feat: add session switcher to VS Code layout

Open recent sessions from the VS Code header
Add compact session switcher mode
Limit session prefetch to the active directory

packages/ui/src/components/layout/VSCodeLayout.tsx

@@ -9,6 +9,8 @@ import { useSessions, useDirectorySync, useSessionMessages, useSessionMessagesRe
 import { useConfigStore } from '@/stores/useConfigStore';
 import { ContextUsageDisplay } from '@/components/ui/ContextUsageDisplay';
 import { McpDropdown } from '@/components/mcp/McpDropdown';
+import { SessionSwitcherDropdown } from '@/components/session/SessionSwitcherDropdown';
+import { useProjectsStore } from '@/stores/useProjectsStore';
 import { cn } from '@/lib/utils';
 import {
   DropdownMenu,
@@ -422,6 +424,7 @@ export const VSCodeLayout: React.FC = () => {
             showMcp
             showContextUsage
             showRateLimits
+            enableSessionSwitcher
           />
           <div className="flex-1 overflow-hidden">
             <ErrorBoundary>
@@ -474,6 +477,7 @@ export const VSCodeLayout: React.FC = () => {
               showMcp
               showContextUsage
               showRateLimits
+              enableSessionSwitcher
             />
             <div className="flex-1 overflow-hidden">
               <ErrorBoundary>
@@ -511,6 +515,7 @@ export const VSCodeLayout: React.FC = () => {
               showMcp
               showContextUsage
               showRateLimits
+              enableSessionSwitcher
             />
             <div className="flex-1 overflow-hidden">
               <ErrorBoundary>
@@ -535,13 +540,15 @@ interface VSCodeHeaderProps {
   showMcp?: boolean;
   showContextUsage?: boolean;
   showRateLimits?: boolean;
+  enableSessionSwitcher?: boolean;
 }
 
-const VSCodeHeader: React.FC<VSCodeHeaderProps> = ({ title, showBack, onBack, onNewSession, onSettings, onAgentManager, showMcp, showContextUsage, showRateLimits }) => {
+const VSCodeHeader: React.FC<VSCodeHeaderProps> = ({ title, showBack, onBack, onNewSession, onSettings, onAgentManager, showMcp, showContextUsage, showRateLimits, enableSessionSwitcher }) => {
   const { t } = useI18n();
   const getCurrentModel = useConfigStore((state) => state.getCurrentModel);
   const providers = useConfigStore((state) => state.providers);
   const currentSessionId = useSessionUIStore((state) => state.currentSessionId);
+  const activeProjectId = useProjectsStore((state) => state.activeProjectId);
   const currentSessionMessages = useSessionMessages(currentSessionId ?? '');
   const currentSessionMessagesResolved = useSessionMessagesResolved(currentSessionId ?? '');
   const quotaResults = useQuotaStore((state) => state.results);
@@ -697,7 +704,19 @@ const VSCodeHeader: React.FC<VSCodeHeaderProps> = ({ title, showBack, onBack, on
           <Icon name="arrow-left" className="h-5 w-5" />
         </button>
       )}
-      <h1 className="text-sm font-medium truncate flex-1" title={title}>{title}</h1>
+      {enableSessionSwitcher ? (
+        <SessionSwitcherDropdown variant="compact" scopeProjectId={activeProjectId}>
+          <button
+            type="button"
+            aria-label={t('sessions.switcher.openAria')}
+            className="flex min-w-0 flex-1 items-center rounded-md px-1 py-0.5 -my-0.5 text-left transition-colors hover:bg-interactive-hover/60 focus-visible:outline-none focus-visible:bg-interactive-hover/60"
+          >
+            <span className="text-sm font-medium truncate" title={title}>{title}</span>
+          </button>
+        </SessionSwitcherDropdown>
+      ) : (
+        <h1 className="text-sm font-medium truncate flex-1" title={title}>{title}</h1>
+      )}
       {onNewSession && (
         <button
           onClick={onNewSession}

packages/ui/src/components/session/SessionSwitcherDropdown.tsx

@@ -11,21 +11,33 @@ import { Icon } from '@/components/icon/Icon';
 import { useSessionUIStore } from '@/sync/session-ui-store';
 import { useGlobalSessionStatus } from '@/sync/sync-context';
 import { useSessionUnseenCount } from '@/sync/notification-store';
+import { useSync } from '@/sync/use-sync';
+import { useDirectoryStore } from '@/stores/useDirectoryStore';
 import { useSwitcherItems, type SwitcherItem } from '@/components/session/sidebar/hooks/useSwitcherItems';
 import { useUIStore } from '@/stores/useUIStore';
 import { resolveGlobalSessionDirectory } from '@/stores/useGlobalSessionsStore';
-import { formatSessionCompactDateLabel, resolveSessionDiffStats } from './sidebar/utils';
+import { formatSessionCompactDateLabel, normalizePath, resolveSessionDiffStats } from './sidebar/utils';
 import type { SessionNode, SessionSummaryMeta } from './sidebar/types';
 import { useI18n } from '@/lib/i18n';
 import { cn } from '@/lib/utils';
 
 type SecondaryMeta = SwitcherItem['secondaryMeta'];
 
+type SwitcherVariant = 'default' | 'compact';
+
 type SessionSwitcherDropdownProps = {
   children: React.ReactNode;
+  variant?: SwitcherVariant;
+  scopeProjectId?: string | null;
+  align?: 'start' | 'center' | 'end';
 };
 
-export function SessionSwitcherDropdown({ children }: SessionSwitcherDropdownProps): React.ReactElement {
+export function SessionSwitcherDropdown({
+  children,
+  variant = 'default',
+  scopeProjectId = null,
+  align = 'start',
+}: SessionSwitcherDropdownProps): React.ReactElement {
   const isOpen = useUIStore((state) => state.isSessionDropdownOpen);
   const setOpen = useUIStore((state) => state.setSessionDropdownOpen);
 
@@ -33,20 +45,80 @@ export function SessionSwitcherDropdown({ children }: SessionSwitcherDropdownPro
     <DropdownMenu open={isOpen} onOpenChange={setOpen} modal={false}>
       <DropdownMenuTrigger asChild>{children}</DropdownMenuTrigger>
       <DropdownMenuContent
-        align="start"
+        align={align}
         sideOffset={6}
-        className="w-[360px] max-w-[calc(100vw-32px)] overflow-hidden p-1"
+        className={cn(
+          'overflow-hidden p-1 max-w-[calc(100vw-32px)]',
+          variant === 'compact' ? 'w-[280px]' : 'w-[360px]',
+        )}
       >
-        {isOpen ? <SwitcherContent onSelect={() => setOpen(false)} /> : null}
+        {isOpen ? (
+          <SwitcherContent
+            onSelect={() => setOpen(false)}
+            variant={variant}
+            scopeProjectId={scopeProjectId}
+          />
+        ) : null}
       </DropdownMenuContent>
     </DropdownMenu>
   );
 }
 
-function SwitcherContent({ onSelect }: { onSelect: () => void }): React.ReactElement {
-  const items = useSwitcherItems(true);
+type SwitcherContentProps = {
+  onSelect: () => void;
+  variant: SwitcherVariant;
+  scopeProjectId: string | null;
+};
+
+function SwitcherContent({ onSelect, variant, scopeProjectId }: SwitcherContentProps): React.ReactElement {
+  const items = useSwitcherItems(true, { scopeProjectId });
+  const currentSessionId = useSessionUIStore((state) => state.currentSessionId);
+  const currentDirectory = useDirectoryStore((state) => state.currentDirectory);
+  const ensureSessionRenderable = useSync().ensureSessionRenderable;
   const { t } = useI18n();
 
+  const prefetchedRef = React.useRef<Set<string>>(new Set());
+
+  React.useEffect(() => {
+    // Prefetch only sessions that live in the currently mounted sync directory.
+    // ensureSessionRenderable closes over SyncProvider's directory, so a cross-directory
+    // call would hit the wrong backend context. Switching to such a session re-mounts
+    // SyncProvider anyway, so the prefetch wouldn't have survived either way.
+    const normalizedCurrent = normalizePath(currentDirectory);
+    const queue: string[] = [];
+    for (const item of items) {
+      const id = item.node.session.id;
+      if (id === currentSessionId) continue;
+      if (prefetchedRef.current.has(id)) continue;
+      const sessionDir = normalizePath(resolveGlobalSessionDirectory(item.node.session));
+      if (!sessionDir || sessionDir !== normalizedCurrent) continue;
+      prefetchedRef.current.add(id);
+      queue.push(id);
+    }
+    if (queue.length === 0) return;
+
+    let cancelled = false;
+    const CONCURRENCY = 2;
+    const runNext = async (): Promise<void> => {
+      while (!cancelled) {
+        const id = queue.shift();
+        if (!id) return;
+        try {
+          await ensureSessionRenderable(id);
+        } catch {
+          // best-effort prefetch; ignore errors
+        }
+      }
+    };
+
+    const workers = Array.from({ length: Math.min(CONCURRENCY, queue.length) }, () => runNext());
+    void Promise.all(workers);
+
+    return () => {
+      cancelled = true;
+    };
+  }, [currentDirectory, currentSessionId, ensureSessionRenderable, items]);
+
   const [expandedParents, setExpandedParents] = React.useState<Set<string>>(new Set());
   const toggleParent = React.useCallback((sessionId: string) => {
     setExpandedParents((prev) => {
@@ -73,6 +145,7 @@ function SwitcherContent({ onSelect }: { onSelect: () => void }): React.ReactEle
               key={item.node.session.id}
               item={item}
               depth={0}
+              variant={variant}
               expandedParents={expandedParents}
               toggleParent={toggleParent}
               closeDropdown={onSelect}
@@ -87,12 +160,13 @@ function SwitcherContent({ onSelect }: { onSelect: () => void }): React.ReactEle
 type SwitcherNodeProps = {
   item: { node: SessionNode; projectId: string | null; groupDirectory: string | null; secondaryMeta: SecondaryMeta };
   depth: number;
+  variant: SwitcherVariant;
   expandedParents: Set<string>;
   toggleParent: (sessionId: string) => void;
   closeDropdown: () => void;
 };
 
-function SwitcherNode({ item, depth, expandedParents, toggleParent, closeDropdown }: SwitcherNodeProps): React.ReactElement {
+function SwitcherNode({ item, depth, variant, expandedParents, toggleParent, closeDropdown }: SwitcherNodeProps): React.ReactElement {
   const { node, secondaryMeta } = item;
   const session = node.session;
   const hasChildren = node.children.length > 0;
@@ -103,6 +177,7 @@ function SwitcherNode({ item, depth, expandedParents, toggleParent, closeDropdow
       <SwitcherRow
         session={session}
         depth={depth}
+        variant={variant}
         secondaryMeta={secondaryMeta}
         hasChildren={hasChildren}
         isExpanded={isExpanded}
@@ -115,6 +190,7 @@ function SwitcherNode({ item, depth, expandedParents, toggleParent, closeDropdow
               key={childNode.session.id}
               item={{ node: childNode, projectId: item.projectId, groupDirectory: item.groupDirectory, secondaryMeta }}
               depth={depth + 1}
+              variant={variant}
               expandedParents={expandedParents}
               toggleParent={toggleParent}
               closeDropdown={closeDropdown}
@@ -128,6 +204,7 @@ function SwitcherNode({ item, depth, expandedParents, toggleParent, closeDropdow
 type SwitcherRowProps = {
   session: Session;
   depth: number;
+  variant: SwitcherVariant;
   secondaryMeta: SecondaryMeta;
   hasChildren: boolean;
   isExpanded: boolean;
@@ -135,7 +212,7 @@ type SwitcherRowProps = {
   closeDropdown: () => void;
 };
 
-function SwitcherRow({ session, depth, secondaryMeta, hasChildren, isExpanded, onToggleExpand, closeDropdown }: SwitcherRowProps): React.ReactElement {
+function SwitcherRow({ session, depth, variant, secondaryMeta, hasChildren, isExpanded, onToggleExpand, closeDropdown }: SwitcherRowProps): React.ReactElement {
   const { t } = useI18n();
   const currentSessionId = useSessionUIStore((state) => state.currentSessionId);
   const setCurrentSession = useSessionUIStore((state) => state.setCurrentSession);
@@ -188,14 +265,8 @@ function SwitcherRow({ session, depth, secondaryMeta, hasChildren, isExpanded, o
       style={{ paddingLeft: 8 + depth * 12 }}
     >
       <div className="flex min-w-0 flex-1 flex-col gap-0.5">
-        <span className={cn('truncate text-[14px] font-normal leading-tight', isActive ? 'text-primary' : 'text-foreground')}>
-          {sessionTitle}
-        </span>
-        <div
-          className="flex min-w-0 items-center gap-1.5 truncate text-muted-foreground/70 leading-tight"
-          style={{ fontSize: 'calc(var(--text-ui-label) * 0.85)' }}
-        >
-          {hasChildren ? (
+        <div className="flex min-w-0 items-center gap-1.5">
+          {variant === 'compact' && hasChildren ? (
             <span
               role="button"
               tabIndex={-1}
@@ -205,28 +276,54 @@ function SwitcherRow({ session, depth, secondaryMeta, hasChildren, isExpanded, o
                 event.stopPropagation();
                 onToggleExpand?.();
               }}
-              className="inline-flex h-3 w-3 flex-shrink-0 items-center justify-center rounded text-muted-foreground/70 hover:text-foreground"
+              className="inline-flex h-3.5 w-3.5 flex-shrink-0 items-center justify-center rounded text-muted-foreground/70 hover:text-foreground"
               aria-label={isExpanded ? t('sessions.sidebar.session.subsessions.collapse') : t('sessions.sidebar.session.subsessions.expand')}
             >
-              {isExpanded ? <Icon name="arrow-down-s" className="h-3 w-3" /> : <Icon name="arrow-right-s" className="h-3 w-3" />}
-            </span>
-          ) : null}
-          <span className="flex-shrink-0">{timeLabel}</span>
-          {projectLabel ? <span className="truncate">{projectLabel}</span> : null}
-          {branchLabel ? (
-            <span className="inline-flex min-w-0 items-center gap-0.5">
-              <Icon name="git-branch" className="h-3 w-3 flex-shrink-0 text-muted-foreground/70" />
-              <span className="truncate">{branchLabel}</span>
-            </span>
-          ) : null}
-          {diffStats ? (
-            <span className="inline-flex flex-shrink-0 items-center gap-0 text-[0.92em]">
-              <span className="text-status-success/80">+{diffStats.additions}</span>
-              <span className="text-muted-foreground/60">/</span>
-              <span className="text-status-error/65">-{diffStats.deletions}</span>
+              {isExpanded ? <Icon name="arrow-down-s" className="h-3.5 w-3.5" /> : <Icon name="arrow-right-s" className="h-3.5 w-3.5" />}
             </span>
           ) : null}
+          <span className={cn('truncate text-[14px] font-normal leading-tight', isActive ? 'text-primary' : 'text-foreground')}>
+            {sessionTitle}
+          </span>
         </div>
+        {variant === 'default' ? (
+          <div
+            className="flex min-w-0 items-center gap-1.5 truncate text-muted-foreground/70 leading-tight"
+            style={{ fontSize: 'calc(var(--text-ui-label) * 0.85)' }}
+          >
+            {hasChildren ? (
+              <span
+                role="button"
+                tabIndex={-1}
+                data-switcher-expand
+                onClick={(event) => {
+                  event.preventDefault();
+                  event.stopPropagation();
+                  onToggleExpand?.();
+                }}
+                className="inline-flex h-3 w-3 flex-shrink-0 items-center justify-center rounded text-muted-foreground/70 hover:text-foreground"
+                aria-label={isExpanded ? t('sessions.sidebar.session.subsessions.collapse') : t('sessions.sidebar.session.subsessions.expand')}
+              >
+                {isExpanded ? <Icon name="arrow-down-s" className="h-3 w-3" /> : <Icon name="arrow-right-s" className="h-3 w-3" />}
+              </span>
+            ) : null}
+            <span className="flex-shrink-0">{timeLabel}</span>
+            {projectLabel ? <span className="truncate">{projectLabel}</span> : null}
+            {branchLabel ? (
+              <span className="inline-flex min-w-0 items-center gap-0.5">
+                <Icon name="git-branch" className="h-3 w-3 flex-shrink-0 text-muted-foreground/70" />
+                <span className="truncate">{branchLabel}</span>
+              </span>
+            ) : null}
+            {diffStats ? (
+              <span className="inline-flex flex-shrink-0 items-center gap-0 text-[0.92em]">
+                <span className="text-status-success/80">+{diffStats.additions}</span>
+                <span className="text-muted-foreground/60">/</span>
+                <span className="text-status-error/65">-{diffStats.deletions}</span>
+              </span>
+            ) : null}
+          </div>
+        ) : null}
       </div>
 
       {isStreaming || showUnreadDot ? (

packages/ui/src/components/session/sidebar/hooks/useSwitcherItems.ts

@@ -21,6 +21,10 @@ export type SwitcherItem = {
 
 const MAX_PARENT_SESSIONS = 7;
 
+type SwitcherItemsOptions = {
+  scopeProjectId?: string | null;
+};
+
 const normalize = (value: string | null | undefined): string | null => {
   if (!value) return null;
   const replaced = value.replace(/\\/g, '/');
@@ -36,7 +40,8 @@ const formatProjectLabel = (project: { label?: string | null; path: string } | n
   return segments[segments.length - 1] ?? null;
 };
 
-export const useSwitcherItems = (enabled: boolean): SwitcherItem[] => {
+export const useSwitcherItems = (enabled: boolean, options: SwitcherItemsOptions = {}): SwitcherItem[] => {
+  const { scopeProjectId = null } = options;
   const activeSessions = useGlobalSessionsStore((state) => state.activeSessions);
   const projects = useProjectsStore((state) => state.projects);
   const pinnedSessionIds = useSessionPinnedStore((state) => state.ids);
@@ -84,6 +89,11 @@ export const useSwitcherItems = (enabled: boolean): SwitcherItem[] => {
     const parents = activeSessions
       .filter((session) => !session.time?.archived)
       .filter((session) => !(session as Session & { parentID?: string | null }).parentID)
+      .filter((session) => {
+        if (!scopeProjectId) return true;
+        const directory = resolveGlobalSessionDirectory(session);
+        return findProjectForDirectory(directory)?.id === scopeProjectId;
+      })
       .sort((a, b) => compareSessionsByPinnedAndTime(a, b, pinnedSessionIds))
       .slice(0, MAX_PARENT_SESSIONS);
 
@@ -111,7 +121,7 @@ export const useSwitcherItems = (enabled: boolean): SwitcherItem[] => {
         },
       };
     });
-  }, [activeSessions, branchesByDirectory, enabled, findProjectForDirectory, pinnedSessionIds]);
+  }, [activeSessions, branchesByDirectory, enabled, findProjectForDirectory, pinnedSessionIds, scopeProjectId]);
 
   React.useEffect(() => {
     if (!enabled || !gitApi) return;