNewDiffCacheAsync =
+        cfg.getBoolean("cache", "diff_cache", "runNewDiffCacheAsync_listFiles", false);
+  }
 
   @Override
   public void configure() {
-    bind(FileInfoJson.class).to(FileInfoJsonComparingImpl.class);
+    if (runNewDiffCacheAsync) {
+      bind(FileInfoJson.class).to(FileInfoJsonComparingImpl.class);
+      return;
+    }
+    bind(FileInfoJson.class)
+        .to(useNewDiffCache ? FileInfoJsonNewImpl.class : FileInfoJsonOldImpl.class);
   }
 }
diff --git a/java/com/google/gerrit/server/change/IncludedInResolver.java b/java/com/google/gerrit/server/change/IncludedInResolver.java
index 99a89bf..9216964 100644
--- a/java/com/google/gerrit/server/change/IncludedInResolver.java
+++ b/java/com/google/gerrit/server/change/IncludedInResolver.java
@@ -26,7 +26,6 @@
 import com.google.common.collect.Lists;
 import com.google.common.flogger.FluentLogger;
 import java.io.IOException;
-import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.HashSet;
@@ -90,17 +89,6 @@
         getMatchingRefNames(allMatchingTagsAndBranches, tags));
   }
 
-  private boolean includedInOne(Collection<Ref> refs) throws IOException {
-    parseCommits(refs);
-    List<RevCommit> before = new ArrayList<>();
-    List<RevCommit> after = new ArrayList<>();
-    partition(before, after);
-    rw.reset();
-    // It is highly likely that the target is reachable from the "after" set
-    // Within the "before" set we are trying to handle cases arising from clock skew
-    return !includedIn(after, 1).isEmpty() || !includedIn(before, 1).isEmpty();
-  }
-
   /** Resolves which tip refs include the target commit. */
   private Set<String> includedIn(Collection<RevCommit> tips, int limit)
       throws IOException, MissingObjectException, IncorrectObjectTypeException {
diff --git a/java/com/google/gerrit/server/config/GerritGlobalModule.java b/java/com/google/gerrit/server/config/GerritGlobalModule.java
index 076ba46..5a74c78 100644
--- a/java/com/google/gerrit/server/config/GerritGlobalModule.java
+++ b/java/com/google/gerrit/server/config/GerritGlobalModule.java
@@ -271,7 +271,7 @@
     install(new IgnoreSelfApprovalRule.Module());
     install(new ReceiveCommitsModule());
     install(new SshAddressesModule());
-    install(new FileInfoJsonModule());
+    install(new FileInfoJsonModule(cfg));
     install(ThreadLocalRequestContext.module());
     install(new ApprovalModule());
 
diff --git a/java/com/google/gerrit/server/project/Reachable.java b/java/com/google/gerrit/server/project/Reachable.java
index 2bf9e54..2adebe7 100644
--- a/java/com/google/gerrit/server/project/Reachable.java
+++ b/java/com/google/gerrit/server/project/Reachable.java
@@ -31,6 +31,8 @@
 import java.util.Collection;
 import java.util.List;
 import java.util.Optional;
+import org.eclipse.jgit.errors.IncorrectObjectTypeException;
+import org.eclipse.jgit.errors.MissingObjectException;
 import org.eclipse.jgit.lib.Ref;
 import org.eclipse.jgit.lib.Repository;
 import org.eclipse.jgit.revwalk.ReachabilityChecker;
@@ -77,7 +79,19 @@
               .filter(refs, repo, RefFilterOptions.defaults());
       Collection<RevCommit> visible = new ArrayList<>();
       for (Ref r : filtered) {
-        visible.add(rw.parseCommit(r.getObjectId()));
+        try {
+          visible.add(rw.parseCommit(r.getObjectId()));
+        } catch (IncorrectObjectTypeException notCommit) {
+          // Its OK for a tag reference to point to a blob or a tree, this
+          // is common in the Linux kernel or git.git repository.
+          continue;
+        } catch (MissingObjectException notHere) {
+          // Log the problem with this branch, but keep processing.
+          logger.atWarning().log(
+              "Reference %s in %s points to dangling object %s",
+              r.getName(), repo.getDirectory(), r.getObjectId());
+          continue;
+        }
       }
 
       // The filtering above already produces a voluminous trace. To separate the permission check
diff --git a/java/com/google/gerrit/testing/InMemoryModule.java b/java/com/google/gerrit/testing/InMemoryModule.java
index cd5032a..7ca763a1 100644
--- a/java/com/google/gerrit/testing/InMemoryModule.java
+++ b/java/com/google/gerrit/testing/InMemoryModule.java
@@ -250,7 +250,7 @@
     install(new RestApiModule());
     install(new OAuthRestModule());
     install(new DefaultProjectNameLockManager.Module());
-    install(new FileInfoJsonModule());
+    install(new FileInfoJsonModule(cfg));
 
     bind(ProjectOperations.class).to(ProjectOperationsImpl.class);
   }
diff --git a/plugins/codemirror-editor b/plugins/codemirror-editor
index 42d5fe0..e0a6721 160000
--- a/plugins/codemirror-editor
+++ b/plugins/codemirror-editor
@@ -1 +1 @@
-Subproject commit 42d5fe041ee2ef6be579c0085396fa5e60889222
+Subproject commit e0a67217ae5359797570481cbb6e8aa1f5e0a7c3
diff --git a/polygerrit-ui/app/api/checks.ts b/polygerrit-ui/app/api/checks.ts
index 2682158..06f9509 100644
--- a/polygerrit-ui/app/api/checks.ts
+++ b/polygerrit-ui/app/api/checks.ts
@@ -28,6 +28,23 @@
    * polling interval to pass.
    */
   announceUpdate(): void;
+
+  /**
+   * Updates an individual result.
+   *
+   * This can be used for lazy loading detailed information. For example, if you
+   * are using the `check-result-expanded` endpoint, then you can load more
+   * result details when the user expands a result row.
+   *
+   * The parameter `run` is only used to *find* the correct run for updating the
+   * result. It will only be used for comparing `change`, `patchset`, `attempt`
+   * and `checkName`. Its properties other than `results` will not be updated.
+   *
+   * For us being able to identify the result that you want to update you have
+   * to set the `externalId` property. An undefined `externalId` will result in
+   * an error.
+   */
+  updateResult(run: CheckRun, result: CheckResult): void;
 }
 
 export declare interface ChecksApiConfig {
@@ -450,4 +467,5 @@
   HELP_PAGE = 'help_page',
   REPORT_BUG = 'report_bug',
   CODE = 'code',
+  FILE_PRESENT = 'file_present',
 }
diff --git a/polygerrit-ui/app/elements/change/gr-change-summary/gr-change-summary.ts b/polygerrit-ui/app/elements/change/gr-change-summary/gr-change-summary.ts
index 251fbf7..c78d6c0 100644
--- a/polygerrit-ui/app/elements/change/gr-change-summary/gr-change-summary.ts
+++ b/polygerrit-ui/app/elements/change/gr-change-summary/gr-change-summary.ts
@@ -36,10 +36,11 @@
   getResultsOf,
   hasCompletedWithoutResults,
   hasResultsOf,
-  iconForCategory,
-  iconForStatus,
+  iconFor,
   isRunning,
   isRunningOrHasCompleted,
+  isStatus,
+  labelFor,
 } from '../../../services/checks/checks-util';
 import {ChangeComments} from '../../diff/gr-comment-api/gr-comment-api';
 import {
@@ -57,6 +58,7 @@
 import {PrimaryTab} from '../../../constants/constants';
 import {ChecksTabState, CommentTabState} from '../../../types/events';
 import {spinnerStyles} from '../../../styles/gr-spinner-styles';
+import {modifierPressed} from '../../../utils/dom-util';
 
 export enum SummaryChipStyles {
   INFO = 'info',
@@ -106,6 +108,9 @@
           background: var(--warning-background-hover);
           box-shadow: var(--elevation-level-1);
         }
+        .summaryChip.warning:focus-within {
+          background: var(--warning-background-focus);
+        }
         .summaryChip.warning iron-icon {
           color: var(--warning-foreground);
         }
@@ -117,6 +122,9 @@
           background: var(--gray-background-hover);
           box-shadow: var(--elevation-level-1);
         }
+        .summaryChip.check:focus-within {
+          background: var(--gray-background-focus);
+        }
         .summaryChip.check iron-icon {
           color: var(--gray-foreground);
         }
@@ -148,7 +156,7 @@
 @customElement('gr-checks-chip')
 export class GrChecksChip extends GrLitElement {
   @property()
-  icon = '';
+  statusOrCategory?: Category | RunStatus;
 
   @property()
   text = '';
@@ -193,6 +201,9 @@
           background: var(--error-background-hover);
           box-shadow: var(--elevation-level-1);
         }
+        .checksChip.error:focus-within {
+          background: var(--error-background-focus);
+        }
         .checksChip.error iron-icon {
           color: var(--error-foreground);
         }
@@ -204,6 +215,9 @@
           background: var(--warning-background-hover);
           box-shadow: var(--elevation-level-1);
         }
+        .checksChip.warning:focus-within {
+          background: var(--warning-background-focus);
+        }
         .checksChip.warning iron-icon {
           color: var(--warning-foreground);
         }
@@ -215,6 +229,9 @@
           background: var(--info-background-hover);
           box-shadow: var(--elevation-level-1);
         }
+        .checksChip.info-outline:focus-within {
+          background: var(--info-background-focus);
+        }
         .checksChip.info-outline iron-icon {
           color: var(--info-foreground);
         }
@@ -226,6 +243,9 @@
           background: var(--success-background-hover);
           box-shadow: var(--elevation-level-1);
         }
+        .checksChip.check-circle-outline:focus-within {
+          background: var(--success-background-focus);
+        }
         .checksChip.check-circle-outline iron-icon {
           color: var(--success-foreground);
         }
@@ -239,6 +259,9 @@
           background: var(--gray-background-hover);
           box-shadow: var(--elevation-level-1);
         }
+        .checksChip.timelapse:focus-within {
+          background: var(--gray-background-focus);
+        }
         .checksChip.timelapse iron-icon {
           color: var(--gray-foreground);
         }
@@ -248,10 +271,25 @@
 
   render() {
     if (!this.text) return;
-    const chipClass = `checksChip font-small ${this.icon}`;
-    const grIcon = `gr-icons:${this.icon}`;
+    if (!this.statusOrCategory) return;
+    const icon = iconFor(this.statusOrCategory);
+    const label = labelFor(this.statusOrCategory);
+    const count = Number(this.text);
+    let ariaLabel = label;
+    if (!isNaN(count)) {
+      const type = isStatus(this.statusOrCategory) ? 'run' : 'result';
+      const plural = count > 1 ? 's' : '';
+      ariaLabel = `${this.text} ${label} ${type}${plural}`;
+    }
+    const chipClass = `checksChip font-small ${icon}`;
+    const grIcon = `gr-icons:${icon}`;
     return html`
-      <div class="${chipClass}" role="button">
+      <div
+        class="${chipClass}"
+        role="link"
+        tabindex="0"
+        aria-label="${ariaLabel}"
+      >
         <iron-icon icon="${grIcon}"></iron-icon>
         <div class="text">${this.text}</div>
         <slot></slot>
@@ -411,18 +449,17 @@
     if (this.errorMessage || this.loginCallback) return;
     if (this.runs.some(isRunningOrHasCompleted)) return;
     const msg = this.someProvidersAreLoading ? 'Loading results' : 'No results';
-    return html`<span class="loading zeroState">${msg}</span>`;
+    return html`<span role="status" class="loading zeroState">${msg}</span>`;
   }
 
   renderChecksChipForCategory(category: Category) {
     if (this.errorMessage || this.loginCallback) return;
-    const icon = iconForCategory(category);
     const runs = this.runs.filter(run => {
       if (hasResultsOf(run, category)) return true;
       return category === Category.SUCCESS && hasCompletedWithoutResults(run);
     });
     const count = (run: CheckRun) => getResultsOf(run, category);
-    return this.renderChecksChip(icon, runs, category, count);
+    return this.renderChecksChip(runs, category, count);
   }
 
   renderChecksChipForStatus(
@@ -430,13 +467,11 @@
     filter: (run: CheckRun) => boolean
   ) {
     if (this.errorMessage || this.loginCallback) return;
-    const icon = iconForStatus(status);
     const runs = this.runs.filter(filter);
-    return this.renderChecksChip(icon, runs, status, () => []);
+    return this.renderChecksChip(runs, status, () => []);
   }
 
   renderChecksChip(
-    icon: string,
     runs: CheckRun[],
     statusOrCategory: RunStatus | Category,
     resultFilter: (run: CheckRun) => CheckResult[]
@@ -462,13 +497,19 @@
         const links = allPrimaryLinks.length === 1 ? allPrimaryLinks : [];
         const text = `${run.checkName}`;
         return html`<gr-checks-chip
-          class="${icon}"
-          .icon="${icon}"
+          .statusOrCategory="${statusOrCategory}"
           .text="${text}"
           @click="${() => this.onChipClick({checkName: run.checkName})}"
+          @keydown="${(e: KeyboardEvent) =>
+            this.onChipKeyDown(e, {checkName: run.checkName})}"
           >${links.map(
             link => html`
-              <a href="${link.url}" target="_blank" @click="${this.onLinkClick}"
+              <a
+                href="${link.url}"
+                target="_blank"
+                @click="${this.onLinkClick}"
+                @keydown="${this.onLinkKeyDown}"
+                aria-label="Link to check details"
                 ><iron-icon class="launch" icon="gr-icons:launch"></iron-icon
               ></a>
             `
@@ -484,19 +525,34 @@
     );
     if (sum === 0) return;
     return html`<gr-checks-chip
-      class="${icon}"
-      .icon="${icon}"
+      .statusOrCategory="${statusOrCategory}"
       .text="${sum}"
       @click="${() => this.onChipClick({statusOrCategory})}"
+      @keydown="${(e: KeyboardEvent) =>
+        this.onChipKeyDown(e, {statusOrCategory})}"
     ></gr-checks-chip>`;
   }
 
+  private onChipKeyDown(e: KeyboardEvent, state: ChecksTabState) {
+    if (modifierPressed(e)) return;
+    // Only react to `return` and `space`.
+    if (e.keyCode !== 13 && e.keyCode !== 32) return;
+    e.preventDefault();
+    e.stopPropagation();
+    this.onChipClick(state);
+  }
+
   private onChipClick(state: ChecksTabState) {
     fireShowPrimaryTab(this, PrimaryTab.CHECKS, false, {
       checksTab: state,
     });
   }
 
+  private onLinkKeyDown(e: KeyboardEvent) {
+    // Prevents onConChipKeyDown() from reacting to <a> link keyboard events.
+    e.stopPropagation();
+  }
+
   private onLinkClick(e: MouseEvent) {
     // Prevents onChipClick() from reacting to <a> link clicks.
     e.stopPropagation();
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 4304734..2ede186e 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
@@ -1254,16 +1254,37 @@
     this.$.fileList.collapseAllDiffs();
   }
 
+  /**
+   * ChangeView is never re-used for different changes. It is safer and simpler
+   * to just re-create another change view when the user switches to a new
+   * change page. Thus we need a reliable way to detect that the change view
+   * does not match the current change number anymore.
+   *
+   * If this method returns true, then the change view should not do anything
+   * anymore. The app element makes sure that an obsolete change view is not
+   * shown anymore, so if the change view is still and doing some update to
+   * itself, then that is not dangerous. But for example it should not call
+   * navigateToChange() anymore. That would very likely cause erroneous
+   * behavior.
+   */
+  private isChangeObsolete() {
+    // While this._changeNum is undefined the change view is fresh and has just
+    // not updated it to params.changeNum yet. Not obsolete in that case.
+    if (this._changeNum === undefined) return false;
+    // this.params reflects the current state of the URL. If this._changeNum
+    // does not match it anymore, then this view must be considered obsolete.
+    return this._changeNum !== this.params?.changeNum;
+  }
+
   _paramsChanged(value: AppElementChangeViewParams) {
     if (value.view !== GerritView.CHANGE) {
       this._initialLoadComplete = false;
       return;
     }
 
-    // Everything in the change view is tied to the change. It seems better to
-    // force the re-creation of the change view when the change number changes.
-    const changeChanged = this._changeNum !== value.changeNum;
-    if (this._changeNum !== undefined && changeChanged) {
+    if (this.isChangeObsolete()) {
+      // Tell the app element that we are not going to handle the new change
+      // number and that they have to create a new change view.
       fireEvent(this, EventType.RECREATE_CHANGE_VIEW);
       return;
     }
@@ -1298,7 +1319,7 @@
 
     // If the change has already been loaded and the parameter change is only
     // in the patch range, then don't do a full reload.
-    if (!changeChanged && patchChanged && patchKnown) {
+    if (this._changeNum !== undefined && patchChanged && patchKnown) {
       if (!patchRange.patchNum) {
         patchRange.patchNum = computeLatestPatchNum(this._allPatchSets);
         rightPatchNumChanged = true;
@@ -2116,6 +2137,7 @@
    * promise resolves.
    */
   loadData(isLocationChange?: boolean, clearPatchset?: boolean) {
+    if (this.isChangeObsolete()) return Promise.resolve([]);
     if (clearPatchset && this._change) {
       GerritNav.navigateToChange(this._change);
       return Promise.resolve([]);
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 5128948..7d47abb 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
@@ -1614,7 +1614,7 @@
     });
   });
 
-  test('don’t reload entire page when patchRange changes', () => {
+  test('don’t reload entire page when patchRange changes', async () => {
     const reloadStub = sinon
       .stub(element, 'loadData')
       .callsFake(() => Promise.resolve([]));
@@ -1629,7 +1629,8 @@
       view: GerritView.CHANGE,
       patchNum: 1 as RevisionPatchSetNum,
     };
-    element._paramsChanged(value);
+    element.params = value;
+    await flush();
     assert.isTrue(reloadStub.calledOnce);
 
     element._initialLoadComplete = true;
@@ -1643,13 +1644,14 @@
 
     value.basePatchNum = 1 as BasePatchSetNum;
     value.patchNum = 2 as RevisionPatchSetNum;
-    element._paramsChanged(value);
+    element.params = {...value};
+    await flush();
     assert.isFalse(reloadStub.calledTwice);
     assert.isTrue(reloadPatchDependentStub.calledOnce);
     assert.isTrue(collapseStub.calledTwice);
   });
 
-  test('reload ported comments when patchNum changes', () => {
+  test('reload ported comments when patchNum changes', async () => {
     sinon.stub(element, 'loadData').callsFake(() => Promise.resolve([]));
     sinon.stub(element, '_getCommitInfo');
     sinon.stub(element.$.fileList, 'reload');
@@ -1665,7 +1667,8 @@
       view: GerritView.CHANGE,
       patchNum: 1 as RevisionPatchSetNum,
     };
-    element._paramsChanged(value);
+    element.params = value;
+    await flush();
 
     element._initialLoadComplete = true;
     element._change = {
@@ -1678,24 +1681,42 @@
 
     value.basePatchNum = 1 as BasePatchSetNum;
     value.patchNum = 2 as RevisionPatchSetNum;
-    element._paramsChanged(value);
+    element.params = {...value};
+    await flush();
     assert.isTrue(reloadPortedCommentsStub.calledOnce);
   });
 
-  test('reload entire page when patchRange doesnt change', () => {
+  test('reload entire page when patchRange doesnt change', async () => {
     const reloadStub = sinon
       .stub(element, 'loadData')
       .callsFake(() => Promise.resolve([]));
     const collapseStub = sinon.stub(element.$.fileList, 'collapseAllDiffs');
     const value: AppElementChangeViewParams = createAppElementChangeViewParams();
-    element._paramsChanged(value);
+    element.params = value;
+    await flush();
     assert.isTrue(reloadStub.calledOnce);
     element._initialLoadComplete = true;
-    element._paramsChanged(value);
+    element.params = {...value};
+    await flush();
     assert.isTrue(reloadStub.calledTwice);
     assert.isTrue(collapseStub.calledTwice);
   });
 
+  test('do not handle new change numbers', async () => {
+    const recreateSpy = sinon.spy();
+    element.addEventListener('recreate-change-view', recreateSpy);
+
+    const value: AppElementChangeViewParams = createAppElementChangeViewParams();
+    element.params = value;
+    await flush();
+    assert.isFalse(recreateSpy.calledOnce);
+
+    value.changeNum = 555111333 as NumericChangeId;
+    element.params = {...value};
+    await flush();
+    assert.isTrue(recreateSpy.calledOnce);
+  });
+
   test('related changes are not updated after other action', done => {
     sinon.stub(element, 'loadData').callsFake(() => Promise.resolve([]));
     flush();
@@ -2026,7 +2047,7 @@
       element.handleScroll();
     });
 
-    test('scrollTop is set correctly', () => {
+    test('scrollTop is set correctly', async () => {
       element.viewState = {scrollTop: TEST_SCROLL_TOP_PX};
 
       sinon.stub(element, 'loadData').callsFake(() => {
@@ -2039,7 +2060,8 @@
 
       // simulate reloading component, which is done when route
       // changes to match a regex of change view type.
-      element._paramsChanged({...createAppElementChangeViewParams()});
+      element.params = {...createAppElementChangeViewParams()};
+      await flush();
     });
 
     test('scrollTop is reset when new change is loaded', () => {
@@ -2591,7 +2613,7 @@
       });
     });
 
-    test('report changeDisplayed on _paramsChanged', done => {
+    test('report changeDisplayed on _paramsChanged', async () => {
       const changeDisplayStub = sinon.stub(
         appContext.reportingService,
         'changeDisplayed'
@@ -2600,16 +2622,14 @@
         appContext.reportingService,
         'changeFullyLoaded'
       );
-      element._paramsChanged({
+      element.params = {
         ...createAppElementChangeViewParams(),
         changeNum: TEST_NUMERIC_CHANGE_ID,
         project: TEST_PROJECT_NAME,
-      });
-      flush(() => {
-        assert.isTrue(changeDisplayStub.called);
-        assert.isTrue(changeFullyLoadedStub.called);
-        done();
-      });
+      };
+      await flush();
+      assert.isTrue(changeDisplayStub.called);
+      assert.isTrue(changeFullyLoadedStub.called);
     });
   });
 
diff --git a/polygerrit-ui/app/elements/change/gr-thread-list/gr-thread-list.ts b/polygerrit-ui/app/elements/change/gr-thread-list/gr-thread-list.ts
index 8283be79..2e8e4ba 100644
--- a/polygerrit-ui/app/elements/change/gr-thread-list/gr-thread-list.ts
+++ b/polygerrit-ui/app/elements/change/gr-thread-list/gr-thread-list.ts
@@ -17,18 +17,20 @@
 import '@polymer/paper-toggle-button/paper-toggle-button';
 import '../../../styles/shared-styles';
 import '../../shared/gr-comment-thread/gr-comment-thread';
+import '../../shared/gr-dropdown-list/gr-dropdown-list';
+
 import {flush} from '@polymer/polymer/lib/legacy/polymer.dom';
 import {PolymerElement} from '@polymer/polymer/polymer-element';
 import {htmlTemplate} from './gr-thread-list_html';
 import {parseDate} from '../../../utils/date-util';
 
 import {CommentSide, SpecialFilePath} from '../../../constants/constants';
-import {customElement, observe, property} from '@polymer/decorators';
+import {computed, customElement, observe, property} from '@polymer/decorators';
 import {
   PolymerSpliceChange,
   PolymerDeepPropertyChange,
 } from '@polymer/polymer/interfaces';
-import {ChangeInfo} from '../../../types/common';
+import {AccountInfo, ChangeInfo} from '../../../types/common';
 import {
   CommentThread,
   isDraft,
@@ -36,11 +38,14 @@
   isDraftThread,
   isRobotThread,
   hasHumanReply,
+  getCommentAuthors,
 } from '../../../utils/comment-util';
 import {pluralize} from '../../../utils/string-util';
 import {fireThreadListModifiedEvent} from '../../../utils/event-util';
-import {assertNever} from '../../../utils/common-util';
+import {assertIsDefined, assertNever} from '../../../utils/common-util';
 import {CommentTabState} from '../../../types/events';
+import {DropdownItem} from '../../shared/gr-dropdown-list/gr-dropdown-list';
+import {GrAccountChip} from '../../shared/gr-account-chip/gr-account-chip';
 
 interface CommentThreadWithInfo {
   thread: CommentThread;
@@ -52,6 +57,13 @@
   updated?: Date;
 }
 
+enum SortDropdownState {
+  TIMESTAMP = 'Latest timestamp',
+  FILES = 'Files',
+}
+
+export const __testOnly_SortDropdownState = SortDropdownState;
+
 @customElement('gr-thread-list')
 export class GrThreadList extends PolymerElement {
   static get template() {
@@ -79,7 +91,7 @@
   @property({
     computed:
       '_computeDisplayedThreads(_sortedThreads.*, unresolvedOnly, ' +
-      '_draftsOnly, onlyShowRobotCommentsWithHumanReply)',
+      '_draftsOnly, onlyShowRobotCommentsWithHumanReply, selectedAuthors)',
     type: Array,
   })
   _displayedThreads: CommentThread[] = [];
@@ -102,6 +114,21 @@
   @property({type: Object, observer: '_commentTabStateChange'})
   commentTabState?: CommentTabState;
 
+  @property({type: Object})
+  sortDropdownValue: SortDropdownState = SortDropdownState.TIMESTAMP;
+
+  @property({type: Array, notify: true})
+  selectedAuthors: AccountInfo[] = [];
+
+  @computed('unresolvedOnly', '_draftsOnly')
+  get commentsDropdownValue() {
+    // set initial value and triggered when comment summary chips are clicked
+    if (this._draftsOnly) return CommentTabState.DRAFTS;
+    return this.unresolvedOnly
+      ? CommentTabState.UNRESOLVED
+      : CommentTabState.SHOW_ALL;
+  }
+
   _showEmptyThreadsMessage(
     threads: CommentThread[],
     displayedThreads: CommentThread[],
@@ -146,7 +173,74 @@
     this.unresolvedOnly = !this.unresolvedOnly;
   }
 
+  getSortDropdownEntires() {
+    return [
+      {text: SortDropdownState.FILES, value: SortDropdownState.FILES},
+      {text: SortDropdownState.TIMESTAMP, value: SortDropdownState.TIMESTAMP},
+    ];
+  }
+
+  getCommentsDropdownEntires(threads: CommentThread[], loggedIn?: boolean) {
+    const items: DropdownItem[] = [
+      {
+        text: `Unresolved (${this._countUnresolved(threads)})`,
+        value: CommentTabState.UNRESOLVED,
+      },
+      {
+        text: `All (${this._countAllThreads(threads)})`,
+        value: CommentTabState.SHOW_ALL,
+      },
+    ];
+    if (loggedIn)
+      items.splice(1, 0, {
+        text: `Drafts (${this._countDrafts(threads)})`,
+        value: CommentTabState.DRAFTS,
+      });
+    return items;
+  }
+
+  getCommentAuthors(threads?: CommentThread[]) {
+    return getCommentAuthors(threads);
+  }
+
+  handleAccountClicked(e: MouseEvent) {
+    const account = (e.target as GrAccountChip).account;
+    assertIsDefined(account, 'account');
+    const index = this.selectedAuthors.findIndex(
+      author => author._account_id === account._account_id
+    );
+    if (index === -1) this.push('selectedAuthors', account);
+    else this.splice('selectedAuthors', index, 1);
+    // re-assign so that isSelected template method is called
+    this.selectedAuthors = [...this.selectedAuthors];
+  }
+
+  isSelected(author: AccountInfo, selectedAuthors: AccountInfo[]) {
+    return selectedAuthors.some(a => a._account_id === author._account_id);
+  }
+
+  handleSortDropdownValueChange(e: CustomEvent) {
+    this.sortDropdownValue = e.detail.value;
+    /*
+     * Ideally we would have updateSortedThreads observe on sortDropdownValue
+     * but the method triggered re-render only when the length of threads
+     * changes, hence keep the explicit resortThreads method
+     */
+    this.resortThreads(this.threads);
+  }
+
+  handleCommentsDropdownValueChange(e: CustomEvent) {
+    const value = e.detail.value;
+    if (value === CommentTabState.UNRESOLVED) this._handleOnlyUnresolved();
+    else if (value === CommentTabState.DRAFTS) this._handleOnlyDrafts();
+    else this._handleAllComments();
+  }
+
   _compareThreads(c1: CommentThreadWithInfo, c2: CommentThreadWithInfo) {
+    if (this.sortDropdownValue === SortDropdownState.TIMESTAMP) {
+      if (c1.updated && c2.updated) return c1.updated > c2.updated ? -1 : 1;
+    }
+
     if (c1.thread.path !== c2.thread.path) {
       // '/PATCHSET' will not come before '/COMMIT' when sorting
       // alphabetically so move it to the front explicitly
@@ -202,6 +296,15 @@
     return 0;
   }
 
+  resortThreads(threads: CommentThread[]) {
+    const threadsWithInfo = threads.map(thread =>
+      this._getThreadWithStatusInfo(thread)
+    );
+    this._sortedThreads = threadsWithInfo
+      .sort((t1, t2) => this._compareThreads(t1, t2))
+      .map(threadInfo => threadInfo.thread);
+  }
+
   /**
    * Observer on threads and update _sortedThreads when needed.
    * Order as follows:
@@ -254,12 +357,7 @@
       return;
     }
 
-    const threadsWithInfo = threads.map(thread =>
-      this._getThreadWithStatusInfo(thread)
-    );
-    this._sortedThreads = threadsWithInfo
-      .sort((t1, t2) => this._compareThreads(t1, t2))
-      .map(threadInfo => threadInfo.thread);
+    this.resortThreads(threads);
   }
 
   _computeDisplayedThreads(
@@ -269,7 +367,8 @@
     >,
     unresolvedOnly?: boolean,
     draftsOnly?: boolean,
-    onlyShowRobotCommentsWithHumanReply?: boolean
+    onlyShowRobotCommentsWithHumanReply?: boolean,
+    selectedAuthors?: AccountInfo[]
   ) {
     if (!sortedThreadsRecord || !sortedThreadsRecord.base) return [];
     return sortedThreadsRecord.base.filter(t =>
@@ -277,7 +376,8 @@
         t,
         unresolvedOnly,
         draftsOnly,
-        onlyShowRobotCommentsWithHumanReply
+        onlyShowRobotCommentsWithHumanReply,
+        selectedAuthors
       )
     );
   }
@@ -287,14 +387,16 @@
     thread: CommentThread,
     unresolvedOnly?: boolean,
     draftsOnly?: boolean,
-    onlyShowRobotCommentsWithHumanReply?: boolean
+    onlyShowRobotCommentsWithHumanReply?: boolean,
+    selectedAuthors?: AccountInfo[]
   ) {
     const threads = displayedThreads.filter(t =>
       this._shouldShowThread(
         t,
         unresolvedOnly,
         draftsOnly,
-        onlyShowRobotCommentsWithHumanReply
+        onlyShowRobotCommentsWithHumanReply,
+        selectedAuthors
       )
     );
     const index = threads.findIndex(t => t.rootId === thread.rootId);
@@ -309,14 +411,16 @@
     thread: CommentThread,
     unresolvedOnly?: boolean,
     draftsOnly?: boolean,
-    onlyShowRobotCommentsWithHumanReply?: boolean
+    onlyShowRobotCommentsWithHumanReply?: boolean,
+    selectedAuthors?: AccountInfo[]
   ) {
     const threads = displayedThreads.filter(t =>
       this._shouldShowThread(
         t,
         unresolvedOnly,
         draftsOnly,
-        onlyShowRobotCommentsWithHumanReply
+        onlyShowRobotCommentsWithHumanReply,
+        selectedAuthors
       )
     );
     const index = threads.findIndex(t => t.rootId === thread.rootId);
@@ -330,7 +434,8 @@
         thread,
         unresolvedOnly,
         draftsOnly,
-        onlyShowRobotCommentsWithHumanReply
+        onlyShowRobotCommentsWithHumanReply,
+        selectedAuthors
       )
     );
   }
@@ -339,7 +444,8 @@
     thread: CommentThread,
     unresolvedOnly?: boolean,
     draftsOnly?: boolean,
-    onlyShowRobotCommentsWithHumanReply?: boolean
+    onlyShowRobotCommentsWithHumanReply?: boolean,
+    selectedAuthors?: AccountInfo[]
   ) {
     if (
       [
@@ -347,11 +453,26 @@
         unresolvedOnly,
         draftsOnly,
         onlyShowRobotCommentsWithHumanReply,
+        selectedAuthors,
       ].includes(undefined)
     ) {
       return false;
     }
 
+    if (selectedAuthors!.length) {
+      if (
+        !thread.comments.some(
+          c =>
+            c.author &&
+            selectedAuthors!.some(
+              author => c.author!._account_id === author._account_id
+            )
+        )
+      ) {
+        return false;
+      }
+    }
+
     if (
       !draftsOnly &&
       !unresolvedOnly &&
diff --git a/polygerrit-ui/app/elements/change/gr-thread-list/gr-thread-list_html.ts b/polygerrit-ui/app/elements/change/gr-thread-list/gr-thread-list_html.ts
index da91095..41beed2 100644
--- a/polygerrit-ui/app/elements/change/gr-thread-list/gr-thread-list_html.ts
+++ b/polygerrit-ui/app/elements/change/gr-thread-list/gr-thread-list_html.ts
@@ -33,7 +33,7 @@
       border-top: 1px solid var(--border-color);
       display: flex;
       justify-content: left;
-      padding: var(--spacing-m) var(--spacing-l);
+      padding: var(--spacing-s) var(--spacing-l);
     }
     .draftsOnly:not(.unresolvedOnly) gr-comment-thread[has-draft],
     .unresolvedOnly:not(.draftsOnly) gr-comment-thread[unresolved],
@@ -48,54 +48,70 @@
       box-shadow: none;
       padding-left: var(--spacing-m);
     }
-    .header .categoryRadio {
-      height: 18px;
-      width: 18px;
-    }
-    .header label {
-      padding-left: 8px;
-      margin-right: 16px;
-    }
     .partypopper{
       margin-right: var(--spacing-s);
     }
+    gr-dropdown-list {
+      --trigger-style: {
+        color: var(--primary-text-color);
+        text-transform: none;
+        font-family: var(--font-family);
+      }
+    }
+    .filter-text, .sort-text, .author-text {
+      margin-right: var(--spacing-s);
+      color: var(--deemphasized-text-color);
+    }
+    .author-text {
+      margin-left: var(--spacing-m);
+    }
+    gr-account-label {
+      --account-max-length: 120px;
+      display: inline-block;
+      user-select: none;
+      --label-border-radius: 8px;
+      margin: 0 var(--spacing-xs);
+      padding: var(--spacing-xs) var(--spacing-m);
+      line-height: var(--line-height-normal);
+      cursor: pointer;
+    }
+    gr-account-label:focus {
+      outline: none;
+    }
+    gr-account-label:hover,
+    gr-account-label:hover {
+      box-shadow: var(--elevation-level-1);
+      cursor: pointer;
+    }
   </style>
   <template is="dom-if" if="[[!hideToggleButtons]]">
     <div class="header">
-        <input
-          class="categoryRadio"
-          id="unresolvedRadio"
-          name="filterComments"
-          type="radio"
-          on-click="_handleOnlyUnresolved"
-          checked="[[unresolvedOnly]]"
-        />
-        <label for="unresolvedRadio">
-          Unresolved ([[_countUnresolved(threads)]])
-        </label>
-        <input
-          class="categoryRadio"
-          id="draftsRadio"
-          name="filterComments"
-          type="radio"
-          on-click="_handleOnlyDrafts"
-          checked="[[_draftsOnly]]"
-          hidden$="[[!loggedIn]]"
-        />
-        <label for="draftsRadio" hidden$="[[!loggedIn]]">
-          Drafts ([[_countDrafts(threads)]])
-        </label>
-        <input
-          class="categoryRadio"
-          id="allRadio"
-          name="filterComments"
-          type="radio"
-          on-click="_handleAllComments"
-          checked="[[_showAllComments(_draftsOnly, unresolvedOnly)]]"
-        />
-        <label for="allRadio">
-          All ([[_countAllThreads(threads)]])
-        </label>
+      <span class="sort-text">Sort By:</span>
+      <gr-dropdown-list
+        id="sortDropdown"
+        value="[[sortDropdownValue]]"
+        on-value-change="handleSortDropdownValueChange"
+        items="[[getSortDropdownEntires()]]"
+      >
+      </gr-dropdown-list>
+      <span class="separator"></span>
+      <span class="filter-text">Filter By:</span>
+      <gr-dropdown-list
+        id="filterDropdown"
+        value="[[commentsDropdownValue]]"
+        on-value-change="handleCommentsDropdownValueChange"
+        items="[[getCommentsDropdownEntires(threads, loggedIn)]]"
+      >
+      </gr-dropdown-list>
+      <span class="author-text">From:</span>
+      <template is="dom-repeat" items="[[getCommentAuthors(threads)]]">
+        <gr-account-label
+          account="[[item]]"
+          on-click="handleAccountClicked"
+          selection-chip-style
+          selected="[[isSelected(item, selectedAuthors)]]"
+        > </gr-account-label>
+      </template>
     </div>
   </template>
   <div id="threads">
@@ -131,7 +147,7 @@
     >
       <template
         is="dom-if"
-        if="[[_shouldRenderSeparator(_displayedThreads, thread, unresolvedOnly, _draftsOnly, onlyShowRobotCommentsWithHumanReply)]]"
+        if="[[_shouldRenderSeparator(_displayedThreads, thread, unresolvedOnly, _draftsOnly, onlyShowRobotCommentsWithHumanReply, selectedAuthors)]]"
       >
         <div class="thread-separator"></div>
       </template>
@@ -142,7 +158,7 @@
         change-num="[[changeNum]]"
         comments="[[thread.comments]]"
         diff-side="[[thread.diffSide]]"
-        show-file-name="[[_isFirstThreadWithFileName(_displayedThreads, thread, unresolvedOnly, _draftsOnly, onlyShowRobotCommentsWithHumanReply)]]"
+        show-file-name="[[_isFirstThreadWithFileName(_displayedThreads, thread, unresolvedOnly, _draftsOnly, onlyShowRobotCommentsWithHumanReply, selectedAuthors)]]"
         project-name="[[change.project]]"
         is-on-parent="[[_isOnParent(thread.commentSide)]]"
         line-num="[[thread.line]]"
diff --git a/polygerrit-ui/app/elements/change/gr-thread-list/gr-thread-list_test.js b/polygerrit-ui/app/elements/change/gr-thread-list/gr-thread-list_test.js
index 3d6cfd4..5c87c4b 100644
--- a/polygerrit-ui/app/elements/change/gr-thread-list/gr-thread-list_test.js
+++ b/polygerrit-ui/app/elements/change/gr-thread-list/gr-thread-list_test.js
@@ -19,6 +19,11 @@
 import './gr-thread-list.js';
 import {dom} from '@polymer/polymer/lib/legacy/polymer.dom.js';
 import {SpecialFilePath} from '../../../constants/constants.js';
+import {CommentTabState} from '../../../types/events.js';
+import {__testOnly_SortDropdownState} from './gr-thread-list.js';
+import {queryAll} from '../../../test/test-utils.js';
+import {accountOrGroupKey} from '../../../utils/account-util.js';
+import {tap} from '@polymer/iron-test-helpers/mock-interactions';
 
 const basicFixture = fixtureFromElement('gr-thread-list');
 
@@ -45,14 +50,14 @@
           {
             path: '/COMMIT_MSG',
             author: {
-              _account_id: 1000000,
+              _account_id: 1000001,
               name: 'user',
               username: 'user',
             },
             patch_set: 4,
             id: 'ecf0b9fa_fe1a5f62',
             line: 5,
-            updated: '2018-02-08 18:49:18.000000000',
+            updated: '1',
             message: 'test',
             unresolved: true,
           },
@@ -61,7 +66,7 @@
             path: '/COMMIT_MSG',
             line: 5,
             in_reply_to: 'ecf0b9fa_fe1a5f62',
-            updated: '2018-02-13 22:48:48.018000000',
+            updated: '1',
             message: 'draft',
             unresolved: true,
             __draft: true,
@@ -74,21 +79,21 @@
         path: '/COMMIT_MSG',
         line: 5,
         rootId: 'ecf0b9fa_fe1a5f62',
-        start_datetime: '2018-02-08 18:49:18.000000000',
+        updated: '1',
       },
       {
         comments: [
           {
             path: 'test.txt',
             author: {
-              _account_id: 1000000,
+              _account_id: 1000002,
               name: 'user',
               username: 'user',
             },
             patch_set: 3,
             id: '09a9fb0a_1484e6cf',
             side: 'PARENT',
-            updated: '2018-02-13 22:47:19.000000000',
+            updated: '2',
             message: 'Some comment on another patchset.',
             unresolved: false,
           },
@@ -96,7 +101,7 @@
         patchNum: 3,
         path: 'test.txt',
         rootId: '09a9fb0a_1484e6cf',
-        start_datetime: '2018-02-13 22:47:19.000000000',
+        updated: '2',
         commentSide: 'PARENT',
       },
       {
@@ -104,13 +109,13 @@
           {
             path: '/COMMIT_MSG',
             author: {
-              _account_id: 1000000,
+              _account_id: 1000002,
               name: 'user',
               username: 'user',
             },
             patch_set: 2,
             id: '8caddf38_44770ec1',
-            updated: '2018-02-13 22:48:40.000000000',
+            updated: '3',
             message: 'Another unresolved comment',
             unresolved: false,
           },
@@ -118,21 +123,21 @@
         patchNum: 2,
         path: '/COMMIT_MSG',
         rootId: '8caddf38_44770ec1',
-        start_datetime: '2018-02-13 22:48:40.000000000',
+        updated: '3',
       },
       {
         comments: [
           {
             path: '/COMMIT_MSG',
             author: {
-              _account_id: 1000000,
+              _account_id: 1000003,
               name: 'user',
               username: 'user',
             },
             patch_set: 2,
             id: 'scaddf38_44770ec1',
             line: 4,
-            updated: '2018-02-14 22:48:40.000000000',
+            updated: '4',
             message: 'Yet another unresolved comment',
             unresolved: true,
           },
@@ -141,7 +146,7 @@
         path: '/COMMIT_MSG',
         line: 4,
         rootId: 'scaddf38_44770ec1',
-        start_datetime: '2018-02-14 22:48:40.000000000',
+        updated: '4',
       },
       {
         comments: [
@@ -149,7 +154,7 @@
             id: 'zcf0b9fa_fe1a5f62',
             path: '/COMMIT_MSG',
             line: 6,
-            updated: '2018-02-15 22:48:48.018000000',
+            updated: '5',
             message: 'resolved draft',
             unresolved: false,
             __draft: true,
@@ -162,14 +167,14 @@
         path: '/COMMIT_MSG',
         line: 6,
         rootId: 'zcf0b9fa_fe1a5f62',
-        start_datetime: '2018-02-09 18:49:18.000000000',
+        updated: '5',
       },
       {
         comments: [
           {
             id: 'patchset_level_1',
             path: SpecialFilePath.PATCHSET_LEVEL_COMMENTS,
-            updated: '2018-02-15 22:48:48.018000000',
+            updated: '6',
             message: 'patchset comment 1',
             unresolved: false,
             __editing: false,
@@ -179,14 +184,14 @@
         patchNum: 2,
         path: SpecialFilePath.PATCHSET_LEVEL_COMMENTS,
         rootId: 'patchset_level_1',
-        start_datetime: '2018-02-09 18:49:18.000000000',
+        updated: '6',
       },
       {
         comments: [
           {
             id: 'patchset_level_2',
             path: SpecialFilePath.PATCHSET_LEVEL_COMMENTS,
-            updated: '2018-02-15 22:48:48.018000000',
+            updated: '7',
             message: 'patchset comment 2',
             unresolved: false,
             __editing: false,
@@ -196,7 +201,7 @@
         patchNum: 3,
         path: SpecialFilePath.PATCHSET_LEVEL_COMMENTS,
         rootId: 'patchset_level_2',
-        start_datetime: '2018-02-09 18:49:18.000000000',
+        updated: '7',
       },
       {
         comments: [
@@ -210,7 +215,7 @@
             patch_set: 4,
             id: 'rc1',
             line: 5,
-            updated: '2019-02-08 18:49:18.000000000',
+            updated: '8',
             message: 'test',
             unresolved: true,
             robot_id: 'rc1',
@@ -220,7 +225,7 @@
         path: '/COMMIT_MSG',
         line: 5,
         rootId: 'rc1',
-        start_datetime: '2019-02-08 18:49:18.000000000',
+        updated: '8',
       },
       {
         comments: [
@@ -234,7 +239,7 @@
             patch_set: 4,
             id: 'rc2',
             line: 7,
-            updated: '2019-03-08 18:49:18.000000000',
+            updated: '9',
             message: 'test',
             unresolved: true,
             robot_id: 'rc2',
@@ -249,7 +254,7 @@
             patch_set: 4,
             id: 'c2_1',
             line: 5,
-            updated: '2019-03-08 18:49:18.000000000',
+            updated: '10',
             message: 'test',
             unresolved: true,
           },
@@ -258,7 +263,7 @@
         path: '/COMMIT_MSG',
         line: 7,
         rootId: 'rc2',
-        start_datetime: '2019-03-08 18:49:18.000000000',
+        updated: '10',
       },
     ];
 
@@ -270,15 +275,15 @@
     });
   });
 
-  test('draft toggle only appears when logged in', () => {
+  test('draft dropdown item only appears when logged in', () => {
     element.loggedIn = false;
-    assert.equal(getComputedStyle(element.shadowRoot
-        .querySelector('#draftsRadio')).display,
-    'none');
+    flush();
+    assert.equal(element.getCommentsDropdownEntires(element.threads,
+        element.loggedIn).length, 2);
     element.loggedIn = true;
-    assert.notEqual(getComputedStyle(element.shadowRoot
-        .querySelector('#draftsRadio')).display,
-    'none');
+    flush();
+    assert.equal(element.getCommentsDropdownEntires(element.threads,
+        element.loggedIn).length, 3);
   });
 
   test('show all threads by default', () => {
@@ -298,13 +303,16 @@
   });
 
   test('showing file name takes visible threads into account', () => {
+    element.sortDropdownValue = __testOnly_SortDropdownState.FILES;
     assert.equal(element._isFirstThreadWithFileName(element._sortedThreads,
         element._sortedThreads[2], element.unresolvedOnly, element._draftsOnly,
-        element.onlyShowRobotCommentsWithHumanReply), true);
+        element.onlyShowRobotCommentsWithHumanReply, element.selectedAuthors),
+    true);
     element.unresolvedOnly = true;
     assert.equal(element._isFirstThreadWithFileName(element._sortedThreads,
         element._sortedThreads[2], element.unresolvedOnly, element._draftsOnly,
-        element.onlyShowRobotCommentsWithHumanReply), false);
+        element.onlyShowRobotCommentsWithHumanReply, element.selectedAuthors),
+    false);
   });
 
   test('onlyShowRobotCommentsWithHumanReply ', () => {
@@ -317,6 +325,10 @@
   });
 
   suite('_compareThreads', () => {
+    setup(() => {
+      element.sortDropdownValue = __testOnly_SortDropdownState.FILES;
+    });
+
     test('patchset comes before any other file', () => {
       const t1 = {thread: {path: SpecialFilePath.PATCHSET_LEVEL_COMMENTS}};
       const t2 = {thread: {path: SpecialFilePath.COMMIT_MESSAGE}};
@@ -448,6 +460,7 @@
   });
 
   test('_computeSortedThreads', () => {
+    element.sortDropdownValue = __testOnly_SortDropdownState.FILES;
     assert.equal(element._sortedThreads.length, 9);
     const expectedSortedRootIds = [
       'patchset_level_2', // Posted on Patchset 3
@@ -465,7 +478,68 @@
     });
   });
 
+  test('_computeSortedThreads with timestamp', () => {
+    element.sortDropdownValue = __testOnly_SortDropdownState.TIMESTAMP;
+    element.resortThreads(element.threads);
+    assert.equal(element._sortedThreads.length, 9);
+    const expectedSortedRootIds = [
+      'rc2',
+      'rc1',
+      'patchset_level_2',
+      'patchset_level_1',
+      'zcf0b9fa_fe1a5f62',
+      'scaddf38_44770ec1',
+      '8caddf38_44770ec1',
+      '09a9fb0a_1484e6cf',
+      'ecf0b9fa_fe1a5f62',
+    ];
+    element._sortedThreads.forEach((thread, index) => {
+      assert.equal(thread.rootId, expectedSortedRootIds[index]);
+    });
+  });
+
+  test('tapping single author chips', () => {
+    const chips = queryAll(element, 'gr-account-label');
+    const authors = Array.from(chips).map(
+        chip => accountOrGroupKey(chip.account))
+        .sort();
+    assert.deepEqual(authors, [1000000, 1000001, 1000002, 1000003]);
+    assert.equal(element.threads.length, 9);
+    assert.equal(element._displayedThreads.length, 9);
+
+    tap(chips[0]); // accountId 1000001
+    flush();
+
+    assert.equal(element.threads.length, 9);
+    assert.equal(element._displayedThreads.length, 1);
+    assert.equal(element._displayedThreads[0].comments[0].author._account_id,
+        1000001);
+
+    tap(chips[0]); // tapping again resets
+    flush();
+    assert.equal(element.threads.length, 9);
+    assert.equal(element._displayedThreads.length, 9);
+  });
+
+  test('tapping multiple author chips', () => {
+    const chips = queryAll(element, 'gr-account-label');
+
+    tap(chips[0]); // accountId 1000001
+    tap(chips[1]); // accountId 1000002
+    flush();
+
+    assert.equal(element.threads.length, 9);
+    assert.equal(element._displayedThreads.length, 3);
+    assert.equal(element._displayedThreads[0].comments[0].author._account_id,
+        1000002);
+    assert.equal(element._displayedThreads[1].comments[0].author._account_id,
+        1000002);
+    assert.equal(element._displayedThreads[2].comments[0].author._account_id,
+        1000001);
+  });
+
   test('thread removal and sort again', () => {
+    element.sortDropdownValue = __testOnly_SortDropdownState.FILES;
     threadElements[1].dispatchEvent(
         new CustomEvent('thread-discard', {
           detail: {rootId: 'rc2'},
@@ -489,6 +563,7 @@
   });
 
   test('modification on thread shold not trigger sort again', () => {
+    element.sortDropdownValue = __testOnly_SortDropdownState.FILES;
     const currentSortedThreads = [...element._sortedThreads];
     for (const thread of currentSortedThreads) {
       thread.comments = [...thread.comments];
@@ -526,6 +601,7 @@
 
   test('non-equal length of sortThreads and threads' +
     ' should trigger sort again', () => {
+    element.sortDropdownValue = __testOnly_SortDropdownState.FILES;
     const modifiedThreads = [...element.threads];
     const currentSortedThreads = [...element._sortedThreads];
     element._sortedThreads = [];
@@ -549,22 +625,23 @@
     });
   });
 
-  test('toggle all shows all all comments', () => {
-    MockInteractions.tap(element.shadowRoot.querySelector(
-        '#allRadio'));
+  test('show all comments', () => {
+    element.handleCommentsDropdownValueChange({detail: {
+      value: CommentTabState.SHOW_ALL}});
     flush();
     assert.equal(getVisibleThreads().length, 9);
   });
 
-  test('toggle unresolved shows all unresolved comments', () => {
-    MockInteractions.tap(element.shadowRoot.querySelector(
-        '#unresolvedRadio'));
+  test('unresolved shows all unresolved comments', () => {
+    element.handleCommentsDropdownValueChange({detail: {
+      value: CommentTabState.UNRESOLVED}});
     flush();
     assert.equal(getVisibleThreads().length, 4);
   });
 
   test('toggle drafts only shows threads with draft comments', () => {
-    MockInteractions.tap(element.shadowRoot.querySelector('#draftsRadio'));
+    element.handleCommentsDropdownValueChange({detail: {
+      value: CommentTabState.DRAFTS}});
     flush();
     assert.equal(getVisibleThreads().length, 2);
   });
diff --git a/polygerrit-ui/app/elements/checks/gr-checks-results.ts b/polygerrit-ui/app/elements/checks/gr-checks-results.ts
index 2ea6dd0..fd8cd80 100644
--- a/polygerrit-ui/app/elements/checks/gr-checks-results.ts
+++ b/polygerrit-ui/app/elements/checks/gr-checks-results.ts
@@ -52,7 +52,7 @@
   fireActionTriggered,
   firstPrimaryLink,
   hasCompletedWithoutResults,
-  iconForCategory,
+  iconFor,
   iconForLink,
   otherPrimaryLinks,
   primaryRunAction,
@@ -60,7 +60,7 @@
   tooltipForLink,
 } from '../../services/checks/checks-util';
 import {assertIsDefined, check} from '../../utils/common-util';
-import {toggleClass, whenVisible} from '../../utils/dom-util';
+import {modifierPressed, toggleClass, whenVisible} from '../../utils/dom-util';
 import {durationString} from '../../utils/date-util';
 import {charsOnly} from '../../utils/string-util';
 import {isAttemptSelected} from './gr-checks-util';
@@ -83,6 +83,9 @@
 
 @customElement('gr-result-row')
 class GrResultRow extends GrLitElement {
+  @query('td.nameCol div.name')
+  nameEl?: HTMLElement;
+
   @property()
   result?: RunResult;
 
@@ -119,9 +122,11 @@
         tr.container {
           border-top: 1px solid var(--border-color);
         }
+        a.link {
+          margin-right: var(--spacing-s);
+        }
         iron-icon.link {
           color: var(--link-color);
-          margin-right: var(--spacing-s);
         }
         td.nameCol div.flex {
           display: flex;
@@ -130,6 +135,7 @@
           overflow: hidden;
           text-overflow: ellipsis;
           margin-right: var(--spacing-s);
+          outline-offset: var(--spacing-xs);
         }
         td.nameCol .space {
           flex-grow: 1;
@@ -137,6 +143,7 @@
         td.nameCol gr-checks-action {
           display: none;
         }
+        tr:focus-within td.nameCol gr-checks-action,
         tr:hover td.nameCol gr-checks-action {
           display: inline-block;
           /* The button should fit into the 20px line-height. The negative
@@ -180,8 +187,13 @@
         tr.container:hover {
           background: var(--hover-background-color);
         }
+        tr.container:focus-within {
+          background: var(--selection-background-color);
+        }
         tr.container td .summary-cell .links,
         tr.container td .summary-cell .actions,
+        tr.container.collapsed:focus-within td .summary-cell .links,
+        tr.container.collapsed:focus-within td .summary-cell .actions,
         tr.container.collapsed:hover td .summary-cell .links,
         tr.container.collapsed:hover td .summary-cell .actions,
         :host(.dropdown-open) tr td .summary-cell .links,
@@ -278,6 +290,10 @@
     super.update(changedProperties);
   }
 
+  focus() {
+    if (this.nameEl) this.nameEl.focus();
+  }
+
   firstUpdated() {
     const loading = this.shadowRoot?.querySelector('.container');
     assertIsDefined(loading, '"Loading" element');
@@ -299,10 +315,18 @@
     }
     return html`
       <tr class="${classMap({container: true, collapsed: !this.isExpanded})}">
-        <td class="nameCol" @click="${this.toggleExpanded}">
+        <td class="nameCol" @click="${this.toggleExpandedClick}">
           <div class="flex">
             <gr-hovercard-run .run="${this.result}"></gr-hovercard-run>
-            <div class="name">${this.result.checkName}</div>
+            <div
+              class="name"
+              role="button"
+              tabindex="0"
+              @click="${this.toggleExpandedClick}"
+              @keydown="${this.toggleExpandedPress}"
+            >
+              ${this.result.checkName}
+            </div>
             <div class="space"></div>
             ${this.renderPrimaryRunAction()}
           </div>
@@ -311,7 +335,7 @@
           <div class="summary-cell">
             ${this.renderLink(firstPrimaryLink(this.result))}
             ${this.renderSummary(this.result.summary)}
-            <div class="message" @click="${this.toggleExpanded}">
+            <div class="message" @click="${this.toggleExpandedClick}">
               ${this.isExpanded ? '' : this.result.message}
             </div>
             ${this.renderLinks()} ${this.renderActions()}
@@ -321,7 +345,7 @@
             ${this.renderLabel()}
           </div>
         </td>
-        <td class="expanderCol" @click="${this.toggleExpanded}">
+        <td class="expanderCol" @click="${this.toggleExpandedClick}">
           <div
             class="show-hide"
             role="switch"
@@ -331,7 +355,7 @@
             aria-label="${this.isExpanded
               ? 'Collapse result row'
               : 'Expand result row'}"
-            @keydown="${this.toggleExpanded}"
+            @keydown="${this.toggleExpandedPress}"
           >
             <iron-icon
               icon="${this.isExpanded
@@ -361,6 +385,23 @@
     ></gr-result-expanded>`;
   }
 
+  private toggleExpandedClick(e: MouseEvent) {
+    if (!this.isExpandable) return;
+    e.preventDefault();
+    e.stopPropagation();
+    this.toggleExpanded();
+  }
+
+  private toggleExpandedPress(e: KeyboardEvent) {
+    if (!this.isExpandable) return;
+    if (modifierPressed(e)) return;
+    // Only react to `return` and `space`.
+    if (e.keyCode !== 13 && e.keyCode !== 32) return;
+    e.preventDefault();
+    e.stopPropagation();
+    this.toggleExpanded();
+  }
+
   private toggleExpanded() {
     if (!this.isExpandable) return;
     this.isExpanded = !this.isExpanded;
@@ -383,10 +424,14 @@
     if (!this.result?.isLatestAttempt) return;
     const info = this.labels?.[label];
     const status = getLabelStatus(info).toLowerCase();
-    const value = valueString(getRepresentativeValue(info));
+    const value = getRepresentativeValue(info);
+    // A neutral vote is not interesting for the user to see and is just
+    // cluttering the UI.
+    if (value === 0) return;
+    const valueStr = valueString(value);
     return html`
       <div class="label ${status}">
-        <span>${label} ${value}</span>
+        <span>${label} ${valueStr}</span>
         <paper-tooltip offset="5" fit-to-visible-bounds="true">
           The check result has (probably) influenced this label vote.
         </paper-tooltip>
@@ -414,7 +459,7 @@
     if (this.isExpanded) return;
     if (!link) return;
     const tooltipText = link.tooltip ?? tooltipForLink(link.icon);
-    return html`<a href="${link.url}" target="_blank"
+    return html`<a href="${link.url}" class="link" target="_blank"
       ><iron-icon
         aria-label="external link to details"
         class="link"
@@ -897,7 +942,7 @@
       ) {
         let cat = statusOrCategory.toString().toLowerCase();
         if (statusOrCategory === RunStatus.COMPLETED) cat = 'success';
-        this.scrollElIntoView(`.categoryHeader .${cat}`);
+        this.scrollElIntoView(`.categoryHeader.${cat} + table gr-result-row`);
       } else if (checkName) {
         this.scrollElIntoView(`gr-result-row.${charsOnly(checkName)}`);
       }
@@ -910,6 +955,7 @@
       // el might be a <gr-result-row> with an empty shadowRoot. Let's wait a
       // moment before trying to find a child element in it.
       setTimeout(() => {
+        if (el) (el as HTMLElement).focus();
         // <gr-result-row> has display:contents and cannot be scrolled into view
         // itself. Thus we are preferring to scroll the first child into view.
         el = el?.shadowRoot?.firstElementChild ?? el;
@@ -1184,7 +1230,7 @@
           <iron-icon class="expandIcon" icon="${icon}"></iron-icon>
           <div class="statusIconWrapper">
             <iron-icon
-              icon="gr-icons:${iconForCategory(category)}"
+              icon="gr-icons:${iconFor(category)}"
               class="statusIcon ${catString}"
             ></iron-icon>
             <span class="title">${catString}</span>
diff --git a/polygerrit-ui/app/elements/checks/gr-checks-runs.ts b/polygerrit-ui/app/elements/checks/gr-checks-runs.ts
index 4f9fd1d..0cf47cd 100644
--- a/polygerrit-ui/app/elements/checks/gr-checks-runs.ts
+++ b/polygerrit-ui/app/elements/checks/gr-checks-runs.ts
@@ -33,7 +33,7 @@
   AttemptDetail,
   compareByWorstCategory,
   fireActionTriggered,
-  iconForCategory,
+  iconFor,
   iconForRun,
   PRIMARY_STATUS_ACTIONS,
   primaryRunAction,
@@ -317,7 +317,7 @@
     if (this.run.status !== RunStatus.RUNNING) return nothing;
     const category = worstCategory(this.run);
     if (!category) return nothing;
-    const icon = iconForCategory(category);
+    const icon = iconFor(category);
     return html`
       <iron-icon class="${icon}" icon="gr-icons:${icon}"></iron-icon>
     `;
diff --git a/polygerrit-ui/app/elements/checks/gr-hovercard-run.ts b/polygerrit-ui/app/elements/checks/gr-hovercard-run.ts
index 59b9de8..9d50b1c 100644
--- a/polygerrit-ui/app/elements/checks/gr-hovercard-run.ts
+++ b/polygerrit-ui/app/elements/checks/gr-hovercard-run.ts
@@ -22,8 +22,7 @@
 import './gr-checks-action';
 import {CheckRun} from '../../services/checks/checks-model';
 import {
-  iconForCategory,
-  iconForStatus,
+  iconFor,
   runActions,
   worstCategory,
 } from '../../services/checks/checks-util';
@@ -43,9 +42,9 @@
   computeIcon(run?: CheckRun) {
     if (!run) return '';
     const category = worstCategory(run);
-    if (category) return iconForCategory(category);
+    if (category) return iconFor(category);
     return run.status === RunStatus.COMPLETED
-      ? iconForStatus(RunStatus.COMPLETED)
+      ? iconFor(RunStatus.COMPLETED)
       : '';
   }
 
diff --git a/polygerrit-ui/app/elements/plugins/gr-checks-api/gr-checks-api.ts b/polygerrit-ui/app/elements/plugins/gr-checks-api/gr-checks-api.ts
index 39d3c8b..087779e 100644
--- a/polygerrit-ui/app/elements/plugins/gr-checks-api/gr-checks-api.ts
+++ b/polygerrit-ui/app/elements/plugins/gr-checks-api/gr-checks-api.ts
@@ -19,6 +19,8 @@
   ChecksApiConfig,
   ChecksProvider,
   ChecksPluginApi,
+  CheckResult,
+  CheckRun,
 } from '../../../api/checks';
 import {appContext} from '../../../services/app-context';
 
@@ -54,6 +56,13 @@
     this.checksService.reload(this.plugin.getPluginName());
   }
 
+  updateResult(run: CheckRun, result: CheckResult) {
+    if (result.externalId === undefined) {
+      throw new Error('ChecksApi.updateResult() was called without externalId');
+    }
+    this.checksService.updateResult(this.plugin.getPluginName(), run, result);
+  }
+
   register(provider: ChecksProvider, config?: ChecksApiConfig): void {
     this.reporting.trackApi(this.plugin, 'checks', 'register');
     if (this.state === State.REGISTERED)
diff --git a/polygerrit-ui/app/elements/shared/gr-icons/gr-icons.ts b/polygerrit-ui/app/elements/shared/gr-icons/gr-icons.ts
index 8968e18..519c24d 100644
--- a/polygerrit-ui/app/elements/shared/gr-icons/gr-icons.ts
+++ b/polygerrit-ui/app/elements/shared/gr-icons/gr-icons.ts
@@ -148,8 +148,10 @@
       <g id="playArrow"><path d="M0 0h24v24H0z" fill="none"/><path d="M8 5v14l11-7z"/></g>
       <!-- This SVG is a copy from material.io https://fonts.google.com/icons?selected=Material%20Icons%3Apause-->
       <g id="pause"><path d="M0 0h24v24H0z" fill="none"/><path d="M6 19h4V5H6v14zm8-14v14h4V5h-4z"/></g>
-      <!-- This SVG is a copy from material.io https://material.io/icons/#code-->
+      <!-- This SVG is a copy from material.io https://fonts.google.com/icons?selected=Material%20Icons%3Acode-->
       <g id="code"><path d="M0 0h24v24H0V0z" fill="none"/><path d="M9.4 16.6L4.8 12l4.6-4.6L8 6l-6 6 6 6 1.4-1.4zm5.2 0l4.6-4.6-4.6-4.6L16 6l6 6-6 6-1.4-1.4z"/></g>
+      <!-- This SVG is a copy from material.io https://fonts.google.com/icons?selected=Material%20Icons%3Afile_present-->
+      <g id="file-present"><path d="M0 0h24v24H0V0z" fill="none"/><path d="M15 2H6c-1.1 0-2 .9-2 2v16c0 1.1.9 2 2 2h12c1.1 0 2-.9 2-2V7l-5-5zM6 20V4h8v4h4v12H6zm10-10v5c0 2.21-1.79 4-4 4s-4-1.79-4-4V8.5c0-1.47 1.26-2.64 2.76-2.49 1.3.13 2.24 1.32 2.24 2.63V15h-2V8.5c0-.28-.22-.5-.5-.5s-.5.22-.5.5V15c0 1.1.9 2 2 2s2-.9 2-2v-5h2z"/></g>
     </defs>
   </svg>
 </iron-iconset-svg>`;
diff --git a/polygerrit-ui/app/services/checks/checks-model.ts b/polygerrit-ui/app/services/checks/checks-model.ts
index 570d80a..3a0bbf2 100644
--- a/polygerrit-ui/app/services/checks/checks-model.ts
+++ b/polygerrit-ui/app/services/checks/checks-model.ts
@@ -114,7 +114,20 @@
   pluginStateSelected: {},
 };
 
-const privateState$ = new BehaviorSubject(initialState);
+// Mutable for testing
+let privateState$ = new BehaviorSubject(initialState);
+
+export function _testOnly_resetState() {
+  privateState$ = new BehaviorSubject(initialState);
+}
+
+export function _testOnly_setState(state: ChecksState) {
+  privateState$.next(state);
+}
+
+export function _testOnly_getState() {
+  return privateState$.getValue();
+}
 
 // Re-exporting as Observable so that you can only subscribe, but not emit.
 export const checksState$: Observable<ChecksState> = privateState$;
@@ -533,6 +546,14 @@
       internalResultId: 'f44r0',
       category: Category.INFO,
       summary: 'Dont be afraid. All TODOs will be eliminated.',
+      actions: [
+        {
+          name: 'Re-Run',
+          tooltip: 'More powerful run than before with a long tooltip, really.',
+          primary: true,
+          callback: () => Promise.resolve({message: 'fake "re-run" triggered'}),
+        },
+      ],
     },
   ],
 };
@@ -711,6 +732,42 @@
   privateState$.next(nextState);
 }
 
+export function updateStateUpdateResult(
+  pluginName: string,
+  updatedRun: CheckRunApi,
+  updatedResult: CheckResultApi,
+  patchset: ChecksPatchset
+) {
+  const nextState = {...privateState$.getValue()};
+  const pluginState = getPluginState(nextState, patchset);
+  let runUpdated = false;
+  const runs: CheckRun[] = pluginState[pluginName].runs.map(run => {
+    if (run.change !== updatedRun.change) return run;
+    if (run.patchset !== updatedRun.patchset) return run;
+    if (run.attempt !== updatedRun.attempt) return run;
+    if (run.checkName !== updatedRun.checkName) return run;
+    let resultUpdated = false;
+    const results: CheckResult[] = (run.results ?? []).map(result => {
+      if (result.externalId && result.externalId === updatedResult.externalId) {
+        runUpdated = true;
+        resultUpdated = true;
+        return {
+          ...updatedResult,
+          internalResultId: result.internalResultId,
+        };
+      }
+      return result;
+    });
+    return resultUpdated ? {...run, results} : run;
+  });
+  if (!runUpdated) return;
+  pluginState[pluginName] = {
+    ...pluginState[pluginName],
+    runs,
+  };
+  privateState$.next(nextState);
+}
+
 export function updateStateSetPatchset(patchsetNumber?: PatchSetNumber) {
   const nextState = {...privateState$.getValue()};
   nextState.patchsetNumberSelected = patchsetNumber;
diff --git a/polygerrit-ui/app/services/checks/checks-model_test.ts b/polygerrit-ui/app/services/checks/checks-model_test.ts
new file mode 100644
index 0000000..f05facb
--- /dev/null
+++ b/polygerrit-ui/app/services/checks/checks-model_test.ts
@@ -0,0 +1,91 @@
+/**
+ * @license
+ * Copyright (C) 2021 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+import '../../test/common-test-setup-karma';
+import './checks-model';
+import {
+  _testOnly_getState,
+  _testOnly_resetState,
+  ChecksPatchset,
+  updateStateSetProvider,
+  updateStateSetResults,
+  updateStateUpdateResult,
+} from './checks-model';
+import {Category, CheckRun, RunStatus} from '../../api/checks';
+
+const PLUGIN_NAME = 'test-plugin';
+
+const RUNS: CheckRun[] = [
+  {
+    checkName: 'MacCheck',
+    change: 123,
+    patchset: 1,
+    attempt: 1,
+    status: RunStatus.COMPLETED,
+    results: [
+      {
+        externalId: 'id-314',
+        category: Category.WARNING,
+        summary: 'Meddle cheddle check and you are weg.',
+      },
+    ],
+  },
+];
+
+suite('checks-model tests', () => {
+  test('updateStateSetProvider', () => {
+    _testOnly_resetState();
+    updateStateSetProvider(PLUGIN_NAME, ChecksPatchset.LATEST);
+    const state = _testOnly_getState().pluginStateLatest[PLUGIN_NAME];
+    assert.deepEqual(state, {
+      pluginName: PLUGIN_NAME,
+      loading: false,
+      runs: [],
+      actions: [],
+      links: [],
+    });
+  });
+
+  test('updateStateSetResults', () => {
+    _testOnly_resetState();
+    updateStateSetResults(PLUGIN_NAME, RUNS, [], [], ChecksPatchset.LATEST);
+    const state = _testOnly_getState().pluginStateLatest[PLUGIN_NAME];
+    assert.lengthOf(state.runs, 1);
+    assert.lengthOf(state.runs[0].results!, 1);
+  });
+
+  test('updateStateUpdateResult', () => {
+    _testOnly_resetState();
+    updateStateSetResults(PLUGIN_NAME, RUNS, [], [], ChecksPatchset.LATEST);
+    let state = _testOnly_getState().pluginStateLatest[PLUGIN_NAME];
+    assert.equal(
+      state.runs[0].results![0].summary,
+      RUNS[0]!.results![0].summary
+    );
+    const result = RUNS[0].results![0];
+    const updatedResult = {...result, summary: 'new'};
+    updateStateUpdateResult(
+      PLUGIN_NAME,
+      RUNS[0],
+      updatedResult,
+      ChecksPatchset.LATEST
+    );
+    state = _testOnly_getState().pluginStateLatest[PLUGIN_NAME];
+    assert.lengthOf(state.runs, 1);
+    assert.lengthOf(state.runs[0].results!, 1);
+    assert.equal(state.runs[0].results![0].summary, 'new');
+  });
+});
diff --git a/polygerrit-ui/app/services/checks/checks-service.ts b/polygerrit-ui/app/services/checks/checks-service.ts
index bc05484..7844fa6 100644
--- a/polygerrit-ui/app/services/checks/checks-service.ts
+++ b/polygerrit-ui/app/services/checks/checks-service.ts
@@ -25,6 +25,8 @@
 } from 'rxjs/operators';
 import {
   ChangeData,
+  CheckResult,
+  CheckRun,
   ChecksApiConfig,
   ChecksProvider,
   FetchResponse,
@@ -41,6 +43,7 @@
   updateStateSetPatchset,
   updateStateSetProvider,
   updateStateSetResults,
+  updateStateUpdateResult,
 } from './checks-model';
 import {
   BehaviorSubject,
@@ -112,6 +115,11 @@
     if (plugin) this.reload(plugin);
   }
 
+  updateResult(pluginName: string, run: CheckRun, result: CheckResult) {
+    updateStateUpdateResult(pluginName, run, result, ChecksPatchset.LATEST);
+    updateStateUpdateResult(pluginName, run, result, ChecksPatchset.SELECTED);
+  }
+
   register(
     pluginName: string,
     provider: ChecksProvider,
@@ -179,15 +187,16 @@
       )
       .subscribe(response => {
         switch (response.responseCode) {
-          case ResponseCode.ERROR:
-            assertIsDefined(response.errorMessage, 'errorMessage');
+          case ResponseCode.ERROR: {
+            const message = response.errorMessage ?? '-';
             this.reporting.reportExecution(Execution.CHECKS_API_ERROR, {
               plugin: pluginName,
-              message: response.errorMessage,
+              message,
             });
-            updateStateSetError(pluginName, response.errorMessage, patchset);
+            updateStateSetError(pluginName, message, patchset);
             break;
-          case ResponseCode.NOT_LOGGED_IN:
+          }
+          case ResponseCode.NOT_LOGGED_IN: {
             assertIsDefined(response.loginCallback, 'loginCallback');
             this.reporting.reportExecution(Execution.CHECKS_API_NOT_LOGGED_IN, {
               plugin: pluginName,
@@ -198,7 +207,8 @@
               patchset
             );
             break;
-          case ResponseCode.OK:
+          }
+          case ResponseCode.OK: {
             updateStateSetResults(
               pluginName,
               response.runs ?? [],
@@ -207,6 +217,7 @@
               patchset
             );
             break;
+          }
         }
       });
   }
diff --git a/polygerrit-ui/app/services/checks/checks-util.ts b/polygerrit-ui/app/services/checks/checks-util.ts
index 9381f30..897308e 100644
--- a/polygerrit-ui/app/services/checks/checks-util.ts
+++ b/polygerrit-ui/app/services/checks/checks-util.ts
@@ -17,11 +17,11 @@
 import {
   Action,
   Category,
-  CheckRun as CheckRunApi,
   CheckResult as CheckResultApi,
+  CheckRun as CheckRunApi,
+  Link,
   LinkIcon,
   RunStatus,
-  Link,
 } from '../../api/checks';
 import {assertNever} from '../../utils/common-util';
 import {CheckResult, CheckRun} from './checks-model';
@@ -45,6 +45,8 @@
       return 'bug';
     case LinkIcon.CODE:
       return 'code';
+    case LinkIcon.FILE_PRESENT:
+      return 'file-present';
     default:
       // We don't throw an assertion error here, because plugins don't have to
       // be written in TypeScript, so we may encounter arbitrary strings for
@@ -70,6 +72,10 @@
       return 'Link to help page';
     case LinkIcon.REPORT_BUG:
       return 'Link for reporting a problem';
+    case LinkIcon.CODE:
+      return 'Link to code';
+    case LinkIcon.FILE_PRESENT:
+      return 'Link to file';
     default:
       // We don't throw an assertion error here, because plugins don't have to
       // be written in TypeScript, so we may encounter arbitrary strings for
@@ -86,8 +92,37 @@
   return undefined;
 }
 
-export function iconForCategory(category: Category) {
-  switch (category) {
+export function isStatus(catStat: Category | RunStatus) {
+  return (
+    catStat === RunStatus.COMPLETED ||
+    catStat === RunStatus.RUNNABLE ||
+    catStat === RunStatus.RUNNING
+  );
+}
+
+export function labelFor(catStat: Category | RunStatus) {
+  switch (catStat) {
+    case Category.ERROR:
+      return 'error';
+    case Category.INFO:
+      return 'info';
+    case Category.WARNING:
+      return 'warning';
+    case Category.SUCCESS:
+      return 'success';
+    case RunStatus.COMPLETED:
+      return 'completed';
+    case RunStatus.RUNNABLE:
+      return 'runnable';
+    case RunStatus.RUNNING:
+      return 'running';
+    default:
+      assertNever(catStat, `Unsupported category/status: ${catStat}`);
+  }
+}
+
+export function iconFor(catStat: Category | RunStatus) {
+  switch (catStat) {
     case Category.ERROR:
       return 'error';
     case Category.INFO:
@@ -96,8 +131,15 @@
       return 'warning';
     case Category.SUCCESS:
       return 'check-circle-outline';
+    // Note that this is only for COMPLETED without results!
+    case RunStatus.COMPLETED:
+      return 'check-circle-outline';
+    case RunStatus.RUNNABLE:
+      return 'placeholder';
+    case RunStatus.RUNNING:
+      return 'timelapse';
     default:
-      assertNever(category, `Unsupported category: ${category}`);
+      assertNever(catStat, `Unsupported category/status: ${catStat}`);
   }
 }
 
@@ -145,24 +187,10 @@
 
 export function iconForRun(run: CheckRun) {
   if (run.status !== RunStatus.COMPLETED) {
-    return iconForStatus(run.status);
+    return iconFor(run.status);
   } else {
     const category = worstCategory(run);
-    return category ? iconForCategory(category) : iconForStatus(run.status);
-  }
-}
-
-export function iconForStatus(status: RunStatus) {
-  switch (status) {
-    // Note that this is only for COMPLETED without results!
-    case RunStatus.COMPLETED:
-      return 'check-circle-outline';
-    case RunStatus.RUNNABLE:
-      return 'placeholder';
-    case RunStatus.RUNNING:
-      return 'timelapse';
-    default:
-      assertNever(status, `Unsupported status: ${status}`);
+    return category ? iconFor(category) : iconFor(run.status);
   }
 }
 
diff --git a/polygerrit-ui/app/utils/comment-util.ts b/polygerrit-ui/app/utils/comment-util.ts
index 2d5f66e..fd276c3 100644
--- a/polygerrit-ui/app/utils/comment-util.ts
+++ b/polygerrit-ui/app/utils/comment-util.ts
@@ -27,6 +27,7 @@
   ContextLine,
   BasePatchSetNum,
   RevisionPatchSetNum,
+  AccountInfo,
 } from '../types/common';
 import {CommentSide, Side, SpecialFilePath} from '../constants/constants';
 import {parseDate} from './date-util';
@@ -330,3 +331,18 @@
   };
   return diff;
 }
+
+export function getCommentAuthors(threads?: CommentThread[]) {
+  if (!threads) return [];
+  const ids = new Set();
+  const authors: AccountInfo[] = [];
+  threads.forEach(t =>
+    t.comments.forEach(c => {
+      if (c.author && !ids.has(c.author._account_id)) {
+        ids.add(c.author._account_id);
+        authors.push(c.author);
+      }
+    })
+  );
+  return authors;
+}
diff --git a/polygerrit-ui/app/utils/dom-util.ts b/polygerrit-ui/app/utils/dom-util.ts
index 4f83881..e7cc956 100644
--- a/polygerrit-ui/app/utils/dom-util.ts
+++ b/polygerrit-ui/app/utils/dom-util.ts
@@ -294,6 +294,11 @@
   }
 }
 
+export function modifierPressed(e: KeyboardEvent) {
+  return e.altKey || e.ctrlKey || e.metaKey || e.shiftKey;
+}
+
+// Deprecated. Try using "normal" KeyboardEvent and modifierPressed() above.
 export function isModifierPressed(event: CustomKeyboardEvent) {
   const e = getKeyboardEvent(event);
   return e.altKey || e.ctrlKey || e.metaKey || e.shiftKey;