hmm you’re very likely hitting a state merge conflict on the same key in the same superstep..
In LangGraph, parallel branches can run in one step, and if both branches write to one state key that has default semantics, that key behaves like “last write wins / single value per step.” If more than one update arrives, LangGraph raises InvalidUpdateError with INVALID_CONCURRENT_GRAPH_UPDATE.
Are you reporting INVALID_CONCURRENT_GRAPH_UPDATE erro?