Hello, our flow run had failed with this error this afternoon.

Failed to set task state with error: HTTPError('400 Client Error: Bad Request for url: <https://api.prefect.io/graphql>')
Traceback (most recent call last):
  File "/usr/local/lib/python3.8/site-packages/prefect/engine/cloud/task_runner.py", line 124, in call_runner_target_handlers
    state = self.client.set_task_run_state(
  File "/usr/local/lib/python3.8/site-packages/prefect/client/client.py", line 1399, in set_task_run_state
    result = self.graphql(
  File "/usr/local/lib/python3.8/site-packages/prefect/client/client.py", line 275, in graphql
    result = <http://self.post|self.post>(
  File "/usr/local/lib/python3.8/site-packages/prefect/client/client.py", line 230, in post
    response = self._request(
  File "/usr/local/lib/python3.8/site-packages/prefect/client/client.py", line 400, in _request
    response = self._send_request(
  File "/usr/local/lib/python3.8/site-packages/prefect/client/client.py", line 333, in _send_request
    response.raise_for_status()
  File "/usr/local/lib/python3.8/site-packages/requests/models.py", line 941, in raise_for_status
    raise HTTPError(http_error_msg, response=self)
requests.exceptions.HTTPError: 400 Client Error: Bad Request for url: <https://api.prefect.io/graphql>

Is it a prefect.io cloud API error? Anything I could do to avoid it or re-try it in a better way?

Hi @Hui Zheng - this means that the GraphQL payload that your client sent could not be interpreted by our API; this is usually caused by poorly formatted GraphQL of some kind. What version of Prefect were you running when you saw this?