{"record":{"id":"44b865d43cbba158","repo":"langchain-ai/langgraph","slug":"auto-generated-error-handler-node-handler-node-n","errorCode":null,"errorMessage":"Auto-generated error handler node `{handler_node_name}` already exists.","messagePattern":"Auto-generated error handler node `(.+?)` already exists\\.","errorType":"validation","errorClass":"ValueError","httpStatus":null,"severity":"error","filePath":"libs/langgraph/langgraph/graph/state.py","lineNumber":870,"sourceCode":"                        and (rargs := get_args(rtn))\n                        and get_origin(rargs[0]) is Literal\n                        and (vals := get_args(rargs[0]))\n                    ):\n                        ends = vals\n        except (NameError, TypeError, StopIteration):\n            pass\n\n        if destinations is not None:\n            ends = destinations\n\n        resolved_input_schema: type[Any] = (\n            input_schema or inferred_input_schema or self.state_schema\n        )\n        handler_node_name: str | None = None\n        if error_handler is not None:\n            handler_node_name = f\"__error_handler__{node}\"\n            if handler_node_name in self.nodes:\n                raise ValueError(\n                    f\"Auto-generated error handler node `{handler_node_name}` already exists.\"\n                )\n            self.nodes[handler_node_name] = StateNodeSpec[Any, ContextT](\n                coerce_to_runnable(error_handler, name=handler_node_name, trace=False),  # type: ignore[arg-type]\n                metadata=None,\n                input_schema=resolved_input_schema,\n                retry_policy=None,\n                cache_policy=None,\n                is_error_handler=True,\n            )\n\n        if input_schema is not None:\n            self.nodes[node] = StateNodeSpec[NodeInputT, ContextT](\n                coerce_to_runnable(action, name=node, trace=False),  # type: ignore[arg-type]\n                metadata,\n                input_schema=input_schema,\n                retry_policy=retry_policy,\n                cache_policy=cache_policy,","sourceCodeStart":852,"sourceCodeEnd":888,"githubUrl":"https://github.com/langchain-ai/langgraph/blob/38031739e551638e373fb553453256c23feeb41f/libs/langgraph/langgraph/graph/state.py#L852-L888","documentation":"Error \"Auto-generated error handler node `{handler_node_name}` already exists.\" thrown in langchain-ai/langgraph.","triggerScenarios":"Thrown at libs/langgraph/langgraph/graph/state.py:870 when the library encounters an invalid state.","commonSituations":"See trigger scenarios.","solutions":[],"exampleFix":null,"handlingStrategy":null,"validationCode":null,"typeGuard":null,"tryCatchPattern":null,"preventionTips":[],"tags":[],"backgroundTag":null,"analyzedSha":"38031739e551638e373fb553453256c23feeb41f","analyzedAt":"2026-08-26T18:02:49.312Z","schemaVersion":2},"datasetVersion":"2026-08-26T21:11:00.512Z"}