{"record":{"id":"f18b4992f4e22b90","repo":"langchain-ai/langgraph","slug":"key-chan-not-in-channels","errorCode":null,"errorMessage":"Key {chan} not in channels","messagePattern":"Key (.+?) not in channels","errorType":"exception","errorClass":"ValueError","httpStatus":null,"severity":"error","filePath":"libs/langgraph/langgraph/pregel/_validate.py","lineNumber":120,"sourceCode":"            if n not in nodes:\n                raise ValueError(f\"Node {n} not in nodes\")\n    if interrupt_before_nodes != \"*\":\n        for n in interrupt_before_nodes:\n            if n not in nodes:\n                raise ValueError(f\"Node {n} not in nodes\")\n\n\ndef validate_keys(\n    keys: str | Sequence[str] | None,\n    channels: Mapping[str, Any],\n) -> None:\n    if isinstance(keys, str):\n        if keys not in channels:\n            raise ValueError(f\"Key {keys} not in channels\")\n    elif keys is not None:\n        for chan in keys:\n            if chan not in channels:\n                raise ValueError(f\"Key {chan} not in channels\")\n","sourceCodeStart":102,"sourceCodeEnd":121,"githubUrl":"https://github.com/langchain-ai/langgraph/blob/38031739e551638e373fb553453256c23feeb41f/libs/langgraph/langgraph/pregel/_validate.py#L102-L121","documentation":"Error \"Key {chan} not in channels\" thrown in langchain-ai/langgraph.","triggerScenarios":"Thrown at libs/langgraph/langgraph/pregel/_validate.py:120 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"}