diff --git a/src/void_tools/cli.py b/src/void_tools/cli.py
index a9f433d..da10dbc 100644
--- a/src/void_tools/cli.py
+++ b/src/void_tools/cli.py
@@ -92,6 +92,7 @@ def cmd_sync(args):
         mapping = {}
         cursor = None
         stop_pagination = False
+        latest_seen_timestamp = ""
         
         while not stop_pagination:
             params = {'limit': min(50, args.limit) if not args.unread_only else 50}
@@ -112,6 +113,10 @@ def cmd_sync(args):
                     stop_pagination = True
                     break
                 
+                # Capture the timestamp of the most recent notification we fetched
+                if not latest_seen_timestamp or notif.indexed_at > latest_seen_timestamp:
+                    latest_seen_timestamp = notif.indexed_at
+                
                 local_id = f"notif_{len(inbox)}"
                 handle = notif.author.handle
                 item = {
@@ -175,6 +180,7 @@ def cmd_sync(args):
         with open("inbox.yaml", "w") as f:
             yaml.dump(inbox, f, sort_keys=False, default_flow_style=False)
             
+        mapping["_sync_timestamp"] = latest_seen_timestamp
         with open(".inbox_mapping.json", "w") as f:
             json.dump(mapping, f)
             
@@ -368,8 +374,11 @@ def cmd_dispatch(args):
     config = outbox.get("config", {})
     if config.get("mark_seen"):
         try:
-            client.app.bsky.notification.update_seen({'seen_at': client.get_current_time_iso()})
-            print("Marked notifications as seen.")
+            seen_at = mapping.get("_sync_timestamp")
+            if not seen_at:
+                seen_at = client.get_current_time_iso()
+            client.app.bsky.notification.update_seen({'seen_at': seen_at})
+            print(f"Marked notifications as seen up to {seen_at}.")
         except Exception as e:
             print(f"Error marking seen: {e}")