diff --git a/plugins/chat/assets/javascripts/discourse/components/chat/thread-list.js b/plugins/chat/assets/javascripts/discourse/components/chat/thread-list.js
index 00347e08e1d..c3d572d5560 100644
--- a/plugins/chat/assets/javascripts/discourse/components/chat/thread-list.js
+++ b/plugins/chat/assets/javascripts/discourse/components/chat/thread-list.js
@@ -19,7 +19,10 @@ export default class ChatThreadList extends Component {
   // are sent to the thread, and we want the list to react in realtime to this.
   get sortedThreads() {
     return this.threadsManager.threads
-      .filter((thread) => !thread.originalMessage.deletedAt)
+      .filter(
+        (thread) =>
+          thread.currentUserMembership && !thread.originalMessage.deletedAt
+      )
       .sort((threadA, threadB) => {
         // If both are unread we just want to sort by last reply date + time descending.
         if (threadA.tracking.unreadCount && threadB.tracking.unreadCount) {
diff --git a/plugins/chat/assets/javascripts/discourse/lib/chat-threads-manager.js b/plugins/chat/assets/javascripts/discourse/lib/chat-threads-manager.js
index f2c1d565232..c890616e166 100644
--- a/plugins/chat/assets/javascripts/discourse/lib/chat-threads-manager.js
+++ b/plugins/chat/assets/javascripts/discourse/lib/chat-threads-manager.js
@@ -66,6 +66,10 @@ export default class ChatThreadsManager {
     }
   }
 
+  remove(threadObject) {
+    delete this._cached[threadObject.id];
+  }
+
   add(channel, threadObject, options = {}) {
     let model;
 
diff --git a/plugins/chat/assets/javascripts/discourse/services/chat-pane-base-subscriptions-manager.js b/plugins/chat/assets/javascripts/discourse/services/chat-pane-base-subscriptions-manager.js
index c4f2b4bb9ff..27f42257b3f 100644
--- a/plugins/chat/assets/javascripts/discourse/services/chat-pane-base-subscriptions-manager.js
+++ b/plugins/chat/assets/javascripts/discourse/services/chat-pane-base-subscriptions-manager.js
@@ -231,6 +231,16 @@ export default class ChatPaneBaseSubscriptionsManager extends Service {
           stagedThread.id = data.thread_id;
           stagedThread.originalMessage.thread = stagedThread;
           stagedThread.originalMessage.thread.preview.replyCount ??= 1;
+
+          // We have to do this because the thread manager cache is keyed by
+          // staged_thread_id, but the thread_id is what we want to use to
+          // look up the thread, otherwise calls to .find() will not return
+          // the thread by its actual ID, and we will end up with double-ups
+          // in places like the thread list when .add() is called.
+          this.model.threadsManager.remove({ id: data.staged_thread_id });
+          this.model.threadsManager.add(this.model, stagedThread, {
+            replace: true,
+          });
         } else if (data.thread_id) {
           this.model.threadsManager
             .find(this.model.id, data.thread_id, { fetchIfNotFound: true })
diff --git a/plugins/chat/spec/system/thread_list/full_page_spec.rb b/plugins/chat/spec/system/thread_list/full_page_spec.rb
index 89cdf66a026..a9dc724c280 100644
--- a/plugins/chat/spec/system/thread_list/full_page_spec.rb
+++ b/plugins/chat/spec/system/thread_list/full_page_spec.rb
@@ -26,6 +26,50 @@ describe "Thread list in side panel | full page", type: :system do
     end
   end
 
+  context "for threads the user is not a participant in" do
+    fab!(:thread_om) { Fabricate(:chat_message, chat_channel: channel) }
+
+    before { chat_system_user_bootstrap(user: other_user, channel: channel) }
+
+    it "does not show existing threads in the channel if the user is not tracking them" do
+      Fabricate(:chat_thread, original_message: thread_om, channel: channel)
+      chat_page.visit_channel(channel)
+      channel_page.open_thread_list
+      expect(page).to have_content(I18n.t("js.chat.threads.none"))
+    end
+
+    it "does not show new threads in the channel in the thread list if the user is not tracking them" do
+      chat_page.visit_channel(channel)
+
+      using_session(:other_user) do |session|
+        sign_in(other_user)
+        chat_page.visit_channel(channel)
+        channel_page.reply_to(thread_om)
+        thread_page.send_message("hey everyone!")
+        expect(channel_page).to have_thread_indicator(thread_om)
+        session.quit
+      end
+
+      channel_page.open_thread_list
+      expect(page).to have_content(I18n.t("js.chat.threads.none"))
+    end
+
+    describe "when the user creates a new thread" do
+      it "does not double up the staged thread and the actual thread in the list" do
+        chat_page.visit_channel(channel)
+        channel_page.reply_to(thread_om)
+        thread_page.send_message("hey everyone!")
+        expect(channel_page).to have_thread_indicator(thread_om)
+        thread_page.close
+        channel_page.open_thread_list
+        expect(page).to have_css(
+          thread_list_page.item_by_id_selector(thread_om.reload.thread_id),
+          count: 1,
+        )
+      end
+    end
+  end
+
   context "when there are threads that the user is participating in" do
     fab!(:thread_1) do
       chat_thread_chain_bootstrap(channel: channel, users: [current_user, other_user])