diff --git a/src/backend/langflow/graph/nodes.py b/src/backend/langflow/graph/nodes.py
index 9db6260e9..21fe0f673 100644
--- a/src/backend/langflow/graph/nodes.py
+++ b/src/backend/langflow/graph/nodes.py
@@ -1,7 +1,12 @@
 from typing import Any, Dict, List, Optional, Union
 
 from langflow.graph.base import Node
-from langflow.graph.utils import extract_input_variables_from_prompt
+from langflow.graph.utils import extract_input_variables_from_prompt, flatten_list
+
+
+class ToolkitNode(Node):
+    def __init__(self, data: Dict):
+        super().__init__(data, base_type="toolkits")
 
 
 class AgentNode(Node):
@@ -47,7 +52,7 @@ class PromptNode(Node):
     def build(
         self,
         force: bool = False,
-        tools: Optional[Union[List[Node], List[ToolNode]]] = None,
+        tools: Optional[List[Union[ToolNode, ToolkitNode]]] = None,
     ) -> Any:
         if not self._built or force:
             if (
@@ -65,8 +70,7 @@ class PromptNode(Node):
                 # flatten the list of tools if it is a list of lists
                 # first check if it is a list
                 if tools and isinstance(tools, list) and isinstance(tools[0], list):
-                    tools = [tool for sublist in tools for tool in sublist]
-
+                    tools = flatten_list(tools)
                 self.params["tools"] = tools
                 prompt_params = [
                     key
@@ -85,30 +89,6 @@ class PromptNode(Node):
         return self._built_object
 
 
-class ChainNode(Node):
-    def __init__(self, data: Dict):
-        super().__init__(data, base_type="chains")
-
-    def build(
-        self,
-        force: bool = False,
-        tools: Optional[Union[List[Node], List[ToolNode]]] = None,
-    ) -> Any:
-        if not self._built or force:
-            # Check if the chain requires a PromptNode
-            for key, value in self.params.items():
-                if isinstance(value, PromptNode):
-                    # Build the PromptNode, passing the tools if available
-                    self.params[key] = value.build(tools=tools, force=force)
-
-            self._build()
-
-        #! Cannot deepcopy SQLDatabaseChain
-        if self.node_type in ["SQLDatabaseChain"]:
-            return self._built_object
-        return self._built_object
-
-
 class LLMNode(Node):
     built_node_type = None
     class_built_object = None
@@ -130,11 +110,6 @@ class LLMNode(Node):
         return self._built_object
 
 
-class ToolkitNode(Node):
-    def __init__(self, data: Dict):
-        super().__init__(data, base_type="toolkits")
-
-
 class FileToolNode(ToolNode):
     def __init__(self, data: Dict):
         super().__init__(data)
@@ -193,3 +168,24 @@ class TextSplitterNode(Node):
         if self._built_object:
             return f"""{self.node_type}({len(self._built_object)} documents)\nDocuments: {self._built_object[:3]}..."""
         return f"{self.node_type}()"
+
+
+class ChainNode(Node):
+    def __init__(self, data: Dict):
+        super().__init__(data, base_type="chains")
+
+    def build(
+        self,
+        force: bool = False,
+        tools: Optional[List[Union[ToolNode, ToolkitNode]]] = None,
+    ) -> Any:
+        if not self._built or force:
+            # Check if the chain requires a PromptNode
+            for key, value in self.params.items():
+                if isinstance(value, PromptNode):
+                    # Build the PromptNode, passing the tools if available
+                    self.params[key] = value.build(tools=tools, force=force)
+
+            self._build()
+
+        return self._built_object
diff --git a/src/backend/langflow/graph/utils.py b/src/backend/langflow/graph/utils.py
index 6d56e933e..e22b27cf5 100644
--- a/src/backend/langflow/graph/utils.py
+++ b/src/backend/langflow/graph/utils.py
@@ -1,4 +1,5 @@
 import re
+from typing import Any, Union
 
 
 def validate_prompt(prompt: str):
@@ -17,3 +18,14 @@ def fix_prompt(prompt: str):
 def extract_input_variables_from_prompt(prompt: str) -> list[str]:
     """Extract input variables from prompt."""
     return re.findall(r"{(.*?)}", prompt)
+
+
+def flatten_list(list_of_lists: list[Union[list, Any]]) -> list:
+    """Flatten list of lists."""
+    new_list = []
+    for item in list_of_lists:
+        if isinstance(item, list):
+            new_list.extend(item)
+        else:
+            new_list.append(item)
+    return new_list