diff --git a/backend/open_webui/models/chat_messages.py b/backend/open_webui/models/chat_messages.py
index b1768d0ff2..44349c1584 100644
--- a/backend/open_webui/models/chat_messages.py
+++ b/backend/open_webui/models/chat_messages.py
@@ -241,6 +241,81 @@ class ChatMessageTable:
             messages = result.scalars().all()
             return [ChatMessageModel.model_validate(message) for message in messages]
 
+    # DB column names that differ from the JSON message keys.
+    DB_TO_JSON_KEY_MAP = {
+        'parent_id': 'parentId',
+        'model_id': 'model',
+        'status_history': 'statusHistory',
+        'created_at': 'timestamp',
+    }
+    # DB-internal columns excluded from the reconstructed message dict.
+    EXCLUDED_COLUMNS = frozenset({'id', 'chat_id', 'user_id', 'updated_at'})
+
+    async def get_messages_map_by_chat_id(self, chat_id: str, db: Optional[AsyncSession] = None) -> Optional[dict]:
+        """Build a {message_id: message_dict} map from chat_message rows.
+
+        Returns the same shape as chat.history.messages so callers
+        (get_message_list, middleware) work unchanged.  Returns None if
+        no rows exist for the chat (caller should fall back to the
+        embedded JSON blob for legacy chats).
+        """
+        async with get_async_db_context(db) as db:
+            result = await db.execute(
+                select(ChatMessage).filter_by(chat_id=chat_id)
+            )
+            rows = result.scalars().all()
+
+        if not rows:
+            return None
+
+        # Strip the composite-id prefix ("{chat_id}-") to recover the
+        # original message_id used as map key.
+        prefix = f'{chat_id}-'
+        prefix_len = len(prefix)
+        col_keys = [c.key for c in ChatMessage.__table__.columns]
+
+        messages_map: dict[str, dict] = {}
+        for row in rows:
+            msg_id = row.id[prefix_len:] if row.id.startswith(prefix) else row.id
+
+            msg: dict = {'id': msg_id}
+            for key in col_keys:
+                if key in self.EXCLUDED_COLUMNS:
+                    continue
+                val = getattr(row, key)
+                if val is None:
+                    continue
+                json_key = self.DB_TO_JSON_KEY_MAP.get(key, key)
+                msg[json_key] = val
+
+            # Ensure content always has a value
+            msg.setdefault('content', '')
+
+            # Mirror usage into info.usage for callers that read it there
+            if 'usage' in msg:
+                msg['info'] = {'usage': msg['usage']}
+
+            messages_map[msg_id] = msg
+
+        # Reconstruct childrenIds from parentId links so that the map
+        # is fully navigable (callers like the frontend rely on this).
+        for msg_id, msg in messages_map.items():
+            parent_id = msg.get('parentId')
+            if parent_id and parent_id in messages_map:
+                parent = messages_map[parent_id]
+                children = parent.get('childrenIds')
+                if children is None:
+                    parent['childrenIds'] = [msg_id]
+                elif msg_id not in children:
+                    children.append(msg_id)
+
+        # Ensure every message has a childrenIds list (leaf nodes get [])
+        for msg in messages_map.values():
+            if 'childrenIds' not in msg:
+                msg['childrenIds'] = []
+
+        return messages_map
+
     async def get_messages_by_user_id(
         self,
         user_id: str,
diff --git a/backend/open_webui/models/chats.py b/backend/open_webui/models/chats.py
index 4dc00e9f84..af999f21cd 100644
--- a/backend/open_webui/models/chats.py
+++ b/backend/open_webui/models/chats.py
@@ -460,6 +460,18 @@ class ChatTable:
             return row[0] or 'New Chat'
 
     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).
+        """
+        # 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:
+            return messages_map
+
+        # No rows — fall back to the embedded JSON blob for legacy chats.
         chat = await self.get_chat_by_id(id)
         if chat is None:
             return None