diff --git a/app.py b/app.py
index b404ef7..b2483f6 100644
--- a/app.py
+++ b/app.py
@@ -174,7 +174,7 @@ def seed_known_users():
 def periodic_seed():
     while True:
         seed_known_users()
-        time.sleep(300)  # 5 Minuten
+        time.sleep(300)
 
 # ============================================================
 # FALLBACK CHECK
@@ -218,6 +218,27 @@ def is_user_in_local_rooms(user_id: str) -> bool:
 
     return False
 
+# ============================================================
+# 🔥 HYBRID DM DETECTION
+# ============================================================
+
+def is_likely_dm_event(event):
+    content = event.get("content", {})
+
+    # 1️⃣ offizielles Flag
+    if content.get("is_direct") is True:
+        return True
+
+    # 2️⃣ Heuristik
+    unsigned = event.get("unsigned", {})
+    state = unsigned.get("invite_room_state", [])
+
+    member_events = [
+        e for e in state if e.get("type") == "m.room.member"
+    ]
+
+    return len(member_events) <= 2
+
 # ============================================================
 # ROUTES
 # ============================================================
@@ -241,16 +262,18 @@ def invite(room_id, event_id):
     # whitelist
     if domain in config.domain_whitelist:
         remember_user(sender)
-        return forward_request("PUT",
+        return forward_request(
+            "PUT",
             f"{config.tuwunel_url}/_matrix/federation/v2/invite/{room_id}/{event_id}",
-            request.headers, payload
+            request.headers,
+            payload
         )
 
     if config.block_external_dms and is_external(sender):
 
         if not is_known_user(sender):
 
-            # 🔥 FALLBACK CHECK
+            # 🔥 fallback check
             if is_user_in_local_rooms(sender):
                 remember_user(sender)
             else: