{"record":{"id":"e4865edc77a661cb","repo":"langchain-ai/langgraph","slug":"transport-must-be-sse-or-websocket","errorCode":null,"errorMessage":"transport must be 'sse' or 'websocket'.","messagePattern":"transport must be 'sse' or 'websocket'\\.","errorType":"exception","errorClass":"ValueError","httpStatus":null,"severity":"error","filePath":"libs/sdk-py/langgraph_sdk/_async/threads.py","lineNumber":774,"sourceCode":"        client-side.\n\n        Args:\n            thread_id: optional explicit thread identifier. Defaults to a\n                fresh UUIDv4.\n            assistant_id: assistant the run will use. Required.\n            headers: optional headers forwarded on every command and event\n                request for this stream session.\n            run_start_timeout: optional seconds to wait for an in-flight\n                `run.start` before subscribing operations raise\n                `asyncio.TimeoutError`. Defaults to `None` (wait forever).\n            transport: event transport to use — `\"sse\"` (default) or\n                `\"websocket\"`.\n\n        Returns:\n            An `AsyncThreadStream` to use as an async context manager.\n        \"\"\"\n        if transport not in (\"sse\", \"websocket\"):\n            raise ValueError(\"transport must be 'sse' or 'websocket'.\")\n        return AsyncThreadStream(\n            http=self.http,\n            thread_id=thread_id if thread_id is not None else str(uuid.uuid4()),\n            assistant_id=assistant_id,\n            headers=headers,\n            run_start_timeout=run_start_timeout,\n            explicit_thread_id=thread_id is not None,\n            transport_kind=transport,\n        )\n\n    async def join_stream(\n        self,\n        thread_id: str,\n        *,\n        last_event_id: str | None = None,\n        stream_mode: ThreadStreamMode | Sequence[ThreadStreamMode] = \"run_modes\",\n        headers: Mapping[str, str] | None = None,\n        params: QueryParamTypes | None = None,","sourceCodeStart":756,"sourceCodeEnd":792,"githubUrl":"https://github.com/langchain-ai/langgraph/blob/38031739e551638e373fb553453256c23feeb41f/libs/sdk-py/langgraph_sdk/_async/threads.py#L756-L792","documentation":"Error \"transport must be 'sse' or 'websocket'.\" thrown in langchain-ai/langgraph.","triggerScenarios":"Thrown at libs/sdk-py/langgraph_sdk/_async/threads.py:774 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"}