GraphLoadError when running "langgraph dev"

[jackliusr]

2026-04-20T14:45:02.234007Z [error ] Traceback (most recent call last):
File "/home/jackl/prjs/agents/sql-agent/.venv/lib/python3.13/site-packages/langgraph_api/graph.py", line 627, in collect_graphs_from_env
graph = await run_in_executor(None, _graph_from_spec, spec)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/jackl/prjs/agents/sql-agent/.venv/lib/python3.13/site-packages/langgraph_api/utils/config.py", line 145, in run_in_executor
return await asyncio.get_running_loop().run_in_executor(
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
...<2 lines>...
)
^
File "/home/jackl/.local/share/uv/python/cpython-3.13.5-linux-x86_64-gnu/lib/python3.13/concurrent/futures/thread.py", line 59, in run
result = self.fn(*self.args, **self.kwargs)
File "/home/jackl/prjs/agents/sql-agent/.venv/lib/python3.13/site-packages/langgraph_api/utils/config.py", line 136, in wrapper
return func(*args, **kwargs)
File "/home/jackl/prjs/agents/sql-agent/.venv/lib/python3.13/site-packages/langgraph_api/timing/timer.py", line 101, in wrapper
return func(*args, **kwargs)
File "/home/jackl/prjs/agents/sql-agent/.venv/lib/python3.13/site-packages/langgraph_api/graph.py", line 800, in _graph_from_spec
raise ValueError(
...<7 lines>...
)
ValueError: Heads up! Your graph 'agent' from './main.py' includes a custom checkpointer (type <class 'langgraph.checkpoint.memory.InMemorySaver'>). With LangGraph API, persistence is handled automatically by the platform, so providing a custom checkpointer (type <class 'langgraph.checkpoint.memory.InMemorySaver'>) here isn't necessary and will be ignored when deployed.

To simplify your setup and use the built-in persistence, please remove the custom checkpointer (type <class 'langgraph.checkpoint.memory.InMemorySaver'>) from your graph definition. If you are looking to customize which postgres database to connect to, please set the POSTGRES_URI environment variable. See https://langchain-ai.github.io/langgraph/cloud/reference/env_var/#postgres_uri_custom for more details.

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
File "/home/jackl/prjs/agents/sql-agent/.venv/lib/python3.13/site-packages/starlette/routing.py", line 638, in lifespan
async with self.lifespan_context(app) as maybe_state:
~~~~~~~~~~~~~~~~~~~~~^^^^^
File "/home/jackl/.local/share/uv/python/cpython-3.13.5-linux-x86_64-gnu/lib/python3.13/contextlib.py", line 214, in aenter
return await anext(self.gen)
^^^^^^^^^^^^^^^^^^^^^
File "/home/jackl/prjs/agents/sql-agent/.venv/lib/python3.13/site-packages/langgraph_api/timing/timer.py", line 227, in combined_lifespan
await stack.enter_async_context(ls(app))
File "/home/jackl/.local/share/uv/python/cpython-3.13.5-linux-x86_64-gnu/lib/python3.13/contextlib.py", line 668, in enter_async_context
result = await _enter(cm)
^^^^^^^^^^^^^^^^
File "/home/jackl/.local/share/uv/python/cpython-3.13.5-linux-x86_64-gnu/lib/python3.13/contextlib.py", line 214, in aenter
return await anext(self.gen)
^^^^^^^^^^^^^^^^^^^^^
File "/home/jackl/prjs/agents/sql-agent/.venv/lib/python3.13/site-packages/langgraph_runtime_inmem/lifespan.py", line 114, in lifespan
await graph.collect_graphs_from_env(True)
File "/home/jackl/prjs/agents/sql-agent/.venv/lib/python3.13/site-packages/langgraph_api/graph.py", line 629, in collect_graphs_from_env
raise GraphLoadError(spec, exc) from exc
langgraph_api.utils.errors.GraphLoadError: Failed to load graph 'agent' from ./main.py: Heads up! Your graph 'agent' from './main.py' includes a custom checkpointer (type <class 'langgraph.checkpoint.memory.InMemorySaver'>). With LangGraph API, persistence is handled automatically by the platform, so providing a custom checkpointer (type <class 'langgraph.checkpoint.memory.InMemorySaver'>) here isn't necessary and will be ignored when deployed.

To simplify your setup and use the built-in persistence, please remove the custom checkpointer (type <class 'langgraph.checkpoint.memory.InMemorySaver'>) from your graph definition. If you are looking to customize which postgres database to connect to, please set the POSTGRES_URI environment variable. See https://langchain-ai.github.io/langgraph/cloud/reference/env_var/#postgres_uri_custom for more details.