revert: restore batched chat history loading

src/renderer/src/App.tsx

@@ -131,7 +131,10 @@ import type {
   ImageViewerItem,
   Message,
 } from "./ChatTimeline";
-import type { ChatScrollSnapshot } from "./ChatHistoryPane";
+import {
+  messageRenderBatchSize,
+  type ChatScrollSnapshot,
+} from "./ChatHistoryPane";
 import { usePaneOrder } from "./pane-order";
 import { getConversationDisplayTitle, isUnusedConversation, type Conversation } from "./chat-conversation";
 import {
@@ -1803,6 +1806,9 @@ function App(): React.JSX.Element {
       ),
     [],
   );
+  const [visibleMessageCounts, setVisibleMessageCounts] = useState<
+    Record<string, number>
+  >({});
   const sidebarRef = useRef<HTMLElement>(null);
   const sidebarToggleRef = useRef<HTMLButtonElement>(null);
   const livePrimarySidebarWidthRef = useRef(primarySidebarWidth);
@@ -1857,6 +1863,15 @@ function App(): React.JSX.Element {
     },
     [],
   );
+  const handleVisibleMessageCountChange = useCallback(
+    (conversationId: string, count: number): void => {
+      setVisibleMessageCounts((current) => ({
+        ...current,
+        [conversationId]: count,
+      }));
+    },
+    [],
+  );
   const closeNarrowSidebar = useCallback((): void => {
     setSidebarOpen(false);
     requestAnimationFrame(() => sidebarToggleRef.current?.focus());
@@ -4565,6 +4580,11 @@ function App(): React.JSX.Element {
       delete next[conversationId];
       return next;
     });
+    setVisibleMessageCounts((current) => {
+      const next = { ...current };
+      delete next[conversationId];
+      return next;
+    });
     setConversationActivity(conversationId, false);
     const remaining = conversationStore.getState().filter(
       (conversation) => conversation.id !== conversationId,
@@ -5921,6 +5941,7 @@ function App(): React.JSX.Element {
         const index = conversation.messages.findIndex(item => item.id === targetId);
         if (index < 0 || !snapshot.messages.some(message => message.id === targetId)) notify({ tone: 'info', message: t('magicNotes:capture.missingMessage') });
         else {
+          setVisibleMessageCounts(current => ({ ...current, [source.conversationId]: Math.max(current[source.conversationId] ?? messageRenderBatchSize, conversation.messages.length - index) }));
           setNoteMessageNavigation({ conversationId: source.conversationId, messageId: targetId, requestId: Date.now() });
         }
       }
@@ -7060,12 +7081,19 @@ function App(): React.JSX.Element {
                         onSelectTask={setSelectedAssistantTaskId}
                         onSetInput={setQuickActionInput}
                         onSetScheduleEnabled={setAssistantScheduleEnabled}
+                        onVisibleMessageCountChange={
+                          handleVisibleMessageCountChange
+                        }
                         quickActions={quickActions}
                         schedules={assistantSchedules}
                         scrollSnapshot={chatScrollSnapshots[conversationId]}
                         selectedAssistantTaskId={selectedAssistantTaskId}
                         store={conversationStore}
                         tasks={tasksByConversation.get(conversationId) ?? emptyConversationTasks}
+                        visibleMessageCount={
+                          visibleMessageCounts[conversationId] ??
+                          messageRenderBatchSize
+                        }
                       />
                     ))}
                     {activeProject?.kind === "channel" &&

src/renderer/src/ConversationHistorySlot.tsx

@@ -37,9 +37,7 @@ function ConversationHistoryLoader({ conversationId, active, load }: {
   </section>;
 }
 
-type PaneProps = Omit<ComponentProps<typeof ChatHistoryPane>, "conversation" | "taskStrip" | "artifactById" | "onVisibleMessageCountChange" | "visibleMessageCount">;
-
-const ignoreVisibleMessageCountChange = (): void => undefined;
+type PaneProps = Omit<ComponentProps<typeof ChatHistoryPane>, "conversation" | "taskStrip" | "artifactById">;
 
 export type ConversationHistorySlotProps = PaneProps & {
   conversationId: string;
@@ -112,12 +110,5 @@ export const ConversationHistorySlot = memo(function ConversationHistorySlot({
       />
     );
   }
-  return <ChatHistoryPane
-    {...paneProps}
-    artifactById={artifactById}
-    conversation={conversation}
-    onVisibleMessageCountChange={ignoreVisibleMessageCountChange}
-    taskStrip={taskStrip}
-    visibleMessageCount={conversation.messages.length}
-  />;
+  return <ChatHistoryPane {...paneProps} artifactById={artifactById} conversation={conversation} taskStrip={taskStrip} />;
 });