INVALID_GRAPH_NODE_RETURN_VALUE

A LangGraph @[StateGraph] received a non-dict return type from a node. Here's an example:

from typing import TypedDict
 
from langgraph.graph import StateGraph
 
class State(TypedDict):
    some_key: str
 
def bad_node(state: State):
    # Should return a dict with a value for "some_key", not a list
    return ["whoops"]
 
builder = StateGraph(State)
builder.add_node(bad_node)
...
 
graph = builder.compile()

Invoking the above graph will result in an error like this:

graph.invoke({ "some_key": "someval" });

InvalidUpdateError: Expected dict, got ['whoops']
For troubleshooting, visit: https://docs.langchain.com/oss/python/langgraph/errors/INVALID_GRAPH_NODE_RETURN_VALUE

Nodes in your graph must return a dict containing one or more keys defined in your state.

Troubleshooting

The following may help resolve this error:

If you have complex logic in your node, make sure all code paths return an appropriate dict for your defined state.

INVALID_CONCURRENT_GRAPH_UPDATE MISSING_CHECKPOINTER