{"record":{"id":"28a388d00cb2644d","repo":"langchain-ai/langgraph","slug":"transport-must-be-sse-or-websocket-28a388","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/_sync/threads.py","lineNumber":751,"sourceCode":"        run_start_timeout: float | None = None,\n        transport: Literal[\"sse\", \"websocket\"] = \"sse\",\n    ) -> SyncThreadStream:\n        \"\"\"Open a v3 thread-centric streaming session.\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 SSE\n                request for this stream session.\n            transport: event transport to use, `\"sse\"` (default) or\n                `\"websocket\"`.\n\n        Returns:\n            A `SyncThreadStream` to use as a context manager.\n        \"\"\"\n        if transport not in (\"sse\", \"websocket\"):\n            raise ValueError(\"transport must be 'sse' or 'websocket'.\")\n        return SyncThreadStream(\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    def join_stream(\n        self,\n        thread_id: str,\n        *,\n        stream_mode: ThreadStreamMode | Sequence[ThreadStreamMode] = \"run_modes\",\n        last_event_id: str | None = None,\n        headers: Mapping[str, str] | None = None,\n        params: QueryParamTypes | None = None,","sourceCodeStart":733,"sourceCodeEnd":769,"githubUrl":"https://github.com/langchain-ai/langgraph/blob/38031739e551638e373fb553453256c23feeb41f/libs/sdk-py/langgraph_sdk/_sync/threads.py#L733-L769","documentation":"Error \"transport must be 'sse' or 'websocket'.\" thrown in langchain-ai/langgraph.","triggerScenarios":"Thrown at libs/sdk-py/langgraph_sdk/_sync/threads.py:751 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"}