langchain-ai/langgraph · error · ValueError

Sync client is not initialized: please provide `url` or `syn

Error message

Sync client is not initialized: please provide `url` or `sync_client` when initializing `RemoteGraph`.

What it means

Error "Sync client is not initialized: please provide `url` or `sync_client` when initializing `RemoteGraph`." thrown in langchain-ai/langgraph.

Source

Thrown at libs/langgraph/langgraph/pregel/remote.py:190

        if client is None and url is not None:
            client = get_client(url=url, api_key=api_key, headers=headers)
        self.client = client

        if sync_client is None and url is not None:
            sync_client = get_sync_client(url=url, api_key=api_key, headers=headers)
        self.sync_client = sync_client

    def _validate_client(self) -> LangGraphClient:
        if self.client is None:
            raise ValueError(
                "Async client is not initialized: please provide `url` or `client` when initializing `RemoteGraph`."
            )
        return self.client

    def _validate_sync_client(self) -> SyncLangGraphClient:
        if self.sync_client is None:
            raise ValueError(
                "Sync client is not initialized: please provide `url` or `sync_client` when initializing `RemoteGraph`."
            )
        return self.sync_client

    def _reject_v3_unsupported(
        self,
        *,
        control: Any,
        transformers: Any,
        interrupt_before: Any,
        interrupt_after: Any,
        extra_kwargs: dict[str, Any],
    ) -> None:
        """Raise NotImplementedError for kwargs unsupported by the v3 streaming path."""
        for name, value in (
            ("control", control),
            ("transformers", transformers),
            ("interrupt_before", interrupt_before),

View on GitHub (pinned to 38031739e5)

When it happens

Trigger: Thrown at libs/langgraph/langgraph/pregel/remote.py:190 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/d5d9b436672e32a0. Report an issue: GitHub.