langchain-ai/langgraph · error · ValueError

extension name must be non-empty.

Error message

extension name must be non-empty.

What it means

Error "extension name must be non-empty." thrown in langchain-ai/langgraph.

Source

Thrown at libs/sdk-py/langgraph_sdk/stream/decoders.py:347

            status, error = _terminal_from_tasks_result(data)
            handle._finish(status, error)
            del self._active[child_path]


class ExtensionsDecoder:
    """Yields `params.data` from one named custom channel.

    Mirrors `_ExtensionProjection._iter` (`_async/stream.py:1278-1299`), with
    an added name filter so it can share one subscription in interleave.

    Args:
        name: The extension name. Only `custom` events whose `data["name"]`
            matches are consumed.
    """

    def __init__(self, name: str):
        if not name:
            raise ValueError("extension name must be non-empty.")
        self._name = name

    def feed(self, event: Mapping[str, Any]) -> Iterable[Any]:
        if event.get("method") != "custom":
            return
        params = event.get("params") or {}
        data = params.get("data")
        if not isinstance(data, dict):
            return
        if data.get("name") != self._name:
            return
        yield data

View on GitHub (pinned to 38031739e5)

When it happens

Trigger: Thrown at libs/sdk-py/langgraph_sdk/stream/decoders.py:347 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/62c833a5f8c3e49d. Report an issue: GitHub.