diff --git a/rdagent/components/coder/factor_coder/CoSTEER/knowledge_management.py b/rdagent/components/coder/factor_coder/CoSTEER/knowledge_management.py
index 701ae0df..ea50d9b7 100644
--- a/rdagent/components/coder/factor_coder/CoSTEER/knowledge_management.py
+++ b/rdagent/components/coder/factor_coder/CoSTEER/knowledge_management.py
@@ -213,10 +213,11 @@ class FactorQueriedGraphKnowledge(FactorQueriedKnowledge):
 
 
 class FactorGraphRAGStrategy(RAGStrategy):
+    prompt = Prompts(file_path=Path(__file__).parent.parent / "prompts.yaml")
+
     def __init__(self, knowledgebase: FactorGraphKnowledgeBase) -> None:
         super().__init__(knowledgebase)
         self.current_generated_trace_count = 0
-        self.prompt = Prompts(file_path=Path(__file__).parent.parent / "prompts.yaml")
 
     def generate_knowledge(
         self,
diff --git a/rdagent/core/proposal.py b/rdagent/core/proposal.py
index b3e4697e..58c044d7 100644
--- a/rdagent/core/proposal.py
+++ b/rdagent/core/proposal.py
@@ -25,12 +25,20 @@ class Hypothesis:
     - Belief
     """
 
-    def __init__(self, hypothesis: str, reason: str, concise_reason: str, concise_observation: str, concise_justification: str, concise_knowledge: str) -> None:
+    def __init__(
+        self,
+        hypothesis: str,
+        reason: str,
+        concise_reason: str,
+        concise_observation: str,
+        concise_justification: str,
+        concise_knowledge: str,
+    ) -> None:
         self.hypothesis: str = hypothesis
         self.reason: str = reason
         self.concise_reason: str = concise_reason
         self.concise_observation: str = concise_observation
-        self.concise_justification: str = concise_justification 
+        self.concise_justification: str = concise_justification
         self.concise_knowledge: str = concise_knowledge
 
     def __str__(self) -> str:
diff --git a/rdagent/core/utils.py b/rdagent/core/utils.py
index 9a19b6a8..cb4a5dc2 100644
--- a/rdagent/core/utils.py
+++ b/rdagent/core/utils.py
@@ -3,8 +3,9 @@ from __future__ import annotations
 import importlib
 import json
 import multiprocessing as mp
+import pickle
 from collections.abc import Callable
-from typing import Any, ClassVar, cast
+from typing import Any, ClassVar, NoReturn, cast
 
 from fuzzywuzzy import fuzz  # type: ignore[import-untyped]
 
@@ -27,13 +28,25 @@ class SingletonBaseClass:
             # TODO: this restriction can be solved.
             exception_message = "Please only use kwargs in Singleton to avoid misunderstanding."
             raise RDAgentException(exception_message)
-        all_args = [(-1, f"{cls.__module__}.{cls.__name__}")] + [(i, args[i]) for i in args] + list(sorted(kwargs.items()))
+        class_name = [(-1, f"{cls.__module__}.{cls.__name__}")]
+        args_l = [(i, args[i]) for i in args]
+        kwargs_l = list(sorted(kwargs.items()))
+        all_args = class_name + args_l + kwargs_l
         kwargs_hash = hash(tuple(all_args))
         if kwargs_hash not in cls._instance_dict:
             cls._instance_dict[kwargs_hash] = super().__new__(cls)  # Corrected call
-            cls._instance_dict[kwargs_hash].__init__(**kwargs)  # Ensure __init__ is called
         return cls._instance_dict[kwargs_hash]
 
+    def __reduce__(self) -> NoReturn:
+        """
+        NOTE:
+        When loading an object from a pickle, the __new__ method does not receive the `kwargs`
+        it was initialized with. This makes it difficult to retrieve the correct singleton object.
+        Therefore, we have made it unpickable.
+        """
+        msg = f"Instances of {self.__class__.__name__} cannot be pickled"
+        raise pickle.PicklingError(msg)
+
 
 def parse_json(response: str) -> Any:
     try:
diff --git a/test/utils/test_misc.py b/test/utils/test_misc.py
index 5d54770d..6fd3b43c 100644
--- a/test/utils/test_misc.py
+++ b/test/utils/test_misc.py
@@ -5,16 +5,29 @@ from rdagent.core.utils import SingletonBaseClass
 
 class A(SingletonBaseClass):
     def __init__(self, **kwargs):
+        print(self, "__init__", kwargs)  # make sure the __init__ is called only once.
         self.kwargs = kwargs
 
+    def __str__(self) -> str:
+        return f"{self.__class__.__name__}.{getattr(self, 'kwargs', None)}"
+
+    def __repr__(self) -> str:
+        return self.__str__()
+
 
 class MiscTest(unittest.TestCase):
     def test_singleton(self):
+        print("a1=================")
         a1 = A()
+        print("a2=================")
         a2 = A()
+        print("a3=================")
         a3 = A(x=3)
+        print("a4=================")
         a4 = A(x=2)
+        print("a5=================")
         a5 = A(b=3)
+        print("a6=================")
         a6 = A(x=3)
 
         # Check that a1 and a2 are the same instance
@@ -37,6 +50,22 @@ class MiscTest(unittest.TestCase):
 
         print(id(a1), id(a2), id(a3), id(a4), id(a5), id(a6))
 
+        print("...................... Start testing pickle ......................")
+
+        # Test pickle
+        import pickle
+
+        with self.assertRaises(pickle.PicklingError):
+            with open("a3.pkl", "wb") as f:
+                pickle.dump(a3, f)
+        # NOTE: If the pickle feature is not disabled,
+        # loading a3.pkl will return a1, and a1 will be updated with a3's attributes.
+        # print(a1.kwargs)
+        # with open("a3.pkl", "rb") as f:
+        #     a3_pkl = pickle.load(f)
+        # print(id(a3), id(a3_pkl))  # not the same object
+        # print(a1.kwargs)  # a1 will be changed.
+
 
 if __name__ == "__main__":
     unittest.main()