fix(stabilization): harden attachment lifecycle and agent guard signals (#5420)

* fix: harden stabilization attachment and agent guards

* fix(uploads): preserve durable references during cleanup

* fix(uploads): close cleanup and compaction races

routes/calendar_routes.py

@@ -13,8 +13,9 @@ from sqlalchemy import or_, and_
 from dateutil.rrule import rrulestr
 
 from core.database import SessionLocal, CalendarCal, CalendarDeletedEvent, CalendarEvent
-from src.auth_helpers import require_user
+from src.auth_helpers import effective_user, require_user
 from src.upload_limits import read_upload_limited, ICS_MAX_BYTES
+from src.upload_handler import reserve_upload_references
 
 logger = logging.getLogger(__name__)
 
@@ -697,9 +698,18 @@ def _expand_rrule(
 
 # ── Routes ──
 
-def setup_calendar_routes() -> APIRouter:
+def setup_calendar_routes(upload_handler=None) -> APIRouter:
     router = APIRouter(prefix="/api/calendar", tags=["calendar"])
 
+    def _reserve_calendar_uploads(request: Request, *values) -> None:
+        missing_id = reserve_upload_references(
+            upload_handler,
+            effective_user(request),
+            *values,
+        )
+        if missing_id:
+            raise HTTPException(409, f"Referenced upload is no longer available: {missing_id}")
+
     # ── CalDAV multi-account helpers ─────────────────────────────────────────
 
     def _get_caldav_accounts(owner: str) -> list:
@@ -1087,6 +1097,7 @@ def setup_calendar_routes() -> APIRouter:
     @router.post("/events")
     async def create_event(request: Request, data: EventCreate):
         owner = _require_user(request)
+        _reserve_calendar_uploads(request, data.color, data.description, data.location)
         db = SessionLocal()
         try:
             cal = None
@@ -1148,6 +1159,7 @@ def setup_calendar_routes() -> APIRouter:
     @router.put("/events/{uid}")
     async def update_event(request: Request, uid: str, data: EventUpdate):
         owner = _require_user(request)
+        _reserve_calendar_uploads(request, data.color, data.description, data.location)
         try:
             base_uid = _resolve_base_uid(uid)
         except ValueError as e:
@@ -1241,6 +1253,7 @@ def setup_calendar_routes() -> APIRouter:
     @router.post("/calendars")
     async def create_calendar(request: Request, name: str = "Imported", color: str = "#5b8abf"):
         owner = _require_user(request)
+        _reserve_calendar_uploads(request, color)
         db = SessionLocal()
         try:
             cal = CalendarCal(
@@ -1263,6 +1276,7 @@ def setup_calendar_routes() -> APIRouter:
     @router.put("/calendars/{cal_id}")
     async def update_calendar(request: Request, cal_id: str, name: str = None, color: str = None):
         owner = _require_user(request)
+        _reserve_calendar_uploads(request, color)
         db = SessionLocal()
         try:
             cal = _get_or_404_calendar(db, cal_id, owner)