Keep older chat history and image previews stable (#2490)

* fix(app): keep timeline history and previews stable

Treat persisted timeline replicas as display-only so authoritative pagination always comes from the daemon. Require renewed user intent between older-history pages unless the viewport genuinely remains at the history edge.

Model assistant image acquisition as loading, loaded, or failed so recreating a preview URL cannot be rendered as an error.

* fix(app): keep file image previews current

* fix(app): stabilize history pagination edges

* fix(app): recover transient timeline loads

* fix(app): retain assistant image previews

* Stabilize history pagination lifecycle

* Stabilize history settlement and image previews

* Retry file images after reconnect

* Keep active previews and pagination requests alive

* Replace image hook tests with typed ports

* Integrate timeline hydration with submission authority

* Harden pre-hydration timeline reconciliation

* Make rewind E2E use real scroll intent

* Preserve live timeline state through hydration

* Keep mounted image attachments retained

* Protect preview persistence and lifecycle hydration

* Preserve idless live assistant continuations

* Preserve timeline rows across delayed hydration

* test(app): cover real assistant image files

* Preserve assistant tool ordering during hydration

packages/app/src/panels/agent-panel.tsx

@@ -72,7 +72,7 @@ import { WorkspaceDraftAgentTab } from "@/composer/draft/workspace-tab";
 import { useCreateFlowStore } from "@/stores/create-flow-store";
 import { buildDraftStoreKey, generateDraftId } from "@/stores/draft-keys";
 import { usePanelStore } from "@/stores/panel-store";
-import { type Agent, useSessionStore } from "@/stores/session-store";
+import { selectAgentTimelineState, type Agent, useSessionStore } from "@/stores/session-store";
 import { useWorkspaceLayoutStore } from "@/stores/workspace-layout-store";
 import { buildWorkspaceTabPersistenceKey } from "@/workspace-tabs/model";
 import type { Theme } from "@/styles/theme";
@@ -792,11 +792,12 @@ function ChatAgentContent({
   const historySyncGeneration = useSessionStore(
     (state) => state.sessions[serverId]?.historySyncGeneration ?? 0,
   );
-  const hasAppliedAuthoritativeHistory = useSessionStore((state) =>
+  const replicaTimelineStatus = useSessionStore((state) =>
     agentId
-      ? state.sessions[serverId]?.agentAuthoritativeHistoryApplied?.get(agentId) === true
-      : false,
+      ? selectAgentTimelineState(state.sessions[serverId], agentId).status
+      : ("cold" as const),
   );
+  const hasAppliedAuthoritativeHistory = replicaTimelineStatus === "synced";
   const agentHistorySyncGeneration = useSessionStore((state) =>
     agentId ? (state.sessions[serverId]?.agentHistorySyncGeneration?.get(agentId) ?? -1) : -1,
   );
@@ -832,7 +833,8 @@ function ChatAgentContent({
     kind: "idle",
   });
 
-  const hasHydratedHistoryBefore = hasAppliedAuthoritativeHistory;
+  const hasHydratedHistoryBefore =
+    hasAppliedAuthoritativeHistory || replicaTimelineStatus === "painted";
 
   const attentionController = useAgentAttentionClear({
     agentId,

packages/app/src/panels/provider-subagent-panel.tsx

@@ -104,10 +104,12 @@ function ProviderSubagentPanel() {
       .catch(() => undefined);
   }, [client, serverId, supported, target.parentAgentId, target.subagentId]);
 
-  const loadOlder = useCallback(() => {
-    if (!client || !supported || isLoadingOlder || !timeline?.hasOlder || !timeline.epoch) return;
+  const loadOlder = useCallback((): boolean => {
+    if (!client || !supported || isLoadingOlder || !timeline?.hasOlder || !timeline.epoch) {
+      return false;
+    }
     const firstSeq = timeline.rows.size ? Math.min(...timeline.rows.keys()) : null;
-    if (firstSeq === null) return;
+    if (firstSeq === null) return false;
     setIsLoadingOlder(true);
     void client
       .fetchProviderSubagentTimeline(target.parentAgentId, target.subagentId, {
@@ -121,6 +123,7 @@ function ProviderSubagentPanel() {
       })
       .catch(() => undefined)
       .finally(() => setIsLoadingOlder(false));
+    return true;
   }, [
     client,
     isLoadingOlder,