diff --git a/routes/calendar_routes.py b/routes/calendar_routes.py
index 3c767f2..da45068 100644
--- a/routes/calendar_routes.py
+++ b/routes/calendar_routes.py
@@ -12,7 +12,7 @@ from dateutil.rrule import rrulestr, rruleset
 from dateutil.rrule import DAILY, WEEKLY, MONTHLY, YEARLY
 
 from core.database import SessionLocal, CalendarCal, CalendarEvent
-from src.auth_helpers import get_current_user
+from src.auth_helpers import get_current_user, require_user
 
 logger = logging.getLogger(__name__)
 
@@ -28,16 +28,17 @@ _SINGLE_USER_MODE = _os.environ.get("ODYSSEUS_SINGLE_USER", "1") != "0"
 
 
 def _require_user(request: Request) -> str:
-    """Return the authenticated user. In multi-user mode an unauthenticated
-    request raises 401; in single-user mode it falls through to
-    FALLBACK_OWNER. Prevents the silent cross-user data write that would
-    happen if a request slipped past auth middleware in a real deployment."""
-    u = get_current_user(request)
-    if u:
-        return u
-    if _SINGLE_USER_MODE:
-        return FALLBACK_OWNER
-    raise HTTPException(401, "Authentication required")
+    """Return the authenticated user. Uses require_user so AUTH_ENABLED=false
+    and single-user mode both work: require_user returns "" when auth is
+    disabled or unconfigured, and only raises 401 when auth is configured but
+    the caller is unauthenticated. Falls back to FALLBACK_OWNER for calendar
+    writes so data isn't stored under an empty owner in single-user mode."""
+    user = require_user(request)
+    if user:
+        return user
+    # require_user returned "" — auth is off or unconfigured (single-user).
+    # Use FALLBACK_OWNER so calendar rows have a stable owner for filtering.
+    return FALLBACK_OWNER
 
 
 def _get_or_404_calendar(db, cal_id: str, owner: str) -> CalendarCal:
diff --git a/routes/memory_routes.py b/routes/memory_routes.py
index d243b99..336f37e 100644
--- a/routes/memory_routes.py
+++ b/routes/memory_routes.py
@@ -27,7 +27,7 @@ from src.request_models import MemoryAddRequest
 from core.database import SessionLocal
 from src.llm_core import llm_call_async
 from services.memory.memory_extractor import audit_memories
-from src.auth_helpers import get_current_user
+from src.auth_helpers import get_current_user, require_user
 from src.endpoint_resolver import resolve_endpoint
 
 logger = logging.getLogger(__name__)
@@ -191,8 +191,7 @@ def setup_memory_routes(memory_manager: MemoryManager, session_manager: SessionM
     @router.post("/extract")
     async def extract_memory(request: Request, session: str = Form(...)) -> Dict[str, List[str]]:
         """Analyze a session's chat history and return memory suggestions."""
-        if not get_current_user(request):
-            raise HTTPException(401, "Not authenticated")
+        require_user(request)
         try:
             sess = session_manager.get_session(session)
         except KeyError:
diff --git a/routes/note_routes.py b/routes/note_routes.py
index 925b4fb..1524afc 100644
--- a/routes/note_routes.py
+++ b/routes/note_routes.py
@@ -683,9 +683,8 @@ def setup_note_routes(task_scheduler=None):
         Returns {synthesis, email_sent}.
         """
         # Gate against anonymous callers — LLM synthesis can burn tokens.
-        from src.auth_helpers import get_current_user as _gcu
-        if not _gcu(request):
-            raise HTTPException(401, "Not authenticated")
+        from src.auth_helpers import require_user as _ru
+        _ru(request)
         body = await request.json()
         note_id = body.get("note_id")
         title = (body.get("title") or "").strip()