diff --git a/langfuse/serializer.py b/langfuse/serializer.py
index 0ddc6828..8a59a9d0 100644
--- a/langfuse/serializer.py
+++ b/langfuse/serializer.py
@@ -20,6 +20,12 @@
     # If Serializable is not available, set it to NoneType
     Serializable = type(None)
 
+# Attempt to import numpy
+try:
+    import numpy as np
+except ImportError:
+    np = None
+
 
 class EventSerializer(JSONEncoder):
     def __init__(self, *args, **kwargs):
@@ -32,6 +38,11 @@ def default(self, obj: Any):
                 # Timezone-awareness check
                 return serialize_datetime(obj)
 
+            # Check if numpy is available and if the object is a numpy scalar
+            # If so, convert it to a Python scalar using the item() method
+            if np is not None and isinstance(obj, np.generic):
+                return obj.item()
+
             if isinstance(obj, (Exception, KeyboardInterrupt)):
                 return f"{type(obj).__name__}: {str(obj)}"
 
@@ -70,8 +81,14 @@ def default(self, obj: Any):
             if Serializable is not None and isinstance(obj, Serializable):
                 return obj.to_json()
 
+            # 64-bit integers might overflow the JavaScript safe integer range.
+            # Since Node.js is run on the server that handles the serialized value,
+            # we need to ensure that integers outside the safe range are converted to strings.
+            if isinstance(obj, (int)):
+                return obj if self.is_js_safe_integer(obj) else str(obj)
+
             # Standard JSON-encodable types
-            if isinstance(obj, (str, int, float, type(None))):
+            if isinstance(obj, (str, float, type(None))):
                 return obj
 
             if isinstance(obj, (tuple, set, frozenset)):
@@ -116,6 +133,18 @@ def encode(self, obj: Any) -> str:
         self.seen.clear()  # Clear seen objects before each encode call
 
         try:
-            return super().encode(obj)
+            return super().encode(self.default(obj))
         except Exception:
             return f'"<not serializable object of type: {type(obj).__name__}>"'  # escaping the string to avoid JSON parsing errors
+
+    @staticmethod
+    def is_js_safe_integer(value: int) -> bool:
+        """Ensure the value is within JavaScript's safe range for integers.
+
+        Python's 64-bit integers can exceed this range, necessitating this check.
+        https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/MAX_SAFE_INTEGER
+        """
+        max_safe_int = 2**53 - 1
+        min_safe_int = -(2**53) + 1
+
+        return min_safe_int <= value <= max_safe_int
diff --git a/tests/test_openai.py b/tests/test_openai.py
index 962c7ba3..6c8ff32d 100644
--- a/tests/test_openai.py
+++ b/tests/test_openai.py
@@ -908,7 +908,7 @@ class StepByStepAIResponse(BaseModel):
 
     response = openai.chat.completions.create(
         name=generation_name,
-        model="gpt-3.5-turbo-0613",
+        model="gpt-3.5-turbo",
         messages=[{"role": "user", "content": "Explain how to assemble a PC"}],
         functions=[
             {
@@ -948,7 +948,7 @@ class StepByStepAIResponse(BaseModel):
 
     response = openai.chat.completions.create(
         name=generation_name,
-        model="gpt-3.5-turbo-0613",
+        model="gpt-3.5-turbo",
         messages=[{"role": "user", "content": "Explain how to assemble a PC"}],
         functions=[
             {
diff --git a/tests/test_serializer.py b/tests/test_serializer.py
new file mode 100644
index 00000000..b1fda2c9
--- /dev/null
+++ b/tests/test_serializer.py
@@ -0,0 +1,183 @@
+from datetime import datetime, date, timezone
+from uuid import UUID
+from enum import Enum
+from dataclasses import dataclass
+from pathlib import Path
+from pydantic import BaseModel
+import json
+import threading
+from langfuse.serializer import (
+    EventSerializer,
+)
+
+
+class TestEnum(Enum):
+    A = 1
+    B = 2
+
+
+@dataclass
+class TestDataclass:
+    field: str
+
+
+class TestBaseModel(BaseModel):
+    field: str
+
+
+def test_datetime():
+    dt = datetime(2023, 1, 1, 12, 0, 0, tzinfo=timezone.utc)
+    serializer = EventSerializer()
+
+    assert serializer.encode(dt) == '"2023-01-01T12:00:00Z"'
+
+
+def test_date():
+    d = date(2023, 1, 1)
+    serializer = EventSerializer()
+    assert serializer.encode(d) == '"2023-01-01"'
+
+
+def test_enum():
+    serializer = EventSerializer()
+    assert serializer.encode(TestEnum.A) == "1"
+
+
+def test_uuid():
+    uuid = UUID("123e4567-e89b-12d3-a456-426614174000")
+    serializer = EventSerializer()
+    assert serializer.encode(uuid) == '"123e4567-e89b-12d3-a456-426614174000"'
+
+
+def test_bytes():
+    b = b"hello"
+    serializer = EventSerializer()
+    assert serializer.encode(b) == '"hello"'
+
+
+def test_dataclass():
+    dc = TestDataclass(field="test")
+    serializer = EventSerializer()
+    assert json.loads(serializer.encode(dc)) == {"field": "test"}
+
+
+def test_pydantic_model():
+    model = TestBaseModel(field="test")
+    serializer = EventSerializer()
+    assert json.loads(serializer.encode(model)) == {"field": "test"}
+
+
+def test_path():
+    path = Path("/tmp/test.txt")
+    serializer = EventSerializer()
+    assert serializer.encode(path) == '"/tmp/test.txt"'
+
+
+def test_tuple_set_frozenset():
+    data = (1, 2, 3)
+    serializer = EventSerializer()
+    assert serializer.encode(data) == "[1, 2, 3]"
+
+    data = {1, 2, 3}
+    assert serializer.encode(data) == "[1, 2, 3]"
+
+    data = frozenset([1, 2, 3])
+    assert json.loads(serializer.encode(data)) == [1, 2, 3]
+
+
+def test_dict():
+    data = {"a": 1, "b": "two"}
+    serializer = EventSerializer()
+
+    assert json.loads(serializer.encode(data)) == data
+
+
+def test_list():
+    data = [1, "two", 3.0]
+    serializer = EventSerializer()
+
+    assert json.loads(serializer.encode(data)) == data
+
+
+def test_nested_structures():
+    data = {"list": [1, 2, 3], "dict": {"a": 1, "b": 2}, "tuple": (4, 5, 6)}
+    serializer = EventSerializer()
+
+    assert json.loads(serializer.encode(data)) == {
+        "list": [1, 2, 3],
+        "dict": {"a": 1, "b": 2},
+        "tuple": [4, 5, 6],
+    }
+
+
+def test_custom_object():
+    class CustomObject:
+        def __init__(self):
+            self.field = "value"
+
+    obj = CustomObject()
+    serializer = EventSerializer()
+
+    assert json.loads(serializer.encode(obj)) == {"field": "value"}
+
+
+def test_circular_reference():
+    class Node:
+        def __init__(self):
+            self.next = None
+
+    node1 = Node()
+    node2 = Node()
+    node1.next = node2
+    node2.next = node1
+
+    serializer = EventSerializer()
+    result = json.loads(serializer.encode(node1))
+
+    assert result == {"next": {"next": "Node"}}
+
+
+def test_not_serializable():
+    class NotSerializable:
+        def __init__(self):
+            self.lock = threading.Lock()
+
+        def __repr__(self):
+            raise Exception("Cannot represent")
+
+    obj = NotSerializable()
+    serializer = EventSerializer()
+
+    assert serializer.encode(obj) == '{"lock": "<lock>"}'
+
+
+def test_exception():
+    ex = ValueError("Test exception")
+    serializer = EventSerializer()
+    assert serializer.encode(ex) == '"ValueError: Test exception"'
+
+
+def test_none():
+    serializer = EventSerializer()
+    assert serializer.encode(None) == "null"
+
+
+def test_slots():
+    class SlotClass:
+        __slots__ = ["field"]
+
+        def __init__(self):
+            self.field = "value"
+
+    obj = SlotClass()
+    serializer = EventSerializer()
+    assert json.loads(serializer.encode(obj)) == {"field": "value"}
+
+
+def test_numpy_float32():
+    import numpy as np
+
+    data = np.float32(1.0)
+    serializer = EventSerializer()
+
+    assert serializer.encode(data) == "1.0"