diff --git a/polygerrit-ui/app/elements/shared/gr-account-list/gr-account-list.ts b/polygerrit-ui/app/elements/shared/gr-account-list/gr-account-list.ts
index 8339df9..07209db 100644
--- a/polygerrit-ui/app/elements/shared/gr-account-list/gr-account-list.ts
+++ b/polygerrit-ui/app/elements/shared/gr-account-list/gr-account-list.ts
@@ -36,6 +36,7 @@
 import {PaperInputElement} from '@polymer/paper-input/paper-input';
 import {IronInputElement} from '@polymer/iron-input';
 import {ReviewerState} from '../../../api/rest-api';
+import {repeat} from 'lit/directives/repeat.js';
 
 const VALID_EMAIL_ALERT = 'Please input a valid email.';
 const VALID_USER_GROUP_ALERT = 'Please input a valid user or group.';
@@ -186,7 +187,9 @@
 
   override render() {
     return html`<div class="list">
-        ${this.accounts.map(
+        ${repeat(
+          this.accounts,
+          account => getUserId(account),
           account => html`
             <gr-account-chip
               .account=${account}
diff --git a/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-js-api-interface-element.ts b/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-js-api-interface-element.ts
index 386a166..46c759b 100644
--- a/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-js-api-interface-element.ts
+++ b/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-js-api-interface-element.ts
@@ -7,6 +7,7 @@
 import {
   ChangeInfo,
   LabelNameToValueMap,
+  PARENT,
   ReviewInput,
   RevisionInfo,
 } from '../../../types/common';
@@ -98,20 +99,22 @@
         return detail.info && detail.info.mergeable;
       },
     };
-    const patchNum = detail.patchNum;
-    const info = detail.info;
+    const {patchNum, info, basePatchNum} = detail;
 
     let revision;
+    let baseRevision;
     for (const rev of Object.values(change.revisions || {})) {
       if (rev._number === patchNum) {
         revision = rev;
-        break;
+      }
+      if (rev._number === basePatchNum) {
+        baseRevision = rev;
       }
     }
 
     for (const cb of this._getEventCallbacks(EventType.SHOW_CHANGE)) {
       try {
-        cb(change, revision, info);
+        cb(change, revision, info, baseRevision ?? PARENT);
       } catch (err: unknown) {
         this.reporting.error(
           'GrJsApiInterface',
diff --git a/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-js-api-types.ts b/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-js-api-types.ts
index a10beab..8e3a87d 100644
--- a/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-js-api-types.ts
+++ b/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-js-api-types.ts
@@ -6,6 +6,7 @@
 import {
   ActionInfo,
   ChangeInfo,
+  BasePatchSetNum,
   PatchSetNum,
   ReviewInput,
   RevisionInfo,
@@ -17,6 +18,7 @@
 
 export interface ShowChangeDetail {
   change?: ParsedChangeInfo;
+  basePatchNum?: BasePatchSetNum;
   patchNum?: PatchSetNum;
   info: {mergeable: boolean | null};
 }
diff --git a/polygerrit-ui/app/models/change/change-model.ts b/polygerrit-ui/app/models/change/change-model.ts
index 6d111aa..c7111f6 100644
--- a/polygerrit-ui/app/models/change/change-model.ts
+++ b/polygerrit-ui/app/models/change/change-model.ts
@@ -407,21 +407,24 @@
     return combineLatest([
       this.viewModel.childView$,
       this.change$,
+      this.basePatchNum$,
       this.patchNum$,
       this.mergeable$,
     ])
       .pipe(
         filter(
-          ([childView, change, patchNum, mergeable]) =>
+          ([childView, change, basePatchNum, patchNum, mergeable]) =>
             childView === ChangeChildView.OVERVIEW &&
             !!change &&
+            !!basePatchNum &&
             !!patchNum &&
             mergeable !== undefined
         )
       )
-      .subscribe(([_, change, patchNum, mergeable]) => {
+      .subscribe(([_, change, basePatchNum, patchNum, mergeable]) => {
         this.pluginLoader.jsApiService.handleShowChange({
           change,
+          basePatchNum,
           patchNum,
           // `?? null` is for the TypeScript compiler only. We have a
           // `mergeable !== undefined` filter above, so this cannot happen.
diff --git a/polygerrit-ui/app/models/change/change-model_test.ts b/polygerrit-ui/app/models/change/change-model_test.ts
index e5d2e36..dc7d9c3 100644
--- a/polygerrit-ui/app/models/change/change-model_test.ts
+++ b/polygerrit-ui/app/models/change/change-model_test.ts
@@ -222,6 +222,7 @@
   });
 
   test('fireShowChange', async () => {
+    await waitForLoadingStatus(LoadingStatus.NOT_LOADED);
     const pluginLoader = testResolver(pluginLoaderToken);
     const jsApiService = pluginLoader.jsApiService;
     const showChangeStub = sinon.stub(jsApiService, 'handleShowChange');
@@ -239,6 +240,7 @@
     const detail: ShowChangeDetail = showChangeStub.lastCall.firstArg;
     assert.equal(detail.change?._number, createParsedChange()._number);
     assert.equal(detail.patchNum, 1 as PatchSetNumber);
+    assert.equal(detail.basePatchNum, PARENT);
     assert.equal(detail.info.mergeable, true);
   });