InvalidUpdateError: Node __copy__ does not exist - LangGraph State Update Failure

OSS Product Help LangGraph
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Description:

I’m encountering a persistent InvalidUpdateError when attempting to update thread state in LangGraph API v0.4.20. The error occurs during state updates and suggests that a node named __copy__ doesn’t exist in my graph definition.

This is happening with langgraph dev –allow-blocking and i put some multiple inputs in studio

Error Details:

langgraph.errors.InvalidUpdateError: Node __copy__ does not exist

Stack Trace Context:

  • Error occurs in graph.aupdate_state() → abulk_update_state() → aperform_superstep()
  • Triggered during POST /threads/{thread_id}/state API call
  • Using LangGraph API v0.4.20 with in-memory runtime v0.12.0

Environment:

  • LangGraph API: 0.4.20
  • LangGraph Runtime: langgraph-runtime-inmem 0.12.0
  • Python: 3.13
  • Development mode with --allow-blocking

Graph Configuration:
My graph is defined with standard nodes and doesn’t explicitly reference any __copy__ node. The error suggests LangGraph is internally trying to access a node that doesn’t exist in my graph definition.

Questions:

  1. What is the __copy__ node and when does LangGraph create it internally?
  2. Is this related to state copying mechanisms during updates?
  3. Are there specific graph configurations that could trigger this error?
  4. Is this a known issue with the recent v0.4.20 update?

The error is blocking state updates entirely and preventing normal workflow execution. Any insights into the root cause or potential workarounds would be greatly appreciated.

2

hey @Petar - would it be possible to share a minimally reproducible example?

3

Fixed!