{"record":{"id":"e43b3feb75fee228","repo":"langchain-ai/langgraph","slug":"protocol-command-did-not-return-a-valid-response-e43b3f","errorCode":null,"errorMessage":"Protocol command did not return a valid response.","messagePattern":"Protocol command did not return a valid response\\.","errorType":"exception","errorClass":"RuntimeError","httpStatus":null,"severity":"error","filePath":"libs/sdk-py/langgraph_sdk/stream/transport/sync_http.py","lineNumber":59,"sourceCode":"        self._default_headers: dict[str, str] = dict(headers or {})\n        self._closed = False\n        self._open_responses: list[httpx.Response] = []\n\n    def send_command(self, command: dict[str, Any]) -> dict[str, Any] | None:\n        if self._closed:\n            raise RuntimeError(\"Protocol transport is closed.\")\n        merged_headers = {**self._default_headers, \"content-type\": \"application/json\"}\n        response = self._client.post(\n            self._commands_url,\n            content=orjson.dumps(command),\n            headers=merged_headers,\n        )\n        response.raise_for_status()\n        if response.status_code in (202, 204):\n            return None\n        payload = orjson.loads(response.content)\n        if not isinstance(payload, dict) or \"id\" not in payload:\n            raise RuntimeError(\"Protocol command did not return a valid response.\")\n        return payload\n\n    def open_event_stream(self, params: dict[str, Any]) -> SyncEventStreamHandle:\n        if self._closed:\n            raise RuntimeError(\"Protocol transport is closed.\")\n        sse_headers = {\n            **self._default_headers,\n            \"content-type\": \"application/json\",\n            \"accept\": \"text/event-stream\",\n            \"cache-control\": \"no-store\",\n        }\n        request = self._client.build_request(\n            \"POST\",\n            self._stream_url,\n            content=orjson.dumps(build_event_stream_body(params)),\n            headers=sse_headers,\n        )\n        stream_cm = self._client.send(request, stream=True)","sourceCodeStart":41,"sourceCodeEnd":77,"githubUrl":"https://github.com/langchain-ai/langgraph/blob/38031739e551638e373fb553453256c23feeb41f/libs/sdk-py/langgraph_sdk/stream/transport/sync_http.py#L41-L77","documentation":"Error \"Protocol command did not return a valid response.\" thrown in langchain-ai/langgraph.","triggerScenarios":"Thrown at libs/sdk-py/langgraph_sdk/stream/transport/sync_http.py:59 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"}