diff --git a/gateway/platforms/msgraph_webhook.py b/gateway/platforms/msgraph_webhook.py
index 9b8e01f6a1..e157cd22a3 100644
--- a/gateway/platforms/msgraph_webhook.py
+++ b/gateway/platforms/msgraph_webhook.py
@@ -80,19 +80,15 @@ class MSGraphWebhookAdapter(BasePlatformAdapter):
         return raw if raw.startswith("/") else f"/{raw}"
 
     @staticmethod
-    def _build_receipt_key(notification: Dict[str, Any]) -> str:
+    def _build_receipt_key(notification: Dict[str, Any]) -> Optional[str]:
         explicit_id = str(notification.get("id") or "").strip()
         if explicit_id:
             return f"id:{explicit_id}"
-        payload = "|".join(
-            [
-                str(notification.get("subscriptionId") or ""),
-                str(notification.get("changeType") or ""),
-                str(notification.get("resource") or ""),
-                json.dumps(notification.get("resourceData") or {}, sort_keys=True),
-            ]
-        )
-        return f"sha1:{sha1(payload.encode('utf-8')).hexdigest()}"
+        return None
+
+    @staticmethod
+    def _normalize_resource_value(resource: str) -> str:
+        return str(resource or "").strip().strip("/")
 
     def set_notification_scheduler(self, scheduler: Optional[NotificationScheduler]) -> None:
         self._notification_scheduler = scheduler
@@ -178,10 +174,11 @@ class MSGraphWebhookAdapter(BasePlatformAdapter):
                 continue
 
             receipt_key = self._build_receipt_key(notification)
-            if self._has_seen_receipt(receipt_key):
-                duplicates += 1
-                continue
-            self._remember_receipt(receipt_key)
+            if receipt_key is not None:
+                if self._has_seen_receipt(receipt_key):
+                    duplicates += 1
+                    continue
+                self._remember_receipt(receipt_key)
 
             accepted += 1
             scheduled += 1
@@ -205,10 +202,20 @@ class MSGraphWebhookAdapter(BasePlatformAdapter):
     def _resource_accepted(self, resource: str) -> bool:
         if not self._accepted_resources:
             return True
+        normalized_resource = self._normalize_resource_value(resource)
         for pattern in self._accepted_resources:
-            if pattern.endswith("*") and resource.startswith(pattern[:-1]):
-                return True
-            if resource == pattern or resource.startswith(f"{pattern}/"):
+            normalized_pattern = self._normalize_resource_value(pattern)
+            if not normalized_pattern:
+                continue
+            if normalized_pattern.endswith("*"):
+                prefix = normalized_pattern[:-1].rstrip("/")
+                if normalized_resource == prefix or normalized_resource.startswith(f"{prefix}/"):
+                    return True
+                continue
+            if (
+                normalized_resource == normalized_pattern
+                or normalized_resource.startswith(f"{normalized_pattern}/")
+            ):
                 return True
         return False
 
@@ -232,8 +239,9 @@ class MSGraphWebhookAdapter(BasePlatformAdapter):
     def _build_message_event(
         self,
         notification: Dict[str, Any],
-        receipt_key: str,
+        receipt_key: Optional[str],
     ) -> MessageEvent:
+        message_id = receipt_key or f"sha1:{sha1(json.dumps(notification, sort_keys=True).encode('utf-8')).hexdigest()}"
         source = self.build_source(
             chat_id=f"msgraph:{notification.get('subscriptionId', 'unknown')}",
             chat_name="msgraph/webhook",
@@ -246,7 +254,7 @@ class MSGraphWebhookAdapter(BasePlatformAdapter):
             message_type=MessageType.TEXT,
             source=source,
             raw_message=notification,
-            message_id=receipt_key,
+            message_id=message_id,
             internal=True,
         )
 
diff --git a/tests/gateway/test_msgraph_webhook.py b/tests/gateway/test_msgraph_webhook.py
index 404156c45f..3c6a4daceb 100644
--- a/tests/gateway/test_msgraph_webhook.py
+++ b/tests/gateway/test_msgraph_webhook.py
@@ -186,6 +186,63 @@ class TestMSGraphNotifications:
 
         assert len(scheduled) == 1
 
+    @pytest.mark.anyio
+    async def test_notifications_without_id_are_not_deduped(self):
+        adapter = _make_adapter()
+        scheduled: list[tuple[dict, object]] = []
+
+        async def _capture(notification, event):
+            scheduled.append((notification, event))
+
+        adapter.set_notification_scheduler(_capture)
+        payload = {
+            "value": [
+                {
+                    "subscriptionId": "sub-1",
+                    "changeType": "updated",
+                    "resource": "communications/onlineMeetings/meeting-3",
+                    "clientState": "expected-client-state",
+                    "resourceData": {"id": "meeting-3"},
+                }
+            ]
+        }
+
+        first = await adapter._handle_notification(_FakeRequest(json_payload=payload))
+        second = await adapter._handle_notification(_FakeRequest(json_payload=payload))
+
+        assert first.status == 202
+        assert second.status == 202
+        second_data = json.loads(second.text)
+        assert second_data["accepted"] == 1
+        assert second_data["duplicates"] == 0
+        assert second_data["scheduled"] == 1
+
+        await asyncio.sleep(0.05)
+
+        assert len(scheduled) == 2
+
+    @pytest.mark.anyio
+    async def test_resource_patterns_accept_leading_slash(self):
+        adapter = _make_adapter(accepted_resources=["/communications/onlineMeetings"])
+        payload = {
+            "value": [
+                {
+                    "id": "notif-slash",
+                    "subscriptionId": "sub-1",
+                    "changeType": "updated",
+                    "resource": "communications/onlineMeetings/meeting-4",
+                    "clientState": "expected-client-state",
+                }
+            ]
+        }
+
+        resp = await adapter._handle_notification(_FakeRequest(json_payload=payload))
+        data = json.loads(resp.text)
+
+        assert resp.status == 202
+        assert data["accepted"] == 1
+        assert data["rejected"] == 0
+
     @pytest.mark.anyio
     async def test_seen_receipts_are_bounded(self):
         adapter = _make_adapter(max_seen_receipts=2)