refactor(web-ui): stabilize flow chat scroll with viewport state machine

src/web-ui/src/app/components/UnifiedTopBar/UnifiedTopBar.tsx

@@ -44,6 +44,7 @@ import { flowChatStore } from '@/flow_chat/store/FlowChatStore';
 import { useSessionProfile } from '../../session-profiles';
 import { getWorkspaceSceneDef } from '../../navigation/workspaceSceneRegistry';
 import { resolveWorkContextForSurface } from '../../navigation/workspaceTopBarContext';
+import { useSessionHeaderContext } from '../../hooks/useSessionHeaderContext';
 import {
   useWorkspaceSurfaceStore,
   type WorkspaceSceneHistoryEntry,
@@ -106,7 +107,7 @@ const UnifiedTopBar: React.FC<UnifiedTopBarProps> = ({
   const { themes, themeId, setTheme, loading: themeLoading } = useTheme();
   const { hasWorkspace } = useLastUsedWorkspace();
   const { warning } = useNotification();
-  const sessionContext = useHeaderStore((s) => s.sessionContext);
+  const sessionContext = useSessionHeaderContext();
   const contextNavOverrides = useHeaderStore((s) => s.contextNavOverrides);
   const requestOpenWorkDock = useWorkDockStore((s) => s.requestOpenWorkDock);
   const works = useWorkStore((s) => s.works);

src/web-ui/src/app/components/WorkDock/NewWorkDialog.tsx

@@ -64,7 +64,7 @@
   initialScopeRequirement?: ProductAppLaunchScopeRequirement;
 }
 
 export function productAppWorkChoice(appId: string): NewWorkAgentChoice {
   return `${PRODUCT_APP_CHOICE_PREFIX}${appId}` as NewWorkAgentChoice;
 }
 
@@ -633,6 +633,9 @@
     try {
       if (startMode === 'agentic-os') {
         const agenticOsSessionId = await openAgenticOsSession();
+        if (!agenticOsSessionId) {
+          throw new Error('Failed to open Agentic OS session');
+        }
         await flowChatManager.sendMessage(
           trimmedObjective,
           agenticOsSessionId,

src/web-ui/src/app/globalOverlayEscape.ts

@@ -9,7 +9,7 @@
  * and when nested UI should consume Esc first.
  */
 
-import { useWorkspaceSurfaceStore } from './navigation/workspaceSurfaceStore';
+import { useWorkspaceSurfaceStore, selectFocusedSessionId } from './navigation/workspaceSurfaceStore';
 import { shortcutManager } from '@/infrastructure/services/ShortcutManager';
 import { ALL_SHORTCUTS } from '@/shared/constants/shortcuts';
 import { flowChatStore } from '@/flow_chat/store/FlowChatStore';
@@ -52,7 +52,7 @@ function isTargetInsideChatShortcutScope(target: EventTarget | null): boolean {
 }
 
 function isActiveSessionProcessing(): boolean {
-  const sid = useWorkspaceSurfaceStore.getState().focusedSessionId;
+  const sid = selectFocusedSessionId(useWorkspaceSurfaceStore.getState());
   if (!sid) return false;
   return stateMachineManager.getCurrentState(sid) === SessionExecutionState.PROCESSING;
 }
@@ -76,7 +76,8 @@ export function installGlobalSurfaceEscapeToHome(): void {
       if (!eventMatchesEscapeToAgenticBinding(event)) return;
       if (shouldDeferForNestedEscapeUi(event)) return;
 
-      const { activeSurface, focusedSessionId } = useWorkspaceSurfaceStore.getState();
+      const { activeSurface } = useWorkspaceSurfaceStore.getState();
+      const focusedSessionId = selectFocusedSessionId(useWorkspaceSurfaceStore.getState());
       if (activeSurface.kind !== 'agentic-os-home') {
         event.preventDefault();
         event.stopImmediatePropagation();

src/web-ui/src/app/hooks/useCurrentSessionTitle.ts

@@ -3,11 +3,11 @@
  * Subscribes to flowChatStore so the value updates reactively.
  */
 
-import { useWorkspaceSurfaceStore } from '../navigation/workspaceSurfaceStore';
+import { useWorkspaceSurfaceStore, selectFocusedSessionId } from '../navigation/workspaceSurfaceStore';
 import { useFlowChatStoreSelector } from '../../flow_chat/hooks/useFlowChatStoreSelector';
 
 export function useCurrentSessionTitle(): string {
-  const focusedSessionId = useWorkspaceSurfaceStore(state => state.focusedSessionId);
+  const focusedSessionId = useWorkspaceSurfaceStore(selectFocusedSessionId);
   return useFlowChatStoreSelector(
     state => {
       const session = focusedSessionId ? state.sessions.get(focusedSessionId) : undefined;

src/web-ui/src/app/hooks/useSessionHeaderContext.ts

@@ -0,0 +1,52 @@
+/**
+ * Derived session header context for UnifiedTopBar.
+ * Single source: focused session from surface store + FlowChatStore session data.
+ */
+
+import { useMemo } from 'react';
+import {
+  getWorkspaceDisplayName,
+  useWorkspaceContext,
+} from '@/infrastructure/contexts/WorkspaceContext';
+import {
+  fallbackWorkspaceFolderLabel,
+  resolveWorkspaceForSession,
+} from '@/flow_chat/utils/sessionOrdering';
+import { useFlowChatStoreSelector } from '@/flow_chat/hooks/useFlowChatStoreSelector';
+import {
+  selectFocusedSessionId,
+  useWorkspaceSurfaceStore,
+} from '../navigation/workspaceSurfaceStore';
+import type { SessionHeaderContext } from '../stores/headerStore';
+
+export function useSessionHeaderContext(): SessionHeaderContext | null {
+  const focusedSessionId = useWorkspaceSurfaceStore(selectFocusedSessionId);
+  const { openedWorkspacesList } = useWorkspaceContext();
+
+  const session = useFlowChatStoreSelector((state) => (
+    focusedSessionId ? state.sessions.get(focusedSessionId) : undefined
+  ));
+
+  return useMemo((): SessionHeaderContext | null => {
+    if (!session?.sessionId || !session.descriptor) {
+      return null;
+    }
+
+    let workspaceDisplayName = '';
+    if (session.workspacePath?.trim()) {
+      const ws = resolveWorkspaceForSession(session, openedWorkspacesList);
+      if (ws) {
+        workspaceDisplayName = getWorkspaceDisplayName(ws).trim();
+      }
+      if (!workspaceDisplayName) {
+        workspaceDisplayName = fallbackWorkspaceFolderLabel(session.workspacePath);
+      }
+    }
+
+    return {
+      descriptor: session.descriptor,
+      workspacePath: session.workspacePath,
+      workspaceDisplayName,
+    };
+  }, [openedWorkspacesList, session]);
+}

src/web-ui/src/app/layout/AppLayout.tsx

@@ -30,7 +30,8 @@ import { useI18n } from '@/infrastructure/i18n';
 import { consumeDeferredNewSessionWorkspace } from '../utils/deferredWorkspaceSession';
 import { appRuntime, runtimePolicy } from '@/infrastructure/app-runtime';
 import { descriptorFromAgentType, getDefaultSessionDescriptor } from '@/flow_chat/domain/sessionDescriptor';
-import { useWorkspaceSurfaceStore } from '../navigation/workspaceSurfaceStore';
+import { useWorkspaceSurfaceStore, selectFocusedSessionId } from '../navigation/workspaceSurfaceStore';
+import { commitStartupHome } from '../navigation/navigationController';
 import './AppLayout.scss';
 
 const log = createLogger('AppLayout');
@@ -177,20 +178,21 @@ const AppLayout: React.FC<AppLayoutProps> = ({ className = '' }) => {
         const initializationPreferredDescriptor = explicitPreferredMode
           ? descriptorFromAgentType(explicitPreferredMode)
           : undefined;
-        const suppressAutoSessionSelection = consumeDeferredNewSessionWorkspace(
-          lastUsedWorkspace.rootPath
-        );
+        consumeDeferredNewSessionWorkspace(lastUsedWorkspace.rootPath);
+
+        commitStartupHome();
 
         const flowChatManager = FlowChatManager.getInstance();
         const initialization = await flowChatManager.initializeWorkspaceSessionState(
           lastUsedWorkspace.rootPath,
           {
             preferredDescriptor: initializationPreferredDescriptor,
-            skipAutoSelectSession: suppressAutoSessionSelection,
+            skipAutoSelectSession: true,
             createDefaultSession: true,
             defaultSessionConfig: {
               workspaceId: lastUsedWorkspace.id,
               workspacePath: lastUsedWorkspace.rootPath,
+              navigate: false,
             },
             defaultSessionDescriptor: initializationPreferredDescriptor ?? getDefaultSessionDescriptor(),
           }
@@ -199,8 +201,7 @@ const AppLayout: React.FC<AppLayoutProps> = ({ className = '' }) => {
         const surfaceState = useWorkspaceSurfaceStore.getState();
         const workspaceScopedActiveId =
           initialization.createdSessionId ||
-          surfaceState.composerTargetSessionId ||
-          surfaceState.focusedSessionId ||
+          selectFocusedSessionId(surfaceState) ||
           initialization.focusedSessionId;
 
         const pendingDescription = sessionStorage.getItem('pendingProjectDescription');
@@ -213,8 +214,7 @@ const AppLayout: React.FC<AppLayoutProps> = ({ className = '' }) => {
               const latestSurfaceState = useWorkspaceSurfaceStore.getState();
               const targetSessionId =
                 pendingTargetSessionId ||
-                latestSurfaceState.composerTargetSessionId ||
-                latestSurfaceState.focusedSessionId;
+                selectFocusedSessionId(latestSurfaceState);
 
               if (!targetSessionId) {
                 log.error('Cannot find active session ID');