diff --git a/metagpt/actions/action_node.py b/metagpt/actions/action_node.py
index 059118637..ef0414ff7 100644
--- a/metagpt/actions/action_node.py
+++ b/metagpt/actions/action_node.py
@@ -38,6 +38,7 @@ class ReviseMode(Enum):
 
 
 TAG = "CONTENT"
+MODE_CODE_FILL = "code_fill"
 
 LANGUAGE_CONSTRAINT = "Language: Please use the same language as Human INPUT."
 FORMAT_CONSTRAINT = f"Format: output wrapped inside [{TAG}][/{TAG}] like format example, nothing else."
@@ -149,8 +150,6 @@ class ActionNode:
     prevs: List["ActionNode"]  # previous nodes
     nexts: List["ActionNode"]  # next nodes
 
-    MODE_CODE_FILL = "code_fill"
-
     def __init__(
         self,
         key: str,