checkpoint: support serde for SecretStr

libs/checkpoint/langgraph/checkpoint/serde/jsonplus.py

@@ -233,6 +233,17 @@ def _msgpack_default(obj: Any) -> Union[str, msgpack.ExtType]:
                 ),
             ),
         )
+    elif hasattr(obj, "get_secret_value") and callable(obj.get_secret_value):
+        return msgpack.ExtType(
+            EXT_CONSTRUCTOR_SINGLE_ARG,
+            _msgpack_enc(
+                (
+                    obj.__class__.__module__,
+                    obj.__class__.__name__,
+                    obj.get_secret_value(),
+                ),
+            ),
+        )
     elif hasattr(obj, "dict") and callable(obj.dict):  # pydantic v1
         return msgpack.ExtType(
             EXT_PYDANTIC_V1,

libs/checkpoint/tests/test_jsonplus.py

@@ -10,8 +10,9 @@ from enum import Enum
 from ipaddress import IPv4Address
 
 import dataclasses_json
-from pydantic import BaseModel
+from pydantic import BaseModel, SecretStr
 from pydantic.v1 import BaseModel as BaseModelV1
+from pydantic.v1 import SecretStr as SecretStrV1
 from zoneinfo import ZoneInfo
 
 from langgraph.checkpoint.serde.jsonplus import JsonPlusSerializer
@@ -109,6 +110,8 @@ def test_serde_jsonplus() -> None:
         "my_pydantic_v1": MyPydanticV1(
             foo="foo", bar=1, inner=InnerPydanticV1(hello="hello")
         ),
+        "my_secret_str": SecretStr("meow"),
+        "my_secret_str_v1": SecretStrV1("meow"),
         "person": Person(name="foo"),
         "a_bool": True,
         "a_none": None,