diff --git a/Documentation/linux-quickstart.txt b/Documentation/linux-quickstart.txt
index c45de05..13873ed 100644
--- a/Documentation/linux-quickstart.txt
+++ b/Documentation/linux-quickstart.txt
@@ -29,10 +29,10 @@
 . Download the desired Gerrit archive.
 
 To view previous archives, see
-link:https://gerrit-releases.storage.googleapis.com/index.html[Gerrit Code Review: Releases,role=external,window=_blank]. The steps below install Gerrit 3.1.3:
+link:https://gerrit-releases.storage.googleapis.com/index.html[Gerrit Code Review: Releases,role=external,window=_blank]. The steps below install Gerrit 3.5.1:
 
 ....
-wget https://gerrit-releases.storage.googleapis.com/gerrit-3.1.3.war
+wget https://gerrit-releases.storage.googleapis.com/gerrit-3.5.1.war
 ....
 
 NOTE: To build and install Gerrit from the source files, see
diff --git a/java/com/google/gerrit/server/permissions/GitVisibleChangeFilter.java b/java/com/google/gerrit/server/permissions/GitVisibleChangeFilter.java
index 5a7b3cb..506d292 100644
--- a/java/com/google/gerrit/server/permissions/GitVisibleChangeFilter.java
+++ b/java/com/google/gerrit/server/permissions/GitVisibleChangeFilter.java
@@ -100,7 +100,11 @@
         .map(
             id -> {
               try {
-                return changeDataFactory.create(projectName, id);
+                ChangeData cd = changeDataFactory.create(projectName, id);
+                cd.notes(); // Make sure notes are available. This will trigger loading notes and
+                // throw an exception in case the change is corrupt and can't be loaded. It will
+                // then be omitted from the result.
+                return cd;
               } catch (Exception e) {
                 // We drop changes that we can't load. The repositories contain 'dead' change refs
                 // and we want to overall operation to continue.
diff --git a/polygerrit-ui/app/elements/change-list/gr-change-list-reviewer-flow/gr-change-list-reviewer-flow.ts b/polygerrit-ui/app/elements/change-list/gr-change-list-reviewer-flow/gr-change-list-reviewer-flow.ts
index 58eec3b..95e9c87 100644
--- a/polygerrit-ui/app/elements/change-list/gr-change-list-reviewer-flow/gr-change-list-reviewer-flow.ts
+++ b/polygerrit-ui/app/elements/change-list/gr-change-list-reviewer-flow/gr-change-list-reviewer-flow.ts
@@ -34,13 +34,9 @@
 import {AccountInputDetail} from '../../shared/gr-account-list/gr-account-list';
 import '@polymer/iron-icon/iron-icon';
 
-const SUGGESTIONS_PROVIDERS_USERS_TYPES_BY_REVIEWER_STATE: Record<
-  ReviewerState,
-  SUGGESTIONS_PROVIDERS_USERS_TYPES
-> = {
+const SUGGESTIONS_PROVIDERS_USERS_TYPES_BY_REVIEWER_STATE = {
   REVIEWER: SUGGESTIONS_PROVIDERS_USERS_TYPES.REVIEWER,
   CC: SUGGESTIONS_PROVIDERS_USERS_TYPES.CC,
-  REMOVED: SUGGESTIONS_PROVIDERS_USERS_TYPES.ANY,
 };
 
 @customElement('gr-change-list-reviewer-flow')
@@ -80,6 +76,8 @@
 
   private restApiService = getAppContext().restApiService;
 
+  private isLoggedIn = false;
+
   static override get styles() {
     return css`
       gr-dialog {
@@ -128,6 +126,11 @@
       this.getConfigModel().serverConfig$,
       serverConfig => (this.serverConfig = serverConfig)
     );
+    subscribe(
+      this,
+      getAppContext().userModel.loggedIn$,
+      isLoggedIn => (this.isLoggedIn = isLoggedIn)
+    );
   }
 
   override render() {
@@ -275,7 +278,7 @@
         ProgressStatus.NOT_STARTED,
       ])
     );
-    for (const state of [ReviewerState.REVIEWER, ReviewerState.CC]) {
+    for (const state of [ReviewerState.REVIEWER, ReviewerState.CC] as const) {
       this.updatedAccountsByReviewerState.set(
         state,
         this.getCurrentAccounts(state)
@@ -396,15 +399,15 @@
   }
 
   private createSuggestionsProvider(
-    state: ReviewerState
+    state: ReviewerState.CC | ReviewerState.REVIEWER
   ): ReviewerSuggestionsProvider {
-    const suggestionsProvider = GrReviewerSuggestionsProvider.create(
+    const suggestionsProvider = new GrReviewerSuggestionsProvider(
       this.restApiService,
-      // TODO: fan out and get suggestions allowed by all changes
-      this.selectedChanges[0]._number,
-      SUGGESTIONS_PROVIDERS_USERS_TYPES_BY_REVIEWER_STATE[state]
+      SUGGESTIONS_PROVIDERS_USERS_TYPES_BY_REVIEWER_STATE[state],
+      this.serverConfig,
+      this.isLoggedIn,
+      ...this.selectedChanges.map(change => change._number)
     );
-    suggestionsProvider.init();
     return suggestionsProvider;
   }
 }
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 9f33990..c03121d 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
@@ -306,7 +306,7 @@
     super.disconnectedCallback();
   }
 
-  scrollToMessage(messageID: string) {
+  async scrollToMessage(messageID: string) {
     const selector = `[data-message-id="${messageID}"]`;
     const el = this.shadowRoot!.querySelector(selector) as
       | GrMessage
@@ -325,6 +325,7 @@
     }
 
     el.message = {...el.message, expanded: true};
+    await el.updateComplete;
     let top = el.offsetTop;
     for (
       let offsetParent = el.offsetParent as HTMLElement | null;
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 30dd257..b9cb616 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
@@ -222,7 +222,7 @@
       assert.isNotOk(query(element, '.showAllActivityToggle'));
     });
 
-    test('scroll to message', () => {
+    test('scroll to message', async () => {
       const allMessageEls = getMessages();
       for (const message of allMessageEls) {
         assertIsDefined(message.message);
@@ -232,7 +232,7 @@
       const scrollToStub = sinon.stub(window, 'scrollTo');
       const highlightStub = sinon.stub(element, '_highlightEl');
 
-      element.scrollToMessage('invalid');
+      await element.scrollToMessage('invalid');
 
       for (const message of allMessageEls) {
         assertIsDefined(message.message);
@@ -243,7 +243,7 @@
       }
 
       const messageID = messages[1].id;
-      element.scrollToMessage(messageID);
+      await element.scrollToMessage(messageID);
       assert.isTrue(
         queryAndAssert<GrMessage>(element, `[data-message-id="${messageID}"]`)
           .message?.expanded
@@ -253,16 +253,16 @@
       assert.isTrue(highlightStub.calledOnce);
     });
 
-    test('scroll to message offscreen', () => {
+    test('scroll to message offscreen', async () => {
       const scrollToStub = sinon.stub(window, 'scrollTo');
       const highlightStub = sinon.stub(element, '_highlightEl');
       element.messages = generateRandomMessages(25);
-      flush();
+      await element.updateComplete;
       assert.isFalse(scrollToStub.called);
       assert.isFalse(highlightStub.called);
 
       const messageID = element.messages[1].id;
-      element.scrollToMessage(messageID);
+      await element.scrollToMessage(messageID);
       assert.isTrue(scrollToStub.calledOnce);
       assert.isTrue(highlightStub.calledOnce);
       assert.isTrue(
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 95572a8..c35b6b3 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
@@ -118,6 +118,7 @@
 import {classMap} from 'lit/directives/class-map';
 import {BindValueChangeEvent, ValueChangedEvent} from '../../../types/events';
 import {customElement, property, state, query} from 'lit/decorators';
+import {subscribe} from '../../lit/subscription-controller';
 
 const STORAGE_DEBOUNCE_INTERVAL_MS = 400;
 
@@ -347,6 +348,8 @@
 
   storeTask?: DelayedTask;
 
+  private isLoggedIn = false;
+
   /** Called in disconnectedCallback. */
   private cleanups: (() => void)[] = [];
 
@@ -687,6 +690,12 @@
     this.addEventListener('remove-reviewer', e => {
       this.reviewersList?.removeAccount((e as CustomEvent).detail.reviewer);
     });
+
+    subscribe(
+      this,
+      getAppContext().userModel.loggedIn$,
+      isLoggedIn => (this.isLoggedIn = isLoggedIn)
+    );
   }
 
   override disconnectedCallback() {
@@ -2079,23 +2088,25 @@
 
   getReviewerSuggestionsProvider(change?: ChangeInfo) {
     if (!change) return;
-    const provider = GrReviewerSuggestionsProvider.create(
+    const provider = new GrReviewerSuggestionsProvider(
       this.restApiService,
-      change._number,
-      SUGGESTIONS_PROVIDERS_USERS_TYPES.REVIEWER
+      SUGGESTIONS_PROVIDERS_USERS_TYPES.REVIEWER,
+      this.serverConfig,
+      this.isLoggedIn,
+      change._number
     );
-    provider.init();
     return provider;
   }
 
   getCcSuggestionsProvider(change?: ChangeInfo) {
     if (!change) return;
-    const provider = GrReviewerSuggestionsProvider.create(
+    const provider = new GrReviewerSuggestionsProvider(
       this.restApiService,
-      change._number,
-      SUGGESTIONS_PROVIDERS_USERS_TYPES.CC
+      SUGGESTIONS_PROVIDERS_USERS_TYPES.CC,
+      this.serverConfig,
+      this.isLoggedIn,
+      change._number
     );
-    provider.init();
     return provider;
   }
 
diff --git a/polygerrit-ui/app/models/dependency.ts b/polygerrit-ui/app/models/dependency.ts
index e7ac242c..f39fa32 100644
--- a/polygerrit-ui/app/models/dependency.ts
+++ b/polygerrit-ui/app/models/dependency.ts
@@ -133,16 +133,35 @@
  */
 export type Provider<T> = () => T;
 
+// Symbols to cache the providers and resolvers to avoid duplicate registration.
+const PROVIDERS_SYMBOL = Symbol('providers');
+const RESOLVERS_SYMBOL = Symbol('resolvers');
+
+interface Registrations {
+  [PROVIDERS_SYMBOL]?: Map<
+    DependencyToken<unknown>,
+    DependencyProvider<unknown>
+  >;
+  [RESOLVERS_SYMBOL]?: Map<DependencyToken<unknown>, Provider<unknown>>;
+}
 /**
  * A producer of a dependency expresses this as a need that results in a promise
  * for the given dependency.
  */
 export function provide<T>(
-  host: ReactiveControllerHost & HTMLElement,
+  host: ReactiveControllerHost & HTMLElement & Registrations,
   dependency: DependencyToken<T>,
   provider: Provider<T>
 ) {
-  host.addController(new DependencyProvider<T>(host, dependency, provider));
+  const hostProviders = (host[PROVIDERS_SYMBOL] ||= new Map());
+  const oldController = hostProviders.get(dependency);
+  if (oldController) {
+    host.removeController(oldController);
+    oldController.hostDisconnected();
+  }
+  const controller = new DependencyProvider<T>(host, dependency, provider);
+  hostProviders.set(dependency, provider);
+  host.addController(controller);
 }
 
 /**
@@ -151,12 +170,18 @@
  * the injected value.
  */
 export function resolve<T>(
-  host: ReactiveControllerHost & HTMLElement,
+  host: ReactiveControllerHost & HTMLElement & Registrations,
   dependency: DependencyToken<T>
 ): Provider<T> {
-  const controller = new DependencySubscriber(host, dependency);
-  host.addController(controller);
-  return () => controller.get();
+  const hostResolvers = (host[RESOLVERS_SYMBOL] ||= new Map());
+  let resolver = hostResolvers.get(dependency);
+  if (!resolver) {
+    const controller = new DependencySubscriber(host, dependency);
+    host.addController(controller);
+    resolver = () => controller.get();
+    hostResolvers.set(dependency, resolver);
+  }
+  return resolver;
 }
 
 /**
diff --git a/polygerrit-ui/app/scripts/gr-reviewer-suggestions-provider/gr-reviewer-suggestions-provider.ts b/polygerrit-ui/app/scripts/gr-reviewer-suggestions-provider/gr-reviewer-suggestions-provider.ts
index d0f79f4..95e7f2a 100644
--- a/polygerrit-ui/app/scripts/gr-reviewer-suggestions-provider/gr-reviewer-suggestions-provider.ts
+++ b/polygerrit-ui/app/scripts/gr-reviewer-suggestions-provider/gr-reviewer-suggestions-provider.ts
@@ -28,25 +28,20 @@
   SuggestedReviewerInfo,
   Suggestion,
 } from '../../types/common';
-import {assertNever} from '../../utils/common-util';
+import {assertNever, intersection} from '../../utils/common-util';
 import {AutocompleteSuggestion} from '../../elements/shared/gr-autocomplete/gr-autocomplete';
+import {allSettled, isFulfilled} from '../../utils/async-util';
+import {notUndefined} from '../../types/types';
+import {accountKey} from '../../utils/account-util';
 
-// TODO(TS): enum name doesn't follow typescript style guid rules
+// TODO(TS): enum name doesn't follow typescript style guide rules
 // Rename it
 export enum SUGGESTIONS_PROVIDERS_USERS_TYPES {
   REVIEWER = 'reviewers',
   CC = 'ccs',
-  ANY = 'any',
 }
 
-export function isAccountSuggestions(s: Suggestion): s is AccountInfo {
-  return (s as AccountInfo)._account_id !== undefined;
-}
-
-type ApiCallCallback = (input: string) => Promise<Suggestion[] | void>;
-
 export interface ReviewerSuggestionsProvider {
-  init(): void;
   getSuggestions(input: string): Promise<Suggestion[]>;
   makeSuggestionItem(
     suggestion: Suggestion
@@ -56,66 +51,33 @@
 export class GrReviewerSuggestionsProvider
   implements ReviewerSuggestionsProvider
 {
-  static create(
-    restApi: RestApiService,
-    changeNumber: NumericChangeId,
-    userType: SUGGESTIONS_PROVIDERS_USERS_TYPES
+  private changeNumbers: NumericChangeId[];
+
+  constructor(
+    private restApi: RestApiService,
+    private type: SUGGESTIONS_PROVIDERS_USERS_TYPES,
+    private config: ServerInfo | undefined,
+    private loggedIn: boolean,
+    ...changeNumbers: NumericChangeId[]
   ) {
-    switch (userType) {
-      case SUGGESTIONS_PROVIDERS_USERS_TYPES.REVIEWER:
-        return new GrReviewerSuggestionsProvider(restApi, input =>
-          restApi.getChangeSuggestedReviewers(changeNumber, input)
-        );
-      case SUGGESTIONS_PROVIDERS_USERS_TYPES.CC:
-        return new GrReviewerSuggestionsProvider(restApi, input =>
-          restApi.getChangeSuggestedCCs(changeNumber, input)
-        );
-      case SUGGESTIONS_PROVIDERS_USERS_TYPES.ANY:
-        return new GrReviewerSuggestionsProvider(restApi, input =>
-          restApi.getSuggestedAccounts(`cansee:${changeNumber} ${input}`)
-        );
-      default:
-        throw new Error(`Unknown users type: ${userType}`);
-    }
+    this.changeNumbers = changeNumbers;
   }
 
-  private initPromise?: Promise<void>;
+  async getSuggestions(input: string): Promise<Suggestion[]> {
+    if (!this.loggedIn) return [];
 
-  config?: ServerInfo;
-
-  loggedIn = false;
-
-  private initialized = false;
-
-  private constructor(
-    private readonly _restAPI: RestApiService,
-    private readonly _apiCall: ApiCallCallback
-  ) {}
-
-  init() {
-    if (this.initPromise) {
-      return this.initPromise;
-    }
-    const getConfigPromise = this._restAPI.getConfig().then(cfg => {
-      this.config = cfg;
-    });
-    const getLoggedInPromise = this._restAPI.getLoggedIn().then(loggedIn => {
-      this.loggedIn = loggedIn;
-    });
-    this.initPromise = Promise.all([getConfigPromise, getLoggedInPromise]).then(
-      () => {
-        this.initialized = true;
-      }
+    const allResults = await allSettled(
+      this.changeNumbers.map(changeNumber =>
+        this.getSuggestionsForChange(changeNumber, input)
+      )
     );
-    return this.initPromise;
-  }
-
-  getSuggestions(input: string): Promise<Suggestion[]> {
-    if (!this.initialized || !this.loggedIn) {
-      return Promise.resolve([]);
-    }
-
-    return this._apiCall(input).then(reviewers => reviewers || []);
+    const allSuggestions = allResults
+      .filter(isFulfilled)
+      .map(result => result.value)
+      .filter(notUndefined);
+    return intersection(allSuggestions, (s1, s2) =>
+      this.areSameSuggestions(s1, s2)
+    );
   }
 
   makeSuggestionItem(
@@ -137,7 +99,7 @@
       };
     }
 
-    if (isAccountSuggestions(suggestion)) {
+    if (this.isAccountSuggestion(suggestion)) {
       // Reviewer is an account suggestion from getSuggestedAccounts.
       return {
         name: getAccountDisplayName(this.config, suggestion),
@@ -146,4 +108,28 @@
     }
     assertNever(suggestion, 'Received an incorrect suggestion');
   }
+
+  private getSuggestionsForChange(
+    changeNumber: NumericChangeId,
+    input: string
+  ): Promise<Suggestion[] | undefined> {
+    return this.type === SUGGESTIONS_PROVIDERS_USERS_TYPES.REVIEWER
+      ? this.restApi.getChangeSuggestedReviewers(changeNumber, input)
+      : this.restApi.getChangeSuggestedCCs(changeNumber, input);
+  }
+
+  private areSameSuggestions(a: Suggestion, b: Suggestion): boolean {
+    if (isReviewerAccountSuggestion(a) && isReviewerAccountSuggestion(b)) {
+      return accountKey(a.account) === accountKey(b.account);
+    } else if (isReviewerGroupSuggestion(a) && isReviewerGroupSuggestion(b)) {
+      return a.group.id === b.group.id;
+    } else if (this.isAccountSuggestion(a) && this.isAccountSuggestion(b)) {
+      return accountKey(a) === accountKey(b);
+    }
+    return false;
+  }
+
+  private isAccountSuggestion(s: Suggestion): s is AccountInfo {
+    return (s as AccountInfo)._account_id !== undefined;
+  }
 }
diff --git a/polygerrit-ui/app/scripts/gr-reviewer-suggestions-provider/gr-reviewer-suggestions-provider_test.ts b/polygerrit-ui/app/scripts/gr-reviewer-suggestions-provider/gr-reviewer-suggestions-provider_test.ts
index 757bcca..3d1a15f 100644
--- a/polygerrit-ui/app/scripts/gr-reviewer-suggestions-provider/gr-reviewer-suggestions-provider_test.ts
+++ b/polygerrit-ui/app/scripts/gr-reviewer-suggestions-provider/gr-reviewer-suggestions-provider_test.ts
@@ -23,237 +23,192 @@
 import {getAppContext} from '../../services/app-context';
 import {stubRestApi} from '../../test/test-utils';
 import {
-  AccountId,
-  AccountInfo,
   ChangeInfo,
-  EmailAddress,
   GroupId,
   GroupName,
   NumericChangeId,
 } from '../../api/rest-api';
-import {SuggestedReviewerInfo} from '../../types/common';
-import {createChange, createServerInfo} from '../../test/test-data-generators';
+import {
+  SuggestedReviewerAccountInfo,
+  SuggestedReviewerGroupInfo,
+} from '../../types/common';
+import {
+  createAccountDetailWithIdNameAndEmail,
+  createChange,
+  createServerInfo,
+} from '../../test/test-data-generators';
 
 suite('GrReviewerSuggestionsProvider tests', () => {
-  let _nextAccountId = 0;
-  function makeAccount(opt_status?: string): AccountInfo {
-    const accountId = ++_nextAccountId;
-    return {
-      _account_id: accountId as AccountId,
-      name: `name ${accountId}`,
-      email: `email ${accountId}` as EmailAddress,
-      status: opt_status,
-    };
-  }
-  let _nextAccountId2 = 0;
-  function makeAccount2(opt_status?: string): AccountInfo {
-    const accountId2 = ++_nextAccountId2;
-    return {
-      _account_id: accountId2 as AccountId,
-      name: `name ${accountId2}`,
-      status: opt_status,
-    };
-  }
-
-  let owner: AccountInfo;
-  let existingReviewer1: AccountInfo;
-  let existingReviewer2: AccountInfo;
-  let suggestion1: SuggestedReviewerInfo;
-  let suggestion2: SuggestedReviewerInfo;
-  let suggestion3: SuggestedReviewerInfo;
+  const suggestion1: SuggestedReviewerAccountInfo = {
+    account: createAccountDetailWithIdNameAndEmail(3),
+    count: 1,
+  };
+  const suggestion2: SuggestedReviewerAccountInfo = {
+    account: createAccountDetailWithIdNameAndEmail(4),
+    count: 1,
+  };
+  const suggestion3: SuggestedReviewerGroupInfo = {
+    group: {
+      id: 'suggested group id' as GroupId,
+      name: 'suggested group' as GroupName,
+    },
+    count: 4,
+  };
+  const change: ChangeInfo = createChange();
+  let getChangeSuggestedReviewersStub: sinon.SinonStub;
+  let getChangeSuggestedCCsStub: sinon.SinonStub;
   let provider: GrReviewerSuggestionsProvider;
 
-  let redundantSuggestion1: SuggestedReviewerInfo;
-  let redundantSuggestion2: SuggestedReviewerInfo;
-  let redundantSuggestion3: SuggestedReviewerInfo;
-  let change: ChangeInfo;
-
-  setup(async () => {
-    owner = makeAccount();
-    existingReviewer1 = makeAccount();
-    existingReviewer2 = makeAccount();
-    suggestion1 = {account: makeAccount(), count: 1};
-    suggestion2 = {account: makeAccount(), count: 1};
-    suggestion3 = {
-      group: {
-        id: 'suggested group id' as GroupId,
-        name: 'suggested group' as GroupName,
-      },
-      count: 1,
-    };
-
-    stubRestApi('getConfig').resolves(createServerInfo());
-
-    change = {
-      ...createChange(),
-      _number: 42 as NumericChangeId,
-      owner,
-      reviewers: {
-        CC: [existingReviewer1],
-        REVIEWER: [existingReviewer2],
-      },
-    };
-
-    await flush();
+  setup(() => {
+    getChangeSuggestedReviewersStub = stubRestApi(
+      'getChangeSuggestedReviewers'
+    ).resolves([suggestion1, suggestion2, suggestion3]);
+    getChangeSuggestedCCsStub = stubRestApi('getChangeSuggestedCCs').resolves([
+      suggestion1,
+      suggestion2,
+      suggestion3,
+    ]);
+    provider = new GrReviewerSuggestionsProvider(
+      getAppContext().restApiService,
+      SUGGESTIONS_PROVIDERS_USERS_TYPES.REVIEWER,
+      createServerInfo(),
+      true,
+      change._number
+    );
   });
 
-  suite('allowAnyUser set to false', () => {
-    setup(async () => {
-      provider = GrReviewerSuggestionsProvider.create(
-        getAppContext().restApiService,
-        change._number,
-        SUGGESTIONS_PROVIDERS_USERS_TYPES.REVIEWER
-      );
-      await provider.init();
-    });
-    suite('stubbed values for _getReviewerSuggestions', () => {
-      let getChangeSuggestedReviewersStub: sinon.SinonStub;
-      setup(() => {
-        getChangeSuggestedReviewersStub = stubRestApi(
-          'getChangeSuggestedReviewers'
-        ).callsFake(() => {
-          redundantSuggestion1 = {account: existingReviewer1, count: 1};
-          redundantSuggestion2 = {account: existingReviewer2, count: 1};
-          redundantSuggestion3 = {account: owner, count: 1};
-          return Promise.resolve([
-            redundantSuggestion1,
-            redundantSuggestion2,
-            redundantSuggestion3,
-            suggestion1,
-            suggestion2,
-            suggestion3,
-          ]);
-        });
-      });
+  test('getSuggestions', async () => {
+    const reviewers = await provider.getSuggestions('');
 
-      test('makeSuggestionItem formats account or group accordingly', () => {
-        let account = makeAccount();
-        const account3 = makeAccount2();
-        let suggestion = provider.makeSuggestionItem({account, count: 1});
-        assert.deepEqual(suggestion, {
-          name: `${account.name} <${account.email}>`,
-          value: {account, count: 1},
-        });
-
-        const group = {name: 'test' as GroupName, id: '5' as GroupId};
-        suggestion = provider.makeSuggestionItem({group, count: 1});
-        assert.deepEqual(suggestion, {
-          name: `${group.name} (group)`,
-          value: {group, count: 1},
-        });
-
-        suggestion = provider.makeSuggestionItem(account);
-        assert.deepEqual(suggestion, {
-          name: `${account.name} <${account.email}>`,
-          value: {account, count: 1},
-        });
-
-        suggestion = provider.makeSuggestionItem({account: {}, count: 1});
-        assert.deepEqual(suggestion, {
-          name: 'Name of user not set',
-          value: {account: {}, count: 1},
-        });
-
-        provider.config = {
-          ...createServerInfo(),
-          user: {
-            anonymous_coward_name: 'Anonymous Coward Name',
-          },
-        };
-
-        suggestion = provider.makeSuggestionItem({account: {}, count: 1});
-        assert.deepEqual(suggestion, {
-          name: 'Anonymous Coward Name',
-          value: {account: {}, count: 1},
-        });
-
-        account = makeAccount('OOO');
-
-        suggestion = provider.makeSuggestionItem({account, count: 1});
-        assert.deepEqual(suggestion, {
-          name: `${account.name} <${account.email}> (OOO)`,
-          value: {account, count: 1},
-        });
-
-        suggestion = provider.makeSuggestionItem(account);
-        assert.deepEqual(suggestion, {
-          name: `${account.name} <${account.email}> (OOO)`,
-          value: {account, count: 1},
-        });
-
-        account3.email = undefined;
-
-        suggestion = provider.makeSuggestionItem(account3);
-        assert.deepEqual(suggestion, {
-          name: account3.name,
-          value: {account: account3, count: 1},
-        });
-      });
-
-      test('getSuggestions', async () => {
-        const reviewers = await provider.getSuggestions('');
-
-        // Default is no filtering.
-        assert.equal(reviewers.length, 6);
-        assert.deepEqual(reviewers, [
-          redundantSuggestion1,
-          redundantSuggestion2,
-          redundantSuggestion3,
-          suggestion1,
-          suggestion2,
-          suggestion3,
-        ]);
-      });
-
-      test('getSuggestions short circuits when logged out', () => {
-        provider.loggedIn = false;
-        return provider.getSuggestions('').then(() => {
-          assert.isFalse(getChangeSuggestedReviewersStub.called);
-          provider.loggedIn = true;
-          return provider.getSuggestions('').then(() => {
-            assert.isTrue(getChangeSuggestedReviewersStub.called);
-          });
-        });
-      });
-    });
-
-    test('getChangeSuggestedReviewers is used', async () => {
-      const suggestReviewerStub = stubRestApi(
-        'getChangeSuggestedReviewers'
-      ).returns(Promise.resolve([]));
-      const suggestAccountStub = stubRestApi('getSuggestedAccounts').returns(
-        Promise.resolve([])
-      );
-
-      await provider.getSuggestions('');
-      assert.isTrue(suggestReviewerStub.calledOnce);
-      assert.isTrue(suggestReviewerStub.calledWith(42 as NumericChangeId, ''));
-      assert.isFalse(suggestAccountStub.called);
-    });
+    assert.sameDeepMembers(reviewers, [suggestion1, suggestion2, suggestion3]);
   });
 
-  suite('allowAnyUser set to true', () => {
-    setup(async () => {
-      provider = GrReviewerSuggestionsProvider.create(
-        getAppContext().restApiService,
-        change._number,
-        SUGGESTIONS_PROVIDERS_USERS_TYPES.ANY
-      );
-      await provider.init();
+  test('getSuggestions short circuits when logged out', async () => {
+    await provider.getSuggestions('');
+    assert.isTrue(getChangeSuggestedReviewersStub.calledOnce);
+
+    // not logged in
+    provider = new GrReviewerSuggestionsProvider(
+      getAppContext().restApiService,
+      SUGGESTIONS_PROVIDERS_USERS_TYPES.REVIEWER,
+      createServerInfo(),
+      false,
+      change._number
+    );
+
+    await provider.getSuggestions('');
+
+    // no additional call is made
+    assert.isTrue(getChangeSuggestedReviewersStub.calledOnce);
+  });
+
+  test('only returns REVIEWER suggestions shared by all changes', async () => {
+    getChangeSuggestedReviewersStub
+      .onSecondCall()
+      .resolves([suggestion2, suggestion3]);
+    provider = new GrReviewerSuggestionsProvider(
+      getAppContext().restApiService,
+      SUGGESTIONS_PROVIDERS_USERS_TYPES.REVIEWER,
+      createServerInfo(),
+      true,
+      ...[change._number, 43 as NumericChangeId]
+    );
+
+    // suggestion1 is excluded because it is not returned for the second
+    // change.
+    assert.sameDeepMembers(await provider.getSuggestions('s'), [
+      suggestion2,
+      suggestion3,
+    ]);
+  });
+
+  test('only returns CC suggestions shared by all changes', async () => {
+    getChangeSuggestedCCsStub
+      .onSecondCall()
+      .resolves([suggestion2, suggestion3]);
+    provider = new GrReviewerSuggestionsProvider(
+      getAppContext().restApiService,
+      SUGGESTIONS_PROVIDERS_USERS_TYPES.CC,
+      createServerInfo(),
+      true,
+      ...[change._number, 43 as NumericChangeId]
+    );
+
+    // suggestion1 is excluded because it is not returned for the second
+    // change.
+    assert.sameDeepMembers(await provider.getSuggestions('s'), [
+      suggestion2,
+      suggestion3,
+    ]);
+  });
+
+  test('makeSuggestionItem formats account or group accordingly', () => {
+    let account = createAccountDetailWithIdNameAndEmail(1);
+    const account3 = createAccountDetailWithIdNameAndEmail(2);
+    let suggestion = provider.makeSuggestionItem({account, count: 1});
+    assert.deepEqual(suggestion, {
+      name: `${account.name} <${account.email}>`,
+      value: {account, count: 1},
     });
 
-    test('getSuggestedAccounts is used', async () => {
-      const suggestReviewerStub = stubRestApi(
-        'getChangeSuggestedReviewers'
-      ).returns(Promise.resolve([]));
-      const suggestAccountStub = stubRestApi('getSuggestedAccounts').returns(
-        Promise.resolve([])
-      );
+    const group = {name: 'test' as GroupName, id: '5' as GroupId};
+    suggestion = provider.makeSuggestionItem({group, count: 1});
+    assert.deepEqual(suggestion, {
+      name: `${group.name} (group)`,
+      value: {group, count: 1},
+    });
 
-      await provider.getSuggestions('');
-      assert.isFalse(suggestReviewerStub.called);
-      assert.isTrue(suggestAccountStub.calledOnce);
-      assert.isTrue(suggestAccountStub.calledWith('cansee:42 '));
+    suggestion = provider.makeSuggestionItem(account);
+    assert.deepEqual(suggestion, {
+      name: `${account.name} <${account.email}>`,
+      value: {account, count: 1},
+    });
+
+    suggestion = provider.makeSuggestionItem({account: {}, count: 1});
+    assert.deepEqual(suggestion, {
+      name: 'Name of user not set',
+      value: {account: {}, count: 1},
+    });
+
+    provider = new GrReviewerSuggestionsProvider(
+      getAppContext().restApiService,
+      SUGGESTIONS_PROVIDERS_USERS_TYPES.REVIEWER,
+      {
+        ...createServerInfo(),
+        user: {
+          anonymous_coward_name: 'Anonymous Coward Name',
+        },
+      },
+      true,
+      change._number
+    );
+
+    suggestion = provider.makeSuggestionItem({account: {}, count: 1});
+    assert.deepEqual(suggestion, {
+      name: 'Anonymous Coward Name',
+      value: {account: {}, count: 1},
+    });
+
+    account = {...createAccountDetailWithIdNameAndEmail(3), status: 'OOO'};
+
+    suggestion = provider.makeSuggestionItem({account, count: 1});
+    assert.deepEqual(suggestion, {
+      name: `${account.name} <${account.email}> (OOO)`,
+      value: {account, count: 1},
+    });
+
+    suggestion = provider.makeSuggestionItem(account);
+    assert.deepEqual(suggestion, {
+      name: `${account.name} <${account.email}> (OOO)`,
+      value: {account, count: 1},
+    });
+
+    account3.email = undefined;
+
+    suggestion = provider.makeSuggestionItem(account3);
+    assert.deepEqual(suggestion, {
+      name: account3.name,
+      value: {account: account3, count: 1},
     });
   });
 });
diff --git a/polygerrit-ui/app/utils/async-util.ts b/polygerrit-ui/app/utils/async-util.ts
index 43fd6f5..981bcae 100644
--- a/polygerrit-ui/app/utils/async-util.ts
+++ b/polygerrit-ui/app/utils/async-util.ts
@@ -147,12 +147,18 @@
 
 export const isFalse = (b: boolean) => b === false;
 
-// An equivalent to Promise.allSettled from ES2020.
-// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise/allSettled
-// TODO: Migrate our tooling to ES2020 and remove this method.
 export type PromiseResult<T> =
   | {status: 'fulfilled'; value: T}
   | {status: 'rejected'; reason: string};
+export function isFulfilled<T>(
+  promiseResult?: PromiseResult<T>
+): promiseResult is PromiseResult<T> & {status: 'fulfilled'} {
+  return promiseResult?.status === 'fulfilled';
+}
+
+// An equivalent to Promise.allSettled from ES2020.
+// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise/allSettled
+// TODO: Migrate our tooling to ES2020 and remove this method.
 export function allSettled<T>(
   promises: Promise<T>[]
 ): Promise<PromiseResult<T>[]> {
diff --git a/polygerrit-ui/app/utils/common-util.ts b/polygerrit-ui/app/utils/common-util.ts
index 9e3bc74..6ccf770 100644
--- a/polygerrit-ui/app/utils/common-util.ts
+++ b/polygerrit-ui/app/utils/common-util.ts
@@ -156,3 +156,22 @@
 export function unique<T>(item: T, index: number, array: T[]) {
   return array.indexOf(item) === index;
 }
+
+/**
+ * Returns the elements that are present in every sub-array. If a compareBy
+ * predicate is passed in, it will be used instead of strict equality.
+ */
+export function intersection<T>(
+  arrays: T[][],
+  compareBy: (t: T, u: T) => boolean = (t, u) => t === u
+): T[] {
+  // Array.prototype.reduce needs either an initialValue or a non-empty array.
+  // Since there is no good initialValue for intersecting (∅ ∩ X = ∅), the
+  // empty array must be checked separately.
+  if (arrays.length === 0) {
+    return [];
+  }
+  return arrays.reduce((result, array) =>
+    result.filter(t => array.find(u => compareBy(t, u)))
+  );
+}
diff --git a/polygerrit-ui/app/utils/common-util_test.ts b/polygerrit-ui/app/utils/common-util_test.ts
index 4156729..8cc523a 100644
--- a/polygerrit-ui/app/utils/common-util_test.ts
+++ b/polygerrit-ui/app/utils/common-util_test.ts
@@ -16,7 +16,12 @@
  */
 
 import '../test/common-test-setup-karma';
-import {hasOwnProperty, areSetsEqual, containsAll} from './common-util';
+import {
+  hasOwnProperty,
+  areSetsEqual,
+  containsAll,
+  intersection,
+} from './common-util';
 
 suite('common-util tests', () => {
   suite('hasOwnProperty', () => {
@@ -68,4 +73,28 @@
     assert.isFalse(containsAll(new Set([1, 2, 3, 4]), new Set([5])));
     assert.isFalse(containsAll(new Set([1, 2, 3, 4]), new Set([1, 2, 3, 5])));
   });
+
+  test('intersections', () => {
+    assert.sameDeepMembers(intersection([]), []);
+    assert.sameDeepMembers(intersection([[1, 2, 3]]), [1, 2, 3]);
+    assert.sameDeepMembers(
+      intersection([
+        [1, 2, 3],
+        [2, 3, 4],
+        [5, 3, 2],
+      ]),
+      [2, 3]
+    );
+
+    const foo1 = {value: 5};
+    const foo2 = {value: 5};
+
+    // these foo's will fail strict equality with each other, but a comparator
+    // can make them intersect.
+    assert.sameDeepMembers(intersection([[foo1], [foo2]]), []);
+    assert.sameDeepMembers(
+      intersection([[foo1], [foo2]], (a, b) => a.value === b.value),
+      [foo1]
+    );
+  });
 });