langchain-ai/langgraph · error · ValueError

Unknown operation type: {type(op)}

Error message

Unknown operation type: {type(op)}

What it means

Error "Unknown operation type: {type(op)}" thrown in langchain-ai/langgraph.

Source

Thrown at libs/checkpoint/langgraph/checkpoint/store/memory/__init__.py:400

View on GitHub (pinned to 38031739e5)

When it happens

Trigger: Thrown at libs/checkpoint/langgraph/checkpoint/store/memory/__init__.py:400 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of langchain-ai/langgraph@38031739e5 (2026-08-26). Data as JSON: /api/errors/7ac878a8f475b3d6. Report an issue: GitHub.