diff --git a/backend/alembic/versions/052_add_session_lock_columns.py b/backend/alembic/versions/052_add_session_lock_columns.py
new file mode 100644
index 0000000..15bc2a1
--- /dev/null
+++ b/backend/alembic/versions/052_add_session_lock_columns.py
@@ -0,0 +1,18 @@
+"""add is_locked and locked_at to user_sessions
+
+Revision ID: 052
+Revises: 051
+"""
+from alembic import op
+import sqlalchemy as sa
+
+revision = "052"
+down_revision = "051"
+
+def upgrade():
+    op.add_column("user_sessions", sa.Column("is_locked", sa.Boolean(), server_default="false", nullable=False))
+    op.add_column("user_sessions", sa.Column("locked_at", sa.DateTime(), nullable=True))
+
+def downgrade():
+    op.drop_column("user_sessions", "locked_at")
+    op.drop_column("user_sessions", "is_locked")
diff --git a/backend/app/models/session.py b/backend/app/models/session.py
index 33a2a21..860b286 100644
--- a/backend/app/models/session.py
+++ b/backend/app/models/session.py
@@ -18,6 +18,10 @@ class UserSession(Base):
     expires_at: Mapped[datetime] = mapped_column(nullable=False)
     revoked: Mapped[bool] = mapped_column(Boolean, default=False)
 
+    # Session lock — persists across page refresh
+    is_locked: Mapped[bool] = mapped_column(Boolean, default=False, server_default="false")
+    locked_at: Mapped[datetime | None] = mapped_column(nullable=True)
+
     # Audit fields for security logging
     ip_address: Mapped[str | None] = mapped_column(String(45), nullable=True)
     user_agent: Mapped[str | None] = mapped_column(String(255), nullable=True)
diff --git a/backend/app/routers/auth.py b/backend/app/routers/auth.py
index c998f32..e944aed 100644
--- a/backend/app/routers/auth.py
+++ b/backend/app/routers/auth.py
@@ -132,6 +132,9 @@ async def get_current_user(
         fresh_token = create_session_token(user_id, session_id)
         _set_session_cookie(response, fresh_token)
 
+    # Stash session on request so lock/unlock endpoints can access it
+    request.state.db_session = db_session
+
     return user
 
 
@@ -542,6 +545,8 @@ async def auth_status(
     authenticated = False
     role = None
 
+    is_locked = False
+
     if not setup_required and session_cookie:
         payload = verify_session_token(session_cookie)
         if payload:
@@ -556,8 +561,10 @@ async def auth_status(
                         UserSession.expires_at > datetime.now(),
                     )
                 )
-                if session_result.scalar_one_or_none() is not None:
+                db_sess = session_result.scalar_one_or_none()
+                if db_sess is not None:
                     authenticated = True
+                    is_locked = db_sess.is_locked
                     user_obj_result = await db.execute(
                         select(User).where(User.id == user_id, User.is_active == True)
                     )
@@ -582,12 +589,28 @@ async def auth_status(
         "role": role,
         "username": u.username if authenticated and u else None,
         "registration_open": registration_open,
+        "is_locked": is_locked,
     }
 
 
+@router.post("/lock")
+async def lock_session(
+    request: Request,
+    db: AsyncSession = Depends(get_db),
+    current_user: User = Depends(get_current_user),
+):
+    """Mark the current session as locked. Frontend must verify password to unlock."""
+    db_session: UserSession = request.state.db_session
+    db_session.is_locked = True
+    db_session.locked_at = datetime.now()
+    await db.commit()
+    return {"locked": True}
+
+
 @router.post("/verify-password")
 async def verify_password(
     data: VerifyPasswordRequest,
+    request: Request,
     db: AsyncSession = Depends(get_db),
     current_user: User = Depends(get_current_user),
 ):
@@ -604,7 +627,12 @@ async def verify_password(
 
     if new_hash:
         current_user.password_hash = new_hash
-        await db.commit()
+
+    # Clear session lock on successful password verification
+    db_session: UserSession = request.state.db_session
+    db_session.is_locked = False
+    db_session.locked_at = None
+    await db.commit()
 
     return {"verified": True}
 
diff --git a/frontend/index.html b/frontend/index.html
index 2da949e..52bf6d2 100644
--- a/frontend/index.html
+++ b/frontend/index.html
@@ -8,6 +8,21 @@
     <meta name="theme-color" content="#09090b" />
     <meta name="mobile-web-app-capable" content="yes" />
     <title>UMBRA</title>
+    <script>
+      // Apply cached accent color before React hydrates to prevent cyan flash
+      (function() {
+        try {
+          var c = localStorage.getItem('umbra-accent-color');
+          if (c) {
+            var p = JSON.parse(c);
+            var s = document.documentElement.style;
+            s.setProperty('--accent-h', p.h);
+            s.setProperty('--accent-s', p.s);
+            s.setProperty('--accent-l', p.l);
+          }
+        } catch(e) {}
+      })();
+    </script>
     <link rel="preconnect" href="https://fonts.googleapis.com" />
     <link rel="preconnect" href="https://fonts.gstatic.com" crossorigin />
     <link href="https://fonts.googleapis.com/css2?family=Sora:wght@400;500;600;700&family=DM+Sans:ital,wght@0,400;0,500;0,600;0,700;1,400&display=swap" rel="stylesheet" />
diff --git a/frontend/src/components/layout/Sidebar.tsx b/frontend/src/components/layout/Sidebar.tsx
index f41b619..54fb7ee 100644
--- a/frontend/src/components/layout/Sidebar.tsx
+++ b/frontend/src/components/layout/Sidebar.tsx
@@ -83,28 +83,20 @@ export default function Sidebar({ collapsed, onToggle, mobileOpen, onMobileClose
     <div>
       <div
         className={cn(
-          'flex items-center gap-3 rounded-lg px-3 py-2 text-sm font-medium transition-all duration-200 border-l-2',
+          'flex items-center gap-3 rounded-lg px-3 py-2 text-sm font-medium transition-all duration-200 border-l-2 cursor-pointer',
           isProjectsActive
             ? 'bg-accent/15 text-accent border-accent'
             : 'text-muted-foreground hover:bg-accent/10 hover:text-accent border-transparent'
         )}
+        onClick={() => {
+          navigate('/projects');
+          if (mobileOpen) onMobileClose();
+        }}
       >
-        <FolderKanban
-          className="h-5 w-5 shrink-0 cursor-pointer"
-          onClick={() => {
-            navigate('/projects');
-            if (mobileOpen) onMobileClose();
-          }}
-        />
+        <FolderKanban className="h-5 w-5 shrink-0" />
         {showExpanded && (
           <>
-            <span
-              className="flex-1 cursor-pointer"
-              onClick={() => {
-                navigate('/projects');
-                if (mobileOpen) onMobileClose();
-              }}
-            >
+            <span className="flex-1">
               Projects
             </span>
             {trackedProjects && trackedProjects.length > 0 && (
diff --git a/frontend/src/hooks/useLock.tsx b/frontend/src/hooks/useLock.tsx
index fed762d..d20ce11 100644
--- a/frontend/src/hooks/useLock.tsx
+++ b/frontend/src/hooks/useLock.tsx
@@ -7,9 +7,10 @@ import {
   useRef,
   type ReactNode,
 } from 'react';
-import { useIsMutating } from '@tanstack/react-query';
+import { useIsMutating, useQueryClient } from '@tanstack/react-query';
 import { useSettings } from '@/hooks/useSettings';
 import api from '@/lib/api';
+import type { AuthStatus } from '@/types';
 
 interface LockContextValue {
   isLocked: boolean;
@@ -23,7 +24,14 @@ const ACTIVITY_EVENTS = ['mousemove', 'keydown', 'click', 'scroll', 'touchstart'
 const THROTTLE_MS = 5_000; // only reset timer every 5s of activity
 
 export function LockProvider({ children }: { children: ReactNode }) {
-  const [isLocked, setIsLocked] = useState(false);
+  const queryClient = useQueryClient();
+
+  // Initialize lock state from the auth status cache (server-persisted)
+  const [isLocked, setIsLocked] = useState(() => {
+    const cached = queryClient.getQueryData<AuthStatus>(['auth']);
+    return cached?.is_locked ?? false;
+  });
+
   const { settings } = useSettings();
   const activeMutations = useIsMutating();
 
@@ -32,8 +40,38 @@ export function LockProvider({ children }: { children: ReactNode }) {
   const activeMutationsRef = useRef(activeMutations);
   activeMutationsRef.current = activeMutations;
 
-  const lock = useCallback(() => {
+  // Sync lock state when auth status is fetched/refetched (e.g. on page refresh)
+  useEffect(() => {
+    const cached = queryClient.getQueryData<AuthStatus>(['auth']);
+    if (cached?.is_locked && !isLocked) {
+      setIsLocked(true);
+    }
+  }, [queryClient, isLocked]);
+
+  // Subscribe to auth query updates to catch server lock state changes
+  useEffect(() => {
+    const unsubscribe = queryClient.getQueryCache().subscribe((event) => {
+      if (
+        event.type === 'updated' &&
+        event.action.type === 'success' &&
+        event.query.queryKey[0] === 'auth'
+      ) {
+        const data = event.query.state.data as AuthStatus | undefined;
+        if (data?.is_locked) {
+          setIsLocked(true);
+        }
+      }
+    });
+    return unsubscribe;
+  }, [queryClient]);
+
+  const lock = useCallback(async () => {
     setIsLocked(true);
+    try {
+      await api.post('/auth/lock');
+    } catch {
+      // Lock locally even if server call fails — defense in depth
+    }
   }, []);
 
   const unlock = useCallback(async (password: string) => {
@@ -41,8 +79,12 @@ export function LockProvider({ children }: { children: ReactNode }) {
     if (data.verified) {
       setIsLocked(false);
       lastActivityRef.current = Date.now();
+      // Update auth cache to reflect unlocked state
+      queryClient.setQueryData<AuthStatus>(['auth'], (old) =>
+        old ? { ...old, is_locked: false } : old
+      );
     }
-  }, []);
+  }, [queryClient]);
 
   // Auto-lock idle timer
   useEffect(() => {
diff --git a/frontend/src/hooks/useTheme.ts b/frontend/src/hooks/useTheme.ts
index 27d4f5d..afecf67 100644
--- a/frontend/src/hooks/useTheme.ts
+++ b/frontend/src/hooks/useTheme.ts
@@ -20,9 +20,16 @@ export function useTheme() {
 
     const preset = ACCENT_PRESETS[settings.accent_color];
     if (preset) {
-      document.documentElement.style.setProperty('--accent-h', preset.h.toString());
-      document.documentElement.style.setProperty('--accent-s', `${preset.s}%`);
-      document.documentElement.style.setProperty('--accent-l', `${preset.l}%`);
+      const h = preset.h.toString();
+      const s = `${preset.s}%`;
+      const l = `${preset.l}%`;
+      document.documentElement.style.setProperty('--accent-h', h);
+      document.documentElement.style.setProperty('--accent-s', s);
+      document.documentElement.style.setProperty('--accent-l', l);
+      // Cache for next page load to prevent cyan flash
+      try {
+        localStorage.setItem('umbra-accent-color', JSON.stringify({ h, s, l }));
+      } catch {}
     }
   }, [settings?.accent_color]);
 
diff --git a/frontend/src/main.tsx b/frontend/src/main.tsx
index 61ca364..b23d8fd 100644
--- a/frontend/src/main.tsx
+++ b/frontend/src/main.tsx
@@ -20,6 +20,7 @@ const queryClient = new QueryClient({
       refetchOnWindowFocus: false,
       retry: 1,
       staleTime: 5 * 60 * 1000,
+      gcTime: 30 * 60 * 1000, // keep cache 30 min to avoid skeleton flash on tab switch
     },
   },
 });
diff --git a/frontend/src/types/index.ts b/frontend/src/types/index.ts
index 5e7339f..420507b 100644
--- a/frontend/src/types/index.ts
+++ b/frontend/src/types/index.ts
@@ -221,6 +221,7 @@ export interface AuthStatus {
   role: UserRole | null;
   username: string | null;
   registration_open: boolean;
+  is_locked: boolean;
 }
 
 // Login response discriminated union