diff --git a/lib/selectors/thread-selectors.js b/lib/selectors/thread-selectors.js
--- a/lib/selectors/thread-selectors.js
+++ b/lib/selectors/thread-selectors.js
@@ -55,7 +55,6 @@
   RelativeMemberInfo,
   MixedRawThreadInfos,
   RawThreadInfos,
-  LegacyThreadInfo,
 } from '../types/thread-types.js';
 import { dateString, dateFromString } from '../utils/date-utils.js';
 import { values } from '../utils/objects.js';
@@ -63,7 +62,7 @@
 const _mapValuesWithKeys = _mapValues.convert({ cap: false });
 
 type ThreadInfoSelectorType = (state: BaseAppState<>) => {
-  +[id: string]: LegacyThreadInfo | ThreadInfo,
+  +[id: string]: ThreadInfo,
 };
 const threadInfoSelector: ThreadInfoSelectorType = createObjectSelector(
   (state: BaseAppState<>) => state.threadStore.threadInfos,
@@ -74,9 +73,9 @@
 
 const communityThreadSelector: (
   state: BaseAppState<>,
-) => $ReadOnlyArray<LegacyThreadInfo | ThreadInfo> = createSelector(
+) => $ReadOnlyArray<ThreadInfo> = createSelector(
   threadInfoSelector,
-  (threadInfos: { +[id: string]: LegacyThreadInfo | ThreadInfo }) => {
+  (threadInfos: { +[id: string]: ThreadInfo }) => {
     const result = [];
     for (const threadID in threadInfos) {
       const threadInfo = threadInfos[threadID];
@@ -91,9 +90,9 @@
 
 const canBeOnScreenThreadInfos: (
   state: BaseAppState<>,
-) => $ReadOnlyArray<LegacyThreadInfo | ThreadInfo> = createSelector(
+) => $ReadOnlyArray<ThreadInfo> = createSelector(
   threadInfoSelector,
-  (threadInfos: { +[id: string]: LegacyThreadInfo | ThreadInfo }) => {
+  (threadInfos: { +[id: string]: ThreadInfo }) => {
     const result = [];
     for (const threadID in threadInfos) {
       const threadInfo = threadInfos[threadID];
@@ -108,13 +107,13 @@
 
 const onScreenThreadInfos: (
   state: BaseAppState<>,
-) => $ReadOnlyArray<LegacyThreadInfo | ThreadInfo> = createSelector(
+) => $ReadOnlyArray<ThreadInfo> = createSelector(
   filteredThreadIDsSelector,
   canBeOnScreenThreadInfos,
   (
     inputThreadIDs: ?$ReadOnlySet<string>,
-    threadInfos: $ReadOnlyArray<LegacyThreadInfo | ThreadInfo>,
-  ): $ReadOnlyArray<LegacyThreadInfo | ThreadInfo> => {
+    threadInfos: $ReadOnlyArray<ThreadInfo>,
+  ): $ReadOnlyArray<ThreadInfo> => {
     const threadIDs = inputThreadIDs;
     if (!threadIDs) {
       return threadInfos;
@@ -125,11 +124,9 @@
 
 const onScreenEntryEditableThreadInfos: (
   state: BaseAppState<>,
-) => $ReadOnlyArray<LegacyThreadInfo | ThreadInfo> = createSelector(
+) => $ReadOnlyArray<ThreadInfo> = createSelector(
   onScreenThreadInfos,
-  (
-    threadInfos: $ReadOnlyArray<LegacyThreadInfo | ThreadInfo>,
-  ): $ReadOnlyArray<LegacyThreadInfo | ThreadInfo> =>
+  (threadInfos: $ReadOnlyArray<ThreadInfo>): $ReadOnlyArray<ThreadInfo> =>
     threadInfos.filter(threadInfo =>
       threadHasPermission(threadInfo, threadPermissions.EDIT_ENTRIES),
     ),
@@ -160,7 +157,7 @@
     daysToEntries: { +[day: string]: string[] },
     startDateString: string,
     endDateString: string,
-    onScreen: $ReadOnlyArray<LegacyThreadInfo | ThreadInfo>,
+    onScreen: $ReadOnlyArray<ThreadInfo>,
     includeDeleted: boolean,
   ) => {
     const allDaysWithinRange: { [string]: string[] } = {},
@@ -189,12 +186,12 @@
 );
 
 const childThreadInfos: (state: BaseAppState<>) => {
-  +[id: string]: $ReadOnlyArray<LegacyThreadInfo | ThreadInfo>,
+  +[id: string]: $ReadOnlyArray<ThreadInfo>,
 } = createSelector(
   threadInfoSelector,
-  (threadInfos: { +[id: string]: LegacyThreadInfo | ThreadInfo }) => {
+  (threadInfos: { +[id: string]: ThreadInfo }) => {
     const result: {
-      [string]: (LegacyThreadInfo | ThreadInfo)[],
+      [string]: ThreadInfo[],
     } = {};
     for (const id in threadInfos) {
       const threadInfo = threadInfos[id];
@@ -203,7 +200,7 @@
         continue;
       }
       if (result[parentThreadID] === undefined) {
-        result[parentThreadID] = ([]: (LegacyThreadInfo | ThreadInfo)[]);
+        result[parentThreadID] = ([]: ThreadInfo[]);
       }
       result[parentThreadID].push(threadInfo);
     }
@@ -212,12 +209,12 @@
 );
 
 const containedThreadInfos: (state: BaseAppState<>) => {
-  +[id: string]: $ReadOnlyArray<LegacyThreadInfo | ThreadInfo>,
+  +[id: string]: $ReadOnlyArray<ThreadInfo>,
 } = createSelector(
   threadInfoSelector,
-  (threadInfos: { +[id: string]: LegacyThreadInfo | ThreadInfo }) => {
+  (threadInfos: { +[id: string]: ThreadInfo }) => {
     const result: {
-      [string]: (LegacyThreadInfo | ThreadInfo)[],
+      [string]: ThreadInfo[],
     } = {};
     for (const id in threadInfos) {
       const threadInfo = threadInfos[id];
@@ -226,7 +223,7 @@
         continue;
       }
       if (result[containingThreadID] === undefined) {
-        result[containingThreadID] = ([]: (LegacyThreadInfo | ThreadInfo)[]);
+        result[containingThreadID] = ([]: ThreadInfo[]);
       }
       result[containingThreadID].push(threadInfo);
     }
@@ -235,7 +232,7 @@
 );
 
 function getMostRecentRawMessageInfo(
-  threadInfo: LegacyThreadInfo | ThreadInfo,
+  threadInfo: ThreadInfo,
   messageStore: MessageStore,
 ): ?RawMessageInfo {
   const thread = messageStore.threads[threadInfo.id];
@@ -253,10 +250,7 @@
 } = createObjectSelector(
   childThreadInfos,
   (state: BaseAppState<>) => state.messageStore,
-  (
-    childThreads: $ReadOnlyArray<LegacyThreadInfo | ThreadInfo>,
-    messageStore: MessageStore,
-  ) => {
+  (childThreads: $ReadOnlyArray<ThreadInfo>, messageStore: MessageStore) => {
     const sidebarInfos = [];
     for (const childThreadInfo of childThreads) {
       if (
@@ -326,16 +320,14 @@
 
 const baseAncestorThreadInfos: (
   threadID: string,
-) => (BaseAppState<>) => $ReadOnlyArray<LegacyThreadInfo | ThreadInfo> = (
-  threadID: string,
-) =>
+) => (BaseAppState<>) => $ReadOnlyArray<ThreadInfo> = (threadID: string) =>
   createSelector(
     (state: BaseAppState<>) => threadInfoSelector(state),
     (threadInfos: {
-      +[id: string]: LegacyThreadInfo | ThreadInfo,
-    }): $ReadOnlyArray<LegacyThreadInfo | ThreadInfo> => {
-      const pathComponents: (LegacyThreadInfo | ThreadInfo)[] = [];
-      let node: ?(LegacyThreadInfo | ThreadInfo) = threadInfos[threadID];
+      +[id: string]: ThreadInfo,
+    }): $ReadOnlyArray<ThreadInfo> => {
+      const pathComponents: ThreadInfo[] = [];
+      let node: ?ThreadInfo = threadInfos[threadID];
       while (node) {
         pathComponents.push(node);
         node = node.parentThreadID ? threadInfos[node.parentThreadID] : null;
@@ -347,8 +339,9 @@
 
 const ancestorThreadInfos: (
   threadID: string,
-) => (state: BaseAppState<>) => $ReadOnlyArray<LegacyThreadInfo | ThreadInfo> =
-  _memoize(baseAncestorThreadInfos);
+) => (state: BaseAppState<>) => $ReadOnlyArray<ThreadInfo> = _memoize(
+  baseAncestorThreadInfos,
+);
 
 const baseOtherUsersButNoOtherAdmins: (
   threadID: string,
@@ -428,19 +421,19 @@
   );
 
 const threadInfoFromSourceMessageIDSelector: (state: BaseAppState<>) => {
-  +[id: string]: LegacyThreadInfo | ThreadInfo,
+  +[id: string]: ThreadInfo,
 } = createSelector(
   (state: BaseAppState<>) => state.threadStore.threadInfos,
   threadInfoSelector,
   (
     rawThreadInfos: RawThreadInfos,
     threadInfos: {
-      +[id: string]: LegacyThreadInfo | ThreadInfo,
+      +[id: string]: ThreadInfo,
     },
   ) => {
     const pendingToRealizedThreadIDs =
       pendingToRealizedThreadIDsSelector(rawThreadInfos);
-    const result: { [string]: LegacyThreadInfo | ThreadInfo } = {};
+    const result: { [string]: ThreadInfo } = {};
     for (const realizedID of pendingToRealizedThreadIDs.values()) {
       const threadInfo = threadInfos[realizedID];
       if (threadInfo && threadInfo.sourceMessageID) {
@@ -496,10 +489,7 @@
     (state: BaseAppState<>) => threadInfoSelector(state)[threadID],
     (state: BaseAppState<>) =>
       containingThreadID ? threadInfoSelector(state)[containingThreadID] : null,
-    (
-      threadInfo: LegacyThreadInfo | ThreadInfo,
-      containingThreadInfo: ?(LegacyThreadInfo | ThreadInfo),
-    ) => {
+    (threadInfo: ThreadInfo, containingThreadInfo: ?ThreadInfo) => {
       return () => {
         let threadAvatar = getAvatarForThread(threadInfo, containingThreadInfo);
         if (threadAvatar.type !== 'emoji') {
@@ -519,14 +509,14 @@
 
 const baseThreadInfosSelectorForThreadType: (
   threadType: ThreadType,
-) => (BaseAppState<>) => $ReadOnlyArray<LegacyThreadInfo | ThreadInfo> = (
+) => (BaseAppState<>) => $ReadOnlyArray<ThreadInfo> = (
   threadType: ThreadType,
 ) =>
   createSelector(
     (state: BaseAppState<>) => threadInfoSelector(state),
     (threadInfos: {
-      +[id: string]: LegacyThreadInfo | ThreadInfo,
-    }): $ReadOnlyArray<LegacyThreadInfo | ThreadInfo> => {
+      +[id: string]: ThreadInfo,
+    }): $ReadOnlyArray<ThreadInfo> => {
       const result = [];
 
       for (const threadID in threadInfos) {
@@ -542,8 +532,9 @@
 
 const threadInfosSelectorForThreadType: (
   threadType: ThreadType,
-) => (state: BaseAppState<>) => $ReadOnlyArray<LegacyThreadInfo | ThreadInfo> =
-  _memoize(baseThreadInfosSelectorForThreadType);
+) => (state: BaseAppState<>) => $ReadOnlyArray<ThreadInfo> = _memoize(
+  baseThreadInfosSelectorForThreadType,
+);
 
 export {
   ancestorThreadInfos,