diff --git a/lib/reducers/message-reducer.js b/lib/reducers/message-reducer.js
--- a/lib/reducers/message-reducer.js
+++ b/lib/reducers/message-reducer.js
@@ -1391,7 +1391,11 @@
         };
       }
       reduxMessageIDsToPrune.push(...removed);
-      if (!newThreadInfos[threadID]?.thick) {
+      const threadType = newThreadInfos[threadID]?.type;
+      if (
+        threadType &&
+        threadSpecs[threadType].protocol.messagesStoredOnServer
+      ) {
         dbMessageIDsToPrune.push(...removed);
       }
 
diff --git a/lib/reducers/thread-reducer.js b/lib/reducers/thread-reducer.js
--- a/lib/reducers/thread-reducer.js
+++ b/lib/reducers/thread-reducer.js
@@ -350,7 +350,7 @@
         continue;
       }
 
-      if (threadInfo.thick) {
+      if (threadInfo.timestamps) {
         if (threadInfo.timestamps.currentUser.unread > mostRecentTime) {
           continue;
         }
diff --git a/lib/shared/dm-ops/delete-entry-spec.js b/lib/shared/dm-ops/delete-entry-spec.js
--- a/lib/shared/dm-ops/delete-entry-spec.js
+++ b/lib/shared/dm-ops/delete-entry-spec.js
@@ -56,7 +56,10 @@
     const { rawMessageInfo } = messageDataWithMessageInfos;
     const rawMessageInfos = [rawMessageInfo];
 
-    invariant(rawEntryInfo?.thick, 'Entry thread should be thick');
+    invariant(
+      rawEntryInfo?.lastUpdatedTime,
+      'Entry should have lastUpdatedTime',
+    );
     const timestamp = rawEntryInfo.lastUpdatedTime;
 
     const notificationsCreationData = {
diff --git a/lib/shared/dm-ops/dm-op-utils.js b/lib/shared/dm-ops/dm-op-utils.js
--- a/lib/shared/dm-ops/dm-op-utils.js
+++ b/lib/shared/dm-ops/dm-op-utils.js
@@ -410,7 +410,7 @@
     const time = Math.max(
       messagesAffectingUnreadStatus.map(message => message.time),
     );
-    invariant(threadInfo.thick, 'Thread should be thick');
+    invariant(threadInfo.timestamps, 'Thread should have timestamps');
 
     if (threadInfo.timestamps.currentUser.unread < time) {
       newUpdateInfos.push({
diff --git a/lib/shared/dm-ops/edit-entry-spec.js b/lib/shared/dm-ops/edit-entry-spec.js
--- a/lib/shared/dm-ops/edit-entry-spec.js
+++ b/lib/shared/dm-ops/edit-entry-spec.js
@@ -57,7 +57,10 @@
     const { rawMessageInfo } = messageDataWithMessageInfos;
     const rawMessageInfos = [rawMessageInfo];
 
-    invariant(rawEntryInfo?.thick, 'Entry should be thick');
+    invariant(
+      rawEntryInfo?.lastUpdatedTime,
+      'Entry should have lastUpdatedTime',
+    );
     const timestamp = rawEntryInfo.lastUpdatedTime;
 
     const notificationsCreationData = {
diff --git a/lib/shared/updates/update-thread-read-status-spec.js b/lib/shared/updates/update-thread-read-status-spec.js
--- a/lib/shared/updates/update-thread-read-status-spec.js
+++ b/lib/shared/updates/update-thread-read-status-spec.js
@@ -34,7 +34,7 @@
     const storeThreadInfo = storeThreadInfos[update.threadID];
 
     let updatedThread;
-    if (storeThreadInfo.thick) {
+    if (storeThreadInfo.timestamps) {
       updatedThread = {
         ...storeThreadInfo,
         currentUser: {
diff --git a/web/modals/history/history-modal.react.js b/web/modals/history/history-modal.react.js
--- a/web/modals/history/history-modal.react.js
+++ b/web/modals/history/history-modal.react.js
@@ -18,6 +18,7 @@
 import { useModalContext } from 'lib/components/modal-provider.react.js';
 import { nonExcludeDeletedCalendarFiltersSelector } from 'lib/selectors/calendar-filter-selectors.js';
 import { createLoadingStatusSelector } from 'lib/selectors/loading-selectors.js';
+import { threadSpecs } from 'lib/shared/threads/thread-specs.js';
 import type {
   EntryInfo,
   CalendarQuery,
@@ -117,10 +118,13 @@
     const threadInfos = this.props.threadInfos;
     if (entryInfos) {
       entries = _flow(
-        _filter(
-          (entryInfo: EntryInfo) =>
-            entryInfo.id && !threadInfos?.[entryInfo.threadID].thick,
-        ),
+        _filter((entryInfo: EntryInfo) => {
+          const threadType = threadInfos?.[entryInfo.threadID].type;
+          const supportsCalendarHistory =
+            !threadType ||
+            threadSpecs[threadType].protocol.supportsCalendarHistory;
+          return entryInfo.id && supportsCalendarHistory;
+        }),
         _map((entryInfo: EntryInfo) => {
           const serverID = entryInfo.id;
           invariant(serverID, 'serverID should be set');