TypeError: Type is not JSON serializable: ProxyUser

OSS Product Help LangGraph
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1

Hi Team

Im running my langgraph agent in the langgraph platform. Im using a deployment in langsmith which deploys my agent straight from GitHub..

After my last deployment im getting this error

TypeError('Type is not JSON serializable: ProxyUser')Traceback (most recent call last):


  File "/usr/local/lib/python3.11/site-packages/langgraph/pregel/main.py", line 2891, in astream
    async with AsyncPregelLoop(


  File "/usr/local/lib/python3.11/site-packages/langgraph/pregel/_loop.py", line 1264, in __aenter__
    saved = await self.checkpointer.aget_tuple(self.checkpoint_config)
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^


  File "/usr/local/lib/python3.11/site-packages/langgraph_executor/remote_checkpointer.py", line 104, in aget_tuple


  File "/usr/local/lib/python3.11/site-packages/langgraph_grpc_common/conversion/config.py", line 217, in config_to_proto


  File "/usr/local/lib/python3.11/site-packages/langgraph_grpc_common/conversion/config.py", line 305, in _inject_configurable_into_proto


  File "/usr/local/lib/python3.11/site-packages/langgraph_grpc_common/conversion/config.py", line 305, in <dictcomp>


TypeError: Type is not JSON serializable: ProxyUser

I dont know where the ProxyUser is coming from it’s not something i have put its the config. I tried to use AI chat to get help but its suggesting a version mismatch, but im not setting any version in my deployment

2

hi @darthShana

could you share your code and your project dependencies along with their versions?

3 
[project]
name = "my_agent"
version = "0.1.0"
description = "Accounting Assistant LangGraph project for deployment to LangGraph Cloud"
authors = [
    {name = "darthShana"}
]
requires-python = ">=3.11,<3.13"
dependencies = [
    "langchain (>=1.1.3,<2.0.0)",
    "langchain-core (>=1.2.0,<2.0.0)",
    "langchain-anthropic (>=1.3.0,<2.0.0)",
    "langchain-community (>=0.4.1,<1.0.0)",
    "langgraph (>=1.0.5,<2.0.0)",
    "boto3>=1.36.6,<2.0.0",
    "pytest>=8.3.4,<9.0.0",
    "bs4>=0.0.2,<0.1.0",
    "html5lib>=1.1,<2.0",
    "pytest-mock>=3.14.0,<4.0.0",
    "poetry-plugin-dotenv>=2.6.1,<3.0.0",
    "langchain-voyageai (>=0.3.0,<1.0.0)",
    "langchain-pinecone (>=0.2.13,<1.0.0)",
    "chevron>=0.14.0,<0.15.0",
    "pandas>=2.2.3,<3.0.0",
    "pyjwt[crypto]>=2.10.1,<3.0.0",
    "langgraph-cli[inmem] (>=0.4.12,<0.5.0)",
    "langsmith[pytest] (>=0.4.59,<1.0.0)",
    "langgraph-api (>=0.7.13,<0.8.0)",
]

[build-system]
requires = ["setuptools>=61.0", "wheel"]
build-backend = "setuptools.build_meta"

[tool.setuptools.packages.find]
include = ["my_agent*"]

[tool.pytest.ini_options]
log_cli = true
log_cli_level = "INFO"
log_cli_format = "%(message)s"
log_file = "pytest.log"
log_file_level = "INFO"
log_file_format = "%(asctime)s [%(levelname)8s] %(message)s (%(filename)s:%(lineno)s)"
log_file_date_format = "%Y-%m-%d %H:%M:%S"
asyncio_mode = "strict"
asyncio_default_fixture_loop_scope = "function"

hey @pawel-twardziak this is my pyproject.toml..

!! i redeployed and it seems to not happen anymore.. however now my client is getting

[Error] ERROR – {value: Object, done: false}
{value: Object, done: false}Object
	handleError (main-DYXHKJI2.js:14:26417)
	next (main-DYXHKJI2.js:14:116949)
	next (main-DYXHKJI2.js:10:3117)
	_next (main-DYXHKJI2.js:10:2800)
	next (main-DYXHKJI2.js:10:2528)
	(anonymous function) (main-DYXHKJI2.js:10:7405)
	Jd (main-DYXHKJI2.js:10:2216)
	next (main-DYXHKJI2.js:10:7242)
	emit (main-DYXHKJI2.js:14:22179)
	run (polyfills-B6TNHZQ6.js:1:1777)
	onHandleError (main-DYXHKJI2.js:14:25557)
	runGuarded (polyfills-B6TNHZQ6.js:1:1957)
	(anonymous function) (polyfills-B6TNHZQ6.js:1:27909)
	$ (polyfills-B6TNHZQ6.js:1:9653)
4

the graph seems to get invoked succesfully, but it the client gets an error

im using

"@langchain/langgraph-sdk": "^1.6.3",
5

how do you integrate with the frontend? Any code you could share?

6

Thanks for your patience here! We’ve rewritten much of the persistence layer of the server in golang, and there were a couple versions where this serialization was impacted.

The client side error is unexpected. If you could help share some code snippets (can send in to support at LangChain dot dev if you don’t wish to publish here) , I can take a look

7

Hey there!

As of yesterday (February 18th 2026, after the reported fix time of the LangSmith Deployments Downtime incident) I started seeing this error as well - and with no material code change to our deploys (changed the value of two integers).

**TypeError('Type is not JSON serializable: ProxyUser')Traceback (most recent call last):

File "/usr/lib/python3.12/site-packages/langgraph/pregel/main.py", line 2891, in astream
async with AsyncPregelLoop(
^^^^^^^^^^^^^^^^

File "/usr/lib/python3.12/site-packages/langgraph/pregel/_loop.py", line 1264, in __aenter__
saved = await self.checkpointer.aget_tuple(self.checkpoint_config)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

File "/usr/lib/python3.12/site-packages/langgraph_executor/remote_checkpointer.py", line 104, in aget_tuple
config=config_to_proto(config),
^^^^^^^^^^^^^^^^^^^^^^^

File "/usr/lib/python3.12/site-packages/langgraph_grpc_common/conversion/config.py", line 217, in config_to_proto
_inject_configurable_into_proto(configurable, pb_config)

File "/usr/lib/python3.12/site-packages/langgraph_grpc_common/conversion/config.py", line 305, in _inject_configurable_into_proto
{k: orjson.dumps(v) for k, v in extra.items()}
^^^^^^^^^^^^^^^

TypeError: Type is not JSON serializable: ProxyUser**

I am observing that my graph starts correctly and successfully runs a couple of nodes. but this error gets triggered as soon as a Subgraph is invoked (the Subgraph was pre-compiled).

    results = await COMPILED_QUERY_SUBGRAPH.ainvoke(

        {"queries": search_queries, "current_date": current_date, "results": []}, config=config

    )

In the above code snippit, ‘queries’ is a list of strings, ‘current_date’ is in fact a string not a datetime object, and ‘config’ is a slightly modified RunnableConfig object.

9

The client error was an issue on my side, looks like the new langgraph version has some different event types, which i needed to handle.

@Aurora your errror looks very similar to mine so i would give a redeploy a try and see if that solves it