diff --git a/backend/open_webui/models/chats.py b/backend/open_webui/models/chats.py
index af999f21cd..51f2f121b3 100644
--- a/backend/open_webui/models/chats.py
+++ b/backend/open_webui/models/chats.py
@@ -459,24 +459,89 @@ class ChatTable:
                 return None
             return row[0] or 'New Chat'
 
+    @staticmethod
+    def get_unresolved_parent_ids(messages_map: dict) -> set[str]:
+        """Return parent IDs referenced by messages but absent from the map.
+
+        An empty set means the message graph is fully connected.
+        """
+        return {
+            msg['parentId']
+            for msg in messages_map.values()
+            if msg.get('parentId') and msg['parentId'] not in messages_map
+        }
+
+    async def backfill_messages_by_chat_id(
+        self, chat_id: str, user_id: str, messages: dict[str, dict]
+    ) -> None:
+        """Write messages to the ``chat_message`` table so future lookups
+        use the fast path.  Errors are logged but never raised.
+        """
+        for message_id, message in messages.items():
+            if not isinstance(message, dict) or not message.get('role'):
+                continue
+            try:
+                await ChatMessages.upsert_message(
+                    message_id=message_id,
+                    chat_id=chat_id,
+                    user_id=user_id,
+                    data=message,
+                )
+            except Exception as e:
+                log.warning('Backfill failed for message %s in chat %s: %s', message_id, chat_id, e)
+
     async def get_messages_map_by_chat_id(self, id: str) -> Optional[dict]:
         """Message map for walking history (see ``get_message_list``).
 
-        Prefer ``chat_message`` rows to avoid loading the large ``chat``
-        JSON blob; fall back to embedded history when no rows exist
-        (legacy chats).
+        Prefer ``chat_message`` rows to avoid loading the large embedded
+        history; fall back to the legacy JSON when no rows exist.
+        When rows exist but the parent-link graph has gaps (e.g. migration
+        failures), missing messages are merged from the legacy history
+        and backfilled so future requests self-heal.
         """
         # Fast path: build from normalized chat_message rows.
         messages_map = await ChatMessages.get_messages_map_by_chat_id(id)
+
         if messages_map is not None:
+            unresolved_ids = self.get_unresolved_parent_ids(messages_map)
+            if not unresolved_ids:
+                return messages_map
+
+            # Graph has gaps — enrich from the legacy embedded history.
+            log.info(
+                'Chat %s: %d unresolved parent reference(s) in chat_message — '
+                'enriching from legacy history',
+                id, len(unresolved_ids),
+            )
+            chat = await self.get_chat_by_id(id)
+            if chat:
+                history_messages = chat.chat.get('history', {}).get('messages', {}) or {}
+                missing_messages = {
+                    message_id: history_messages[message_id]
+                    for message_id in unresolved_ids
+                    if message_id in history_messages
+                }
+
+                if missing_messages:
+                    messages_map.update(missing_messages)
+
+                    # Backfill so future requests use the fast path.
+                    await self.backfill_messages_by_chat_id(id, chat.user_id, missing_messages)
+
             return messages_map
 
-        # No rows — fall back to the embedded JSON blob for legacy chats.
+        # No rows — fall back to the legacy embedded history.
         chat = await self.get_chat_by_id(id)
         if chat is None:
             return None
 
-        return chat.chat.get('history', {}).get('messages', {}) or {}
+        history_messages = chat.chat.get('history', {}).get('messages', {}) or {}
+
+        # Backfill so future requests use the fast path.
+        if history_messages:
+            await self.backfill_messages_by_chat_id(id, chat.user_id, history_messages)
+
+        return history_messages
 
     async def get_message_by_id_and_message_id(self, id: str, message_id: str) -> Optional[dict]:
         chat = await self.get_chat_by_id(id)