{"record":{"id":"405f375b3d069d93","repo":"langchain-ai/langgraph","slug":"output-channel-chan-not-in-known-channels-r","errorCode":null,"errorMessage":"Output channel '{chan}' not in known channels: '{repr(sorted(channels))[:100]}'","messagePattern":"Output channel '(.+?)' not in known channels: '(.+?)'","errorType":"exception","errorClass":"ValueError","httpStatus":null,"severity":"error","filePath":"libs/langgraph/langgraph/pregel/_validate.py","lineNumber":95,"sourceCode":"        if all(chan not in subscribed_channels for chan in input_channels):\n            raise ValueError(\n                f\"None of the input channels {input_channels} \"\n                f\"are subscribed to by any node\"\n            )\n\n    all_output_channels = set[str]()\n    if isinstance(output_channels, str):\n        all_output_channels.add(output_channels)\n    else:\n        all_output_channels.update(output_channels)\n    if isinstance(stream_channels, str):\n        all_output_channels.add(stream_channels)\n    elif stream_channels is not None:\n        all_output_channels.update(stream_channels)\n\n    for chan in all_output_channels:\n        if chan not in channels:\n            raise ValueError(\n                f\"Output channel '{chan}' not \"\n                f\"in known channels: '{repr(sorted(channels))[:100]}'\"\n            )\n\n    if interrupt_after_nodes != \"*\":\n        for n in interrupt_after_nodes:\n            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:","sourceCodeStart":77,"sourceCodeEnd":113,"githubUrl":"https://github.com/langchain-ai/langgraph/blob/38031739e551638e373fb553453256c23feeb41f/libs/langgraph/langgraph/pregel/_validate.py#L77-L113","documentation":"Error \"Output channel '{chan}' not in known channels: '{repr(sorted(channels))[:100]}'\" thrown in langchain-ai/langgraph.","triggerScenarios":"Thrown at libs/langgraph/langgraph/pregel/_validate.py:95 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"}