diff --git a/python/langsmith/client.py b/python/langsmith/client.py
index 4b7659d2c..08face41b 100644
--- a/python/langsmith/client.py
+++ b/python/langsmith/client.py
@@ -151,12 +151,24 @@ def _default_retry_config() -> Retry:
     return Retry(**retry_params)  # type: ignore
 
 
-def _serialize_json(obj: Any) -> Any:
-    if isinstance(obj, datetime.datetime):
-        return obj.isoformat()
-    if isinstance(obj, uuid.UUID):
-        return str(obj)
+_PRIMITIVE_TYPES = (str, int, float, bool, tuple, list, dict)
+_MAX_DEPTH = 3
+
+
+def _serialize_json(obj: Any, depth: int = 0) -> Any:
     try:
+        if isinstance(obj, datetime.datetime):
+            return obj.isoformat()
+        if isinstance(obj, uuid.UUID):
+            return str(obj)
+        if obj is None or isinstance(obj, _PRIMITIVE_TYPES):
+            return obj
+        if isinstance(obj, set):
+            return list(obj)
+        if isinstance(obj, bytes):
+            return obj.decode("utf-8")
+        if depth >= _MAX_DEPTH:
+            return repr(obj)
         serialization_methods = [
             ("model_dump_json", True),  # Pydantic V2
             ("json", True),  # Pydantic V1
@@ -178,15 +190,17 @@ def _serialize_json(obj: Any) -> Any:
         if dataclasses.is_dataclass(obj):
             # Regular dataclass
             return dataclasses.asdict(obj)
-        try:
-            if hasattr(obj, "__slots__"):
-                return {slot: getattr(obj, slot) for slot in obj.__slots__}
-            else:
-                return vars(obj)
-        except Exception as e:
-            logger.debug(f"Failed to serialize {type(obj)} to JSON using vars: {e}")
+        if hasattr(obj, "__slots__"):
+            all_attrs = {slot: getattr(obj, slot, None) for slot in obj.__slots__}
+        elif hasattr(obj, "__dict__"):
+            all_attrs = vars(obj)
+        else:
             return repr(obj)
-    except Exception as e:
+        return {
+            k: _serialize_json(v, depth=depth + 1) if v is not obj else repr(v)
+            for k, v in all_attrs.items()
+        }
+    except BaseException as e:
         logger.debug(f"Failed to serialize {type(obj)} to JSON: {e}")
         return repr(obj)
 
diff --git a/python/tests/unit_tests/test_client.py b/python/tests/unit_tests/test_client.py
index f2ceeee78..0e5302183 100644
--- a/python/tests/unit_tests/test_client.py
+++ b/python/tests/unit_tests/test_client.py
@@ -2,15 +2,17 @@
 import asyncio
 import dataclasses
 import gc
+import itertools
 import json
 import os
+import threading
 import time
 import uuid
 import weakref
 from datetime import datetime
 from enum import Enum
 from io import BytesIO
-from typing import NamedTuple, Optional
+from typing import Any, NamedTuple, Optional
 from unittest import mock
 from unittest.mock import MagicMock, patch
 
@@ -459,6 +461,17 @@ class MyClass:
         def __init__(self, x: int) -> None:
             self.x = x
             self.y = "y"
+            self.a_list = [1, 2, 3]
+            self.a_tuple = (1, 2, 3)
+            self.a_set = {1, 2, 3}
+            self.a_dict = {"foo": "bar"}
+            self.my_bytes = b"foo"
+
+    class ClassWithTee:
+        def __init__(self) -> None:
+            tee_a, tee_b = itertools.tee(range(10))
+            self.tee_a = tee_a
+            self.tee_b = tee_b
 
     class MyClassWithSlots:
         __slots__ = ["x", "y"]
@@ -497,10 +510,30 @@ class AttrDict:
     current_time = datetime.now()
 
     class NestedClass:
-        __slots__ = ["person"]
+        __slots__ = ["person", "lock"]
 
         def __init__(self) -> None:
             self.person = Person(name="foo")
+            self.lock = [threading.Lock()]
+
+    class CyclicClass:
+        def __init__(self) -> None:
+            self.cyclic = self
+
+        def __repr__(self) -> str:
+            return "SoCyclic"
+
+    class CyclicClass2:
+        def __init__(self) -> None:
+            self.cyclic: Any = None
+            self.other: Any = None
+
+        def __repr__(self) -> str:
+            return "SoCyclic2"
+
+    cycle_2 = CyclicClass2()
+    cycle_2.cyclic = CyclicClass2()
+    cycle_2.cyclic.other = cycle_2
 
     class MyNamedTuple(NamedTuple):
         foo: str
@@ -510,6 +543,7 @@ class MyNamedTuple(NamedTuple):
         "uid": uid,
         "time": current_time,
         "my_class": MyClass(1),
+        "class_with_tee": ClassWithTee(),
         "my_slotted_class": MyClassWithSlots(1),
         "my_dataclass": MyDataclass("foo", 1),
         "my_enum": MyEnum.FOO,
@@ -523,13 +557,26 @@ class MyNamedTuple(NamedTuple):
         "nested_class": NestedClass(),
         "attr_dict": AttrDict(foo="foo", bar=1),
         "named_tuple": MyNamedTuple(foo="foo", bar=1),
+        "cyclic": CyclicClass(),
+        "cyclic2": cycle_2,
     }
 
     res = json.loads(json.dumps(to_serialize, default=_serialize_json))
     expected = {
         "uid": str(uid),
         "time": current_time.isoformat(),
-        "my_class": {"x": 1, "y": "y"},
+        "my_class": {
+            "x": 1,
+            "y": "y",
+            "a_list": [1, 2, 3],
+            "a_tuple": [1, 2, 3],
+            "a_set": [1, 2, 3],
+            "a_dict": {"foo": "bar"},
+            "my_bytes": "foo",
+        },
+        "class_with_tee": lambda val: all(
+            ["_tee object" in val[key] for key in ["tee_a", "tee_b"]]
+        ),
         "my_slotted_class": {"x": 1, "y": "y"},
         "my_dataclass": {"foo": "foo", "bar": 1},
         "my_enum": "foo",
@@ -540,11 +587,22 @@ class MyNamedTuple(NamedTuple):
         "a_str": "foo",
         "an_int": 1,
         "a_float": 1.1,
-        "nested_class": {"person": {"name": "foo"}},
+        "nested_class": (
+            lambda val: val["person"] == {"name": "foo"}
+            and "_thread.lock object" in str(val.get("lock"))
+        ),
         "attr_dict": {"foo": "foo", "bar": 1},
         "named_tuple": ["foo", 1],
+        "cyclic": {"cyclic": "SoCyclic"},
+        # We don't really care about this case just want to not err
+        "cyclic2": lambda _: True,
     }
-    assert res == expected
+    assert set(expected) == set(res)
+    for k, v in expected.items():
+        if callable(v):
+            assert v(res[k])
+        else:
+            assert res[k] == v
 
 
 def test_host_url() -> None: