diff --git a/polygerrit-ui/app/elements/admin/gr-admin-group-list/gr-admin-group-list.ts b/polygerrit-ui/app/elements/admin/gr-admin-group-list/gr-admin-group-list.ts
index 893a997..b30619e 100644
--- a/polygerrit-ui/app/elements/admin/gr-admin-group-list/gr-admin-group-list.ts
+++ b/polygerrit-ui/app/elements/admin/gr-admin-group-list/gr-admin-group-list.ts
@@ -61,7 +61,7 @@
   override connectedCallback() {
     super.connectedCallback();
     this.getCreateGroupCapability();
-    fireTitleChange(this, 'Groups');
+    fireTitleChange('Groups');
   }
 
   static override get styles() {
diff --git a/polygerrit-ui/app/elements/admin/gr-group-audit-log/gr-group-audit-log.ts b/polygerrit-ui/app/elements/admin/gr-group-audit-log/gr-group-audit-log.ts
index e0c0d30..f4a7bf3 100644
--- a/polygerrit-ui/app/elements/admin/gr-group-audit-log/gr-group-audit-log.ts
+++ b/polygerrit-ui/app/elements/admin/gr-group-audit-log/gr-group-audit-log.ts
@@ -40,7 +40,7 @@
 
   override connectedCallback() {
     super.connectedCallback();
-    fireTitleChange(this, 'Audit Log');
+    fireTitleChange('Audit Log');
   }
 
   static override get styles() {
diff --git a/polygerrit-ui/app/elements/admin/gr-group-members/gr-group-members.ts b/polygerrit-ui/app/elements/admin/gr-group-members/gr-group-members.ts
index f8d9934..cffde7a 100644
--- a/polygerrit-ui/app/elements/admin/gr-group-members/gr-group-members.ts
+++ b/polygerrit-ui/app/elements/admin/gr-group-members/gr-group-members.ts
@@ -129,7 +129,7 @@
     super.connectedCallback();
     this.loadGroupDetails();
 
-    fireTitleChange(this, 'Members');
+    fireTitleChange('Members');
   }
 
   static override get styles() {
diff --git a/polygerrit-ui/app/elements/admin/gr-group/gr-group.ts b/polygerrit-ui/app/elements/admin/gr-group/gr-group.ts
index 1ec83efa8..223a700 100644
--- a/polygerrit-ui/app/elements/admin/gr-group/gr-group.ts
+++ b/polygerrit-ui/app/elements/admin/gr-group/gr-group.ts
@@ -342,7 +342,7 @@
     this.groupConfig = config;
     this.originalOptionsVisibleToAll = config?.options?.visible_to_all;
 
-    fireTitleChange(this, config.name);
+    fireTitleChange(config.name);
 
     await Promise.all(promises);
     this.loading = false;
diff --git a/polygerrit-ui/app/elements/admin/gr-plugin-list/gr-plugin-list.ts b/polygerrit-ui/app/elements/admin/gr-plugin-list/gr-plugin-list.ts
index a2de840..cb17de7 100644
--- a/polygerrit-ui/app/elements/admin/gr-plugin-list/gr-plugin-list.ts
+++ b/polygerrit-ui/app/elements/admin/gr-plugin-list/gr-plugin-list.ts
@@ -47,7 +47,7 @@
 
   override connectedCallback() {
     super.connectedCallback();
-    fireTitleChange(this, 'Plugins');
+    fireTitleChange('Plugins');
   }
 
   static override get styles() {
diff --git a/polygerrit-ui/app/elements/admin/gr-repo-commands/gr-repo-commands.ts b/polygerrit-ui/app/elements/admin/gr-repo-commands/gr-repo-commands.ts
index 11cfaab..553de0e 100644
--- a/polygerrit-ui/app/elements/admin/gr-repo-commands/gr-repo-commands.ts
+++ b/polygerrit-ui/app/elements/admin/gr-repo-commands/gr-repo-commands.ts
@@ -91,7 +91,7 @@
 
   override connectedCallback() {
     super.connectedCallback();
-    fireTitleChange(this, 'Repo Commands');
+    fireTitleChange('Repo Commands');
   }
 
   static override get styles() {
diff --git a/polygerrit-ui/app/elements/admin/gr-repo-list/gr-repo-list.ts b/polygerrit-ui/app/elements/admin/gr-repo-list/gr-repo-list.ts
index 4837f1a..5318500 100644
--- a/polygerrit-ui/app/elements/admin/gr-repo-list/gr-repo-list.ts
+++ b/polygerrit-ui/app/elements/admin/gr-repo-list/gr-repo-list.ts
@@ -59,7 +59,7 @@
   override async connectedCallback() {
     super.connectedCallback();
     await this.getCreateRepoCapability();
-    fireTitleChange(this, 'Repos');
+    fireTitleChange('Repos');
     this.maybeOpenCreateModal(this.params);
   }
 
diff --git a/polygerrit-ui/app/elements/admin/gr-repo/gr-repo.ts b/polygerrit-ui/app/elements/admin/gr-repo/gr-repo.ts
index 3599224..4bbd533 100644
--- a/polygerrit-ui/app/elements/admin/gr-repo/gr-repo.ts
+++ b/polygerrit-ui/app/elements/admin/gr-repo/gr-repo.ts
@@ -134,7 +134,7 @@
   override connectedCallback() {
     super.connectedCallback();
 
-    fireTitleChange(this, `${this.repo}`);
+    fireTitleChange(`${this.repo}`);
   }
 
   static override get styles() {
diff --git a/polygerrit-ui/app/elements/change-list/gr-change-list-bulk-abandon-flow/gr-change-list-bulk-abandon-flow.ts b/polygerrit-ui/app/elements/change-list/gr-change-list-bulk-abandon-flow/gr-change-list-bulk-abandon-flow.ts
index df63780..2ca7f36 100644
--- a/polygerrit-ui/app/elements/change-list/gr-change-list-bulk-abandon-flow/gr-change-list-bulk-abandon-flow.ts
+++ b/polygerrit-ui/app/elements/change-list/gr-change-list-bulk-abandon-flow/gr-change-list-bulk-abandon-flow.ts
@@ -147,7 +147,7 @@
   private handleClose() {
     this.actionModal.close();
     fireAlert(this, 'Reloading page..');
-    fireReload(this, true);
+    fireReload(this);
   }
 }
 
diff --git a/polygerrit-ui/app/elements/change-list/gr-change-list-bulk-vote-flow/gr-change-list-bulk-vote-flow.ts b/polygerrit-ui/app/elements/change-list/gr-change-list-bulk-vote-flow/gr-change-list-bulk-vote-flow.ts
index db82523..6d7045a 100644
--- a/polygerrit-ui/app/elements/change-list/gr-change-list-bulk-vote-flow/gr-change-list-bulk-vote-flow.ts
+++ b/polygerrit-ui/app/elements/change-list/gr-change-list-bulk-vote-flow/gr-change-list-bulk-vote-flow.ts
@@ -308,7 +308,7 @@
     this.actionModal.close();
     if (getOverallStatus(this.progressByChange) === ProgressStatus.NOT_STARTED)
       return;
-    fireReload(this, true);
+    fireReload(this);
   }
 
   private async handleConfirm() {
diff --git a/polygerrit-ui/app/elements/change-list/gr-change-list-view/gr-change-list-view.ts b/polygerrit-ui/app/elements/change-list/gr-change-list-view/gr-change-list-view.ts
index 8afc283..07a27c6 100644
--- a/polygerrit-ui/app/elements/change-list/gr-change-list-view/gr-change-list-view.ts
+++ b/polygerrit-ui/app/elements/change-list/gr-change-list-view/gr-change-list-view.ts
@@ -32,12 +32,6 @@
 
 @customElement('gr-change-list-view')
 export class GrChangeListView extends LitElement {
-  /**
-   * Fired when the title of the page should change.
-   *
-   * @event title-change
-   */
-
   @query('#prevArrow') protected prevArrow?: HTMLAnchorElement;
 
   @query('#nextArrow') protected nextArrow?: HTMLAnchorElement;
@@ -248,7 +242,7 @@
 
   override updated(changedProperties: PropertyValues) {
     if (changedProperties.has('query')) {
-      fireTitleChange(this, this.query);
+      fireTitleChange(this.query);
     }
   }
 
diff --git a/polygerrit-ui/app/elements/change-list/gr-dashboard-view/gr-dashboard-view.ts b/polygerrit-ui/app/elements/change-list/gr-dashboard-view/gr-dashboard-view.ts
index 70f1755..cb6d047 100644
--- a/polygerrit-ui/app/elements/change-list/gr-dashboard-view/gr-dashboard-view.ts
+++ b/polygerrit-ui/app/elements/change-list/gr-dashboard-view/gr-dashboard-view.ts
@@ -68,12 +68,6 @@
 
 @customElement('gr-dashboard-view')
 export class GrDashboardView extends LitElement {
-  /**
-   * Fired when the title of the page should change.
-   *
-   * @event title-change
-   */
-
   @query('#confirmDeleteDialog') protected confirmDeleteDialog?: GrDialog;
 
   @query('#commandsDialog') protected commandsDialog?: GrCreateCommandsDialog;
@@ -404,7 +398,7 @@
     return dashboardPromise
       .then(res => {
         if (res && res.title) {
-          fireTitleChange(this, res.title);
+          fireTitleChange(res.title);
         }
         return this.fetchDashboardChanges(res, checkForNewUser);
       })
@@ -413,7 +407,7 @@
         this.reporting.dashboardDisplayed();
       })
       .catch(err => {
-        fireTitleChange(this, title || this.computeTitle(user));
+        fireTitleChange(title || this.computeTitle(user));
         this.reporting.error('Dashboard reload', err);
       })
       .finally(() => {
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 0b96ce7..4eee3cb 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
@@ -81,7 +81,6 @@
   fireAlert,
   fireError,
   fireNoBubbleNoCompose,
-  fireReload,
 } from '../../../utils/event-util';
 import {
   getApprovalInfo,
@@ -393,9 +392,6 @@
   @property({type: Boolean})
   disableEdit = false;
 
-  @property({type: Boolean})
-  _hasKnownChainState = false;
-
   // private but used in test
   @state() _hideQuickApproveAction = false;
 
@@ -411,9 +407,6 @@
   @property({type: String})
   commitNum?: CommitId;
 
-  @property({type: Boolean})
-  hasParent?: boolean;
-
   @state() latestPatchNum?: PatchSetNumber;
 
   @property({type: String})
@@ -678,14 +671,12 @@
         <gr-confirm-rebase-dialog
           id="confirmRebase"
           class="confirmDialog"
-          .changeNumber=${this.change?._number}
           @confirm-rebase=${this.handleRebaseConfirm}
           @cancel=${this.handleConfirmDialogCancel}
           .disableActions=${this.inProgressActionKeys.has(
             RevisionActions.REBASE
           )}
           .branch=${this.change?.branch}
-          .hasParent=${this.hasParent}
           .rebaseOnCurrent=${this.revisionRebaseAction
             ? !!this.revisionRebaseAction.enabled
             : null}
@@ -810,10 +801,6 @@
   }
 
   override willUpdate(changedProperties: PropertyValues) {
-    if (changedProperties.has('hasParent')) {
-      this.computeChainState();
-    }
-
     if (changedProperties.has('change')) {
       this.reload();
       this.actions = this.change?.actions ?? {};
@@ -1543,22 +1530,10 @@
     return key === '/' ? key : `/${key}`;
   }
 
-  /**
-   * _hasKnownChainState set to true true if hasParent is defined (can be
-   * either true or false). set to false otherwise.
-   *
-   * private but used in test
-   */
-  computeChainState() {
-    this._hasKnownChainState = true;
-  }
-
-  // private but used in test
-  calculateDisabled(action: UIActionInfo) {
-    if (action.__key === 'rebase') {
-      // Rebase button is only disabled when change has no parent(s).
-      return this._hasKnownChainState === false;
-    }
+  private calculateDisabled(action: UIActionInfo) {
+    // TODO(b/270972983): Remove this special casing once the backend is more
+    // aggressive about setting`enabled:true`.
+    if (action.__key === 'rebase') return false;
     return !action.enabled;
   }
 
@@ -1893,7 +1868,7 @@
           // Hide rebase dialog only if the action succeeds
           this.actionsModal?.close();
           this.hideAllDialogs();
-          fireReload(this, true);
+          this.getChangeModel().navigateToChangeResetReload();
           break;
         case ChangeActions.REVERT_SUBMISSION: {
           const revertSubmistionInfo = obj as unknown as RevertSubmissionInfo;
@@ -1909,7 +1884,7 @@
           break;
         }
         default:
-          fireReload(this, true);
+          this.getChangeModel().navigateToChangeResetReload();
           break;
       }
     });
@@ -1977,7 +1952,7 @@
               'Cannot set label: a newer patch has been ' +
               'uploaded to this change.',
             action: 'Reload',
-            callback: () => fireReload(this, true),
+            callback: () => this.getChangeModel().navigateToChangeResetReload(),
           });
 
           // Because this is not a network error, call the cleanup function
diff --git a/polygerrit-ui/app/elements/change/gr-change-actions/gr-change-actions_test.ts b/polygerrit-ui/app/elements/change/gr-change-actions/gr-change-actions_test.ts
index 277eddd..946191b 100644
--- a/polygerrit-ui/app/elements/change/gr-change-actions/gr-change-actions_test.ts
+++ b/polygerrit-ui/app/elements/change/gr-change-actions/gr-change-actions_test.ts
@@ -40,7 +40,7 @@
   TopicName,
 } from '../../../types/common';
 import {ActionType} from '../../../api/change-actions';
-import {SinonFakeTimers} from 'sinon';
+import {SinonFakeTimers, SinonStubbedMember} from 'sinon';
 import {IronAutogrowTextareaElement} from '@polymer/iron-autogrow-textarea';
 import {GrButton} from '../../shared/gr-button/gr-button';
 import {GrDialog} from '../../shared/gr-dialog/gr-dialog';
@@ -56,10 +56,17 @@
 import {testResolver} from '../../../test/common-test-setup';
 import {storageServiceToken} from '../../../services/storage/gr-storage_impl';
 import {pluginLoaderToken} from '../../shared/gr-js-api-interface/gr-plugin-loader';
+import {
+  ChangeModel,
+  changeModelToken,
+} from '../../../models/change/change-model';
 
 // TODO(dhruvsri): remove use of _populateRevertMessage as it's private
 suite('gr-change-actions tests', () => {
   let element: GrChangeActions;
+  let navigateResetStub: SinonStubbedMember<
+    ChangeModel['navigateToChangeResetReload']
+  >;
 
   suite('basic tests', () => {
     setup(async () => {
@@ -139,6 +146,10 @@
         _account_id: 123 as AccountId,
       };
       stubRestApi('getRepoBranches').returns(Promise.resolve([]));
+      navigateResetStub = sinon.stub(
+        testResolver(changeModelToken),
+        'navigateToChangeResetReload'
+      );
 
       await element.updateComplete;
       await element.reload();
@@ -177,14 +188,13 @@
                 title="Rebase onto tip of branch or parent change"
               >
                 <gr-button
-                  aria-disabled="true"
+                  aria-disabled="false"
                   class="rebase"
                   data-action-key="rebase"
                   data-label="Rebase"
-                  disabled=""
                   link=""
                   role="button"
-                  tabindex="-1"
+                  tabindex="0"
                 >
                   <gr-icon icon="rebase"> </gr-icon>
                   Rebase
@@ -570,34 +580,6 @@
       assert.equal(fireActionStub.callCount, 0);
     });
 
-    test('chain state', async () => {
-      assert.equal(element._hasKnownChainState, false);
-      element.hasParent = true;
-      await element.updateComplete;
-      assert.equal(element._hasKnownChainState, true);
-    });
-
-    test('calculateDisabled', () => {
-      const action = {
-        __key: 'rebase',
-        enabled: true,
-        __type: ActionType.CHANGE,
-        label: 'l',
-      };
-      element._hasKnownChainState = false;
-      assert.equal(element.calculateDisabled(action), true);
-
-      action.__key = 'delete';
-      assert.equal(element.calculateDisabled(action), false);
-
-      action.__key = 'rebase';
-      element._hasKnownChainState = true;
-      assert.equal(element.calculateDisabled(action), false);
-
-      action.enabled = false;
-      assert.equal(element.calculateDisabled(action), false);
-    });
-
     test('rebase change', async () => {
       const fireActionStub = sinon.stub(element, 'fireAction');
       const fetchChangesStub = sinon
@@ -606,7 +588,6 @@
           'fetchRecentChanges'
         )
         .returns(Promise.resolve([]));
-      element._hasKnownChainState = true;
       await element.updateComplete;
       queryAndAssert<GrButton>(
         element,
@@ -642,13 +623,11 @@
     });
 
     test('rebase change fires reload event', async () => {
-      const eventStub = sinon.stub(element, 'dispatchEvent');
       await element.handleResponse(
         {__key: 'rebase', __type: ActionType.CHANGE, label: 'l'},
         new Response()
       );
-      assert.isTrue(eventStub.called);
-      assert.equal(eventStub.lastCall.args[0].type, 'reload');
+      assert.isTrue(navigateResetStub.called);
     });
 
     test("rebase dialog gets recent changes each time it's opened", async () => {
@@ -658,7 +637,6 @@
           'fetchRecentChanges'
         )
         .returns(Promise.resolve([]));
-      element._hasKnownChainState = true;
       await element.updateComplete;
       const rebaseButton = queryAndAssert<GrButton>(
         element,
@@ -683,7 +661,6 @@
     });
 
     test('two dialogs are not shown at the same time', async () => {
-      element._hasKnownChainState = true;
       await element.updateComplete;
       queryAndAssert<GrButton>(
         element,
diff --git a/polygerrit-ui/app/elements/change/gr-change-metadata/gr-change-metadata.ts b/polygerrit-ui/app/elements/change/gr-change-metadata/gr-change-metadata.ts
index 54752b0..b7851a6 100644
--- a/polygerrit-ui/app/elements/change/gr-change-metadata/gr-change-metadata.ts
+++ b/polygerrit-ui/app/elements/change/gr-change-metadata/gr-change-metadata.ts
@@ -126,6 +126,7 @@
 
   @property({type: Object}) revision?: RevisionInfo | EditRevisionInfo;
 
+  // TODO: Just use `revision.commit` instead.
   @property({type: Object}) commitInfo?: CommitInfoWithRequiredCommit;
 
   @property({type: Object}) serverConfig?: ServerInfo;
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 9dee851..a64dcd2 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
@@ -34,27 +34,16 @@
 import {ChangeStarToggleStarDetail} from '../../shared/gr-change-star/gr-change-star';
 import {GrEditConstants} from '../../edit/gr-edit-constants';
 import {pluralize} from '../../../utils/string-util';
-import {whenVisible} from '../../../utils/dom-util';
+import {untilRendered, whenVisible} from '../../../utils/dom-util';
 import {navigationToken} from '../../core/gr-navigation/gr-navigation';
-import {RevisionInfo as RevisionInfoClass} from '../../shared/revision-info/revision-info';
-import {
-  ChangeStatus,
-  DefaultBase,
-  Tab,
-  DiffViewMode,
-} from '../../../constants/constants';
+import {ChangeStatus, Tab, DiffViewMode} from '../../../constants/constants';
 import {getAppContext} from '../../../services/app-context';
 import {
   computeAllPatchSets,
   computeLatestPatchNum,
-  findEdit,
-  findEditParentRevision,
   PatchSet,
 } from '../../../utils/patch-set-util';
 import {
-  changeIsAbandoned,
-  changeIsMerged,
-  changeIsOpen,
   changeStatuses,
   isInvolved,
   roleDetails,
@@ -63,37 +52,27 @@
 import {GrApplyFixDialog} from '../../diff/gr-apply-fix-dialog/gr-apply-fix-dialog';
 import {GrFileListHeader} from '../gr-file-list-header/gr-file-list-header';
 import {GrEditableContent} from '../../shared/gr-editable-content/gr-editable-content';
-import {GrRelatedChangesList} from '../gr-related-changes-list/gr-related-changes-list';
 import {GrChangeStar} from '../../shared/gr-change-star/gr-change-star';
 import {GrChangeActions} from '../gr-change-actions/gr-change-actions';
 import {
   AccountDetailInfo,
   ActionNameToActionInfoMap,
   BasePatchSetNum,
-  ChangeId,
   ChangeInfo,
   CommentThread,
-  CommitId,
-  CommitInfo,
   ConfigInfo,
   DetailedLabelInfo,
   EDIT,
   LabelNameToInfoMap,
   NumericChangeId,
   PARENT,
-  PatchRange,
   PatchSetNum,
-  PatchSetNumber,
-  PreferencesInfo,
   QuickLabelInfo,
-  RelatedChangeAndCommitInfo,
-  RelatedChangesInfo,
   RevisionInfo,
   RevisionPatchSetNum,
   ServerInfo,
   UrlEncodedCommentId,
   isRobot,
-  ChangeStates,
 } from '../../../types/common';
 import {FocusTarget, GrReplyDialog} from '../gr-reply-dialog/gr-reply-dialog';
 import {GrIncludedInDialog} from '../gr-included-in-dialog/gr-included-in-dialog';
@@ -127,16 +106,15 @@
   fireDialogChange,
   fire,
   fireReload,
-  fireTitleChange,
 } from '../../../utils/event-util';
 import {
   debounce,
   DelayedTask,
   throttleWrap,
   until,
+  waitUntil,
 } from '../../../utils/async-util';
-import {Interaction, Timing} from '../../../constants/reporting';
-import {getRevertCreatedChangeIds} from '../../../utils/message-util';
+import {Interaction} from '../../../constants/reporting';
 import {
   getAddedByReason,
   getRemovedByReason,
@@ -152,7 +130,7 @@
 import {resolve} from '../../../models/dependency';
 import {checksModelToken} from '../../../models/checks/checks-model';
 import {changeModelToken} from '../../../models/change/change-model';
-import {css, html, LitElement, nothing, PropertyValues} from 'lit';
+import {css, html, LitElement, nothing} from 'lit';
 import {a11yStyles} from '../../../styles/gr-a11y-styles';
 import {paperStyles} from '../../../styles/gr-paper-styles';
 import {sharedStyles} from '../../../styles/shared-styles';
@@ -162,7 +140,6 @@
 import {FilesExpandedState} from '../gr-file-list-constants';
 import {subscribe} from '../../lit/subscription-controller';
 import {configModelToken} from '../../../models/config/config-model';
-import {filesModelToken} from '../../../models/change/files-model';
 import {getBaseUrl, prependOrigin} from '../../../utils/url-util';
 import {CopyLink, GrCopyLinks} from '../gr-copy-links/gr-copy-links';
 import {
@@ -176,6 +153,7 @@
 import {userModelToken} from '../../../models/user/user-model';
 import {pluginLoaderToken} from '../../shared/gr-js-api-interface/gr-plugin-loader';
 import {modalStyles} from '../../../styles/gr-modal-styles';
+import {relatedChangesModelToken} from '../../../models/change/related-changes-model';
 
 const MIN_LINES_FOR_COMMIT_COLLAPSE = 18;
 
@@ -199,17 +177,9 @@
 // Making the tab names more unique in case a plugin adds one with same name
 const ROBOT_COMMENTS_LIMIT = 10;
 
-export type ChangeViewPatchRange = Partial<PatchRange>;
-
 @customElement('gr-change-view')
 export class GrChangeView extends LitElement {
   /**
-   * Fired when the title of the page should change.
-   *
-   * @event title-change
-   */
-
-  /**
    * Fired if an error occurs when fetching the change data.
    *
    * @event page-error
@@ -265,35 +235,18 @@
 
   @query('gr-copy-links') private copyLinksDropdown?: GrCopyLinks;
 
-  private _viewState?: ChangeViewState;
-
-  @property({type: Object})
-  get viewState() {
-    return this._viewState;
-  }
-
-  set viewState(viewState: ChangeViewState | undefined) {
-    if (this._viewState === viewState) return;
-    const oldViewState = this._viewState;
-    this._viewState = viewState;
-    this.viewStateChanged();
-    this.requestUpdate('viewState', oldViewState);
-  }
+  @state()
+  viewState?: ChangeViewState;
 
   @property({type: String})
   backPage?: string;
 
   @state()
-  private hasParent?: boolean;
-
-  // Private but used in tests.
-  @state()
   commentThreads?: CommentThread[];
 
   // Don't use, use serverConfig instead.
   private _serverConfig?: ServerInfo;
 
-  // Private but used in tests.
   @state()
   get serverConfig() {
     return this._serverConfig;
@@ -310,10 +263,6 @@
   @state()
   private account?: AccountDetailInfo;
 
-  // Private but used in tests.
-  @state()
-  prefs?: PreferencesInfo;
-
   canStartReview() {
     return !!(
       this.change &&
@@ -341,38 +290,19 @@
 
   // Private but used in tests.
   @state()
-  commitInfo?: CommitInfo;
-
-  // Private but used in tests.
-  @state()
   changeNum?: NumericChangeId;
 
   @state()
   private editingCommitMessage = false;
 
   @state()
-  private latestCommitMessage: string | null = '';
+  private latestCommitMessage = '';
 
-  // Use patchRange getter/setter.
-  private _patchRange?: ChangeViewPatchRange;
+  @state() basePatchNum: BasePatchSetNum = PARENT;
 
-  // Private but used in tests.
-  @state()
-  get patchRange() {
-    return this._patchRange;
-  }
+  @state() patchNum?: RevisionPatchSetNum;
 
-  set patchRange(patchRange: ChangeViewPatchRange | undefined) {
-    if (this._patchRange === patchRange) return;
-    const oldPatchRange = this._patchRange;
-    this._patchRange = patchRange;
-    this.patchNumChanged();
-    this.requestUpdate('patchRange', oldPatchRange);
-  }
-
-  // Private but used in tests.
-  @state()
-  selectedRevision?: RevisionInfo | EditRevisionInfo;
+  @state() revision?: RevisionInfo | EditRevisionInfo;
 
   /**
    * <gr-change-actions> populates this via two-way data binding.
@@ -400,30 +330,14 @@
 
   // Private but used in tests.
   @state()
-  initialLoadComplete = false;
-
-  // Private but used in tests.
-  @state()
   replyDisabled = true;
 
-  // Private but used in tests.
-  @state()
-  changeStatuses: ChangeStates[] = [];
-
   @state()
   private updateCheckTimerHandle?: number | null;
 
   // Private but used in tests.
-  getEditMode() {
-    if (!this.patchRange || !this.viewState) {
-      return false;
-    }
-
-    if (this.viewState.edit) {
-      return true;
-    }
-
-    return this.patchRange.patchNum === EDIT;
+  getEditMode(): boolean {
+    return !!this.viewState?.edit || this.patchNum === EDIT;
   }
 
   isSubmitEnabled(): boolean {
@@ -434,9 +348,7 @@
     );
   }
 
-  // Private but used in tests.
-  @state()
-  mergeable: boolean | null = null;
+  @state() mergeable?: boolean;
 
   /**
    * Plugins can provide (multiple) tabs. For each plugin tab we render an
@@ -503,7 +415,7 @@
   private tabState?: TabState;
 
   @state()
-  private revertedChange?: ChangeInfo;
+  private revertingChange?: ChangeInfo;
 
   // Private but used in tests.
   @state()
@@ -530,10 +442,13 @@
 
   private readonly getConfigModel = resolve(this, configModelToken);
 
-  private readonly getFilesModel = resolve(this, filesModelToken);
-
   private readonly getViewModel = resolve(this, changeViewModelToken);
 
+  private readonly getRelatedChangesModel = resolve(
+    this,
+    relatedChangesModelToken
+  );
+
   private readonly getShortcutsService = resolve(this, shortcutsServiceToken);
 
   private scrollTask?: DelayedTask;
@@ -581,14 +496,7 @@
       this.handleCommitMessageCancel()
     );
     this.addEventListener('open-fix-preview', e => this.onOpenFixPreview(e));
-
     this.addEventListener('show-tab', e => this.setActiveTab(e));
-    this.addEventListener('reload', e => {
-      this.loadData(
-        /* isLocationChange= */ false,
-        /* clearPatchset= */ e.detail && e.detail.clearPatchset
-      );
-    });
   }
 
   private setupShortcuts() {
@@ -596,7 +504,7 @@
     this.shortcutsController.addAbstract(Shortcut.EMOJI_DROPDOWN, () => {}); // docOnly
     this.shortcutsController.addAbstract(Shortcut.MENTIONS_DROPDOWN, () => {}); // docOnly
     this.shortcutsController.addAbstract(Shortcut.REFRESH_CHANGE, () =>
-      fireReload(this, true)
+      this.getChangeModel().navigateToChangeResetReload()
     );
     this.shortcutsController.addAbstract(Shortcut.OPEN_REPLY_DIALOG, () =>
       this.handleOpenReplyDialog()
@@ -666,7 +574,21 @@
     subscribe(
       this,
       () => this.getViewModel().tab$,
-      t => (this.activeTab = t ?? Tab.FILES)
+      t => (this.activeTab = t)
+    );
+    subscribe(
+      this,
+      () => this.getViewModel().commentId$,
+      commentId => (this.scrollCommentId = commentId)
+    );
+    subscribe(
+      this,
+      () => this.getViewModel().openReplyDialog$,
+      openReplyDialog => {
+        // Here we are relying on `this.loggedIn` being set *before*
+        // `openReplyDialog`, but that is fine for this feature.
+        if (openReplyDialog && this.loggedIn) this.handleOpenReplyDialog();
+      }
     );
     subscribe(
       this,
@@ -687,6 +609,11 @@
       () => this.getViewModel().childView$,
       childView => {
         this.isViewCurrent = childView === ChangeChildView.OVERVIEW;
+        // When coming back from ChangeChildView.DIFF we want to restore the
+        // scroll position to what it was before leaving the OVERVIEW page.
+        if (this.isViewCurrent) {
+          document.documentElement.scrollTop = this.scrollPosition ?? 0;
+        }
       }
     );
     subscribe(
@@ -728,6 +655,49 @@
     );
     subscribe(
       this,
+      () => this.getChangeModel().changeNum$,
+      changeNum => {
+        // The change view is tied to a specific change number, so don't update
+        // changeNum to undefined and only set it once.
+        if (changeNum && !this.changeNum) this.changeNum = changeNum;
+      }
+    );
+    subscribe(
+      this,
+      () => this.getChangeModel().patchNum$,
+      patchNum => (this.patchNum = patchNum)
+    );
+    subscribe(
+      this,
+      () => this.getChangeModel().basePatchNum$,
+      basePatchNum => (this.basePatchNum = basePatchNum)
+    );
+    subscribe(
+      this,
+      () => this.getChangeModel().mergeable$,
+      mergeable => (this.mergeable = mergeable)
+    );
+    subscribe(
+      this,
+      () => this.getChangeModel().revision$,
+      revision => (this.revision = revision)
+    );
+    subscribe(
+      this,
+      () => this.getChangeModel().changeLoadingStatus$,
+      status => (this.loading = status !== LoadingStatus.LOADED)
+    );
+    subscribe(
+      this,
+      () => this.getChangeModel().latestRevision$,
+      revision => {
+        this.latestCommitMessage = this.prepareCommitMsgForLinkify(
+          revision?.commit?.message ?? ''
+        );
+      }
+    );
+    subscribe(
+      this,
       () => this.getUserModel().account$,
       account => {
         this.account = account;
@@ -755,6 +725,13 @@
         this.projectConfig = config;
       }
     );
+    subscribe(
+      this,
+      () => this.getRelatedChangesModel().revertingChange$,
+      revertingChange => {
+        this.revertingChange = revertingChange;
+      }
+    );
   }
 
   override connectedCallback() {
@@ -769,6 +746,8 @@
   }
 
   override firstUpdated() {
+    this.maybeScrollToMessage(window.location.hash);
+    this.maybeShowRevertDialog();
     // _onTabSizingChanged is called when iron-items-changed event is fired
     // from iron-selectable but that is called before the element is present
     // in view which whereas the method requires paper tabs already be visible
@@ -807,8 +786,7 @@
             new Error('Mismatch of headers and content.')
           );
         }
-      })
-      .then(() => this.initActiveTab());
+      });
 
     this.throttledToggleChangeStar = throttleWrap<KeyboardEvent>(_ =>
       this.handleToggleChangeStar()
@@ -830,16 +808,6 @@
     super.disconnectedCallback();
   }
 
-  protected override willUpdate(changedProperties: PropertyValues): void {
-    if (
-      changedProperties.has('change') ||
-      changedProperties.has('mergeable') ||
-      changedProperties.has('currentRevisionActions')
-    ) {
-      this.changeStatuses = this.computeChangeStatusChips();
-    }
-  }
-
   static override get styles() {
     return [
       a11yStyles,
@@ -1050,7 +1018,7 @@
           .relatedChanges {
             padding: 0;
           }
-          #relatedChanges {
+          .relatedChanges gr-related-changes-list {
             padding-top: var(--spacing-l);
           }
           #commitAndRelated {
@@ -1219,12 +1187,14 @@
   }
 
   private renderHeaderTitle() {
-    const resolveWeblinks = this.commitInfo?.resolve_conflicts_web_links ?? [];
+    const changeStatuses = this.computeChangeStatusChips();
+    const resolveWeblinks =
+      this.revision?.commit?.resolve_conflicts_web_links ?? [];
     return html` <div class="headerTitle">
       <div class="changeStatuses">
-        ${this.changeStatuses.map(
+        ${changeStatuses.map(
           status => html` <gr-change-status
-            .revertedChange=${this.revertedChange}
+            .revertedChange=${this.revertingChange}
             .status=${status}
             .resolveWeblinks=${resolveWeblinks}
           ></gr-change-status>`
@@ -1323,11 +1293,10 @@
         id="actions"
         .change=${this.change}
         .disableEdit=${false}
-        .hasParent=${this.hasParent}
         .account=${this.account}
         .changeNum=${this.changeNum}
         .changeStatus=${this.change?.status}
-        .commitNum=${this.commitInfo?.commit}
+        .commitNum=${this.revision?.commit?.commit}
         .commitMessage=${this.latestCommitMessage}
         .editMode=${this.getEditMode()}
         .privateByDefault=${this.projectConfig?.private_by_default}
@@ -1353,10 +1322,10 @@
         <gr-change-metadata
           id="metadata"
           .change=${this.change}
-          .revertedChange=${this.revertedChange}
+          .revertedChange=${this.revertingChange}
           .account=${this.account}
-          .revision=${this.selectedRevision}
-          .commitInfo=${this.commitInfo}
+          .revision=${this.revision}
+          .commitInfo=${this.revision?.commit}
           .serverConfig=${this.serverConfig}
           .parentIsCurrent=${this.isParentCurrent()}
           .repoConfig=${this.projectConfig}
@@ -1396,7 +1365,7 @@
                 remove-zero-width-space=""
               >
                 <gr-formatted-text
-                  .content=${this.latestCommitMessage ?? ''}
+                  .content=${this.latestCommitMessage}
                   .markdown=${false}
                 ></gr-formatted-text>
               </gr-editable-content>
@@ -1406,18 +1375,12 @@
             <gr-endpoint-decorator name="commit-container">
               <gr-endpoint-param name="change" .value=${this.change}>
               </gr-endpoint-param>
-              <gr-endpoint-param
-                name="revision"
-                .value=${this.selectedRevision}
-              >
+              <gr-endpoint-param name="revision" .value=${this.revision}>
               </gr-endpoint-param>
             </gr-endpoint-decorator>
           </div>
           <div class="relatedChanges">
-            <gr-related-changes-list
-              id="relatedChanges"
-              .mergeable=${this.mergeable}
-            ></gr-related-changes-list>
+            <gr-related-changes-list></gr-related-changes-list>
           </div>
           <div class="emptySpace"></div>
         </div>
@@ -1460,10 +1423,7 @@
               <gr-endpoint-decorator name=${tabHeader}>
                 <gr-endpoint-param name="change" .value=${this.change}>
                 </gr-endpoint-param>
-                <gr-endpoint-param
-                  name="revision"
-                  .value=${this.selectedRevision}
-                >
+                <gr-endpoint-param name="revision" .value=${this.revision}>
                 </gr-endpoint-param>
               </gr-endpoint-decorator>
             </paper-tab>
@@ -1499,7 +1459,7 @@
           .account=${this.account}
           .change=${this.change}
           .changeNum=${this.changeNum}
-          .commitInfo=${this.commitInfo}
+          .commitInfo=${this.revision?.commit}
           .changeUrl=${this.computeChangeUrl()}
           .editMode=${this.getEditMode()}
           .loggedIn=${this.loggedIn}
@@ -1594,7 +1554,7 @@
       <gr-endpoint-decorator .name=${pluginTabContentEndpoint}>
         <gr-endpoint-param name="change" .value=${this.change}>
         </gr-endpoint-param>
-        <gr-endpoint-param name="revision" .value=${this.selectedRevision}></gr-endpoint-param>
+        <gr-endpoint-param name="revision" .value=${this.revision}></gr-endpoint-param>
         </gr-endpoint-param>
       </gr-endpoint-decorator>
     `;
@@ -1605,7 +1565,7 @@
       <gr-endpoint-decorator name="change-view-integration">
         <gr-endpoint-param name="change" .value=${this.change}>
         </gr-endpoint-param>
-        <gr-endpoint-param name="revision" .value=${this.selectedRevision}>
+        <gr-endpoint-param name="revision" .value=${this.revision}>
         </gr-endpoint-param>
       </gr-endpoint-decorator>
 
@@ -1619,7 +1579,7 @@
         <gr-messages-list
           .labels=${this.change?.labels}
           .messages=${this.change?.messages}
-          .reviewerUpdates=${this.change?.reviewer_updates}
+          .reviewerUpdates=${this.change?.reviewer_updates ?? []}
           @message-anchor-tap=${this.handleMessageAnchorTap}
         ></gr-messages-list>
       </section>
@@ -1629,11 +1589,12 @@
   override updated() {
     const tabs = [...queryAll<HTMLElement>(this.tabs!, 'paper-tab')];
     const tabIndex = tabs.findIndex(t => t.dataset['name'] === this.activeTab);
-    assert(tabIndex !== -1, `tab ${this.activeTab} not found`);
 
-    if (this.tabs!.selected !== tabIndex) {
+    if (tabIndex !== -1 && this.tabs!.selected !== tabIndex) {
       this.tabs!.selected = tabIndex;
     }
+    this.reportChangeDisplayed();
+    this.reportFullyLoaded();
   }
 
   private readonly handleScroll = () => {
@@ -1720,7 +1681,8 @@
   }
 
   private handleContentChanged(e: ValueChangedEvent) {
-    this.latestCommitMessage = e.detail.value;
+    // optimistic update
+    this.latestCommitMessage = e.detail.value ?? '';
   }
 
   // Private but used in tests.
@@ -1747,9 +1709,8 @@
           return;
         }
 
-        this.latestCommitMessage = this.prepareCommitMsgForLinkify(message);
         this.editingCommitMessage = false;
-        fireReload(this, true);
+        this.getChangeModel().navigateToChangeResetReload();
       })
       .catch(() => {
         assertIsDefined(this.commitMessageEditor);
@@ -1762,19 +1723,12 @@
   }
 
   private computeChangeStatusChips() {
-    if (!this.change) {
-      return [];
-    }
-
-    // Show no chips until mergeability is loaded.
-    if (this.mergeable === null) {
-      return [];
-    }
+    if (!this.change || this.mergeable === undefined) return [];
 
     const options = {
-      includeDerived: true,
-      mergeable: !!this.mergeable,
+      mergeable: this.mergeable,
       submitEnabled: !!this.isSubmitEnabled(),
+      revertingChangeStatus: this.revertingChange?.status,
     };
     return changeStatuses(this.change as ChangeInfo, options);
   }
@@ -1942,16 +1896,9 @@
 
   // Private but used in tests.
   handleReplySent() {
-    this.addEventListener(
-      'change-details-loaded',
-      () => {
-        this.reporting.timeEnd(Timing.SEND_REPLY);
-      },
-      {once: true}
-    );
     assertIsDefined(this.replyModal);
     this.replyModal.close();
-    fireReload(this);
+    this.getChangeModel().navigateToChangeResetReload();
   }
 
   private handleReplyCancel() {
@@ -2002,158 +1949,14 @@
   }
 
   // Private but used in tests.
-  hasPatchRangeChanged(viewState: ChangeViewState) {
-    if (!this.patchRange) return false;
-    if (this.patchRange.basePatchNum !== viewState.basePatchNum) return true;
-    return this.hasPatchNumChanged(viewState);
-  }
-
-  // Private but used in tests.
-  hasPatchNumChanged(viewState: ChangeViewState) {
-    if (!this.patchRange) return false;
-    if (viewState.patchNum !== undefined) {
-      return this.patchRange.patchNum !== viewState.patchNum;
-    } else {
-      // value.patchNum === undefined specifies the latest patchset
-      return (
-        this.patchRange.patchNum !== computeLatestPatchNum(this.allPatchSets)
-      );
-    }
-  }
-
-  // Private but used in tests.
-  viewStateChanged() {
-    if (!this.viewState) return;
-    if (this.isChangeObsolete()) return;
-
-    if (this.viewState.basePatchNum === undefined)
-      this.viewState.basePatchNum = PARENT;
-
-    const patchChanged = this.hasPatchRangeChanged(this.viewState);
-
-    this.patchRange = {
-      patchNum: this.viewState.patchNum,
-      basePatchNum: this.viewState.basePatchNum,
-    };
-    this.scrollCommentId = this.viewState.commentId;
-
-    const patchKnown =
-      !this.patchRange.patchNum ||
-      (this.allPatchSets ?? []).some(
-        ps => ps.num === this.patchRange!.patchNum
-      );
-    // _allPatchsets does not know value.patchNum so force a reload.
-    const forceReload = this.viewState.forceReload || !patchKnown;
-
-    // If changeNum is defined that means the change has already been
-    // rendered once before so a full reload is not required.
-    if (this.changeNum !== undefined && !forceReload) {
-      if (!this.patchRange.patchNum) {
-        this.patchRange = {
-          ...this.patchRange,
-          patchNum: computeLatestPatchNum(this.allPatchSets),
-        };
-      }
-      if (patchChanged) {
-        // We need to collapse all diffs when viewState changes so that a non
-        // existing diff is not requested. See Issue 125270 for more details.
-        this.fileList?.resetFileState();
-        this.fileList?.collapseAllDiffs();
-        this.reloadPatchNumDependentResources();
-      }
-
-      // If there is no change in patchset or changeNum, such as when user goes
-      // to the diff view and then comes back to change page then there is no
-      // need to reload anything and we render the change view component as is.
-      document.documentElement.scrollTop = this.scrollPosition ?? 0;
-      this.reporting.reportInteraction('change-view-re-rendered');
-      this.updateTitle(this.change);
-      // We still need to check if post load tasks need to be done such as when
-      // user wants to open the reply dialog when in the diff page, the change
-      // page should open the reply dialog
-      this.performPostLoadTasks();
-      return;
-    }
-
-    // We need to collapse all diffs when viewState changes so that a non
-    // existing diff is not requested. See Issue 125270 for more details.
-    this.updateComplete.then(() => {
-      assertIsDefined(this.fileList);
-      this.fileList?.collapseAllDiffs();
-      this.fileList?.resetFileState();
-    });
-
-    // If the change was loaded before, then we are firing a 'reload' event
-    // instead of calling `loadData()` directly for two reasons:
-    // 1. We want to avoid code such as `this.initialLoadComplete = false` that
-    //    is only relevant for the initial load of a change.
-    // 2. We have to somehow trigger the change-model reloading. Otherwise
-    //    this.change is not updated.
-    if (this.changeNum) {
-      if (!this._patchRange?.patchNum) {
-        this._patchRange = {
-          basePatchNum: PARENT,
-          patchNum: computeLatestPatchNum(this.allPatchSets),
-        };
-      }
-      fireReload(this);
-      return;
-    }
-
-    this.initialLoadComplete = false;
-    this.changeNum = this.viewState.changeNum;
-    this.loadData(true).then(() => {
-      this.performPostLoadTasks();
-    });
-
-    this.getPluginLoader()
-      .awaitPluginsLoaded()
-      .then(() => {
-        this.initActiveTab();
-      });
-  }
-
-  private initActiveTab() {
-    let tab = Tab.FILES;
-    if (this.viewState?.tab) {
-      tab = this.viewState?.tab as Tab;
-    } else if (this.viewState?.commentId) {
-      tab = Tab.COMMENT_THREADS;
-    }
-    this.setActiveTab(new CustomEvent('show-tab', {detail: {tab}}));
-  }
-
-  // Private but used in tests.
-  sendShowChangeEvent() {
-    assertIsDefined(this.patchRange, 'patchRange');
-    this.getPluginLoader().jsApiService.handleShowChange({
-      change: this.change,
-      patchNum: this.patchRange.patchNum,
-      info: {mergeable: this.mergeable},
-    });
-  }
-
-  private performPostLoadTasks() {
-    this.maybeShowReplyDialog();
-    this.maybeShowRevertDialog();
-
-    this.sendShowChangeEvent();
-
-    this.updateComplete.then(() => {
-      this.maybeScrollToMessage(window.location.hash);
-      this.initialLoadComplete = true;
-    });
-  }
-
-  // Private but used in tests.
   handleMessageAnchorTap(e: CustomEvent<{id: string}>) {
     assertIsDefined(this.change, 'change');
-    assertIsDefined(this.patchRange, 'patchRange');
+    assertIsDefined(this.patchNum, 'patchNum');
     const hash = PREFIX + e.detail.id;
     const url = createChangeUrl({
       change: this.change,
-      patchNum: this.patchRange.patchNum,
-      basePatchNum: this.patchRange.basePatchNum,
+      patchNum: this.patchNum,
+      basePatchNum: this.basePatchNum,
       edit: this.getEditMode(),
       messageHash: hash,
     });
@@ -2161,9 +1964,10 @@
   }
 
   // Private but used in tests.
-  maybeScrollToMessage(hash: string) {
-    if (hash.startsWith(PREFIX) && this.messagesList) {
-      this.messagesList.scrollToMessage(hash.substr(PREFIX.length));
+  async maybeScrollToMessage(hash: string) {
+    if (hash.startsWith(PREFIX)) {
+      await waitUntil(() => !!this.messagesList);
+      this.messagesList!.scrollToMessage(hash.substr(PREFIX.length));
     }
   }
 
@@ -2186,39 +1990,18 @@
   }
 
   // Private but used in tests.
-  maybeShowRevertDialog() {
-    this.getPluginLoader()
-      .awaitPluginsLoaded()
-      .then(() => {
-        if (
-          !this.loggedIn ||
-          !this.change ||
-          this.change.status !== ChangeStatus.MERGED
-        ) {
-          // Do not display dialog if not logged-in or the change is not
-          // merged.
-          return;
-        }
-        if (this._getUrlParameter('revert')) {
-          assertIsDefined(this.actions);
-          this.actions.showRevertDialog();
-        }
-      });
-  }
+  async maybeShowRevertDialog() {
+    if (!this._getUrlParameter('revert')) return;
 
-  private maybeShowReplyDialog() {
-    if (!this.loggedIn) return;
-    if (this.viewState?.openReplyDialog) {
-      this.openReplyDialog(FocusTarget.ANY);
+    await this.getPluginLoader().awaitPluginsLoaded();
+    await waitUntil(() => !!this.actions);
+    await waitUntil(() => !!this.change);
+
+    if (this.change?.status === ChangeStatus.MERGED && this.loggedIn) {
+      this.actions!.showRevertDialog();
     }
   }
 
-  private updateTitle(change?: ChangeInfo | ParsedChangeInfo) {
-    if (!change) return;
-    const title = `${change.subject} (${change._number})`;
-    fireTitleChange(this, title);
-  }
-
   // Private but used in tests.
   changeChanged(oldChange: ParsedChangeInfo | undefined) {
     this.allPatchSets = computeAllPatchSets(this.change);
@@ -2232,57 +2015,11 @@
       this.currentRobotCommentsPatchSet =
         this.change.revisions[this.change.current_revision]._number;
     }
-    if (!this.change || !this.patchRange || !this.allPatchSets) {
-      return;
-    }
-
-    // We get the parent first so we keep the original value for basePatchNum
-    // and not the updated value.
-    const parent = this.getBasePatchNum();
-
-    this.patchRange = {
-      ...this.patchRange,
-      basePatchNum: parent,
-      patchNum:
-        this.patchRange.patchNum || computeLatestPatchNum(this.allPatchSets),
-    };
-    this.updateTitle(this.change);
   }
 
   /**
-   * Gets base patch number, if it is a parent try and decide from
-   * preference whether to default to `auto merge`, `Parent 1` or `PARENT`.
-   * Private but used in tests.
+   * This is the URL equivalent of changeModel.navigateToChangeResetReload().
    */
-  getBasePatchNum() {
-    if (
-      this.patchRange &&
-      this.patchRange.basePatchNum &&
-      this.patchRange.basePatchNum !== PARENT
-    ) {
-      return this.patchRange.basePatchNum;
-    }
-
-    const revisionInfo = this.getRevisionInfo();
-    if (!revisionInfo) return PARENT;
-
-    // TODO: It is a bit unclear why `1` is used here instead of
-    // `patchRange.patchNum`. Maybe that is a bug? Maybe if one patchset
-    // is a merge commit, then all patchsets are merge commits??
-    const isMerge = revisionInfo.isMergeCommit(1 as PatchSetNumber);
-    const preferFirst =
-      this.prefs &&
-      this.prefs.default_base_for_merges === DefaultBase.FIRST_PARENT;
-
-    // Verified via reportExecution that -1 is returned(1-5 times per day)
-    // changeChanged does set this.patchRange?.patchNum so it's still unclear
-    // how it is undefined.
-    if (isMerge && preferFirst && !this.patchRange?.patchNum) {
-      return -1 as BasePatchSetNum;
-    }
-    return PARENT;
-  }
-
   private computeChangeUrl(forceReload?: boolean) {
     if (!this.change) return undefined;
     return createChangeUrl({
@@ -2358,13 +2095,13 @@
   // Private but used in tests.
   handleDiffAgainstBase() {
     assertIsDefined(this.change, 'change');
-    assertIsDefined(this.patchRange, 'patchRange');
-    if (this.patchRange.basePatchNum === PARENT) {
+    assertIsDefined(this.patchNum, 'patchNum');
+    if (this.basePatchNum === PARENT) {
       fireAlert(this, 'Base is already selected.');
       return;
     }
     this.getNavigation().setUrl(
-      createChangeUrl({change: this.change, patchNum: this.patchRange.patchNum})
+      createChangeUrl({change: this.change, patchNum: this.patchNum})
     );
   }
 
@@ -2372,16 +2109,16 @@
   handleDiffBaseAgainstLeft() {
     if (this.viewState?.childView !== ChangeChildView.OVERVIEW) return;
     assertIsDefined(this.change, 'change');
-    assertIsDefined(this.patchRange, 'patchRange');
+    assertIsDefined(this.patchNum, 'patchNum');
 
-    if (this.patchRange.basePatchNum === PARENT) {
+    if (this.basePatchNum === PARENT) {
       fireAlert(this, 'Left is already base.');
       return;
     }
     this.getNavigation().setUrl(
       createChangeUrl({
         change: this.change,
-        patchNum: this.patchRange.basePatchNum as RevisionPatchSetNum,
+        patchNum: this.basePatchNum as RevisionPatchSetNum,
       })
     );
   }
@@ -2389,9 +2126,9 @@
   // Private but used in tests.
   handleDiffAgainstLatest() {
     assertIsDefined(this.change, 'change');
-    assertIsDefined(this.patchRange, 'patchRange');
+    assertIsDefined(this.patchNum, 'patchNum');
     const latestPatchNum = computeLatestPatchNum(this.allPatchSets);
-    if (this.patchRange.patchNum === latestPatchNum) {
+    if (this.patchNum === latestPatchNum) {
       fireAlert(this, 'Latest is already selected.');
       return;
     }
@@ -2399,7 +2136,7 @@
       createChangeUrl({
         change: this.change,
         patchNum: latestPatchNum,
-        basePatchNum: this.patchRange.basePatchNum,
+        basePatchNum: this.basePatchNum,
       })
     );
   }
@@ -2407,9 +2144,9 @@
   // Private but used in tests.
   handleDiffRightAgainstLatest() {
     assertIsDefined(this.change, 'change');
-    assertIsDefined(this.patchRange, 'patchRange');
+    assertIsDefined(this.patchNum, 'patchNum');
     const latestPatchNum = computeLatestPatchNum(this.allPatchSets);
-    if (this.patchRange.patchNum === latestPatchNum) {
+    if (this.patchNum === latestPatchNum) {
       fireAlert(this, 'Right is already latest.');
       return;
     }
@@ -2417,7 +2154,7 @@
       createChangeUrl({
         change: this.change,
         patchNum: latestPatchNum,
-        basePatchNum: this.patchRange.patchNum as BasePatchSetNum,
+        basePatchNum: this.patchNum as BasePatchSetNum,
       })
     );
   }
@@ -2425,12 +2162,9 @@
   // Private but used in tests.
   handleDiffBaseAgainstLatest() {
     assertIsDefined(this.change, 'change');
-    assertIsDefined(this.patchRange, 'patchRange');
+    assertIsDefined(this.patchNum, 'patchNum');
     const latestPatchNum = computeLatestPatchNum(this.allPatchSets);
-    if (
-      this.patchRange.patchNum === latestPatchNum &&
-      this.patchRange.basePatchNum === PARENT
-    ) {
+    if (this.patchNum === latestPatchNum && this.basePatchNum === PARENT) {
       fireAlert(this, 'Already diffing base against latest.');
       return;
     }
@@ -2524,179 +2258,11 @@
     // TODO(wyatta) switch linkify sequence, see issue 5526.
     // This is a zero-with space. It is added to prevent the linkify library
     // from including R= or CC= as part of the email address.
+    // TODO: Is this comment referring to the ba-linkify library that we are
+    // not using anymore? If so, then remove this hack.
     return msg.replace(REVIEWERS_REGEX, '$1=\u200B');
   }
 
-  /**
-   * Utility function to make the necessary modifications to a change in the
-   * case an edit exists.
-   * Private but used in tests.
-   */
-  processEdit(change: ParsedChangeInfo) {
-    const revisions = Object.values(change.revisions || {});
-    const editRev = findEdit(revisions);
-    const editParentRev = findEditParentRevision(revisions);
-    if (
-      !editRev &&
-      this.patchRange?.patchNum === EDIT &&
-      changeIsOpen(change)
-    ) {
-      fireAlert(this, 'Change edit not found. Please create a change edit.');
-      fireReload(this, true);
-      return;
-    }
-
-    if (
-      !editRev &&
-      (changeIsMerged(change) || changeIsAbandoned(change)) &&
-      this.getEditMode()
-    ) {
-      fireAlert(
-        this,
-        'Change edits cannot be created if change is merged or abandoned. Redirecting to non edit mode.'
-      );
-      fireReload(this, true);
-      return;
-    }
-
-    if (!editRev) return;
-    assertIsDefined(this.patchRange, 'patchRange');
-    assertIsDefined(editRev.commit.commit, 'editRev.commit.commit');
-    assertIsDefined(editParentRev, 'editParentRev');
-
-    const latestPsNum = computeLatestPatchNum(computeAllPatchSets(change));
-    // If the change was loaded without a specific patchset, then this normally
-    // means that the *latest* patchset should be loaded. But if there is an
-    // active edit, then automatically switch to that edit as the current
-    // patchset.
-    // TODO: This goes together with `change.current_revision` being set, which
-    // is under change-model control. `patchRange.patchNum` should eventually
-    // also be model managed, so we can reconcile these two code snippets into
-    // one location.
-    if (!this.viewModelPatchNum && latestPsNum === editParentRev._number) {
-      this.patchRange = {...this.patchRange, patchNum: EDIT};
-      // The file list is not reactive (yet) with regards to patch range
-      // changes, so we have to actively trigger it.
-      this.reloadPatchNumDependentResources();
-    }
-  }
-
-  computeRevertSubmitted(change?: ChangeInfo | ParsedChangeInfo) {
-    if (!change?.messages) return;
-    Promise.all(
-      getRevertCreatedChangeIds(change.messages).map(changeId =>
-        this.restApiService.getChange(changeId)
-      )
-    ).then(changes => {
-      // if a change is deleted then getChanges returns null for that changeId
-      changes = changes.filter(
-        change => change && change.status !== ChangeStatus.ABANDONED
-      );
-      if (!changes.length) return;
-      const submittedRevert = changes.find(
-        change => change?.status === ChangeStatus.MERGED
-      );
-      if (!this.changeStatuses) return;
-      // Protect against `computeRevertSubmitted()` being called twice.
-      // TODO: Convert this to be rxjs based, so computeRevertSubmitted() is not
-      // actively called, but instead we can subscribe to something.
-      if (this.changeStatuses.includes(ChangeStates.REVERT_SUBMITTED)) return;
-      if (this.changeStatuses.includes(ChangeStates.REVERT_CREATED)) return;
-      if (submittedRevert) {
-        this.revertedChange = submittedRevert;
-        this.changeStatuses = this.changeStatuses.concat([
-          ChangeStates.REVERT_SUBMITTED,
-        ]);
-      } else {
-        if (changes[0]) this.revertedChange = changes[0];
-        this.changeStatuses = this.changeStatuses.concat([
-          ChangeStates.REVERT_CREATED,
-        ]);
-      }
-    });
-  }
-
-  private async untilModelLoaded() {
-    // NOTE: Wait until this page is connected before determining whether the
-    // model is loaded.  This can happen when viewState changes when setting up
-    // this view. It's unclear whether this issue is related to Polymer
-    // specifically.
-    if (!this.isConnected) {
-      await until(this.connected$, connected => connected);
-    }
-    await until(
-      this.getChangeModel().changeLoadingStatus$,
-      status => status === LoadingStatus.LOADED
-    );
-  }
-
-  /**
-   * Process edits
-   * Check if a revert of this change has been submitted
-   * Calculate selected revision
-   */
-  // private but used in tests
-  async performPostChangeLoadTasks() {
-    assertIsDefined(this.changeNum, 'changeNum');
-
-    const prefCompletes = this.restApiService.getPreferences();
-    await this.untilModelLoaded();
-
-    this.prefs = await prefCompletes;
-
-    if (!this.change) return false;
-
-    this.processEdit(this.change);
-    // Issue 4190: Coalesce missing topics to null.
-    // TODO(TS): code needs second thought,
-    // it might be that nulls were assigned to trigger some bindings
-    if (!this.change.topic) {
-      this.change.topic = null as unknown as undefined;
-    }
-    if (!this.change.reviewer_updates) {
-      this.change.reviewer_updates = null as unknown as undefined;
-    }
-    const latestRevisionSha = this.getLatestRevisionSHA(this.change);
-    if (!latestRevisionSha)
-      throw new Error('Could not find latest Revision Sha');
-    const currentRevision = this.change.revisions[latestRevisionSha];
-    if (currentRevision.commit && currentRevision.commit.message) {
-      this.latestCommitMessage = this.prepareCommitMsgForLinkify(
-        currentRevision.commit.message
-      );
-    } else {
-      this.latestCommitMessage = null;
-    }
-
-    this.computeRevertSubmitted(this.change);
-    if (
-      !this.patchRange ||
-      !this.patchRange.patchNum ||
-      this.patchRange.patchNum === currentRevision._number
-    ) {
-      // CommitInfo.commit is optional, and may need patching.
-      if (currentRevision.commit && !currentRevision.commit.commit) {
-        currentRevision.commit.commit = latestRevisionSha as CommitId;
-      }
-      this.commitInfo = currentRevision.commit;
-      this.selectedRevision = currentRevision;
-      // TODO: Fetch and process files.
-    } else {
-      if (!this.change?.revisions || !this.patchRange) return false;
-      this.selectedRevision = Object.values(this.change.revisions).find(
-        revision => {
-          // edit patchset is a special one
-          const thePatchNum = this.patchRange!.patchNum;
-          if (thePatchNum === EDIT) {
-            return revision._number === thePatchNum;
-          }
-          return revision._number === Number(`${thePatchNum}`);
-        }
-      );
-    }
-    return true;
-  }
-
   private isParentCurrent() {
     const revisionActions = this.currentRevisionActions;
     if (revisionActions && revisionActions.rebase) {
@@ -2706,226 +2272,35 @@
     }
   }
 
-  // Private but used in tests.
-  getLatestCommitMessage() {
-    assertIsDefined(this.changeNum, 'changeNum');
-    const lastpatchNum = computeLatestPatchNum(this.allPatchSets);
-    if (lastpatchNum === undefined)
-      throw new Error('missing lastPatchNum property');
-    return this.restApiService
-      .getChangeCommitInfo(this.changeNum, lastpatchNum)
-      .then(commitInfo => {
-        if (!commitInfo) return;
-        this.latestCommitMessage = this.prepareCommitMsgForLinkify(
-          commitInfo.message
-        );
-      });
+  private async reportChangeDisplayed() {
+    await waitUntil(() => !!this.metadata);
+    await untilRendered(this.metadata!);
+    await waitUntil(() => !!this.fileList);
+    await untilRendered(this.fileList!);
+    await waitUntil(() => !!this.messagesList);
+    await untilRendered(this.messagesList!);
+    // We are ending the timer after each change view update, because ending a
+    // timer that was not started is a no-op. :-)
+    if (this.change && this.isConnected && !this.isChangeObsolete()) {
+      this.reporting.changeDisplayed(roleDetails(this.change, this.account));
+    }
   }
 
-  // Private but used in tests.
-  getLatestRevisionSHA(change: ChangeInfo | ParsedChangeInfo) {
-    if (change.current_revision) return change.current_revision;
-    // current_revision may not be present in the case where the latest rev is
-    // a draft and the user doesn’t have permission to view that rev.
-    let latestRev = null;
-    let latestPatchNum = -1 as PatchSetNum;
-    for (const [rev, revInfo] of Object.entries(change.revisions ?? {})) {
-      if (revInfo._number > latestPatchNum) {
-        latestRev = rev;
-        latestPatchNum = revInfo._number;
-      }
+  private async reportFullyLoaded() {
+    await waitUntil(() => !!this.metadata);
+    await untilRendered(this.metadata!);
+    await waitUntil(() => !!this.fileList);
+    await untilRendered(this.fileList!);
+    await waitUntil(() => !!this.messagesList);
+    await untilRendered(this.messagesList!);
+    await waitUntil(() => this.mergeable !== undefined);
+    await until(this.getCommentsModel().comments$, c => c !== undefined);
+    await until(this.getCommentsModel().drafts$, c => c !== undefined);
+    // We are ending the timer after each change view update, because ending a
+    // timer that was not started is a no-op. :-)
+    if (this.change && this.isConnected && !this.isChangeObsolete()) {
+      this.reporting.changeFullyLoaded();
     }
-    return latestRev;
-  }
-
-  // visible for testing
-  loadAndSetCommitInfo() {
-    assertIsDefined(this.changeNum, 'changeNum');
-    assertIsDefined(this.patchRange?.patchNum, 'patchRange.patchNum');
-    return this.restApiService
-      .getChangeCommitInfo(this.changeNum, this.patchRange.patchNum)
-      .then(commitInfo => {
-        this.commitInfo = commitInfo;
-      });
-  }
-
-  /**
-   * Reload the change.
-   *
-   * @param isLocationChange Reloads the related changes
-   * when true and ends reporting events that started on location change.
-   * @param clearPatchset Reloads the change ignoring any patchset
-   * choice made.
-   * @return A promise that resolves when the core data has loaded.
-   * Some non-core data loading may still be in-flight when the core data
-   * promise resolves.
-   */
-  loadData(isLocationChange?: boolean, clearPatchset?: boolean) {
-    if (this.isChangeObsolete()) return Promise.resolve();
-    if (clearPatchset && this.change) {
-      this.getNavigation().setUrl(
-        createChangeUrl({change: this.change, forceReload: true})
-      );
-      return Promise.resolve();
-    }
-    this.loading = true;
-    this.reporting.time(Timing.CHANGE_RELOAD);
-    this.reporting.time(Timing.CHANGE_DATA);
-
-    // Array to house all promises related to data requests.
-    const allDataPromises: Promise<unknown>[] = [];
-
-    // Resolves when the change detail and the edit patch set (if available)
-    // are loaded.
-    const detailCompletes = this.untilModelLoaded();
-    allDataPromises.push(detailCompletes);
-
-    // Resolves when the loading flag is set to false, meaning that some
-    // change content may start appearing.
-    const loadingFlagSet = detailCompletes.then(() => {
-      this.loading = false;
-      this.performPostChangeLoadTasks();
-    });
-
-    let coreDataPromise;
-
-    // If the patch number is specified
-    if (this.patchRange && this.patchRange.patchNum) {
-      // Because a specific patchset is specified, reload the resources that
-      // are keyed by patch number or patch range.
-      const patchResourcesLoaded = this.reloadPatchNumDependentResources();
-      allDataPromises.push(patchResourcesLoaded);
-
-      // Promise resolves when the change detail and patch dependent resources
-      // have loaded.
-      coreDataPromise = Promise.all([patchResourcesLoaded, loadingFlagSet]);
-    } else {
-      const latestCommitMessageLoaded = loadingFlagSet.then(() => {
-        // If the latest commit message is known, there is nothing to do.
-        if (this.latestCommitMessage) {
-          return Promise.resolve();
-        }
-        return this.getLatestCommitMessage();
-      });
-      allDataPromises.push(latestCommitMessageLoaded);
-
-      coreDataPromise = loadingFlagSet;
-    }
-    const mergeabilityLoaded = coreDataPromise.then(() =>
-      this.getMergeability()
-    );
-    allDataPromises.push(mergeabilityLoaded);
-
-    coreDataPromise.then(() => {
-      fire(this, 'change-details-loaded', {});
-      this.reporting.timeEnd(Timing.CHANGE_RELOAD);
-      if (isLocationChange) {
-        this.reporting.changeDisplayed(roleDetails(this.change, this.account));
-      }
-    });
-
-    if (isLocationChange) {
-      this.editingCommitMessage = false;
-    }
-    const relatedChangesLoaded = coreDataPromise.then(() => {
-      let relatedChangesPromise:
-        | Promise<RelatedChangesInfo | undefined>
-        | undefined;
-      const patchNum = computeLatestPatchNum(this.allPatchSets);
-      if (this.change && patchNum) {
-        relatedChangesPromise = this.restApiService
-          .getRelatedChanges(this.change._number, patchNum)
-          .then(response => {
-            if (this.change && response) {
-              this.hasParent = this.calculateHasParent(
-                this.change.change_id,
-                response.changes
-              );
-            }
-            return response;
-          });
-      }
-      return this.getRelatedChangesList()?.reload(relatedChangesPromise);
-    });
-    allDataPromises.push(relatedChangesLoaded);
-    allDataPromises.push(this.filesLoaded());
-
-    Promise.all(allDataPromises).then(() => {
-      // Loading of commments data is no longer part of this reporting
-      this.reporting.timeEnd(Timing.CHANGE_DATA);
-      if (isLocationChange) {
-        this.reporting.changeFullyLoaded();
-      }
-    });
-
-    return coreDataPromise;
-  }
-
-  private async filesLoaded() {
-    if (!this.isConnected) await until(this.connected$, connected => connected);
-    await until(this.getFilesModel().files$, f => f.length > 0);
-  }
-
-  /**
-   * Determines whether or not the given change has a parent change. If there
-   * is a relation chain, and the change id is not the last item of the
-   * relation chain, there is a parent.
-   *
-   * Private but used in tests.
-   */
-  calculateHasParent(
-    currentChangeId: ChangeId,
-    relatedChanges: RelatedChangeAndCommitInfo[]
-  ) {
-    return (
-      relatedChanges.length > 0 &&
-      relatedChanges[relatedChanges.length - 1].change_id !== currentChangeId
-    );
-  }
-
-  /**
-   * Kicks off requests for resources that rely on the patch range
-   * (`this.patchRange`) being defined.
-   */
-  reloadPatchNumDependentResources() {
-    return this.loadAndSetCommitInfo();
-  }
-
-  // Private but used in tests
-  getMergeability(): Promise<void> {
-    if (!this.change) {
-      this.mergeable = null;
-      return Promise.resolve();
-    }
-    // If the change is closed, it is not mergeable. Note: already merged
-    // changes are obviously not mergeable, but the mergeability API will not
-    // answer for abandoned changes.
-    if (
-      this.change.status === ChangeStatus.MERGED ||
-      this.change.status === ChangeStatus.ABANDONED
-    ) {
-      this.mergeable = false;
-      return Promise.resolve();
-    }
-
-    if (!this.changeNum) {
-      return Promise.reject(new Error('missing required changeNum property'));
-    }
-
-    // If mergeable bit was already returned in detail REST endpoint, use it.
-    if (this.change.mergeable !== undefined) {
-      this.mergeable = this.change.mergeable;
-      return Promise.resolve();
-    }
-
-    this.mergeable = null;
-    return this.restApiService
-      .getMergeable(this.changeNum)
-      .then(mergableInfo => {
-        if (mergableInfo) {
-          this.mergeable = mergableInfo.mergeable;
-        }
-      });
   }
 
   /**
@@ -2941,13 +2316,11 @@
     );
   }
 
-  private computeCommitCollapsible() {
-    if (!this.latestCommitMessage) {
-      return false;
-    }
+  private computeCommitCollapsible(): boolean {
     return (
+      !!this.latestCommitMessage &&
       this.latestCommitMessage.split('\n').length >=
-      MIN_LINES_FOR_COMMIT_COLLAPSE
+        MIN_LINES_FOR_COMMIT_COLLAPSE
     );
   }
 
@@ -3008,7 +2381,7 @@
             dismissOnNavigation: true,
             showDismiss: true,
             action: 'Reload',
-            callback: () => fireReload(this, true),
+            callback: () => this.getChangeModel().navigateToChangeResetReload(),
           });
         });
     }, this.serverConfig.change.update_delay * 1000);
@@ -3047,7 +2420,7 @@
       );
     if (!controls) throw new Error('Missing edit controls');
     assertIsDefined(this.change, 'change');
-    assertIsDefined(this.patchRange, 'patchRange');
+    assertIsDefined(this.patchNum, 'patchNum');
 
     const path = e.detail.path;
     switch (e.detail.action) {
@@ -3055,12 +2428,12 @@
         controls.openDeleteDialog(path);
         break;
       case GrEditConstants.Actions.OPEN.id:
-        assertIsDefined(this.patchRange.patchNum, 'patchset number');
+        assertIsDefined(this.patchNum, 'patchset number');
         this.getNavigation().setUrl(
           createEditUrl({
             changeNum: this.change._number,
             repo: this.change.project,
-            patchNum: this.patchRange.patchNum,
+            patchNum: this.patchNum,
             editView: {path},
           })
         );
@@ -3074,21 +2447,6 @@
     }
   }
 
-  private patchNumChanged() {
-    if (!this.selectedRevision || !this.patchRange?.patchNum) {
-      return;
-    }
-    assertIsDefined(this.change, 'change');
-
-    if (this.patchRange.patchNum === this.selectedRevision._number) {
-      return;
-    }
-    if (!this.change.revisions) return;
-    this.selectedRevision = Object.values(this.change.revisions).find(
-      revision => revision._number === this.patchRange!.patchNum
-    );
-  }
-
   /**
    * If an edit exists already, load it. Otherwise, toggle edit mode via the
    * navigation API.
@@ -3118,11 +2476,11 @@
 
   private handleStopEditTap() {
     assertIsDefined(this.change, 'change');
-    assertIsDefined(this.patchRange, 'patchRange');
+    assertIsDefined(this.patchNum, 'patchNum');
     this.getNavigation().setUrl(
       createChangeUrl({
         change: this.change,
-        patchNum: this.patchRange.patchNum,
+        patchNum: this.patchNum,
         forceReload: true,
       })
     );
@@ -3152,17 +2510,6 @@
     fire(this, 'hide-alert', {});
   }
 
-  private getRevisionInfo(): RevisionInfoClass | undefined {
-    if (this.change === undefined) return undefined;
-    return new RevisionInfoClass(this.change);
-  }
-
-  getRelatedChangesList() {
-    return this.shadowRoot!.querySelector<GrRelatedChangesList>(
-      '#relatedChanges'
-    );
-  }
-
   createTitle(shortcutName: Shortcut, section: ShortcutSection) {
     return this.getShortcutsService().createTitle(shortcutName, section);
   }
@@ -3177,7 +2524,6 @@
 declare global {
   interface HTMLElementEventMap {
     'toggle-star': CustomEvent<ChangeStarToggleStarDetail>;
-    'change-details-loaded': CustomEvent<{}>;
   }
   interface HTMLElementTagNameMap {
     'gr-change-view': GrChangeView;
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 21b163f..5331558 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
@@ -10,9 +10,7 @@
 import {
   ChangeStatus,
   CommentSide,
-  DefaultBase,
   DiffViewMode,
-  MessageTag,
   createDefaultPreferences,
   Tab,
 } from '../../../constants/constants';
@@ -25,64 +23,43 @@
   queryAndAssert,
   stubFlags,
   stubRestApi,
-  waitEventLoop,
   waitUntil,
   waitUntilVisible,
 } from '../../../test/test-utils';
 import {
   createChangeViewState,
-  createApproval,
-  createChange,
   createChangeMessages,
-  createCommit,
-  createMergeable,
-  createPreferences,
   createRevision,
   createRevisions,
   createServerInfo,
   createUserConfig,
   TEST_NUMERIC_CHANGE_ID,
   TEST_PROJECT_NAME,
-  createEditRevision,
-  createAccountWithIdNameAndEmail,
   createChangeViewChange,
-  createRelatedChangeAndCommitInfo,
   createAccountDetailWithId,
   createParsedChange,
 } from '../../../test/test-data-generators';
 import {GrChangeView} from './gr-change-view';
 import {
   AccountId,
-  ApprovalInfo,
   BasePatchSetNum,
-  ChangeId,
-  ChangeInfo,
   CommitId,
   EDIT,
   NumericChangeId,
   PARENT,
-  RelatedChangeAndCommitInfo,
-  ReviewInputTag,
-  RevisionInfo,
   RevisionPatchSetNum,
   RobotId,
   RobotCommentInfo,
   Timestamp,
   UrlEncodedCommentId,
-  DetailedLabelInfo,
   RepoName,
-  QuickLabelInfo,
-  PatchSetNumber,
   CommentThread,
-  ChangeStates,
   SavingState,
 } from '../../../types/common';
 import {GrEditControls} from '../../edit/gr-edit-controls/gr-edit-controls';
-import {SinonFakeTimers, SinonStubbedMember} from 'sinon';
-import {RestApiService} from '../../../services/gr-rest-api/gr-rest-api';
+import {SinonFakeTimers} from 'sinon';
 import {GerritView} from '../../../services/router/router-model';
 import {ParsedChangeInfo} from '../../../types/types';
-import {GrRelatedChangesList} from '../gr-related-changes-list/gr-related-changes-list';
 import {
   ChangeModel,
   changeModelToken,
@@ -92,9 +69,7 @@
 import {GrChangeStar} from '../../shared/gr-change-star/gr-change-star';
 import {GrThreadList} from '../gr-thread-list/gr-thread-list';
 import {assertIsDefined} from '../../../utils/common-util';
-import {DEFAULT_NUM_FILES_SHOWN} from '../gr-file-list/gr-file-list';
 import {fixture, html, assert} from '@open-wc/testing';
-import {deepClone} from '../../../utils/deep-util';
 import {Modifier} from '../../../utils/dom-util';
 import {GrButton} from '../../shared/gr-button/gr-button';
 import {GrCopyLinks} from '../gr-copy-links/gr-copy-links';
@@ -103,6 +78,7 @@
 import {testResolver} from '../../../test/common-test-setup';
 import {UserModel, userModelToken} from '../../../models/user/user-model';
 import {pluginLoaderToken} from '../../shared/gr-js-api-interface/gr-plugin-loader';
+import {commentsModelToken} from '../../../models/comments/comments-model';
 
 suite('gr-change-view tests', () => {
   let element: GrChangeView;
@@ -457,8 +433,7 @@
                     </gr-endpoint-decorator>
                   </div>
                   <div class="relatedChanges">
-                    <gr-related-changes-list id="relatedChanges">
-                    </gr-related-changes-list>
+                    <gr-related-changes-list></gr-related-changes-list>
                   </div>
                   <div class="emptySpace"></div>
                 </div>
@@ -544,10 +519,7 @@
 
   test('handleMessageAnchorTap', async () => {
     element.changeNum = 1 as NumericChangeId;
-    element.patchRange = {
-      basePatchNum: PARENT,
-      patchNum: 1 as RevisionPatchSetNum,
-    };
+    element.patchNum = 1 as RevisionPatchSetNum;
     element.change = createChangeViewChange();
     await element.updateComplete;
     const replaceStateStub = sinon.stub(history, 'replaceState');
@@ -563,10 +535,8 @@
       ...createChangeViewChange(),
       revisions: createRevisions(10),
     };
-    element.patchRange = {
-      patchNum: 3 as RevisionPatchSetNum,
-      basePatchNum: 1 as BasePatchSetNum,
-    };
+    element.basePatchNum = 1 as BasePatchSetNum;
+    element.patchNum = 3 as RevisionPatchSetNum;
     element.handleDiffAgainstBase();
     assert.isTrue(setUrlStub.called);
     assert.equal(setUrlStub.lastCall.firstArg, '/c/test-project/+/42/3');
@@ -577,10 +547,8 @@
       ...createChangeViewChange(),
       revisions: createRevisions(10),
     };
-    element.patchRange = {
-      basePatchNum: 1 as BasePatchSetNum,
-      patchNum: 3 as RevisionPatchSetNum,
-    };
+    element.basePatchNum = 1 as BasePatchSetNum;
+    element.patchNum = 3 as RevisionPatchSetNum;
     element.handleDiffAgainstLatest();
     assert.isTrue(setUrlStub.called);
     assert.equal(setUrlStub.lastCall.firstArg, '/c/test-project/+/42/1..10');
@@ -591,10 +559,8 @@
       ...createChangeViewChange(),
       revisions: createRevisions(10),
     };
-    element.patchRange = {
-      patchNum: 3 as RevisionPatchSetNum,
-      basePatchNum: 1 as BasePatchSetNum,
-    };
+    element.basePatchNum = 1 as BasePatchSetNum;
+    element.patchNum = 3 as RevisionPatchSetNum;
     element.handleDiffBaseAgainstLeft();
     assert.isTrue(setUrlStub.called);
     assert.equal(setUrlStub.lastCall.firstArg, '/c/test-project/+/42/1');
@@ -605,10 +571,8 @@
       ...createChangeViewChange(),
       revisions: createRevisions(10),
     };
-    element.patchRange = {
-      basePatchNum: 1 as BasePatchSetNum,
-      patchNum: 3 as RevisionPatchSetNum,
-    };
+    element.basePatchNum = 1 as BasePatchSetNum;
+    element.patchNum = 3 as RevisionPatchSetNum;
     element.handleDiffRightAgainstLatest();
     assert.isTrue(setUrlStub.called);
     assert.equal(setUrlStub.lastCall.firstArg, '/c/test-project/+/42/3..10');
@@ -619,10 +583,8 @@
       ...createChangeViewChange(),
       revisions: createRevisions(10),
     };
-    element.patchRange = {
-      basePatchNum: 1 as BasePatchSetNum,
-      patchNum: 3 as RevisionPatchSetNum,
-    };
+    element.basePatchNum = 1 as BasePatchSetNum;
+    element.patchNum = 3 as RevisionPatchSetNum;
     element.handleDiffBaseAgainstLatest();
     assert.isTrue(setUrlStub.called);
     assert.equal(setUrlStub.lastCall.firstArg, '/c/test-project/+/42/10');
@@ -640,10 +602,8 @@
     const removeFromAttentionSetStub = stubRestApi(
       'removeFromAttentionSet'
     ).returns(Promise.resolve(new Response()));
-    element.patchRange = {
-      basePatchNum: 1 as BasePatchSetNum,
-      patchNum: 3 as RevisionPatchSetNum,
-    };
+    element.basePatchNum = 1 as BasePatchSetNum;
+    element.patchNum = 3 as RevisionPatchSetNum;
     await element.updateComplete;
     assert.isNotOk(element.change.attention_set);
     element.handleToggleAttentionSet();
@@ -698,19 +658,6 @@
       assert.equal(element.activeTab, 'change-view-tab-header-url');
     });
 
-    test('param change should switch primary tab correctly', async () => {
-      assert.equal(element.activeTab, Tab.FILES);
-      // view is required
-      element.changeNum = undefined;
-      element.viewState = {
-        ...createChangeViewState(),
-        ...element.viewState,
-        tab: Tab.COMMENT_THREADS,
-      };
-      await element.updateComplete;
-      assert.equal(element.activeTab, Tab.COMMENT_THREADS);
-    });
-
     test('invalid param change should not switch primary tab', async () => {
       assert.equal(element.activeTab, Tab.FILES);
       // view is required
@@ -815,8 +762,6 @@
       stubRestApi('getChangeDetail').returns(
         Promise.resolve(createParsedChange())
       );
-      sinon.stub(element, 'performPostChangeLoadTasks');
-      sinon.stub(element, 'getMergeability');
       const change = {
         ...createChangeViewChange(),
         revisions: createRevisions(1),
@@ -946,10 +891,8 @@
   suite('thread list and change log tabs', () => {
     setup(() => {
       element.changeNum = TEST_NUMERIC_CHANGE_ID;
-      element.patchRange = {
-        basePatchNum: PARENT,
-        patchNum: 1 as RevisionPatchSetNum,
-      };
+      element.basePatchNum = PARENT;
+      element.patchNum = 1 as RevisionPatchSetNum;
       element.change = {
         ...createChangeViewChange(),
         revisions: {
@@ -969,12 +912,6 @@
           },
         },
       };
-      const relatedChanges = element.shadowRoot!.querySelector(
-        '#relatedChanges'
-      ) as GrRelatedChangesList;
-      sinon.stub(relatedChanges, 'reload');
-      sinon.stub(element, 'loadData').returns(Promise.resolve());
-      sinon.spy(element, 'viewStateChanged');
       element.viewState = createChangeViewState();
     });
   });
@@ -1154,183 +1091,6 @@
     );
   });
 
-  test('changeStatuses', async () => {
-    element.loading = false;
-    element.change = {
-      ...createChangeViewChange(),
-      revisions: {
-        rev2: createRevision(2),
-        rev1: createRevision(1),
-        rev13: createRevision(13),
-        rev3: createRevision(3),
-      },
-      current_revision: 'rev3' as CommitId,
-      status: ChangeStatus.MERGED,
-      labels: {
-        test: {
-          all: [],
-          default_value: 0,
-          values: {},
-          approved: {},
-        },
-      },
-    };
-    element.mergeable = true;
-    await element.updateComplete;
-    const expectedStatuses = [ChangeStates.MERGED];
-    assert.deepEqual(element.changeStatuses, expectedStatuses);
-    const statusChips =
-      element.shadowRoot!.querySelectorAll('gr-change-status');
-    assert.equal(statusChips.length, 1);
-  });
-
-  suite('ChangeStatus revert', () => {
-    test('do not show any chip if no revert created', async () => {
-      const change = {
-        ...createParsedChange(),
-        messages: createChangeMessages(2),
-      };
-      const getChangeStub = stubRestApi('getChange');
-      getChangeStub.onFirstCall().returns(
-        Promise.resolve({
-          ...createChange(),
-        })
-      );
-      getChangeStub.onSecondCall().returns(
-        Promise.resolve({
-          ...createChange(),
-        })
-      );
-      element.change = change;
-      element.mergeable = true;
-      element.currentRevisionActions = {submit: {enabled: true}};
-      assert.isTrue(element.isSubmitEnabled());
-      await element.updateComplete;
-      element.computeRevertSubmitted(element.change);
-      await element.updateComplete;
-      assert.isFalse(
-        element.changeStatuses?.includes(ChangeStates.REVERT_SUBMITTED)
-      );
-      assert.isFalse(
-        element.changeStatuses?.includes(ChangeStates.REVERT_CREATED)
-      );
-    });
-
-    test('do not show any chip if all reverts are abandoned', async () => {
-      const change = {
-        ...createParsedChange(),
-        messages: createChangeMessages(2),
-      };
-      change.messages[0].message = 'Created a revert of this change as 12345';
-      change.messages[0].tag = MessageTag.TAG_REVERT as ReviewInputTag;
-
-      change.messages[1].message = 'Created a revert of this change as 23456';
-      change.messages[1].tag = MessageTag.TAG_REVERT as ReviewInputTag;
-
-      const getChangeStub = stubRestApi('getChange');
-      getChangeStub.onFirstCall().returns(
-        Promise.resolve({
-          ...createChange(),
-          status: ChangeStatus.ABANDONED,
-        })
-      );
-      getChangeStub.onSecondCall().returns(
-        Promise.resolve({
-          ...createChange(),
-          status: ChangeStatus.ABANDONED,
-        })
-      );
-      element.change = change;
-      element.mergeable = true;
-      element.currentRevisionActions = {submit: {enabled: true}};
-      assert.isTrue(element.isSubmitEnabled());
-      await element.updateComplete;
-      element.computeRevertSubmitted(element.change);
-      await element.updateComplete;
-      assert.isFalse(
-        element.changeStatuses?.includes(ChangeStates.REVERT_SUBMITTED)
-      );
-      assert.isFalse(
-        element.changeStatuses?.includes(ChangeStates.REVERT_CREATED)
-      );
-    });
-
-    test('show revert created if no revert is merged', async () => {
-      const change = {
-        ...createParsedChange(),
-        messages: createChangeMessages(2),
-      };
-      change.messages[0].message = 'Created a revert of this change as 12345';
-      change.messages[0].tag = MessageTag.TAG_REVERT as ReviewInputTag;
-
-      change.messages[1].message = 'Created a revert of this change as 23456';
-      change.messages[1].tag = MessageTag.TAG_REVERT as ReviewInputTag;
-
-      const getChangeStub = stubRestApi('getChange');
-      getChangeStub.onFirstCall().returns(
-        Promise.resolve({
-          ...createChange(),
-        })
-      );
-      getChangeStub.onSecondCall().returns(
-        Promise.resolve({
-          ...createChange(),
-        })
-      );
-      element.change = change;
-      element.mergeable = true;
-      element.currentRevisionActions = {submit: {enabled: true}};
-      assert.isTrue(element.isSubmitEnabled());
-      await element.updateComplete;
-      element.computeRevertSubmitted(element.change);
-      // Wait for promises to settle.
-      await waitEventLoop();
-      await element.updateComplete;
-      assert.isFalse(
-        element.changeStatuses?.includes(ChangeStates.REVERT_SUBMITTED)
-      );
-      assert.isTrue(
-        element.changeStatuses?.includes(ChangeStates.REVERT_CREATED)
-      );
-    });
-
-    test('show revert submitted if revert is merged', async () => {
-      const change = {
-        ...createParsedChange(),
-        messages: createChangeMessages(2),
-      };
-      change.messages[0].message = 'Created a revert of this change as 12345';
-      change.messages[0].tag = MessageTag.TAG_REVERT as ReviewInputTag;
-      const getChangeStub = stubRestApi('getChange');
-      getChangeStub.onFirstCall().returns(
-        Promise.resolve({
-          ...createChange(),
-          status: ChangeStatus.MERGED,
-        })
-      );
-      getChangeStub.onSecondCall().returns(
-        Promise.resolve({
-          ...createChange(),
-        })
-      );
-      element.change = change;
-      element.mergeable = true;
-      element.currentRevisionActions = {submit: {enabled: true}};
-      assert.isTrue(element.isSubmitEnabled());
-      await element.updateComplete;
-      element.computeRevertSubmitted(element.change);
-      // Wait for promises to settle.
-      await waitEventLoop();
-      await element.updateComplete;
-      assert.isFalse(
-        element.changeStatuses?.includes(ChangeStates.REVERT_CREATED)
-      );
-      assert.isTrue(
-        element.changeStatuses?.includes(ChangeStates.REVERT_SUBMITTED)
-      );
-    });
-  });
-
   test('diff preferences open when open-diff-prefs is fired', async () => {
     await element.updateComplete;
     assertIsDefined(element.fileList);
@@ -1368,66 +1128,6 @@
     assert.isTrue(element.isSubmitEnabled());
   });
 
-  test('reload is called when an approved label is removed', async () => {
-    const vote: ApprovalInfo = {
-      ...createApproval(),
-      _account_id: 1 as AccountId,
-      name: 'bojack',
-      value: 1,
-    };
-    element.changeNum = TEST_NUMERIC_CHANGE_ID;
-    element.patchRange = {
-      basePatchNum: PARENT,
-      patchNum: 1 as RevisionPatchSetNum,
-    };
-    const change = {
-      ...createParsedChange(),
-      owner: createAccountWithIdNameAndEmail(),
-      revisions: {
-        rev2: createRevision(2),
-        rev1: createRevision(1),
-        rev13: createRevision(13),
-        rev3: createRevision(3),
-      },
-      current_revision: 'rev3' as CommitId,
-      status: ChangeStatus.NEW,
-      labels: {
-        test: {
-          all: [vote],
-          default_value: 0,
-          values: {},
-          approved: {},
-        },
-      },
-    };
-    element.change = change;
-    await element.updateComplete;
-    const reloadStub = sinon.stub(element, 'loadData');
-    const newChange = {...element.change};
-    (newChange.labels!.test! as DetailedLabelInfo).all = [];
-    element.change = deepClone(newChange);
-    await element.updateComplete;
-    assert.isFalse(reloadStub.called);
-
-    assert.isDefined(element.change);
-    const testLabels: DetailedLabelInfo & QuickLabelInfo =
-      newChange.labels!.test;
-    assertIsDefined(testLabels);
-    testLabels.all!.push(vote);
-    testLabels.all!.push(vote);
-    testLabels.approved = vote;
-    element.change = deepClone(newChange);
-    await element.updateComplete;
-    assert.isFalse(reloadStub.called);
-
-    assert.isDefined(element.change);
-    (newChange.labels!.test! as DetailedLabelInfo).all = [];
-    element.change = deepClone(newChange);
-    await element.updateComplete;
-    assert.isTrue(reloadStub.called);
-    assert.isTrue(reloadStub.calledOnce);
-  });
-
   test('reply button has updated count when there are drafts', () => {
     const getLabel = (canReview: boolean) => {
       element.change!.actions!.ready = {enabled: canReview};
@@ -1448,134 +1148,6 @@
     assert.equal(getLabel(true), 'Start Review (3)');
   });
 
-  test('change num change', async () => {
-    const change = {
-      ...createChangeViewChange(),
-      labels: {},
-    } as ParsedChangeInfo;
-    element.changeNum = undefined;
-    element.patchRange = {
-      basePatchNum: PARENT,
-      patchNum: 2 as RevisionPatchSetNum,
-    };
-    element.change = change;
-    assertIsDefined(element.fileList);
-    assert.equal(element.fileList.numFilesShown, DEFAULT_NUM_FILES_SHOWN);
-    element.fileList.numFilesShown = 150;
-    element.fileList.selectedIndex = 15;
-    await element.updateComplete;
-
-    element.changeNum = 2 as NumericChangeId;
-    element.viewState = {
-      ...createChangeViewState(),
-      changeNum: 2 as NumericChangeId,
-    };
-    await element.updateComplete;
-    assert.equal(element.fileList.numFilesShown, DEFAULT_NUM_FILES_SHOWN);
-    assert.equal(element.fileList.selectedIndex, 0);
-  });
-
-  test('don’t reload entire page when patchRange changes', async () => {
-    const reloadStub = sinon
-      .stub(element, 'loadData')
-      .callsFake(() => Promise.resolve());
-    const reloadPatchDependentStub = sinon
-      .stub(element, 'reloadPatchNumDependentResources')
-      .callsFake(() => Promise.resolve());
-    assertIsDefined(element.fileList);
-    await element.fileList.updateComplete;
-    const collapseStub = sinon.stub(element.fileList, 'collapseAllDiffs');
-    const value: ChangeViewState = {
-      ...createChangeViewState(),
-      view: GerritView.CHANGE,
-      patchNum: 1 as RevisionPatchSetNum,
-    };
-    element.changeNum = undefined;
-    element.viewState = value;
-    await element.updateComplete;
-    assert.isTrue(reloadStub.calledOnce);
-
-    element.initialLoadComplete = true;
-    element.fileList.selectedIndex = 15;
-    element.change = {
-      ...createChangeViewChange(),
-      revisions: {
-        rev1: createRevision(1),
-        rev2: createRevision(2),
-      },
-    };
-
-    value.basePatchNum = 1 as BasePatchSetNum;
-    value.patchNum = 2 as RevisionPatchSetNum;
-    element.viewState = {...value};
-    await element.updateComplete;
-    await waitEventLoop();
-    assert.equal(element.fileList.selectedIndex, 0);
-    assert.isFalse(reloadStub.calledTwice);
-    assert.isTrue(reloadPatchDependentStub.calledOnce);
-    assert.isTrue(collapseStub.calledTwice);
-  });
-
-  test('do not reload entire page when patchRange doesnt change', async () => {
-    assertIsDefined(element.fileList);
-    const reloadStub = sinon
-      .stub(element, 'loadData')
-      .callsFake(() => Promise.resolve());
-    const collapseStub = sinon.stub(element.fileList, 'collapseAllDiffs');
-    const value: ChangeViewState = createChangeViewState();
-    element.viewState = value;
-    // change already loaded
-    assert.isOk(element.changeNum);
-    await element.updateComplete;
-    assert.isFalse(reloadStub.calledOnce);
-    element.initialLoadComplete = true;
-    element.viewState = {...value};
-    await element.updateComplete;
-    assert.isFalse(reloadStub.calledTwice);
-    assert.isFalse(collapseStub.calledTwice);
-  });
-
-  test('forceReload updates the change', async () => {
-    assertIsDefined(element.fileList);
-    const getChangeStub = stubRestApi('getChangeDetail').returns(
-      Promise.resolve(createParsedChange())
-    );
-    const loadDataStub = sinon
-      .stub(element, 'loadData')
-      .callsFake(() => Promise.resolve());
-    const collapseStub = sinon.stub(element.fileList, 'collapseAllDiffs');
-    element.viewState = {...createChangeViewState(), forceReload: true};
-    await element.updateComplete;
-    assert.isTrue(getChangeStub.called);
-    assert.isTrue(loadDataStub.called);
-    assert.isTrue(collapseStub.called);
-    // patchNum is set by changeChanged, so this verifies that change was set.
-    assert.isOk(element.patchRange?.patchNum);
-  });
-
-  test('related changes are updated when loadData is called', async () => {
-    await element.updateComplete;
-    const relatedChanges = element.shadowRoot!.querySelector(
-      '#relatedChanges'
-    ) as GrRelatedChangesList;
-    const reloadStub = sinon.stub(relatedChanges, 'reload');
-    stubRestApi('getMergeable').returns(
-      Promise.resolve({...createMergeable(), mergeable: true})
-    );
-
-    element.viewState = createChangeViewState();
-    changeModel.setState({
-      loadingStatus: LoadingStatus.LOADED,
-      change: {
-        ...createChangeViewChange(),
-      },
-    });
-
-    await element.loadData(true);
-    assert.isFalse(setUrlStub.called);
-    assert.isTrue(reloadStub.called);
-  });
-
   test('computeCopyTextForTitle', () => {
     element.change = {
       ...createChangeViewChange(),
@@ -1593,26 +1165,6 @@
     );
   });
 
-  test('get latest revision', () => {
-    let change: ChangeInfo = {
-      ...createChange(),
-      revisions: {
-        rev1: createRevision(1),
-        rev3: createRevision(3),
-      },
-      current_revision: 'rev3' as CommitId,
-    };
-    assert.equal(element.getLatestRevisionSHA(change), 'rev3');
-    change = {
-      ...createChange(),
-      revisions: {
-        rev1: createRevision(1),
-      },
-      current_revision: undefined,
-    };
-    assert.equal(element.getLatestRevisionSHA(change), 'rev1');
-  });
-
   test('show commit message edit button', () => {
     const change = createParsedChange();
     const mergedChanged: ParsedChangeInfo = {
@@ -1635,6 +1187,7 @@
   });
 
   test('handleCommitMessageSave trims trailing whitespace', async () => {
+    element.changeNum = TEST_NUMERIC_CHANGE_ID;
     element.change = createChangeViewChange();
     // Response code is 500, because we want to avoid window reloading
     const putStub = stubRestApi('putChangeCommitMessage').returns(
@@ -1655,85 +1208,6 @@
     assert.equal(putStub.lastCall.args[1], '\n\n\n\n\n\n\n\n');
   });
 
-  test('topic is coalesced to null', async () => {
-    sinon.stub(element, 'changeChanged');
-    changeModel.setState({
-      loadingStatus: LoadingStatus.LOADED,
-      change: {
-        ...createChangeViewChange(),
-        labels: {},
-        current_revision: 'foo' as CommitId,
-        revisions: {foo: createRevision()},
-      },
-    });
-
-    await element.performPostChangeLoadTasks();
-    assert.isNull(element.change!.topic);
-  });
-
-  test('commit sha is populated from getChangeDetail', async () => {
-    changeModel.setState({
-      loadingStatus: LoadingStatus.LOADED,
-      change: {
-        ...createChangeViewChange(),
-        labels: {},
-        current_revision: 'foo' as CommitId,
-        revisions: {foo: createRevision()},
-      },
-    });
-
-    await element.performPostChangeLoadTasks();
-    assert.equal('foo', element.commitInfo!.commit);
-  });
-
-  test('getBasePatchNum', async () => {
-    element.change = {
-      ...createChangeViewChange(),
-      revisions: {
-        '98da160735fb81604b4c40e93c368f380539dd0e': createRevision(),
-      },
-    };
-    element.patchRange = {
-      basePatchNum: PARENT,
-    };
-    await element.updateComplete;
-    assert.equal(element.getBasePatchNum(), PARENT);
-
-    element.prefs = {
-      ...createPreferences(),
-      default_base_for_merges: DefaultBase.FIRST_PARENT,
-    };
-
-    element.change = {
-      ...createChangeViewChange(),
-      revisions: {
-        '98da160735fb81604b4c40e93c368f380539dd0e': {
-          ...createRevision(1),
-          commit: {
-            ...createCommit(),
-            parents: [
-              {
-                commit: '6e12bdf1176eb4ab24d8491ba3b6d0704409cde8' as CommitId,
-                subject: 'test',
-              },
-              {
-                commit: '22f7db4754b5d9816fc581f3d9a6c0ef8429c841' as CommitId,
-                subject: 'test3',
-              },
-            ],
-          },
-        },
-      },
-    };
-    await element.updateComplete;
-    assert.equal(element.getBasePatchNum(), -1 as BasePatchSetNum);
-
-    element.patchRange.basePatchNum = PARENT;
-    element.patchRange.patchNum = 1 as RevisionPatchSetNum;
-    await element.updateComplete;
-    assert.equal(element.getBasePatchNum(), PARENT);
-  });
-
   test('openReplyDialog called with `ANY` when coming from tap event', async () => {
     await element.updateComplete;
     assertIsDefined(element.replyBtn);
@@ -1787,10 +1261,8 @@
       .stub(testResolver(pluginLoaderToken), 'awaitPluginsLoaded')
       .callsFake(() => Promise.resolve());
 
-    element.patchRange = {
-      basePatchNum: PARENT,
-      patchNum: 2 as RevisionPatchSetNum,
-    };
+    element.basePatchNum = PARENT;
+    element.patchNum = 2 as RevisionPatchSetNum;
     element.change = {
       ...createChangeViewChange(),
       revisions: {
@@ -1854,14 +1326,18 @@
   });
 
   test('maybeScrollToMessage', async () => {
+    element.change = {
+      ...createChangeViewChange(),
+      messages: createChangeMessages(1),
+    };
     await element.updateComplete;
     const scrollStub = sinon.stub(element.messagesList!, 'scrollToMessage');
 
-    element.maybeScrollToMessage('');
+    await element.maybeScrollToMessage('');
     assert.isFalse(scrollStub.called);
-    element.maybeScrollToMessage('message');
+    await element.maybeScrollToMessage('message');
     assert.isFalse(scrollStub.called);
-    element.maybeScrollToMessage('#message-TEST');
+    await element.maybeScrollToMessage('#message-TEST');
     assert.isTrue(scrollStub.called);
     assert.equal(scrollStub.lastCall.args[0], 'TEST');
   });
@@ -1869,6 +1345,8 @@
   test('computeEditMode', async () => {
     const callCompute = async (viewState: ChangeViewState) => {
       element.viewState = viewState;
+      element.patchNum = viewState.patchNum;
+      element.basePatchNum = viewState.basePatchNum ?? PARENT;
       await element.updateComplete;
       return element.getEditMode();
     };
@@ -1896,46 +1374,8 @@
     );
   });
 
-  test('processEdit', () => {
-    element.patchRange = {};
-    const change: ParsedChangeInfo = {
-      ...createChangeViewChange(),
-      current_revision: 'foo' as CommitId,
-      revisions: {
-        foo: {...createRevision()},
-      },
-    };
-
-    // With no edit, nothing happens.
-    element.processEdit(change);
-    assert.equal(element.patchRange.patchNum, undefined);
-
-    change.revisions['bar'] = {
-      _number: EDIT,
-      basePatchNum: 1 as BasePatchSetNum,
-      commit: {
-        ...createCommit(),
-        commit: 'bar' as CommitId,
-      },
-      fetch: {},
-    };
-
-    // When edit is set, but not patchNum, then switch to edit ps.
-    element.processEdit(change);
-    assert.equal(element.patchRange.patchNum, EDIT);
-
-    // When edit is set, but patchNum as well, then keep patchNum.
-    element.patchRange.patchNum = 5 as RevisionPatchSetNum;
-    element.viewModelPatchNum = 5 as RevisionPatchSetNum;
-    element.processEdit(change);
-    assert.equal(element.patchRange.patchNum, 5 as RevisionPatchSetNum);
-  });
-
   test('file-action-tap handling', async () => {
-    element.patchRange = {
-      basePatchNum: PARENT,
-      patchNum: 1 as RevisionPatchSetNum,
-    };
+    element.patchNum = 1 as RevisionPatchSetNum;
     element.change = {
       ...createChangeViewChange(),
     };
@@ -2006,109 +1446,6 @@
     assert.isTrue(setUrlStub.called);
   });
 
-  test('selectedRevision updates when patchNum is changed', async () => {
-    const revision1: RevisionInfo = createRevision(1);
-    const revision2: RevisionInfo = createRevision(2);
-    changeModel.setState({
-      loadingStatus: LoadingStatus.LOADED,
-      change: {
-        ...createChangeViewChange(),
-        revisions: {
-          aaa: revision1,
-          bbb: revision2,
-        },
-        labels: {},
-        actions: {},
-        current_revision: 'bbb' as CommitId,
-      },
-    });
-    userModel.setPreferences(createPreferences());
-
-    element.patchRange = {patchNum: 2 as RevisionPatchSetNum};
-    await element.performPostChangeLoadTasks();
-    assert.strictEqual(element.selectedRevision, revision2);
-
-    element.patchRange = {patchNum: 1 as RevisionPatchSetNum};
-    await element.updateComplete;
-    assert.strictEqual(element.selectedRevision, revision1);
-  });
-
-  test('selectedRevision is assigned when patchNum is edit', async () => {
-    const revision1 = createRevision(1);
-    const revision2 = createRevision(2);
-    const revision3 = createEditRevision();
-    changeModel.setState({
-      loadingStatus: LoadingStatus.LOADED,
-      change: {
-        ...createChangeViewChange(),
-        revisions: {
-          aaa: revision1,
-          bbb: revision2,
-          ccc: revision3,
-        },
-        labels: {},
-        actions: {},
-        current_revision: 'ccc' as CommitId,
-      },
-    });
-    stubRestApi('getPreferences').returns(Promise.resolve(createPreferences()));
-
-    element.patchRange = {patchNum: EDIT};
-    await element.performPostChangeLoadTasks();
-    assert.strictEqual(element.selectedRevision, revision3);
-  });
-
-  test('sendShowChangeEvent', () => {
-    const change = {...createChangeViewChange(), labels: {}};
-    element.change = {...change};
-    element.patchRange = {patchNum: 4 as RevisionPatchSetNum};
-    element.mergeable = true;
-    const showStub = sinon.stub(
-      testResolver(pluginLoaderToken).jsApiService,
-      'handleShowChange'
-    );
-    element.sendShowChangeEvent();
-    assert.isTrue(showStub.calledOnce);
-    assert.deepEqual(showStub.lastCall.args[0], {
-      change,
-      patchNum: 4 as PatchSetNumber,
-      info: {mergeable: true},
-    });
-  });
-
-  test('patch range changed', () => {
-    element.patchRange = undefined;
-    element.change = createChangeViewChange();
-    element.change.revisions = createRevisions(4);
-    element.change.current_revision = '1' as CommitId;
-    element.change = {...element.change};
-
-    const viewState = createChangeViewState();
-
-    assert.isFalse(element.hasPatchRangeChanged(viewState));
-    assert.isFalse(element.hasPatchNumChanged(viewState));
-
-    viewState.basePatchNum = PARENT;
-    // undefined means navigate to latest patchset
-    viewState.patchNum = undefined;
-
-    element.patchRange = {
-      patchNum: 2 as RevisionPatchSetNum,
-      basePatchNum: PARENT,
-    };
-
-    assert.isTrue(element.hasPatchRangeChanged(viewState));
-    assert.isTrue(element.hasPatchNumChanged(viewState));
-
-    element.patchRange = {
-      patchNum: 4 as RevisionPatchSetNum,
-      basePatchNum: PARENT,
-    };
-
-    assert.isFalse(element.hasPatchRangeChanged(viewState));
-    assert.isFalse(element.hasPatchNumChanged(viewState));
-  });
-
   suite('handleEditTap', () => {
     let fireEdit: () => void;
 
@@ -2157,7 +1494,7 @@
       const newChange = {...element.change};
       newChange.revisions.rev2 = createRevision(2);
       element.change = newChange;
-      element.patchRange = {patchNum: 2 as RevisionPatchSetNum};
+      element.patchNum = 2 as RevisionPatchSetNum;
       await element.updateComplete;
 
       fireEdit();
@@ -2178,7 +1515,7 @@
     assertIsDefined(element.actions);
     sinon.stub(element.metadata, 'computeLabelNames');
 
-    element.patchRange = {patchNum: 1 as RevisionPatchSetNum};
+    element.patchNum = 1 as RevisionPatchSetNum;
     element.actions.dispatchEvent(
       new CustomEvent('stop-edit-tap', {bubbles: false})
     );
@@ -2193,7 +1530,7 @@
   suite('plugin endpoints', () => {
     test('endpoint params', async () => {
       element.change = {...createChangeViewChange(), labels: {}};
-      element.selectedRevision = createRevision();
+      element.revision = createRevision();
       const promise = mockPromise();
       window.Gerrit.install(
         promise.resolve,
@@ -2207,43 +1544,7 @@
         .getLastAttached();
       assert.strictEqual((hookEl as any).plugin, plugin);
       assert.strictEqual((hookEl as any).change, element.change);
-      assert.strictEqual((hookEl as any).revision, element.selectedRevision);
-    });
-  });
-
-  suite('getMergeability', () => {
-    let getMergeableStub: SinonStubbedMember<RestApiService['getMergeable']>;
-    setup(() => {
-      element.change = {...createChangeViewChange(), labels: {}};
-      getMergeableStub = stubRestApi('getMergeable').returns(
-        Promise.resolve({...createMergeable(), mergeable: true})
-      );
-    });
-
-    test('merged change', () => {
-      element.mergeable = null;
-      element.change!.status = ChangeStatus.MERGED;
-      return element.getMergeability().then(() => {
-        assert.isFalse(element.mergeable);
-        assert.isFalse(getMergeableStub.called);
-      });
-    });
-
-    test('abandoned change', () => {
-      element.mergeable = null;
-      element.change!.status = ChangeStatus.ABANDONED;
-      return element.getMergeability().then(() => {
-        assert.isFalse(element.mergeable);
-        assert.isFalse(getMergeableStub.called);
-      });
-    });
-
-    test('open change', () => {
-      element.mergeable = null;
-      return element.getMergeability().then(() => {
-        assert.isTrue(element.mergeable);
-        assert.isTrue(getMergeableStub.called);
-      });
+      assert.strictEqual((hookEl as any).revision, element.revision);
     });
   });
 
@@ -2265,18 +1566,8 @@
 
   suite('gr-reporting tests', () => {
     setup(() => {
-      element.patchRange = {
-        basePatchNum: PARENT,
-        patchNum: 1 as RevisionPatchSetNum,
-      };
-      sinon
-        .stub(element, 'performPostChangeLoadTasks')
-        .returns(Promise.resolve(false));
-      sinon.stub(element, 'getMergeability').returns(Promise.resolve());
-      sinon.stub(element, 'getLatestCommitMessage').returns(Promise.resolve());
-      sinon
-        .stub(element, 'reloadPatchNumDependentResources')
-        .returns(Promise.resolve());
+      element.basePatchNum = PARENT;
+      element.patchNum = 1 as RevisionPatchSetNum;
     });
 
     test("don't report changeDisplayed on reply", async () => {
@@ -2294,7 +1585,8 @@
       assert.isFalse(changeFullyLoadedStub.called);
     });
 
-    test('report changeDisplayed on viewStateChanged', async () => {
+    test('report changeDisplayed and changeFullyLoaded', async () => {
+      const commentsModel = testResolver(commentsModelToken);
       stubRestApi('getChangeOrEditFiles').resolves({
         'a-file.js': {},
       });
@@ -2322,32 +1614,23 @@
           revisions: {foo: createRevision()},
         },
       });
-      await element.updateComplete;
-      await waitEventLoop();
+
+      await waitUntil(() => changeDisplayStub.called);
       assert.isTrue(changeDisplayStub.called);
+      assert.isFalse(changeFullyLoadedStub.called);
+
+      element.mergeable = true;
+      commentsModel.setState({
+        comments: {},
+        drafts: {},
+        discardedDrafts: [],
+      });
+
+      await waitUntil(() => changeFullyLoadedStub.called);
       assert.isTrue(changeFullyLoadedStub.called);
     });
   });
 
-  test('calculateHasParent', () => {
-    const changeId = '123' as ChangeId;
-    const relatedChanges: RelatedChangeAndCommitInfo[] = [];
-
-    assert.equal(element.calculateHasParent(changeId, relatedChanges), false);
-
-    relatedChanges.push({
-      ...createRelatedChangeAndCommitInfo(),
-      change_id: '123' as ChangeId,
-    });
-    assert.equal(element.calculateHasParent(changeId, relatedChanges), false);
-
-    relatedChanges.push({
-      ...createRelatedChangeAndCommitInfo(),
-      change_id: '234' as ChangeId,
-    });
-    assert.equal(element.calculateHasParent(changeId, relatedChanges), true);
-  });
-
   test('renders sha in copy links', async () => {
     stubFlags('isEnabled').returns(true);
     const sha = '123' as CommitId;
diff --git a/polygerrit-ui/app/elements/change/gr-confirm-rebase-dialog/gr-confirm-rebase-dialog.ts b/polygerrit-ui/app/elements/change/gr-confirm-rebase-dialog/gr-confirm-rebase-dialog.ts
index 166d895..6ad416e 100644
--- a/polygerrit-ui/app/elements/change/gr-confirm-rebase-dialog/gr-confirm-rebase-dialog.ts
+++ b/polygerrit-ui/app/elements/change/gr-confirm-rebase-dialog/gr-confirm-rebase-dialog.ts
@@ -28,8 +28,9 @@
 import {fireNoBubbleNoCompose} from '../../../utils/event-util';
 import {resolve} from '../../../models/dependency';
 import {changeModelToken} from '../../../models/change/change-model';
-import {subscribe} from '../../lit/subscription-controller';
 import {userModelToken} from '../../../models/user/user-model';
+import {relatedChangesModelToken} from '../../../models/change/related-changes-model';
+import {subscribe} from '../../lit/subscription-controller';
 
 export interface RebaseChange {
   name: string;
@@ -63,12 +64,6 @@
   @property({type: String})
   branch?: BranchName;
 
-  @property({type: Number})
-  changeNumber?: NumericChangeId;
-
-  @property({type: Boolean})
-  hasParent?: boolean;
-
   @property({type: Boolean})
   rebaseOnCurrent?: boolean;
 
@@ -76,6 +71,12 @@
   disableActions = false;
 
   @state()
+  changeNum?: NumericChangeId;
+
+  @state()
+  hasParent?: boolean;
+
+  @state()
   text = '';
 
   @state()
@@ -91,16 +92,16 @@
   allowConflicts = false;
 
   @query('#rebaseOnParentInput')
-  private rebaseOnParentInput!: HTMLInputElement;
+  private rebaseOnParentInput?: HTMLInputElement;
 
   @query('#rebaseOnTipInput')
-  private rebaseOnTipInput!: HTMLInputElement;
+  private rebaseOnTipInput?: HTMLInputElement;
 
   @query('#rebaseOnOtherInput')
-  rebaseOnOtherInput!: HTMLInputElement;
+  rebaseOnOtherInput?: HTMLInputElement;
 
   @query('#rebaseAllowConflicts')
-  private rebaseAllowConflicts!: HTMLInputElement;
+  private rebaseAllowConflicts?: HTMLInputElement;
 
   @query('#rebaseChain')
   private rebaseChain?: HTMLInputElement;
@@ -120,6 +121,11 @@
 
   private readonly getUserModel = resolve(this, userModelToken);
 
+  private readonly getRelatedChangesModel = resolve(
+    this,
+    relatedChangesModelToken
+  );
+
   constructor() {
     super();
     this.query = input => this.getChangeSuggestions(input);
@@ -133,6 +139,16 @@
       () => this.getChangeModel().latestUploader$,
       x => (this.uploader = x)
     );
+    subscribe(
+      this,
+      () => this.getChangeModel().changeNum$,
+      x => (this.changeNum = x)
+    );
+    subscribe(
+      this,
+      () => this.getRelatedChangesModel().hasParent$,
+      x => (this.hasParent = x)
+    );
   }
 
   override willUpdate(changedProperties: PropertyValues): void {
@@ -199,6 +215,9 @@
               Rebase on parent change
             </label>
           </div>
+          <div class="message" ?hidden=${this.hasParent !== undefined}>
+            Still loading parent information ...
+          </div>
           <div
             id="parentUpToDateMsg"
             class="message"
@@ -361,8 +380,7 @@
   ): AutocompleteSuggestion[] {
     return changes
       .filter(
-        change =>
-          change.name.includes(input) && change.value !== this.changeNumber
+        change => change.name.includes(input) && change.value !== this.changeNum
       )
       .map(
         change =>
@@ -393,10 +411,10 @@
    * should be rebased on top of its current parent.
    */
   getSelectedBase() {
-    if (this.rebaseOnParentInput.checked) {
+    if (this.rebaseOnParentInput?.checked) {
       return null;
     }
-    if (this.rebaseOnTipInput.checked) {
+    if (this.rebaseOnTipInput?.checked) {
       return '';
     }
     if (!this.text) {
@@ -412,7 +430,7 @@
     e.stopPropagation();
     const detail: ConfirmRebaseEventDetail = {
       base: this.getSelectedBase(),
-      allowConflicts: this.rebaseAllowConflicts.checked,
+      allowConflicts: !!this.rebaseAllowConflicts?.checked,
       rebaseChain: !!this.rebaseChain?.checked,
       onBehalfOfUploader: this.rebaseOnBehalfOfUploader(),
     };
@@ -437,7 +455,7 @@
   }
 
   private handleEnterChangeNumberClick() {
-    this.rebaseOnOtherInput.checked = true;
+    if (this.rebaseOnOtherInput) this.rebaseOnOtherInput.checked = true;
   }
 
   /**
@@ -451,11 +469,11 @@
     }
 
     if (this.displayParentOption()) {
-      this.rebaseOnParentInput.checked = true;
+      if (this.rebaseOnParentInput) this.rebaseOnParentInput.checked = true;
     } else if (this.displayTipOption()) {
-      this.rebaseOnTipInput.checked = true;
+      if (this.rebaseOnTipInput) this.rebaseOnTipInput.checked = true;
     } else {
-      this.rebaseOnOtherInput.checked = true;
+      if (this.rebaseOnOtherInput) this.rebaseOnOtherInput.checked = true;
     }
   }
 }
diff --git a/polygerrit-ui/app/elements/change/gr-confirm-rebase-dialog/gr-confirm-rebase-dialog_test.ts b/polygerrit-ui/app/elements/change/gr-confirm-rebase-dialog/gr-confirm-rebase-dialog_test.ts
index 8d907c9..24f8a34 100644
--- a/polygerrit-ui/app/elements/change/gr-confirm-rebase-dialog/gr-confirm-rebase-dialog_test.ts
+++ b/polygerrit-ui/app/elements/change/gr-confirm-rebase-dialog/gr-confirm-rebase-dialog_test.ts
@@ -44,6 +44,7 @@
 
   test('render', async () => {
     element.branch = 'test' as BranchName;
+    element.hasParent = false;
     await element.updateComplete;
     assert.shadowDom.equal(
       element,
@@ -60,6 +61,9 @@
               Rebase on parent change
             </label>
           </div>
+          <div class="message" hidden="">
+            Still loading parent information ...
+          </div>
           <div class="message" hidden="" id="parentUpToDateMsg">
             This change is up to date with its parent.
           </div>
@@ -239,7 +243,7 @@
     element.hasParent = false;
     await element.updateComplete;
 
-    assert.isTrue(element.rebaseOnOtherInput.checked);
+    assert.isTrue(element.rebaseOnOtherInput?.checked);
     assert.isTrue(
       queryAndAssert(element, '#rebaseOnParent').hasAttribute('hidden')
     );
@@ -360,7 +364,7 @@
       assert.equal(element.filterChanges('awesome', recentChanges).length, 3);
       assert.equal(element.filterChanges('third', recentChanges).length, 1);
 
-      element.changeNumber = 123 as NumericChangeId;
+      element.changeNum = 123 as NumericChangeId;
       await element.updateComplete;
 
       assert.equal(element.filterChanges('123', recentChanges).length, 0);
diff --git a/polygerrit-ui/app/elements/change/gr-file-list/gr-file-list.ts b/polygerrit-ui/app/elements/change/gr-file-list/gr-file-list.ts
index c206d57..62693ea 100644
--- a/polygerrit-ui/app/elements/change/gr-file-list/gr-file-list.ts
+++ b/polygerrit-ui/app/elements/change/gr-file-list/gr-file-list.ts
@@ -826,6 +826,13 @@
 
   override willUpdate(changedProperties: PropertyValues): void {
     if (
+      changedProperties.has('patchNum') ||
+      changedProperties.has('basePatchNum')
+    ) {
+      this.resetFileState();
+      this.collapseAllDiffs();
+    }
+    if (
       changedProperties.has('diffPrefs') ||
       changedProperties.has('diffViewMode')
     ) {
diff --git a/polygerrit-ui/app/elements/change/gr-messages-list/gr-messages-list.ts b/polygerrit-ui/app/elements/change/gr-messages-list/gr-messages-list.ts
index 9a069a4..ac087cef 100644
--- a/polygerrit-ui/app/elements/change/gr-messages-list/gr-messages-list.ts
+++ b/polygerrit-ui/app/elements/change/gr-messages-list/gr-messages-list.ts
@@ -46,6 +46,7 @@
   shortcutsServiceToken,
 } from '../../../services/shortcuts/shortcuts-service';
 import {GrFormattedText} from '../../shared/gr-formatted-text/gr-formatted-text';
+import {waitUntil} from '../../../utils/async-util';
 
 /**
  * The content of the enum is also used in the UI for the button text.
@@ -439,6 +440,9 @@
   }
 
   async scrollToMessage(messageID: string) {
+    await waitUntil(() => this.messages.length > 0);
+    await this.updateComplete;
+
     const selector = `[data-message-id="${messageID}"]`;
     const el = this.shadowRoot!.querySelector(selector) as
       | GrMessage
diff --git a/polygerrit-ui/app/elements/change/gr-messages-list/gr-messages-list_test.ts b/polygerrit-ui/app/elements/change/gr-messages-list/gr-messages-list_test.ts
index 0217aa8..df04f68 100644
--- a/polygerrit-ui/app/elements/change/gr-messages-list/gr-messages-list_test.ts
+++ b/polygerrit-ui/app/elements/change/gr-messages-list/gr-messages-list_test.ts
@@ -195,9 +195,9 @@
       }
     });
 
-    test('expand/collapse from external keypress', () => {
+    test('expand/collapse from external keypress', async () => {
       // Start with one expanded message. -> not all collapsed
-      element.scrollToMessage(messages[1].id);
+      await element.scrollToMessage(messages[1].id);
       assert.isFalse(
         [...getMessages()].filter(m => m.message?.expanded).length === 0
       );
diff --git a/polygerrit-ui/app/elements/change/gr-related-changes-list/gr-related-changes-list.ts b/polygerrit-ui/app/elements/change/gr-related-changes-list/gr-related-changes-list.ts
index 05acb29..6bdabec 100644
--- a/polygerrit-ui/app/elements/change/gr-related-changes-list/gr-related-changes-list.ts
+++ b/polygerrit-ui/app/elements/change/gr-related-changes-list/gr-related-changes-list.ts
@@ -11,31 +11,26 @@
 import '../../shared/gr-icon/gr-icon';
 import {classMap} from 'lit/directives/class-map.js';
 import {LitElement, css, html, TemplateResult} from 'lit';
-import {customElement, property, state} from 'lit/decorators.js';
+import {customElement, state} from 'lit/decorators.js';
 import {sharedStyles} from '../../../styles/shared-styles';
 import {
   ChangeInfo,
   CommitId,
   PatchSetNumber,
   RelatedChangeAndCommitInfo,
-  RelatedChangesInfo,
   RevisionPatchSetNum,
   SubmittedTogetherInfo,
 } from '../../../types/common';
-import {getAppContext} from '../../../services/app-context';
 import {ParsedChangeInfo} from '../../../types/types';
 import {truncatePath} from '../../../utils/path-list-util';
 import {pluralize} from '../../../utils/string-util';
-import {
-  changeIsOpen,
-  getChangeNumber,
-  getRevisionKey,
-} from '../../../utils/change-util';
+import {getChangeNumber, getRevisionKey} from '../../../utils/change-util';
 import {DEFALT_NUM_CHANGES_WHEN_COLLAPSED} from './gr-related-collapse';
 import {createChangeUrl} from '../../../models/views/change';
 import {subscribe} from '../../lit/subscription-controller';
 import {resolve} from '../../../models/dependency';
 import {changeModelToken} from '../../../models/change/change-model';
+import {relatedChangesModelToken} from '../../../models/change/related-changes-model';
 
 export interface ChangeMarkersInList {
   showCurrentChangeArrow: boolean;
@@ -54,9 +49,6 @@
 
 @customElement('gr-related-changes-list')
 export class GrRelatedChangesList extends LitElement {
-  @property({type: Boolean})
-  mergeable?: boolean;
-
   @state()
   change?: ParsedChangeInfo;
 
@@ -81,10 +73,13 @@
   @state()
   sameTopicChanges: ChangeInfo[] = [];
 
-  private readonly restApiService = getAppContext().restApiService;
-
   private readonly getChangeModel = resolve(this, changeModelToken);
 
+  private readonly getRelatedChangesModel = resolve(
+    this,
+    relatedChangesModelToken
+  );
+
   constructor() {
     super();
     subscribe(
@@ -97,6 +92,31 @@
       () => this.getChangeModel().latestPatchNum$,
       x => (this.latestPatchNum = x)
     );
+    subscribe(
+      this,
+      () => this.getRelatedChangesModel().relatedChanges$,
+      x => (this.relatedChanges = x ?? [])
+    );
+    subscribe(
+      this,
+      () => this.getRelatedChangesModel().submittedTogether$,
+      x => (this.submittedTogether = x)
+    );
+    subscribe(
+      this,
+      () => this.getRelatedChangesModel().cherryPicks$,
+      x => (this.cherryPickChanges = x ?? [])
+    );
+    subscribe(
+      this,
+      () => this.getRelatedChangesModel().conflictingChanges$,
+      x => (this.conflictingChanges = x ?? [])
+    );
+    subscribe(
+      this,
+      () => this.getRelatedChangesModel().sameTopicChanges$,
+      x => (this.sameTopicChanges = x ?? [])
+    );
   }
 
   static override get styles() {
@@ -586,72 +606,6 @@
     return html`<span class="marker space"></span>`;
   }
 
-  reload(getRelatedChanges?: Promise<RelatedChangesInfo | undefined>) {
-    const change = this.change;
-    if (!change) return Promise.reject(new Error('change missing'));
-    if (!this.latestPatchNum)
-      return Promise.reject(new Error('latestPatchNum missing'));
-    if (!getRelatedChanges) {
-      getRelatedChanges = this.restApiService.getRelatedChanges(
-        change._number,
-        this.latestPatchNum
-      );
-    }
-    const promises: Array<Promise<void>> = [
-      getRelatedChanges.then(response => {
-        if (!response) {
-          throw new Error('getRelatedChanges returned undefined response');
-        }
-        this.relatedChanges = response?.changes ?? [];
-      }),
-      this.restApiService
-        .getChangesSubmittedTogether(change._number)
-        .then(response => {
-          this.submittedTogether = response;
-        }),
-      this.restApiService
-        .getChangeCherryPicks(change.project, change.change_id, change._number)
-        .then(response => {
-          this.cherryPickChanges = response || [];
-        }),
-    ];
-
-    // Get conflicts if change is open and is mergeable.
-    // Mergeable is output of restApiServict.getMergeable from gr-change-view
-    if (changeIsOpen(change) && this.mergeable) {
-      promises.push(
-        this.restApiService
-          .getChangeConflicts(change._number)
-          .then(response => {
-            this.conflictingChanges = response ?? [];
-          })
-      );
-    }
-    if (change.topic) {
-      const changeTopic = change.topic;
-      promises.push(
-        this.restApiService.getConfig().then(config => {
-          if (config && !config.change.submit_whole_topic) {
-            return this.restApiService
-              .getChangesWithSameTopic(changeTopic, {
-                openChangesOnly: true,
-                changeToExclude: change._number,
-              })
-              .then(response => {
-                if (changeTopic === this.change?.topic) {
-                  this.sameTopicChanges = response ?? [];
-                }
-              });
-          }
-          this.sameTopicChanges = [];
-          return Promise.resolve();
-        })
-      );
-    }
-
-    return Promise.all(promises);
-  }
-
   /**
    * Do the given objects describe the same change? Compares the changes by
    * their numbers.
diff --git a/polygerrit-ui/app/elements/change/gr-related-changes-list/gr-related-changes-list_test.ts b/polygerrit-ui/app/elements/change/gr-related-changes-list/gr-related-changes-list_test.ts
index 571b5b5..24a8217 100644
--- a/polygerrit-ui/app/elements/change/gr-related-changes-list/gr-related-changes-list_test.ts
+++ b/polygerrit-ui/app/elements/change/gr-related-changes-list/gr-related-changes-list_test.ts
@@ -4,10 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 import {fixture, html, assert} from '@open-wc/testing';
-import {SinonStubbedMember} from 'sinon';
 import {PluginApi} from '../../../api/plugin';
-import {ChangeStatus} from '../../../constants/constants';
-import {RestApiService} from '../../../services/gr-rest-api/gr-rest-api';
 import '../../../test/common-test-setup';
 import {testResolver} from '../../../test/common-test-setup';
 import {
@@ -19,12 +16,7 @@
   createRevision,
   createSubmittedTogetherInfo,
 } from '../../../test/test-data-generators';
-import {
-  query,
-  queryAndAssert,
-  stubRestApi,
-  waitEventLoop,
-} from '../../../test/test-utils';
+import {query, queryAndAssert, waitEventLoop} from '../../../test/test-utils';
 import {
   ChangeId,
   ChangeInfo,
@@ -196,16 +188,10 @@
     });
 
     test('render', async () => {
-      stubRestApi('getRelatedChanges').returns(
-        Promise.resolve(relatedChangeInfo)
-      );
-      stubRestApi('getChangesSubmittedTogether').returns(
-        Promise.resolve(submittedTogether)
-      );
-      stubRestApi('getChangeCherryPicks').returns(
-        Promise.resolve([createChange()])
-      );
-      await element.reload();
+      element.relatedChanges = relatedChangeInfo.changes;
+      element.submittedTogether = submittedTogether;
+      element.cherryPickChanges = [createChange()];
+      await element.updateComplete;
 
       assert.shadowDom.equal(
         element,
@@ -262,10 +248,9 @@
     });
 
     test('first list', async () => {
-      stubRestApi('getRelatedChanges').returns(
-        Promise.resolve(relatedChangeInfo)
-      );
-      await element.reload();
+      element.relatedChanges = relatedChangeInfo.changes;
+      await element.updateComplete;
+
       const section = queryAndAssert<HTMLElement>(element, '#relatedChanges');
       const relatedChanges = queryAndAssert<GrRelatedCollapse>(
         section,
@@ -275,13 +260,10 @@
     });
 
     test('first empty second non-empty', async () => {
-      stubRestApi('getRelatedChanges').returns(
-        Promise.resolve(createRelatedChangesInfo())
-      );
-      stubRestApi('getChangesSubmittedTogether').returns(
-        Promise.resolve(submittedTogether)
-      );
-      await element.reload();
+      element.relatedChanges = createRelatedChangesInfo().changes;
+      element.submittedTogether = submittedTogether;
+      await element.updateComplete;
+
       const relatedChanges = query<HTMLElement>(element, '#relatedChanges');
       assert.notExists(relatedChanges);
       const submittedTogetherSection = queryAndAssert<GrRelatedCollapse>(
@@ -292,16 +274,10 @@
     });
 
     test('first non-empty second empty third non-empty', async () => {
-      stubRestApi('getRelatedChanges').returns(
-        Promise.resolve(relatedChangeInfo)
-      );
-      stubRestApi('getChangesSubmittedTogether').returns(
-        Promise.resolve(createSubmittedTogetherInfo())
-      );
-      stubRestApi('getChangeCherryPicks').returns(
-        Promise.resolve([createChange()])
-      );
-      await element.reload();
+      element.relatedChanges = relatedChangeInfo.changes;
+      element.submittedTogether = createSubmittedTogetherInfo();
+      element.cherryPickChanges = [createChange()];
+      await element.updateComplete;
 
       const relatedChanges = queryAndAssert<GrRelatedCollapse>(
         queryAndAssert<HTMLElement>(element, '#relatedChanges'),
@@ -364,67 +340,6 @@
     assert.equal(getChangeNumber(change2), 1);
   });
 
-  suite('get conflicts tests', () => {
-    let element: GrRelatedChangesList;
-    let conflictsStub: SinonStubbedMember<RestApiService['getChangeConflicts']>;
-
-    setup(async () => {
-      element = await fixture(
-        html`<gr-related-changes-list></gr-related-changes-list>`
-      );
-      conflictsStub = stubRestApi('getChangeConflicts').returns(
-        Promise.resolve(undefined)
-      );
-    });
-
-    test('request conflicts if open and mergeable', () => {
-      element.latestPatchNum = 7 as PatchSetNumber;
-      element.change = {
-        ...createParsedChange(),
-        change_id: '123' as ChangeId,
-        status: ChangeStatus.NEW,
-      };
-      element.mergeable = true;
-      element.reload();
-      assert.isTrue(conflictsStub.called);
-    });
-
-    test('does not request conflicts if closed and mergeable', () => {
-      element.latestPatchNum = 7 as PatchSetNumber;
-      element.change = {
-        ...createParsedChange(),
-        change_id: '123' as ChangeId,
-        status: ChangeStatus.NEW,
-      };
-      element.reload();
-      assert.isFalse(conflictsStub.called);
-    });
-
-    test('does not request conflicts if open and not mergeable', () => {
-      element.latestPatchNum = 7 as PatchSetNumber;
-      element.change = {
-        ...createParsedChange(),
-        change_id: '123' as ChangeId,
-        status: ChangeStatus.NEW,
-      };
-      element.mergeable = false;
-      element.reload();
-      assert.isFalse(conflictsStub.called);
-    });
-
-    test('doesnt request conflicts if closed and not mergeable', () => {
-      element.latestPatchNum = 7 as PatchSetNumber;
-      element.change = {
-        ...createParsedChange(),
-        change_id: '123' as ChangeId,
-        status: ChangeStatus.NEW,
-      };
-      element.mergeable = false;
-      element.reload();
-      assert.isFalse(conflictsStub.called);
-    });
-  });
-
   test('connected revisions', () => {
     const change: ParsedChangeInfo = {
       ...createParsedChange(),
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 2483a51..f41236b 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
@@ -88,7 +88,6 @@
   fire,
   fireNoBubble,
   fireIronAnnounce,
-  fireReload,
   fireServerError,
 } from '../../../utils/event-util';
 import {ErrorCallback} from '../../../api/rest';
@@ -1338,6 +1337,7 @@
 
   // visible for testing
   async send(includeComments: boolean, startReview: boolean) {
+    // The change model will end this timing when the change was reloaded.
     this.reporting.time(Timing.SEND_REPLY);
     const labels = this.getLabelScores().getLabelValues();
 
@@ -1929,7 +1929,7 @@
   }
 
   _reload() {
-    fireReload(this, true);
+    this.getChangeModel().navigateToChangeResetReload();
     this.cancel();
   }
 
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 2766114..98f65c0 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
@@ -327,7 +327,7 @@
         review
       )
       .then(() => {
-        fireReload(this, true);
+        fireReload(this);
       });
   }
 
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 304f9ea..aa6bb7a4 100644
--- a/polygerrit-ui/app/elements/core/gr-router/gr-router.ts
+++ b/polygerrit-ui/app/elements/core/gr-router/gr-router.ts
@@ -1326,10 +1326,10 @@
     };
 
     const queryMap = new URLSearchParams(ctx.querystring);
-    if (queryMap.has('forceReload')) state.forceReload = true;
     if (queryMap.has('openReplyDialog')) state.openReplyDialog = true;
 
     const tab = queryMap.get('tab');
+    if (queryMap.has('forceReload')) state.forceReload = true;
     if (tab) state.tab = tab;
     const checksPatchset = Number(queryMap.get('checksPatchset'));
     if (Number.isInteger(checksPatchset) && checksPatchset > 0) {
@@ -1422,6 +1422,8 @@
       view: GerritView.CHANGE,
       childView: ChangeChildView.OVERVIEW,
     };
+    const queryMap = new URLSearchParams(ctx.querystring);
+    if (queryMap.has('forceReload')) state.forceReload = true;
     assertIsDefined(state.repo);
     this.reporting.setRepoName(state.repo);
     this.reporting.setChangeId(changeNum);
@@ -1443,6 +1445,8 @@
       childView: ChangeChildView.DIFF,
       diffView: {path: ctx.params[8]},
     };
+    const queryMap = new URLSearchParams(ctx.querystring);
+    if (queryMap.has('forceReload')) state.forceReload = true;
     const address = this.parseLineAddress(ctx.hash);
     if (address) {
       state.diffView!.leftSide = address.leftSide;
@@ -1493,6 +1497,8 @@
       childView: ChangeChildView.EDIT,
       editView: {path: ctx.params[3], lineNum: Number(ctx.hash)},
     };
+    const queryMap = new URLSearchParams(ctx.querystring);
+    if (queryMap.has('forceReload')) state.forceReload = true;
     this.normalizePatchRangeParams(state);
     // Note that router model view must be updated before view models.
     this.setState(state);
@@ -1516,14 +1522,7 @@
     };
     const tab = queryMap.get('tab');
     if (tab) state.tab = tab;
-    if (queryMap.has('forceReload')) {
-      state.forceReload = true;
-      history.replaceState(
-        null,
-        '',
-        location.href.replace(/[?&]forceReload=true/, '')
-      );
-    }
+    if (queryMap.has('forceReload')) state.forceReload = true;
     this.normalizePatchRangeParams(state);
     // Note that router model view must be updated before view models.
     this.setState(state);
diff --git a/polygerrit-ui/app/elements/diff/gr-diff-view/gr-diff-view.ts b/polygerrit-ui/app/elements/diff/gr-diff-view/gr-diff-view.ts
index 4687fc1..bdb634b 100644
--- a/polygerrit-ui/app/elements/diff/gr-diff-view/gr-diff-view.ts
+++ b/polygerrit-ui/app/elements/diff/gr-diff-view/gr-diff-view.ts
@@ -59,7 +59,7 @@
 import {CommentSide, DiffViewMode, Side} from '../../../constants/constants';
 import {GrApplyFixDialog} from '../gr-apply-fix-dialog/gr-apply-fix-dialog';
 import {OpenFixPreviewEvent, ValueChangedEvent} from '../../../types/events';
-import {fireAlert, fire, fireTitleChange} from '../../../utils/event-util';
+import {fireAlert, fire} from '../../../utils/event-util';
 import {assertIsDefined, queryAndAssert} from '../../../utils/common-util';
 import {toggleClass, whenVisible} from '../../../utils/dom-util';
 import {CursorMoveResult} from '../../../api/core';
@@ -115,12 +115,6 @@
 @customElement('gr-diff-view')
 export class GrDiffView extends LitElement {
   /**
-   * Fired when the title of the page should change.
-   *
-   * @event title-change
-   */
-
-  /**
    * Fired when user tries to navigate away while comments are pending save.
    *
    * @event show-alert
@@ -187,21 +181,7 @@
   @state()
   files: Files = {sortedPaths: [], changeFilesByPath: {}};
 
-  // Private but used in tests
-  // Use path getter/setter.
-  _path?: string;
-
-  get path() {
-    return this._path;
-  }
-
-  set path(path: string | undefined) {
-    if (this._path === path) return;
-    const oldPath = this._path;
-    this._path = path;
-    this.pathChanged();
-    this.requestUpdate('path', oldPath);
-  }
+  @state() path?: string;
 
   /** Allows us to react when the user switches to the DIFF view. */
   // Private but used in tests.
@@ -1404,12 +1384,6 @@
     };
   }
 
-  private pathChanged() {
-    if (this.path) {
-      fireTitleChange(this, computeTruncatedPath(this.path));
-    }
-  }
-
   // Private but used in tests
   formatFilesForDropdown(): DropdownItem[] {
     if (!this.files) return [];
diff --git a/polygerrit-ui/app/elements/diff/gr-patch-range-select/gr-patch-range-select.ts b/polygerrit-ui/app/elements/diff/gr-patch-range-select/gr-patch-range-select.ts
index e1dfd1f..3082979 100644
--- a/polygerrit-ui/app/elements/diff/gr-patch-range-select/gr-patch-range-select.ts
+++ b/polygerrit-ui/app/elements/diff/gr-patch-range-select/gr-patch-range-select.ts
@@ -14,7 +14,6 @@
   getParentIndex,
   getRevisionByPatchNum,
   isMergeParent,
-  sortRevisions,
   PatchSet,
   convertToPatchSetNum,
 } from '../../../utils/patch-set-util';
@@ -159,7 +158,7 @@
     subscribe(
       this,
       () => this.getChangeModel().revisions$,
-      x => (this.sortedRevisions = sortRevisions(Object.values(x || {})))
+      x => (this.sortedRevisions = x)
     );
     subscribe(
       this,
diff --git a/polygerrit-ui/app/elements/documentation/gr-documentation-search/gr-documentation-search.ts b/polygerrit-ui/app/elements/documentation/gr-documentation-search/gr-documentation-search.ts
index 6dbdca6..a8bc84c 100644
--- a/polygerrit-ui/app/elements/documentation/gr-documentation-search/gr-documentation-search.ts
+++ b/polygerrit-ui/app/elements/documentation/gr-documentation-search/gr-documentation-search.ts
@@ -45,7 +45,7 @@
 
   override connectedCallback() {
     super.connectedCallback();
-    fireTitleChange(this, 'Documentation Search');
+    fireTitleChange('Documentation Search');
   }
 
   static override get styles() {
diff --git a/polygerrit-ui/app/elements/edit/gr-edit-controls/gr-edit-controls.ts b/polygerrit-ui/app/elements/edit/gr-edit-controls/gr-edit-controls.ts
index 0fc754c..5786112 100644
--- a/polygerrit-ui/app/elements/edit/gr-edit-controls/gr-edit-controls.ts
+++ b/polygerrit-ui/app/elements/edit/gr-edit-controls/gr-edit-controls.ts
@@ -18,7 +18,7 @@
   GrAutocomplete,
 } from '../../shared/gr-autocomplete/gr-autocomplete';
 import {getAppContext} from '../../../services/app-context';
-import {fireAlert, fireReload} from '../../../utils/event-util';
+import {fireAlert} from '../../../utils/event-util';
 import {
   assertIsDefined,
   query as queryUtil,
@@ -34,6 +34,7 @@
 import {modalStyles} from '../../../styles/gr-modal-styles';
 import {whenVisible} from '../../../utils/dom-util';
 import {throwingErrorCallback} from '../../shared/gr-rest-api-interface/gr-rest-apis/gr-rest-api-helper';
+import {changeModelToken} from '../../../models/change/change-model';
 
 @customElement('gr-edit-controls')
 export class GrEditControls extends LitElement {
@@ -77,6 +78,8 @@
 
   private readonly restApiService = getAppContext().restApiService;
 
+  private readonly getChangeModel = resolve(this, changeModelToken);
+
   private readonly getNavigation = resolve(this, navigationToken);
 
   static override get styles() {
@@ -451,7 +454,7 @@
           return;
         }
         this.closeDialog(this.openDialog);
-        fireReload(this, true);
+        this.getChangeModel().navigateToChangeResetReload();
       });
   }
 
@@ -471,7 +474,7 @@
           return;
         }
         this.closeDialog(dialog);
-        fireReload(this, true);
+        this.getChangeModel().navigateToChangeResetReload();
       });
   };
 
@@ -489,7 +492,7 @@
           return;
         }
         this.closeDialog(dialog);
-        fireReload(this, true);
+        this.getChangeModel().navigateToChangeResetReload();
       });
   };
 
@@ -507,7 +510,7 @@
           return;
         }
         this.closeDialog(dialog);
-        fireReload(this, true);
+        this.getChangeModel().navigateToChangeResetReload();
       });
   };
 
diff --git a/polygerrit-ui/app/elements/edit/gr-edit-controls/gr-edit-controls_test.ts b/polygerrit-ui/app/elements/edit/gr-edit-controls/gr-edit-controls_test.ts
index 0729f21..0e6778a 100644
--- a/polygerrit-ui/app/elements/edit/gr-edit-controls/gr-edit-controls_test.ts
+++ b/polygerrit-ui/app/elements/edit/gr-edit-controls/gr-edit-controls_test.ts
@@ -26,8 +26,12 @@
 import {fixture, html, assert} from '@open-wc/testing';
 import {GrButton} from '../../shared/gr-button/gr-button';
 import '../../shared/gr-dialog/gr-dialog';
-import {waitForEventOnce} from '../../../utils/event-util';
 import {testResolver} from '../../../test/common-test-setup';
+import {
+  ChangeModel,
+  changeModelToken,
+} from '../../../models/change/change-model';
+import {SinonStubbedMember} from 'sinon';
 
 suite('gr-edit-controls tests', () => {
   let element: GrEditControls;
@@ -36,6 +40,9 @@
   let closeDialogSpy: sinon.SinonSpy;
   let hideDialogStub: sinon.SinonStub;
   let queryStub: sinon.SinonStub;
+  let navigateResetStub: SinonStubbedMember<
+    ChangeModel['navigateToChangeResetReload']
+  >;
 
   setup(async () => {
     element = await fixture<GrEditControls>(html`
@@ -47,6 +54,10 @@
     closeDialogSpy = sinon.spy(element, 'closeDialog');
     hideDialogStub = sinon.stub(element, 'hideAllDialogs');
     queryStub = stubRestApi('queryChangeFiles').returns(Promise.resolve([]));
+    navigateResetStub = sinon.stub(
+      testResolver(changeModelToken),
+      'navigateToChangeResetReload'
+    );
     await element.updateComplete;
   });
 
@@ -298,7 +309,7 @@
       assert.isTrue(deleteStub.called);
       await deleteStub.lastCall.returnValue;
       assert.equal(element.path, '');
-      assert.equal(eventStub.firstCall.args[0].type, 'reload');
+      assert.equal(navigateResetStub.callCount, 1);
       assert.isTrue(closeDialogSpy.called);
     });
 
@@ -397,7 +408,7 @@
 
       await renameStub.lastCall.returnValue;
       assert.equal(element.path, '');
-      assert.equal(eventStub.firstCall.args[0].type, 'reload');
+      assert.equal(navigateResetStub.callCount, 1);
       assert.isTrue(closeDialogSpy.called);
     });
 
@@ -485,7 +496,7 @@
       assert.equal(restoreStub.lastCall.args[1], 'src/test.cpp');
       return restoreStub.lastCall.returnValue.then(() => {
         assert.equal(element.path, '');
-        assert.equal(eventStub.firstCall.args[0].type, 'reload');
+        assert.equal(navigateResetStub.callCount, 1);
         assert.isTrue(closeDialogSpy.called);
       });
     });
@@ -553,7 +564,8 @@
       assert.equal(fileStub.lastCall.args[0], 1);
       assert.equal(fileStub.lastCall.args[1], 'test.php');
       assert.equal(fileStub.lastCall.args[2], 'base64');
-      await waitForEventOnce(element, 'reload');
+      await waitUntil(() => navigateResetStub.called);
+      assert.equal(navigateResetStub.callCount, 1);
     });
   });
 
diff --git a/polygerrit-ui/app/elements/edit/gr-editor-view/gr-editor-view.ts b/polygerrit-ui/app/elements/edit/gr-editor-view/gr-editor-view.ts
index 878c5e9..f37a3d9 100644
--- a/polygerrit-ui/app/elements/edit/gr-editor-view/gr-editor-view.ts
+++ b/polygerrit-ui/app/elements/edit/gr-editor-view/gr-editor-view.ts
@@ -9,7 +9,6 @@
 import '../../shared/gr-editable-label/gr-editable-label';
 import '../gr-default-editor/gr-default-editor';
 import {navigationToken} from '../../core/gr-navigation/gr-navigation';
-import {computeTruncatedPath} from '../../../utils/path-list-util';
 import {
   EditPreferencesInfo,
   Base64FileContent,
@@ -17,11 +16,7 @@
 } from '../../../types/common';
 import {ParsedChangeInfo} from '../../../types/types';
 import {HttpMethod, NotifyType} from '../../../constants/constants';
-import {
-  fireAlert,
-  fireTitleChange,
-  fireReload,
-} from '../../../utils/event-util';
+import {fireAlert} from '../../../utils/event-util';
 import {getAppContext} from '../../../services/app-context';
 import {ErrorCallback} from '../../../api/rest';
 import {assertIsDefined} from '../../../utils/common-util';
@@ -57,12 +52,6 @@
 @customElement('gr-editor-view')
 export class GrEditorView extends LitElement {
   /**
-   * Fired when the title of the page should change.
-   *
-   * @event title-change
-   */
-
-  /**
    * Fired to notify the user of
    *
    * @event show-alert
@@ -333,17 +322,6 @@
   viewStateChanged() {
     if (this.viewState?.childView !== ChangeChildView.EDIT) return;
 
-    // NOTE: This may be called before attachment (e.g. while parentElement is
-    // null). Fire title-change in an async so that, if attachment to the DOM
-    // has been queued, the event can bubble up to the handler in gr-app.
-    setTimeout(() => {
-      if (!this.viewState) return;
-      const title = `Editing ${computeTruncatedPath(
-        this.viewState.editView?.path
-      )}`;
-      fireTitleChange(this, title);
-    });
-
     const promises = [];
     promises.push(this.getFileData());
     return Promise.all(promises);
@@ -512,13 +490,7 @@
         )
         .then(() => {
           assertIsDefined(this.change, 'change');
-          // TODO: `forceReload: true` does not seem to work as expected: The patchset is not
-          // updated. Thus we are also calling `fireReload()` here. That can probably be
-          // cleaned up once the change-view was migrated to fully relying on the change model.
-          fireReload(this);
-          this.getNavigation().setUrl(
-            createChangeUrl({change: this.change, forceReload: true})
-          );
+          this.getChangeModel().navigateToChangeResetReload();
         });
     });
   };
diff --git a/polygerrit-ui/app/elements/gr-app-element.ts b/polygerrit-ui/app/elements/gr-app-element.ts
index 98f1f25..58d7105 100644
--- a/polygerrit-ui/app/elements/gr-app-element.ts
+++ b/polygerrit-ui/app/elements/gr-app-element.ts
@@ -177,7 +177,7 @@
     document.addEventListener('page-error', e => {
       this.handlePageError(e);
     });
-    this.addEventListener('title-change', e => {
+    document.addEventListener('title-change', e => {
       this.handleTitleChange(e);
     });
     this.addEventListener('dialog-change', e => {
diff --git a/polygerrit-ui/app/elements/settings/gr-cla-view/gr-cla-view.ts b/polygerrit-ui/app/elements/settings/gr-cla-view/gr-cla-view.ts
index 2f835f7..a2b61e0 100644
--- a/polygerrit-ui/app/elements/settings/gr-cla-view/gr-cla-view.ts
+++ b/polygerrit-ui/app/elements/settings/gr-cla-view/gr-cla-view.ts
@@ -53,7 +53,7 @@
     super.connectedCallback();
     this.loadData();
 
-    fireTitleChange(this, 'New Contributor Agreement');
+    fireTitleChange('New Contributor Agreement');
   }
 
   static override get styles() {
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 2695ea7..24a18c9 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
@@ -81,12 +81,6 @@
 @customElement('gr-settings-view')
 export class GrSettingsView extends LitElement {
   /**
-   * Fired when the title of the page should change.
-   *
-   * @event title-change
-   */
-
-  /**
    * Fired with email confirmation text, or when the page reloads.
    *
    * @event show-alert
@@ -261,7 +255,7 @@
     // Polymer 2: anchor tag won't work on shadow DOM
     // we need to manually calling scrollIntoView when hash changed
     document.addEventListener('location-change', this.handleLocationChange);
-    fireTitleChange(this, 'Settings');
+    fireTitleChange('Settings');
   }
 
   override firstUpdated() {
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 a0d7fab..0bcb09c 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
@@ -544,10 +544,8 @@
 
   test('calls the title-change event', async () => {
     const titleChangedStub = sinon.stub();
-
-    // Create a new view.
     const newElement = document.createElement('gr-settings-view');
-    newElement.addEventListener('title-change', titleChangedStub);
+    document.addEventListener('title-change', titleChangedStub);
 
     const div = await fixture(html`<div></div>`);
     div.appendChild(newElement);
diff --git a/polygerrit-ui/app/elements/shared/gr-hovercard-account/gr-hovercard-account-contents.ts b/polygerrit-ui/app/elements/shared/gr-hovercard-account/gr-hovercard-account-contents.ts
index 14c2c15..394015e 100644
--- a/polygerrit-ui/app/elements/shared/gr-hovercard-account/gr-hovercard-account-contents.ts
+++ b/polygerrit-ui/app/elements/shared/gr-hovercard-account/gr-hovercard-account-contents.ts
@@ -43,7 +43,7 @@
 import {configModelToken} from '../../../models/config/config-model';
 import {createSearchUrl} from '../../../models/views/search';
 import {createDashboardUrl} from '../../../models/views/dashboard';
-import {fire} from '../../../utils/event-util';
+import {fire, fireReload} from '../../../utils/event-util';
 import {userModelToken} from '../../../models/user/user-model';
 
 @customElement('gr-hovercard-account-contents')
@@ -445,7 +445,7 @@
               this.getReviewerState(this.change!)
           );
         }
-        fire(this, 'reload', {clearPatchset: true});
+        fireReload(this);
       });
   }
 
@@ -464,7 +464,7 @@
         if (!response || !response.ok) {
           throw new Error('something went wrong when removing user');
         }
-        fire(this, 'reload', {clearPatchset: true});
+        fireReload(this);
         return response;
       });
   }
diff --git a/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-change-actions-js-api_test.ts b/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-change-actions-js-api_test.ts
index ae93977..4977ec5 100644
--- a/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-change-actions-js-api_test.ts
+++ b/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-change-actions-js-api_test.ts
@@ -56,7 +56,6 @@
         <gr-change-actions></gr-change-actions>
       `);
       element.change = {} as ChangeViewChangeInfo;
-      element._hasKnownChainState = false;
       window.Gerrit.install(
         p => {
           plugin = p;
diff --git a/polygerrit-ui/app/models/change/change-model.ts b/polygerrit-ui/app/models/change/change-model.ts
index b6b9de7..6d111aa 100644
--- a/polygerrit-ui/app/models/change/change-model.ts
+++ b/polygerrit-ui/app/models/change/change-model.ts
@@ -5,6 +5,7 @@
  */
 import {
   BasePatchSetNum,
+  ChangeInfo,
   EditInfo,
   EDIT,
   PARENT,
@@ -13,25 +14,20 @@
   PreferencesInfo,
   RevisionPatchSetNum,
   PatchSetNumber,
+  CommitId,
 } from '../../types/common';
-import {DefaultBase} from '../../constants/constants';
-import {combineLatest, from, fromEvent, Observable, forkJoin, of} from 'rxjs';
-import {
-  map,
-  filter,
-  withLatestFrom,
-  startWith,
-  switchMap,
-} from 'rxjs/operators';
+import {ChangeStatus, DefaultBase} from '../../constants/constants';
+import {combineLatest, from, Observable, forkJoin, of} from 'rxjs';
+import {map, filter, withLatestFrom, switchMap} from 'rxjs/operators';
 import {
   computeAllPatchSets,
   computeLatestPatchNum,
   computeLatestPatchNumWithEdit,
+  findEdit,
+  sortRevisions,
 } from '../../utils/patch-set-util';
-import {ParsedChangeInfo} from '../../types/types';
-import {fireAlert} from '../../utils/event-util';
-
-import {ChangeInfo} from '../../types/common';
+import {isDefined, ParsedChangeInfo} from '../../types/types';
+import {fireAlert, fireTitleChange} from '../../utils/event-util';
 import {RestApiService} from '../../services/gr-rest-api/gr-rest-api';
 import {select} from '../../utils/observable-util';
 import {assertIsDefined} from '../../utils/common-util';
@@ -40,12 +36,18 @@
 import {define} from '../dependency';
 import {isOwner} from '../../utils/change-util';
 import {
+  ChangeChildView,
   ChangeViewModel,
   createChangeUrl,
   createDiffUrl,
   createEditUrl,
 } from '../views/change';
 import {NavigationService} from '../../elements/core/gr-navigation/gr-navigation';
+import {getRevertCreatedChangeIds} from '../../utils/message-util';
+import {computeTruncatedPath} from '../../utils/path-list-util';
+import {PluginLoader} from '../../elements/shared/gr-js-api-interface/gr-plugin-loader';
+import {ReportingService} from '../../services/gr-reporting/gr-reporting';
+import {Timing} from '../../constants/reporting';
 
 export enum LoadingStatus {
   NOT_LOADED = 'NOT_LOADED',
@@ -69,6 +71,39 @@
    * Undefined means it's still loading and empty set means no files reviewed.
    */
   reviewedFiles?: string[];
+  /**
+   * Either filled from `change.mergeable`, or from a dedicated REST API call.
+   * Is initially `undefined`, such that you can identify whether this
+   * information has already been loaded once for this change or not. Will never
+   * go back to `undefined` after being set for a change.
+   */
+  mergeable?: boolean;
+}
+
+/**
+ * `change.revisions` is a dictionary mapping the revision sha to RevisionInfo,
+ * but the info object itself does not contain the sha, which is a problem when
+ * working with just the info objects.
+ *
+ * So we are iterating over the map here and are assigning the sha map key to
+ * the property `revision.commit.commit`.
+ *
+ * As usual we are treating data objects as immutable, so we are doind a lot of
+ * cloning here.
+ */
+export function updateRevisionsWithCommitShas(changeInput?: ParsedChangeInfo) {
+  if (!changeInput?.revisions) return changeInput;
+  const changeOutput = {...changeInput, revisions: {...changeInput.revisions}};
+  for (const sha of Object.keys(changeOutput.revisions)) {
+    const revision = changeOutput.revisions[sha];
+    if (revision?.commit && !revision.commit.commit) {
+      changeOutput.revisions[sha] = {
+        ...revision,
+        commit: {...revision.commit, commit: sha as CommitId},
+      };
+    }
+  }
+  return changeOutput;
 }
 
 /**
@@ -168,20 +203,36 @@
     changeState => changeState.loadingStatus
   );
 
+  public readonly loading$ = select(
+    this.changeLoadingStatus$,
+    status =>
+      status === LoadingStatus.LOADING || status === LoadingStatus.RELOADING
+  );
+
   public readonly reviewedFiles$ = select(
     this.state$,
     changeState => changeState?.reviewedFiles
   );
 
+  public readonly mergeable$ = select(
+    this.state$,
+    changeState => changeState.mergeable
+  );
+
   public readonly changeNum$ = select(this.change$, change => change?._number);
 
+  public readonly changeId$ = select(this.change$, change => change?.change_id);
+
   public readonly repo$ = select(this.change$, change => change?.project);
 
+  public readonly topic$ = select(this.change$, change => change?.topic);
+
+  public readonly status$ = select(this.change$, change => change?.status);
+
   public readonly labels$ = select(this.change$, change => change?.labels);
 
-  public readonly revisions$ = select(
-    this.change$,
-    change => change?.revisions
+  public readonly revisions$ = select(this.change$, change =>
+    sortRevisions(Object.values(change?.revisions || {}))
   );
 
   public readonly patchsets$ = select(this.change$, change =>
@@ -264,49 +315,56 @@
         computeBase(viewModelBasePatchNum, patchNum, change, preferences)
     );
 
+  private selectRevision(
+    revisionNum$: Observable<RevisionPatchSetNum | undefined>
+  ) {
+    return select(
+      combineLatest([this.revisions$, revisionNum$]),
+      ([revisions, patchNum]) => {
+        if (!revisions || !patchNum) return undefined;
+        return Object.values(revisions).find(
+          revision => revision._number === patchNum
+        );
+      }
+    );
+  }
+
+  public readonly revision$ = this.selectRevision(this.patchNum$);
+
+  public readonly latestRevision$ = this.selectRevision(this.latestPatchNum$);
+
   public readonly isOwner$: Observable<boolean> = select(
     combineLatest([this.change$, this.userModel.account$]),
     ([change, account]) => isOwner(change, account)
   );
 
-  // For usage in `combineLatest` we need `startWith` such that reload$ has an
-  // initial value.
-  readonly reload$: Observable<unknown> = fromEvent(document, 'reload').pipe(
-    startWith(undefined)
+  public readonly messages$ = select(this.change$, change => change?.messages);
+
+  public readonly revertingChangeIds$ = select(this.messages$, messages =>
+    getRevertCreatedChangeIds(messages ?? [])
   );
 
   constructor(
     private readonly navigation: NavigationService,
     private readonly viewModel: ChangeViewModel,
     private readonly restApiService: RestApiService,
-    private readonly userModel: UserModel
+    private readonly userModel: UserModel,
+    private readonly pluginLoader: PluginLoader,
+    private readonly reporting: ReportingService
   ) {
     super(initialState);
     this.subscriptions = [
-      combineLatest([this.viewModel.changeNum$, this.reload$])
-        .pipe(
-          map(([changeNum, _]) => changeNum),
-          switchMap(changeNum => {
-            if (changeNum !== undefined) this.updateStateLoading(changeNum);
-            const change = from(this.restApiService.getChangeDetail(changeNum));
-            const edit = from(this.restApiService.getChangeEdit(changeNum));
-            return forkJoin([change, edit]);
-          }),
-          withLatestFrom(this.viewModel.patchNum$),
-          map(([[change, edit], patchNum]) =>
-            updateChangeWithEdit(change, edit, patchNum)
-          )
-        )
-        .subscribe(change => {
-          // The change service is currently a singleton, so we have to be
-          // careful to avoid situations where the application state is
-          // partially set for the old change where the user is coming from,
-          // and partially for the new change where the user is navigating to.
-          // So setting the change explicitly to undefined when the user
-          // moves away from diff and change pages (changeNum === undefined)
-          // helps with that.
-          this.updateStateChange(change ?? undefined);
-        }),
+      this.loadChange(),
+      this.loadMergeable(),
+      this.loadReviewedFiles(),
+      this.setOverviewTitle(),
+      this.setDiffTitle(),
+      this.setEditTitle(),
+      this.reportChangeReload(),
+      this.reportSendReply(),
+      this.fireShowChange(),
+      this.refuseEditForOpenChange(),
+      this.refuseEditForClosedChange(),
       this.change$.subscribe(change => (this.change = change)),
       this.patchNum$.subscribe(patchNum => (this.patchNum = patchNum)),
       this.basePatchNum$.subscribe(
@@ -315,20 +373,215 @@
       this.latestPatchNum$.subscribe(
         latestPatchNum => (this.latestPatchNum = latestPatchNum)
       ),
-      combineLatest([this.patchNum$, this.changeNum$, this.userModel.loggedIn$])
-        .pipe(
-          switchMap(([patchNum, changeNum, loggedIn]) => {
-            if (!changeNum || !patchNum || !loggedIn) {
-              this.updateStateReviewedFiles([]);
-              return of(undefined);
-            }
-            return from(this.fetchReviewedFiles(patchNum, changeNum));
-          })
-        )
-        .subscribe(),
     ];
   }
 
+  private reportSendReply() {
+    return this.changeLoadingStatus$.subscribe(loadingStatus => {
+      // We are ending the timer on each change load, because ending a timer
+      // that was not started is a no-op. :-)
+      if (loadingStatus === LoadingStatus.LOADED) {
+        this.reporting.timeEnd(Timing.SEND_REPLY);
+      }
+    });
+  }
+
+  private reportChangeReload() {
+    return this.changeLoadingStatus$.subscribe(loadingStatus => {
+      if (
+        loadingStatus === LoadingStatus.LOADING ||
+        loadingStatus === LoadingStatus.RELOADING
+      ) {
+        this.reporting.time(Timing.CHANGE_RELOAD);
+      }
+      if (
+        loadingStatus === LoadingStatus.LOADED ||
+        loadingStatus === LoadingStatus.NOT_LOADED
+      ) {
+        this.reporting.timeEnd(Timing.CHANGE_RELOAD);
+      }
+    });
+  }
+
+  private fireShowChange() {
+    return combineLatest([
+      this.viewModel.childView$,
+      this.change$,
+      this.patchNum$,
+      this.mergeable$,
+    ])
+      .pipe(
+        filter(
+          ([childView, change, patchNum, mergeable]) =>
+            childView === ChangeChildView.OVERVIEW &&
+            !!change &&
+            !!patchNum &&
+            mergeable !== undefined
+        )
+      )
+      .subscribe(([_, change, patchNum, mergeable]) => {
+        this.pluginLoader.jsApiService.handleShowChange({
+          change,
+          patchNum,
+          // `?? null` is for the TypeScript compiler only. We have a
+          // `mergeable !== undefined` filter above, so this cannot happen.
+          // It would be nice to change `ShowChangeDetail` to accept `undefined`
+          // instaed of `null`, but that would be a Plugin API change ...
+          info: {mergeable: mergeable ?? null},
+        });
+      });
+  }
+
+  private refuseEditForOpenChange() {
+    return combineLatest([this.revisions$, this.patchNum$, this.status$])
+      .pipe(
+        filter(
+          ([revisions, patchNum, status]) =>
+            status === ChangeStatus.NEW &&
+            revisions.length > 0 &&
+            patchNum === EDIT
+        )
+      )
+      .subscribe(([revisions]) => {
+        const editRev = findEdit(revisions);
+        if (!editRev) {
+          const msg = 'Change edit not found. Please create a change edit.';
+          fireAlert(document, msg);
+          this.navigateToChangeResetReload();
+        }
+      });
+  }
+
+  private refuseEditForClosedChange() {
+    return combineLatest([
+      this.revisions$,
+      this.viewModel.edit$,
+      this.patchNum$,
+      this.status$,
+    ])
+      .pipe(
+        filter(
+          ([revisions, edit, patchNum, status]) =>
+            (status === ChangeStatus.ABANDONED ||
+              status === ChangeStatus.MERGED) &&
+            revisions.length > 0 &&
+            (patchNum === EDIT || edit)
+        )
+      )
+      .subscribe(([revisions]) => {
+        const editRev = findEdit(revisions);
+        if (!editRev) {
+          const msg =
+            'Change edits cannot be created if change is merged ' +
+            'or abandoned. Redirecting to non edit mode.';
+          fireAlert(document, msg);
+          this.navigateToChangeResetReload();
+        }
+      });
+  }
+
+  private setOverviewTitle() {
+    return combineLatest([this.viewModel.childView$, this.change$])
+      .pipe(
+        filter(([childView, _]) => childView === ChangeChildView.OVERVIEW),
+        map(([_, change]) => change),
+        filter(isDefined)
+      )
+      .subscribe(change => {
+        const title = `${change.subject} (${change._number})`;
+        fireTitleChange(title);
+      });
+  }
+
+  private setDiffTitle() {
+    return combineLatest([this.viewModel.childView$, this.viewModel.diffPath$])
+      .pipe(
+        filter(([childView, _]) => childView === ChangeChildView.DIFF),
+        map(([_, diffPath]) => diffPath),
+        filter(isDefined)
+      )
+      .subscribe(diffPath => {
+        const title = computeTruncatedPath(diffPath);
+        fireTitleChange(title);
+      });
+  }
+
+  private setEditTitle() {
+    return combineLatest([this.viewModel.childView$, this.viewModel.editPath$])
+      .pipe(
+        filter(([childView, _]) => childView === ChangeChildView.EDIT),
+        map(([_, editPath]) => editPath),
+        filter(isDefined)
+      )
+      .subscribe(editPath => {
+        const title = `Editing ${computeTruncatedPath(editPath)}`;
+        fireTitleChange(title);
+      });
+  }
+
+  private loadReviewedFiles() {
+    return combineLatest([
+      this.patchNum$,
+      this.changeNum$,
+      this.userModel.loggedIn$,
+    ])
+      .pipe(
+        switchMap(([patchNum, changeNum, loggedIn]) => {
+          if (!changeNum || !patchNum || !loggedIn) {
+            this.updateStateReviewedFiles([]);
+            return of(undefined);
+          }
+          return from(this.fetchReviewedFiles(patchNum, changeNum));
+        })
+      )
+      .subscribe();
+  }
+
+  private loadMergeable() {
+    return this.change$
+      .pipe(
+        switchMap(change => {
+          if (change?._number === undefined) return of(undefined);
+          if (change.mergeable !== undefined) return of(change.mergeable);
+          if (change.status === ChangeStatus.MERGED) return of(false);
+          if (change.status === ChangeStatus.ABANDONED) return of(false);
+          return from(
+            this.restApiService
+              .getMergeable(change._number)
+              .then(mergableInfo => mergableInfo?.mergeable ?? false)
+          );
+        })
+      )
+      .subscribe(mergeable => this.updateState({mergeable}));
+  }
+
+  private loadChange() {
+    return this.viewModel.changeNum$
+      .pipe(
+        switchMap(changeNum => {
+          if (changeNum !== undefined) this.updateStateLoading(changeNum);
+          const change = from(this.restApiService.getChangeDetail(changeNum));
+          const edit = from(this.restApiService.getChangeEdit(changeNum));
+          return forkJoin([change, edit]);
+        }),
+        withLatestFrom(this.viewModel.patchNum$),
+        map(([[change, edit], patchNum]) =>
+          updateChangeWithEdit(change, edit, patchNum)
+        ),
+        map(updateRevisionsWithCommitShas)
+      )
+      .subscribe(change => {
+        // The change service is currently a singleton, so we have to be
+        // careful to avoid situations where the application state is
+        // partially set for the old change where the user is coming from,
+        // and partially for the new change where the user is navigating to.
+        // So setting the change explicitly to undefined when the user
+        // moves away from diff and change pages (changeNum === undefined)
+        // helps with that.
+        this.updateStateChange(change ?? undefined);
+      });
+  }
+
   updateStateReviewedFiles(reviewedFiles: string[]) {
     this.updateState({reviewedFiles});
   }
@@ -430,12 +683,27 @@
     });
   }
 
+  // Mainly used for navigating from DIFF to OVERVIEW.
   navigateToChange(openReplyDialog = false) {
     const url = this.changeUrl(openReplyDialog);
     if (!url) return;
     this.navigation.setUrl(url);
   }
 
+  /**
+   * Wipes all URL parameters and other view state and goes to the change
+   * overview page, forcing a reload.
+   *
+   * This will also wipe the `patchNum`, so will always go to the latest
+   * patchset.
+   */
+  navigateToChangeResetReload() {
+    if (!this.change) return;
+    const url = createChangeUrl({change: this.change, forceReload: true});
+    if (!url) return;
+    this.navigation.setUrl(url);
+  }
+
   editUrl(editView: {path: string; lineNum?: number}) {
     if (!this.change) return;
     return createEditUrl({
diff --git a/polygerrit-ui/app/models/change/change-model_test.ts b/polygerrit-ui/app/models/change/change-model_test.ts
index c11c15b..e5d2e36 100644
--- a/polygerrit-ui/app/models/change/change-model_test.ts
+++ b/polygerrit-ui/app/models/change/change-model_test.ts
@@ -7,10 +7,12 @@
 import {ChangeStatus} from '../../constants/constants';
 import '../../test/common-test-setup';
 import {
+  TEST_NUMERIC_CHANGE_ID,
   createChange,
   createChangeMessageInfo,
   createChangeViewState,
   createEditInfo,
+  createMergeable,
   createParsedChange,
   createRevision,
 } from '../../test/test-data-generators';
@@ -29,13 +31,34 @@
 } from '../../types/common';
 import {ParsedChangeInfo} from '../../types/types';
 import {getAppContext} from '../../services/app-context';
-import {ChangeState, LoadingStatus, updateChangeWithEdit} from './change-model';
+import {
+  ChangeState,
+  LoadingStatus,
+  updateChangeWithEdit,
+  updateRevisionsWithCommitShas,
+} from './change-model';
 import {ChangeModel} from './change-model';
 import {assert} from '@open-wc/testing';
 import {testResolver} from '../../test/common-test-setup';
 import {userModelToken} from '../user/user-model';
-import {changeViewModelToken} from '../views/change';
+import {
+  ChangeChildView,
+  ChangeViewModel,
+  changeViewModelToken,
+} from '../views/change';
 import {navigationToken} from '../../elements/core/gr-navigation/gr-navigation';
+import {SinonStub} from 'sinon';
+import {pluginLoaderToken} from '../../elements/shared/gr-js-api-interface/gr-plugin-loader';
+import {ShowChangeDetail} from '../../elements/shared/gr-js-api-interface/gr-js-api-types';
+
+suite('updateRevisionsWithCommitShas() tests', () => {
+  test('undefined edit', async () => {
+    const change = createParsedChange();
+    const updated = updateRevisionsWithCommitShas(change);
+    assert.equal(change?.revisions?.['abc'].commit?.commit, undefined);
+    assert.equal(updated?.revisions?.['abc'].commit?.commit, 'abc' as CommitId);
+  });
+});
 
 suite('updateChangeWithEdit() tests', () => {
   test('undefined change', async () => {
@@ -69,6 +92,7 @@
 });
 
 suite('change model tests', () => {
+  let changeViewModel: ChangeViewModel;
   let changeModel: ChangeModel;
   let knownChange: ParsedChangeInfo;
   const testCompleted = new Subject<void>();
@@ -84,25 +108,20 @@
   }
 
   setup(() => {
+    changeViewModel = testResolver(changeViewModelToken);
     changeModel = new ChangeModel(
       testResolver(navigationToken),
-      testResolver(changeViewModelToken),
+      changeViewModel,
       getAppContext().restApiService,
-      testResolver(userModelToken)
+      testResolver(userModelToken),
+      testResolver(pluginLoaderToken),
+      getAppContext().reportingService
     );
     knownChange = {
       ...createChange(),
       revisions: {
-        sha1: {
-          ...createRevision(1),
-          description: 'patch 1',
-          _number: 1 as PatchSetNumber,
-        },
-        sha2: {
-          ...createRevision(2),
-          description: 'patch 2',
-          _number: 2 as PatchSetNumber,
-        },
+        sha1: {...createRevision(1), description: 'patch 1'},
+        sha2: {...createRevision(2), description: 'patch 2'},
       },
       status: ChangeStatus.NEW,
       current_revision: 'abc' as CommitId,
@@ -115,6 +134,114 @@
     changeModel.finalize();
   });
 
+  suite('mergeability', async () => {
+    let getMergeableStub: SinonStub;
+    let mergeableApiResponse = false;
+
+    setup(() => {
+      getMergeableStub = stubRestApi('getMergeable').callsFake(() =>
+        Promise.resolve(createMergeable(mergeableApiResponse))
+      );
+    });
+
+    test('mergeability initially undefined', async () => {
+      waitUntilObserved(
+        changeModel.mergeable$,
+        mergeable => mergeable === undefined
+      );
+      assert.isFalse(getMergeableStub.called);
+    });
+
+    test('mergeability true from change', async () => {
+      changeModel.updateStateChange({...knownChange, mergeable: true});
+
+      waitUntilObserved(
+        changeModel.mergeable$,
+        mergeable => mergeable === true
+      );
+      assert.isFalse(getMergeableStub.called);
+    });
+
+    test('mergeability false from change', async () => {
+      changeModel.updateStateChange({...knownChange, mergeable: false});
+
+      waitUntilObserved(
+        changeModel.mergeable$,
+        mergeable => mergeable === true
+      );
+      assert.isFalse(getMergeableStub.called);
+    });
+
+    test('mergeability false for MERGED change', async () => {
+      changeModel.updateStateChange({
+        ...knownChange,
+        status: ChangeStatus.MERGED,
+      });
+
+      waitUntilObserved(
+        changeModel.mergeable$,
+        mergeable => mergeable === false
+      );
+      assert.isFalse(getMergeableStub.called);
+    });
+
+    test('mergeability false for ABANDONED change', async () => {
+      changeModel.updateStateChange({
+        ...knownChange,
+        status: ChangeStatus.ABANDONED,
+      });
+
+      waitUntilObserved(
+        changeModel.mergeable$,
+        mergeable => mergeable === false
+      );
+      assert.isFalse(getMergeableStub.called);
+    });
+
+    test('mergeability true from API', async () => {
+      mergeableApiResponse = true;
+      changeModel.updateStateChange(knownChange);
+
+      waitUntilObserved(
+        changeModel.mergeable$,
+        mergeable => mergeable === true
+      );
+      assert.isTrue(getMergeableStub.calledOnce);
+    });
+
+    test('mergeability false from API', async () => {
+      mergeableApiResponse = false;
+      changeModel.updateStateChange(knownChange);
+
+      waitUntilObserved(
+        changeModel.mergeable$,
+        mergeable => mergeable === false
+      );
+      assert.isTrue(getMergeableStub.calledOnce);
+    });
+  });
+
+  test('fireShowChange', async () => {
+    const pluginLoader = testResolver(pluginLoaderToken);
+    const jsApiService = pluginLoader.jsApiService;
+    const showChangeStub = sinon.stub(jsApiService, 'handleShowChange');
+
+    changeViewModel.updateState({
+      childView: ChangeChildView.OVERVIEW,
+      patchNum: 1 as PatchSetNumber,
+    });
+    changeModel.updateState({
+      change: createParsedChange(),
+      mergeable: true,
+    });
+
+    assert.isTrue(showChangeStub.calledOnce);
+    const detail: ShowChangeDetail = showChangeStub.lastCall.firstArg;
+    assert.equal(detail.change?._number, createParsedChange()._number);
+    assert.equal(detail.patchNum, 1 as PatchSetNumber);
+    assert.equal(detail.info.mergeable, true);
+  });
+
   test('load a change', async () => {
     const promise = mockPromise<ParsedChangeInfo | undefined>();
     const stub = stubRestApi('getChangeDetail').callsFake(() => promise);
@@ -132,7 +259,7 @@
     promise.resolve(knownChange);
     state = await waitForLoadingStatus(LoadingStatus.LOADED);
     assert.equal(stub.callCount, 1);
-    assert.equal(state?.change, knownChange);
+    assert.deepEqual(state?.change, updateRevisionsWithCommitShas(knownChange));
   });
 
   test('reload a change', async () => {
@@ -143,17 +270,20 @@
     testResolver(changeViewModelToken).setState(createChangeViewState());
     promise.resolve(knownChange);
     state = await waitForLoadingStatus(LoadingStatus.LOADED);
+    assert.equal(stub.callCount, 1);
 
     // Reloading same change
     document.dispatchEvent(new CustomEvent('reload'));
     state = await waitForLoadingStatus(LoadingStatus.RELOADING);
-    assert.equal(stub.callCount, 2);
-    assert.equal(state?.change, knownChange);
+    assert.equal(stub.callCount, 3);
+    assert.equal(stub.getCall(1).firstArg, undefined);
+    assert.equal(stub.getCall(2).firstArg, TEST_NUMERIC_CHANGE_ID);
+    assert.deepEqual(state?.change, updateRevisionsWithCommitShas(knownChange));
 
     promise.resolve(knownChange);
     state = await waitForLoadingStatus(LoadingStatus.LOADED);
-    assert.equal(stub.callCount, 2);
-    assert.equal(state?.change, knownChange);
+    assert.equal(stub.callCount, 3);
+    assert.deepEqual(state?.change, updateRevisionsWithCommitShas(knownChange));
   });
 
   test('navigating to another change', async () => {
@@ -183,7 +313,7 @@
     promise.resolve(otherChange);
     state = await waitForLoadingStatus(LoadingStatus.LOADED);
     assert.equal(stub.callCount, 2);
-    assert.equal(state?.change, otherChange);
+    assert.deepEqual(state?.change, updateRevisionsWithCommitShas(otherChange));
   });
 
   test('navigating to dashboard', async () => {
@@ -211,7 +341,7 @@
     testResolver(changeViewModelToken).setState(createChangeViewState());
     state = await waitForLoadingStatus(LoadingStatus.LOADED);
     assert.equal(stub.callCount, 3);
-    assert.equal(state?.change, knownChange);
+    assert.deepEqual(state?.change, updateRevisionsWithCommitShas(knownChange));
   });
 
   test('changeModel.fetchChangeUpdates on latest', async () => {
@@ -294,4 +424,28 @@
     changeModel.updateStateChange(createParsedChange());
     assert.equal(spy.callCount, 2);
   });
+
+  test('revision$ selector latest', async () => {
+    changeViewModel.updateState({patchNum: undefined});
+    changeModel.updateState({change: knownChange});
+    await waitUntilObserved(changeModel.revision$, x => x?._number === 2);
+  });
+
+  test('revision$ selector 1', async () => {
+    changeViewModel.updateState({patchNum: 1 as PatchSetNumber});
+    changeModel.updateState({change: knownChange});
+    await waitUntilObserved(changeModel.revision$, x => x?._number === 1);
+  });
+
+  test('latestRevision$ selector latest', async () => {
+    changeViewModel.updateState({patchNum: undefined});
+    changeModel.updateState({change: knownChange});
+    await waitUntilObserved(changeModel.latestRevision$, x => x?._number === 2);
+  });
+
+  test('latestRevision$ selector 1', async () => {
+    changeViewModel.updateState({patchNum: 1 as PatchSetNumber});
+    changeModel.updateState({change: knownChange});
+    await waitUntilObserved(changeModel.latestRevision$, x => x?._number === 2);
+  });
 });
diff --git a/polygerrit-ui/app/models/change/files-model.ts b/polygerrit-ui/app/models/change/files-model.ts
index b7ff16f..c01b718 100644
--- a/polygerrit-ui/app/models/change/files-model.ts
+++ b/polygerrit-ui/app/models/change/files-model.ts
@@ -22,6 +22,8 @@
 import {define} from '../dependency';
 import {ChangeModel} from './change-model';
 import {CommentsModel} from '../comments/comments-model';
+import {Timing} from '../../constants/reporting';
+import {ReportingService} from '../../services/gr-reporting/gr-reporting';
 
 export type FileNameToNormalizedFileInfoMap = {
   [name: string]: NormalizedFileInfo;
@@ -141,10 +143,13 @@
   constructor(
     readonly changeModel: ChangeModel,
     readonly commentsModel: CommentsModel,
-    readonly restApiService: RestApiService
+    readonly restApiService: RestApiService,
+    private readonly reporting: ReportingService
   ) {
     super(initialState);
     this.subscriptions = [
+      this.reportChangeDataStart(),
+      this.reportChangeDataEnd(),
       this.subscribeToFiles(
         (psLeft, psRight) => {
           return {basePatchNum: psLeft, patchNum: psRight};
@@ -176,6 +181,26 @@
     ];
   }
 
+  private reportChangeDataStart() {
+    return combineLatest([this.changeModel.loading$]).subscribe(
+      ([changeLoading]) => {
+        if (changeLoading) {
+          this.reporting.time(Timing.CHANGE_DATA);
+        }
+      }
+    );
+  }
+
+  private reportChangeDataEnd() {
+    return combineLatest([this.changeModel.loading$, this.files$]).subscribe(
+      ([changeLoading, files]) => {
+        if (!changeLoading && files.length > 0) {
+          this.reporting.timeEnd(Timing.CHANGE_DATA);
+        }
+      }
+    );
+  }
+
   private subscribeToFiles(
     rangeChooser: (
       basePatchNum: BasePatchSetNum,
@@ -184,13 +209,12 @@
     filesToState: (files: NormalizedFileInfo[]) => Partial<FilesState>
   ) {
     return combineLatest([
-      this.changeModel.reload$,
       this.changeModel.changeNum$,
       this.changeModel.basePatchNum$,
       this.changeModel.patchNum$,
     ])
       .pipe(
-        switchMap(([_, changeNum, basePatchNum, patchNum]) => {
+        switchMap(([changeNum, basePatchNum, patchNum]) => {
           if (!changeNum || !patchNum) return of({});
           const range = rangeChooser(basePatchNum, patchNum);
           if (!range) return of({});
diff --git a/polygerrit-ui/app/models/change/related-changes-model.ts b/polygerrit-ui/app/models/change/related-changes-model.ts
new file mode 100644
index 0000000..9ae4295
--- /dev/null
+++ b/polygerrit-ui/app/models/change/related-changes-model.ts
@@ -0,0 +1,242 @@
+/**
+ * @license
+ * Copyright 2023 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+import {
+  ChangeInfo,
+  RelatedChangeAndCommitInfo,
+  SubmittedTogetherInfo,
+} from '../../types/common';
+import {RestApiService} from '../../services/gr-rest-api/gr-rest-api';
+import {select} from '../../utils/observable-util';
+import {Model} from '../model';
+import {define} from '../dependency';
+import {ChangeModel} from './change-model';
+import {combineLatest, forkJoin, from, of} from 'rxjs';
+import {map, switchMap} from 'rxjs/operators';
+import {ConfigModel} from '../config/config-model';
+import {ChangeStatus} from '../../api/rest-api';
+import {isDefined} from '../../types/types';
+
+export interface RelatedChangesState {
+  /** `undefined` means "not yet loaded". */
+  relatedChanges?: RelatedChangeAndCommitInfo[];
+  submittedTogether?: SubmittedTogetherInfo;
+  cherryPicks?: ChangeInfo[];
+  conflictingChanges?: ChangeInfo[];
+  sameTopicChanges?: ChangeInfo[];
+  revertingChanges: ChangeInfo[];
+}
+
+const initialState: RelatedChangesState = {
+  relatedChanges: undefined,
+  submittedTogether: undefined,
+  cherryPicks: undefined,
+  conflictingChanges: undefined,
+  sameTopicChanges: undefined,
+  revertingChanges: [],
+};
+
+export const relatedChangesModelToken = define<RelatedChangesModel>(
+  'related-changes-model'
+);
+
+export class RelatedChangesModel extends Model<RelatedChangesState> {
+  public readonly relatedChanges$ = select(
+    this.state$,
+    state => state.relatedChanges
+  );
+
+  public readonly submittedTogether$ = select(
+    this.state$,
+    state => state.submittedTogether
+  );
+
+  public readonly cherryPicks$ = select(
+    this.state$,
+    state => state.cherryPicks
+  );
+
+  public readonly conflictingChanges$ = select(
+    this.state$,
+    state => state.conflictingChanges
+  );
+
+  public readonly sameTopicChanges$ = select(
+    this.state$,
+    state => state.sameTopicChanges
+  );
+
+  /**
+   * Emits all changes that have reverted the current change, based on
+   * information from parsed change messages. Abandoned changes are not
+   * included.
+   */
+  public readonly revertingChanges$ = select(
+    this.state$,
+    state => state.revertingChanges
+  );
+
+  /**
+   * Emits one reverting change (if there is any) from revertingChanges$.
+   * It prefers MERGED changes. Otherwise the choice is random.
+   */
+  public readonly revertingChange$ = select(
+    this.revertingChanges$,
+    revertingChanges => {
+      if (revertingChanges.length === 0) return undefined;
+      const submittedRevert = revertingChanges.find(
+        c => c.status === ChangeStatus.MERGED
+      );
+      if (submittedRevert) return submittedRevert;
+      return revertingChanges[0];
+    }
+  );
+
+  /**
+   * Determines whether the change has a parent change. If there
+   * is a relation chain, and the change id is not the last item of the
+   * relation chain, then there is a parent.
+   */
+  public readonly hasParent$ = select(
+    combineLatest([this.changeModel.change$, this.relatedChanges$]),
+    ([change, relatedChanges]) => {
+      if (!change) return undefined;
+      if (relatedChanges === undefined) return undefined;
+      if (relatedChanges.length === 0) return false;
+      const lastChangeId = relatedChanges[relatedChanges.length - 1].change_id;
+      return lastChangeId !== change.change_id;
+    }
+  );
+
+  constructor(
+    readonly changeModel: ChangeModel,
+    readonly configModel: ConfigModel,
+    readonly restApiService: RestApiService
+  ) {
+    super(initialState);
+    this.subscriptions = [
+      this.loadRelatedChanges(),
+      this.loadSubmittedTogether(),
+      this.loadCherryPicks(),
+      this.loadConflictingChanges(),
+      this.loadSameTopicChanges(),
+      this.loadRevertingChanges(),
+    ];
+  }
+
+  private loadRelatedChanges() {
+    return combineLatest([
+      this.changeModel.changeNum$,
+      this.changeModel.latestPatchNum$,
+    ])
+      .pipe(
+        switchMap(([changeNum, latestPatchNum]) => {
+          if (!changeNum || !latestPatchNum) return of(undefined);
+          return from(
+            this.restApiService
+              .getRelatedChanges(changeNum, latestPatchNum)
+              .then(info => info?.changes ?? [])
+          );
+        })
+      )
+      .subscribe(relatedChanges => {
+        this.updateState({relatedChanges});
+      });
+  }
+
+  private loadSubmittedTogether() {
+    return this.changeModel.changeNum$
+      .pipe(
+        switchMap(changeNum => {
+          if (!changeNum) return of(undefined);
+          return from(
+            this.restApiService.getChangesSubmittedTogether(changeNum)
+          );
+        })
+      )
+      .subscribe(submittedTogether => {
+        this.updateState({submittedTogether});
+      });
+  }
+
+  private loadCherryPicks() {
+    return combineLatest([
+      this.changeModel.changeNum$,
+      this.changeModel.changeId$,
+      this.changeModel.repo$,
+    ])
+      .pipe(
+        switchMap(([changeNum, changeId, repo]) => {
+          if (!changeNum || !changeId || !repo) return of(undefined);
+          return from(
+            this.restApiService.getChangeCherryPicks(repo, changeId, changeNum)
+          );
+        })
+      )
+      .subscribe(cherryPicks => {
+        this.updateState({cherryPicks});
+      });
+  }
+
+  private loadConflictingChanges() {
+    return combineLatest([
+      this.changeModel.changeNum$,
+      this.changeModel.status$,
+      this.changeModel.mergeable$,
+    ])
+      .pipe(
+        switchMap(([changeNum, status, mergeable]) => {
+          if (!changeNum || !status || !mergeable) return of(undefined);
+          if (status !== ChangeStatus.NEW) return of(undefined);
+          return from(this.restApiService.getChangeConflicts(changeNum));
+        })
+      )
+      .subscribe(conflictingChanges => {
+        this.updateState({conflictingChanges});
+      });
+  }
+
+  private loadSameTopicChanges() {
+    return combineLatest([
+      this.changeModel.changeNum$,
+      this.changeModel.topic$,
+      this.configModel.serverConfig$,
+    ])
+      .pipe(
+        switchMap(([changeNum, topic, config]) => {
+          if (!changeNum || !topic || !config) return of(undefined);
+          if (config.change.submit_whole_topic) return of(undefined);
+          return from(
+            this.restApiService.getChangesWithSameTopic(topic, {
+              openChangesOnly: true,
+              changeToExclude: changeNum,
+            })
+          );
+        })
+      )
+      .subscribe(sameTopicChanges => {
+        this.updateState({sameTopicChanges});
+      });
+  }
+
+  private loadRevertingChanges() {
+    return this.changeModel.revertingChangeIds$
+      .pipe(
+        switchMap(changeIds => {
+          if (!changeIds?.length) return of([]);
+          return forkJoin(
+            changeIds.map(changeId =>
+              from(this.restApiService.getChange(changeId))
+            )
+          );
+        }),
+        map(changes => changes.filter(isDefined)),
+        map(changes => changes.filter(c => c.status !== ChangeStatus.ABANDONED))
+      )
+      .subscribe(revertingChanges => {
+        this.updateState({revertingChanges});
+      });
+  }
+}
diff --git a/polygerrit-ui/app/models/change/related-changes-model_test.ts b/polygerrit-ui/app/models/change/related-changes-model_test.ts
new file mode 100644
index 0000000..295f284
--- /dev/null
+++ b/polygerrit-ui/app/models/change/related-changes-model_test.ts
@@ -0,0 +1,286 @@
+/**
+ * @license
+ * Copyright 2023 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+import '../../test/common-test-setup';
+import {getAppContext} from '../../services/app-context';
+import {ChangeModel, changeModelToken} from '../change/change-model';
+import {assert} from '@open-wc/testing';
+import {testResolver} from '../../test/common-test-setup';
+import {RelatedChangesModel} from './related-changes-model';
+import {configModelToken} from '../config/config-model';
+import {SinonStub} from 'sinon';
+import {
+  ChangeInfo,
+  RelatedChangesInfo,
+  SubmittedTogetherInfo,
+} from '../../types/common';
+import {stubRestApi, waitUntilObserved} from '../../test/test-utils';
+import {
+  createParsedChange,
+  createRelatedChangesInfo,
+  createRelatedChangeAndCommitInfo,
+  createChange,
+  createChangeMessage,
+} from '../../test/test-data-generators';
+import {ChangeStatus, ReviewInputTag, TopicName} from '../../api/rest-api';
+import {MessageTag} from '../../constants/constants';
+
+suite('related-changes-model tests', () => {
+  let model: RelatedChangesModel;
+  let changeModel: ChangeModel;
+
+  setup(async () => {
+    changeModel = testResolver(changeModelToken);
+    model = new RelatedChangesModel(
+      changeModel,
+      testResolver(configModelToken),
+      getAppContext().restApiService
+    );
+    await waitUntilObserved(changeModel.change$, c => c === undefined);
+  });
+
+  teardown(() => {
+    model.finalize();
+  });
+
+  test('register and fetch', async () => {
+    assert.equal('', '');
+  });
+
+  suite('related changes and hasParent', async () => {
+    let getRelatedChangesStub: SinonStub;
+    let getRelatedChangesResponse: RelatedChangesInfo;
+    let hasParent: boolean | undefined;
+
+    setup(() => {
+      getRelatedChangesStub = stubRestApi('getRelatedChanges').callsFake(() =>
+        Promise.resolve(getRelatedChangesResponse)
+      );
+      model.hasParent$.subscribe(x => (hasParent = x));
+    });
+
+    test('relatedChanges initially undefined', async () => {
+      await waitUntilObserved(
+        model.relatedChanges$,
+        relatedChanges => relatedChanges === undefined
+      );
+      assert.isFalse(getRelatedChangesStub.called);
+      assert.isUndefined(hasParent);
+    });
+
+    test('relatedChanges loading empty', async () => {
+      changeModel.updateStateChange({...createParsedChange()});
+
+      await waitUntilObserved(
+        model.relatedChanges$,
+        relatedChanges => relatedChanges?.length === 0
+      );
+      assert.isTrue(getRelatedChangesStub.calledOnce);
+      assert.isFalse(hasParent);
+    });
+
+    test('relatedChanges loading one change', async () => {
+      getRelatedChangesResponse = {
+        ...createRelatedChangesInfo(),
+        changes: [createRelatedChangeAndCommitInfo()],
+      };
+      changeModel.updateStateChange({...createParsedChange()});
+
+      await waitUntilObserved(
+        model.relatedChanges$,
+        relatedChanges => relatedChanges?.length === 1
+      );
+      assert.isTrue(getRelatedChangesStub.calledOnce);
+      assert.isTrue(hasParent);
+    });
+  });
+
+  suite('loadSubmittedTogether', async () => {
+    let getChangesSubmittedTogetherStub: SinonStub;
+    let getChangesSubmittedTogetherResponse: SubmittedTogetherInfo;
+
+    setup(() => {
+      getChangesSubmittedTogetherStub = stubRestApi(
+        'getChangesSubmittedTogether'
+      ).callsFake(() => Promise.resolve(getChangesSubmittedTogetherResponse));
+    });
+
+    test('submittedTogether initially undefined', async () => {
+      await waitUntilObserved(
+        model.submittedTogether$,
+        submittedTogether => submittedTogether === undefined
+      );
+      assert.isFalse(getChangesSubmittedTogetherStub.called);
+    });
+
+    test('submittedTogether emits', async () => {
+      getChangesSubmittedTogetherResponse = {
+        changes: [createChange()],
+        non_visible_changes: 0,
+      };
+      changeModel.updateStateChange({...createParsedChange()});
+
+      await waitUntilObserved(
+        model.submittedTogether$,
+        submittedTogether => submittedTogether?.changes?.length === 1
+      );
+      assert.isTrue(getChangesSubmittedTogetherStub.calledOnce);
+    });
+  });
+
+  suite('loadCherryPicks', async () => {
+    let getChangeCherryPicksStub: SinonStub;
+    let getChangeCherryPicksResponse: ChangeInfo[];
+
+    setup(() => {
+      getChangeCherryPicksStub = stubRestApi('getChangeCherryPicks').callsFake(
+        () => Promise.resolve(getChangeCherryPicksResponse)
+      );
+    });
+
+    test('cherryPicks initially undefined', async () => {
+      await waitUntilObserved(
+        model.cherryPicks$,
+        cherryPicks => cherryPicks === undefined
+      );
+      assert.isFalse(getChangeCherryPicksStub.called);
+    });
+
+    test('cherryPicks emits', async () => {
+      getChangeCherryPicksResponse = [createChange()];
+      changeModel.updateStateChange({...createParsedChange()});
+
+      await waitUntilObserved(
+        model.cherryPicks$,
+        cherryPicks => cherryPicks?.length === 1
+      );
+      assert.isTrue(getChangeCherryPicksStub.calledOnce);
+    });
+  });
+
+  suite('loadConflictingChanges', async () => {
+    let getChangeConflictsStub: SinonStub;
+    let getChangeConflictsResponse: ChangeInfo[];
+
+    setup(() => {
+      getChangeConflictsStub = stubRestApi('getChangeConflicts').callsFake(() =>
+        Promise.resolve(getChangeConflictsResponse)
+      );
+    });
+
+    test('conflictingChanges initially undefined', async () => {
+      await waitUntilObserved(
+        model.conflictingChanges$,
+        conflictingChanges => conflictingChanges === undefined
+      );
+      assert.isFalse(getChangeConflictsStub.called);
+    });
+
+    test('conflictingChanges not loaded for merged changes', async () => {
+      getChangeConflictsResponse = [createChange()];
+      changeModel.updateStateChange({
+        ...createParsedChange(),
+        mergeable: true,
+        status: ChangeStatus.MERGED,
+      });
+
+      await waitUntilObserved(
+        model.conflictingChanges$,
+        conflictingChanges => conflictingChanges === undefined
+      );
+      assert.isFalse(getChangeConflictsStub.called);
+    });
+
+    test('conflictingChanges emits', async () => {
+      getChangeConflictsResponse = [createChange()];
+      changeModel.updateStateChange({...createParsedChange(), mergeable: true});
+
+      await waitUntilObserved(
+        model.conflictingChanges$,
+        conflictingChanges => conflictingChanges?.length === 1
+      );
+      assert.isTrue(getChangeConflictsStub.calledOnce);
+    });
+  });
+
+  suite('loadSameTopicChanges', async () => {
+    let getChangesWithSameTopicStub: SinonStub;
+    let getChangesWithSameTopicResponse: ChangeInfo[];
+
+    setup(() => {
+      getChangesWithSameTopicStub = stubRestApi(
+        'getChangesWithSameTopic'
+      ).callsFake(() => Promise.resolve(getChangesWithSameTopicResponse));
+    });
+
+    test('sameTopicChanges initially undefined', async () => {
+      await waitUntilObserved(
+        model.sameTopicChanges$,
+        sameTopicChanges => sameTopicChanges === undefined
+      );
+      assert.isFalse(getChangesWithSameTopicStub.called);
+    });
+
+    test('sameTopicChanges emits', async () => {
+      getChangesWithSameTopicResponse = [createChange()];
+      changeModel.updateStateChange({
+        ...createParsedChange(),
+        topic: 'test-topic' as TopicName,
+      });
+
+      await waitUntilObserved(
+        model.sameTopicChanges$,
+        sameTopicChanges => sameTopicChanges?.length === 1
+      );
+      assert.isTrue(getChangesWithSameTopicStub.calledOnce);
+    });
+  });
+
+  suite('loadRevertingChanges', async () => {
+    let getChangeStub: SinonStub;
+
+    setup(() => {
+      getChangeStub = stubRestApi('getChange').callsFake(() =>
+        Promise.resolve(createChange())
+      );
+    });
+
+    test('revertingChanges initially empty', async () => {
+      await waitUntilObserved(
+        model.revertingChanges$,
+        revertingChanges => revertingChanges.length === 0
+      );
+      assert.isFalse(getChangeStub.called);
+    });
+
+    test('revertingChanges empty when change does not contain a revert message', async () => {
+      changeModel.updateStateChange(createParsedChange());
+      await waitUntilObserved(
+        model.revertingChanges$,
+        revertingChanges => revertingChanges.length === 0
+      );
+      assert.isFalse(getChangeStub.called);
+    });
+
+    test('revertingChanges emits', async () => {
+      changeModel.updateStateChange({
+        ...createParsedChange(),
+        messages: [
+          {
+            ...createChangeMessage(),
+            message: 'Created a revert of this change as 123',
+            tag: MessageTag.TAG_REVERT as ReviewInputTag,
+          },
+        ],
+      });
+
+      await waitUntilObserved(
+        model.revertingChanges$,
+        revertingChanges => revertingChanges?.length === 1
+      );
+      assert.isTrue(getChangeStub.calledOnce);
+    });
+  });
+});
diff --git a/polygerrit-ui/app/models/checks/checks-model.ts b/polygerrit-ui/app/models/checks/checks-model.ts
index 2aa4aa4..729d46f 100644
--- a/polygerrit-ui/app/models/checks/checks-model.ts
+++ b/polygerrit-ui/app/models/checks/checks-model.ts
@@ -195,8 +195,6 @@
 
   private readonly documentVisibilityChange$ = new BehaviorSubject(undefined);
 
-  private readonly reloadListener: () => void;
-
   private readonly visibilityChangeListener: () => void;
 
   public checksSelectedPatchsetNumber$ = select(
@@ -414,8 +412,6 @@
       'visibilitychange',
       this.visibilityChangeListener
     );
-    this.reloadListener = () => this.reloadAll();
-    document.addEventListener('reload', this.reloadListener);
   }
 
   private reportStats(state: {[name: string]: ChecksProviderState}) {
@@ -459,7 +455,6 @@
   }
 
   override finalize() {
-    document.removeEventListener('reload', this.reloadListener);
     document.removeEventListener(
       'visibilitychange',
       this.visibilityChangeListener
diff --git a/polygerrit-ui/app/models/comments/comments-model.ts b/polygerrit-ui/app/models/comments/comments-model.ts
index 5f40393..ac832a1 100644
--- a/polygerrit-ui/app/models/comments/comments-model.ts
+++ b/polygerrit-ui/app/models/comments/comments-model.ts
@@ -424,8 +424,6 @@
 
   private patchNum?: PatchSetNum;
 
-  private readonly reloadListener: () => void;
-
   private drafts: {[path: string]: DraftInfo[]} = {};
 
   private draftToastTask?: DelayedTask;
@@ -495,16 +493,6 @@
         this.reloadAllPortedComments();
       })
     );
-    this.reloadListener = () => {
-      this.reloadAllComments();
-      this.reloadAllPortedComments();
-    };
-    document.addEventListener('reload', this.reloadListener);
-  }
-
-  override finalize() {
-    document.removeEventListener('reload', this.reloadListener);
-    super.finalize();
   }
 
   // Note that this does *not* reload ported comments.
diff --git a/polygerrit-ui/app/models/views/change.ts b/polygerrit-ui/app/models/views/change.ts
index d2a0dd8..713d401 100644
--- a/polygerrit-ui/app/models/views/change.ts
+++ b/polygerrit-ui/app/models/views/change.ts
@@ -69,9 +69,16 @@
 
   /** for scrolling a Change Log message into view in gr-change-view */
   messageHash?: string;
-  /** for logging where the user came from */
+  /**
+   * For logging where the user came from. This is handled by the router, so
+   * this is not inspected by the model.
+   */
   usp?: string;
-  /** triggers all change related data to be reloaded */
+  /**
+   * Triggers all change related data to be reloaded. This is implemented by
+   * intercepting change view state updates and `forceReload` causing the view
+   * state to be wiped clean as `undefined` in an intermediate update.
+   */
   forceReload?: boolean;
   /** triggers opening the reply dialog */
   openReplyDialog?: boolean;
@@ -261,6 +268,20 @@
     state => state?.basePatchNum
   );
 
+  public readonly openReplyDialog$ = select(
+    this.state$,
+    state => state?.openReplyDialog
+  );
+
+  public readonly commentId$ = select(this.state$, state => state?.commentId);
+
+  public readonly edit$ = select(this.state$, state => !!state?.edit);
+
+  public readonly editPath$ = select(
+    this.state$,
+    state => state?.editView?.path
+  );
+
   public readonly diffPath$ = select(
     this.state$,
     state => state?.diffView?.path
@@ -278,7 +299,11 @@
 
   public readonly childView$ = select(this.state$, state => state?.childView);
 
-  public readonly tab$ = select(this.state$, state => state?.tab);
+  public readonly tab$ = select(this.state$, state => {
+    if (state?.commentId) return Tab.COMMENT_THREADS;
+    if (state?.tab) return state.tab;
+    return Tab.FILES;
+  });
 
   public readonly checksPatchset$ = select(
     this.state$,
@@ -310,6 +335,39 @@
         });
       }
     });
+    document.addEventListener('reload', this.reload);
+  }
+
+  override finalize(): void {
+    document.removeEventListener('reload', this.reload);
+  }
+
+  /**
+   * Calling this is the same as firing the 'reload' event. This is also the
+   * same as adding `forceReload` parameter in the URL. See below.
+   */
+  reload = () => {
+    const state = this.getState();
+    if (state !== undefined) this.forceLoad(state);
+  };
+
+  /**
+   * This is the destination of where the `reload()` method, the `reload` event
+   * and the `forceReload` URL parameter all end up.
+   */
+  private forceLoad(state: ChangeViewState) {
+    this.setState(undefined);
+    // We have to do this in a timeout, because we need the `undefined` value to
+    // be processed by all observers first and thus have the "reset" completed.
+    setTimeout(() => this.setState({...state, forceReload: undefined}));
+  }
+
+  override setState(state: ChangeViewState | undefined): void {
+    if (state?.forceReload) {
+      this.forceLoad(state);
+    } else {
+      super.setState(state);
+    }
   }
 
   toggleSelectedCheckRun(checkName: string) {
diff --git a/polygerrit-ui/app/services/app-context-init.ts b/polygerrit-ui/app/services/app-context-init.ts
index 3b9d3bb..8589ae3 100644
--- a/polygerrit-ui/app/services/app-context-init.ts
+++ b/polygerrit-ui/app/services/app-context-init.ts
@@ -68,6 +68,10 @@
   ServiceWorkerInstaller,
   serviceWorkerInstallerToken,
 } from './service-worker-installer';
+import {
+  RelatedChangesModel,
+  relatedChangesModelToken,
+} from '../models/change/related-changes-model';
 
 /**
  * The AppContext lazy initializator for all services
@@ -151,7 +155,9 @@
           resolver(navigationToken),
           resolver(changeViewModelToken),
           appContext.restApiService,
-          resolver(userModelToken)
+          resolver(userModelToken),
+          resolver(pluginLoaderToken),
+          appContext.reportingService
         ),
     ],
     [
@@ -172,7 +178,8 @@
         new FilesModel(
           resolver(changeModelToken),
           resolver(commentsModelToken),
-          appContext.restApiService
+          appContext.restApiService,
+          appContext.reportingService
         ),
     ],
     [
@@ -181,6 +188,15 @@
         new ConfigModel(resolver(changeModelToken), appContext.restApiService),
     ],
     [
+      relatedChangesModelToken,
+      () =>
+        new RelatedChangesModel(
+          resolver(changeModelToken),
+          resolver(configModelToken),
+          appContext.restApiService
+        ),
+    ],
+    [
       pluginLoaderToken,
       () =>
         new PluginLoader(
diff --git a/polygerrit-ui/app/test/mocks/gr-rest-api_mock.ts b/polygerrit-ui/app/test/mocks/gr-rest-api_mock.ts
index b60ace5..f8e4160 100644
--- a/polygerrit-ui/app/test/mocks/gr-rest-api_mock.ts
+++ b/polygerrit-ui/app/test/mocks/gr-rest-api_mock.ts
@@ -67,6 +67,7 @@
   createChange,
   createCommit,
   createConfig,
+  createMergeable,
   createPreferences,
   createServerInfo,
   createSubmittedTogetherInfo,
@@ -368,7 +369,7 @@
     return Promise.resolve(true);
   },
   getMergeable(): Promise<MergeableInfo | undefined> {
-    throw new Error('getMergeable() not implemented by RestApiMock.');
+    return Promise.resolve(createMergeable());
   },
   getPlugins(): Promise<{[p: string]: PluginInfo} | undefined> {
     return Promise.resolve({});
diff --git a/polygerrit-ui/app/test/test-data-generators.ts b/polygerrit-ui/app/test/test-data-generators.ts
index a92e932..dce8e4b 100644
--- a/polygerrit-ui/app/test/test-data-generators.ts
+++ b/polygerrit-ui/app/test/test-data-generators.ts
@@ -672,10 +672,10 @@
   };
 }
 
-export function createMergeable(): MergeableInfo {
+export function createMergeable(mergeable = false): MergeableInfo {
   return {
     submit_type: SubmitType.MERGE_IF_NECESSARY,
-    mergeable: false,
+    mergeable,
   };
 }
 
diff --git a/polygerrit-ui/app/test/test-utils.ts b/polygerrit-ui/app/test/test-utils.ts
index d897423..6e20dd4 100644
--- a/polygerrit-ui/app/test/test-utils.ts
+++ b/polygerrit-ui/app/test/test-utils.ts
@@ -16,8 +16,9 @@
 import {assert} from '@open-wc/testing';
 import {Route, ViewState} from '../models/views/base';
 import {PageContext} from '../elements/core/gr-router/gr-page';
+import {waitUntil} from '../utils/async-util';
 export {query, queryAll, queryAndAssert} from '../utils/common-util';
-export {mockPromise} from '../utils/async-util';
+export {mockPromise, waitUntil} from '../utils/async-util';
 export type {MockPromise} from '../utils/async-util';
 
 export function isHidden(el: Element | undefined | null) {
@@ -149,32 +150,6 @@
   return queryAndAssert<E>(el, selector);
 }
 
-export async function waitUntil(
-  predicate: (() => boolean) | (() => Promise<boolean>),
-  message = 'The waitUntil() predicate is still false after 1000 ms.',
-  timeout_ms = 1000
-): Promise<void> {
-  const start = Date.now();
-  let sleep = 0;
-  if (await predicate()) return Promise.resolve();
-  const error = new Error(message);
-  return new Promise((resolve, reject) => {
-    const waiter = async () => {
-      if (await predicate()) {
-        resolve();
-        return;
-      }
-      if (Date.now() - start >= timeout_ms) {
-        reject(error);
-        return;
-      }
-      setTimeout(waiter, sleep);
-      sleep = sleep === 0 ? 1 : sleep * 4;
-    };
-    waiter();
-  });
-}
-
 export async function waitUntilVisible(element: Element): Promise<void> {
   return new Promise(resolve => {
     whenVisible(element, () => resolve());
diff --git a/polygerrit-ui/app/types/events.ts b/polygerrit-ui/app/types/events.ts
index 4bf0c78..922d779 100644
--- a/polygerrit-ui/app/types/events.ts
+++ b/polygerrit-ui/app/types/events.ts
@@ -52,14 +52,13 @@
     'open-fix-preview': OpenFixPreviewEvent;
     'reply-to-comment': ReplyToCommentEvent;
     // prettier-ignore
-    'reload': ReloadEvent;
+    'reload': CustomEvent<{}>;
     'remove-reviewer': RemoveReviewerEvent;
     'show-alert': ShowAlertEvent;
     'show-error': ShowErrorEvent;
     'show-tab': SwitchTabEvent;
     'show-secondary-tab': SwitchTabEvent;
     'tap-item': TapItemEvent;
-    'title-change': TitleChangeEvent;
   }
 }
 
@@ -69,11 +68,12 @@
     'network-error': NetworkErrorEvent;
     'page-error': PageErrorEvent;
     // prettier-ignore
-    'reload': ReloadEvent;
+    'reload': CustomEvent<{}>;
     'server-error': ServerErrorEvent;
     'show-alert': ShowAlertEvent;
     'show-error': ShowErrorEvent;
     'auth-error': AuthErrorEvent;
+    'title-change': TitleChangeEvent;
   }
 }
 
@@ -186,11 +186,6 @@
 }
 export type PageErrorEvent = CustomEvent<PageErrorEventDetail>;
 
-export interface ReloadEventDetail {
-  clearPatchset: boolean;
-}
-export type ReloadEvent = CustomEvent<ReloadEventDetail>;
-
 export interface RemoveAccountEventDetail {
   account: AccountInfo;
 }
diff --git a/polygerrit-ui/app/utils/async-util.ts b/polygerrit-ui/app/utils/async-util.ts
index 2dde07a..32a6867 100644
--- a/polygerrit-ui/app/utils/async-util.ts
+++ b/polygerrit-ui/app/utils/async-util.ts
@@ -371,3 +371,29 @@
     setTimeout(resolve, timeoutMs);
   });
 }
+
+export async function waitUntil(
+  predicate: (() => boolean) | (() => Promise<boolean>),
+  message = 'The waitUntil() predicate is still false after 1000 ms.',
+  timeout_ms = 1000
+): Promise<void> {
+  if (await predicate()) return Promise.resolve();
+  const start = Date.now();
+  let sleep = 10;
+  const error = new Error(message);
+  return new Promise((resolve, reject) => {
+    const waiter = async () => {
+      if (await predicate()) {
+        resolve();
+        return;
+      }
+      if (Date.now() - start >= timeout_ms) {
+        reject(error);
+        return;
+      }
+      setTimeout(waiter, sleep);
+      sleep *= 2;
+    };
+    waiter();
+  });
+}
diff --git a/polygerrit-ui/app/utils/change-util.ts b/polygerrit-ui/app/utils/change-util.ts
index 5dda8d6..4490afa 100644
--- a/polygerrit-ui/app/utils/change-util.ts
+++ b/polygerrit-ui/app/utils/change-util.ts
@@ -20,6 +20,8 @@
 interface ChangeStatusesOptions {
   mergeable: boolean; // This can be wrong! See WARNING above
   submitEnabled: boolean; // This can be wrong! See WARNING above
+  /** Is there a reverting change and if so, what status has it? */
+  revertingChangeStatus?: ChangeStatus;
 }
 
 export const ChangeDiffType = {
@@ -158,6 +160,12 @@
 ): ChangeStates[] {
   const states = [];
   if (change.status === ChangeStatus.MERGED) {
+    if (options?.revertingChangeStatus === ChangeStatus.MERGED) {
+      return [ChangeStates.MERGED, ChangeStates.REVERT_SUBMITTED];
+    }
+    if (options?.revertingChangeStatus !== undefined) {
+      return [ChangeStates.MERGED, ChangeStates.REVERT_CREATED];
+    }
     return [ChangeStates.MERGED];
   }
   if (change.status === ChangeStatus.ABANDONED) {
diff --git a/polygerrit-ui/app/utils/change-util_test.ts b/polygerrit-ui/app/utils/change-util_test.ts
index ccaa1db..f768145 100644
--- a/polygerrit-ui/app/utils/change-util_test.ts
+++ b/polygerrit-ui/app/utils/change-util_test.ts
@@ -129,6 +129,32 @@
     assert.deepEqual(changeStatuses(change), [ChangeStates.MERGED]);
   });
 
+  test('Merged and Reverted status', () => {
+    const change = {
+      ...createChange(),
+      revisions: createRevisions(1),
+      current_revision: 'rev1' as CommitId,
+      status: ChangeStatus.MERGED,
+    };
+    assert.deepEqual(changeStatuses(change), [ChangeStates.MERGED]);
+    assert.deepEqual(
+      changeStatuses(change, {
+        revertingChangeStatus: ChangeStatus.NEW,
+        mergeable: true,
+        submitEnabled: true,
+      }),
+      [ChangeStates.MERGED, ChangeStates.REVERT_CREATED]
+    );
+    assert.deepEqual(
+      changeStatuses(change, {
+        revertingChangeStatus: ChangeStatus.MERGED,
+        mergeable: true,
+        submitEnabled: true,
+      }),
+      [ChangeStates.MERGED, ChangeStates.REVERT_SUBMITTED]
+    );
+  });
+
   test('Abandoned status', () => {
     const change = {
       ...createChange(),
diff --git a/polygerrit-ui/app/utils/event-util.ts b/polygerrit-ui/app/utils/event-util.ts
index 3704557..af545e7 100644
--- a/polygerrit-ui/app/utils/event-util.ts
+++ b/polygerrit-ui/app/utils/event-util.ts
@@ -95,8 +95,8 @@
   fire(document, 'network-error', {error});
 }
 
-export function fireTitleChange(target: EventTarget, title: string) {
-  fire(target, 'title-change', {title});
+export function fireTitleChange(title: string) {
+  fire(document, 'title-change', {title});
 }
 
 // TODO(milutin) - remove once new gr-dialog will do it out of the box
@@ -122,8 +122,8 @@
   fire(target, 'show-tab', detail);
 }
 
-export function fireReload(target: EventTarget, clearPatchset?: boolean) {
-  fire(target, 'reload', {clearPatchset: !!clearPatchset});
+export function fireReload(target: EventTarget) {
+  fire(target, 'reload', {});
 }
 
 export function waitForEventOnce<K extends keyof HTMLElementEventMap>(
diff --git a/polygerrit-ui/app/utils/message-util_test.ts b/polygerrit-ui/app/utils/message-util_test.ts
new file mode 100644
index 0000000..22a5e4d
--- /dev/null
+++ b/polygerrit-ui/app/utils/message-util_test.ts
@@ -0,0 +1,37 @@
+/**
+ * @license
+ * Copyright 2023 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+import {getRevertCreatedChangeIds} from './message-util';
+import {assert} from '@open-wc/testing';
+import {MessageTag} from '../constants/constants';
+import {ChangeId, ReviewInputTag} from '../api/rest-api';
+import {createChangeMessage} from '../test/test-data-generators';
+
+suite('message-util tests', () => {
+  test('getRevertCreatedChangeIds', () => {
+    const messages = [
+      {
+        ...createChangeMessage(),
+        message: 'Created a revert of this change as 123',
+        tag: MessageTag.TAG_REVERT as ReviewInputTag,
+      },
+      {
+        ...createChangeMessage(),
+        message: 'Created a revert of this change as xyz',
+        tag: MessageTag.TAG_REVERT as ReviewInputTag,
+      },
+      {
+        ...createChangeMessage(),
+        message: 'Created a revert of this change as abc',
+        tag: undefined,
+      },
+    ];
+
+    assert.deepEqual(getRevertCreatedChangeIds(messages), [
+      '123' as ChangeId,
+      'xyz' as ChangeId,
+    ]);
+  });
+});
diff --git a/polygerrit-ui/app/utils/patch-set-util.ts b/polygerrit-ui/app/utils/patch-set-util.ts
index 7e16ad9..7f3b6eb 100644
--- a/polygerrit-ui/app/utils/patch-set-util.ts
+++ b/polygerrit-ui/app/utils/patch-set-util.ts
@@ -35,11 +35,6 @@
   wip?: boolean;
 }
 
-interface PatchRange {
-  patchNum?: RevisionPatchSetNum;
-  basePatchNum?: BasePatchSetNum;
-}
-
 /**
  * Whether the given patch is a numbered parent of a merge (i.e. a negative
  * number).
@@ -294,10 +289,6 @@
   return allPatchSets[0].num === EDIT;
 }
 
-export function hasEditPatchsetLoaded(patchRange: PatchRange) {
-  return patchRange.patchNum === EDIT;
-}
-
 /**
  * @param revisions A sorted array of revisions.
  *