Experimental() got an unexpected keyword argument '_enable_new_api_stack'

How severe does this issue affect your experience of using Ray?

  • None: Just asking a question out of curiosity
  • Low: It annoys or frustrates me for a moment.
  • Medium: It contributes to significant difficulty to complete my task, but I can work around it.
  • High: It blocks me to complete my task.

My code from RL Modules (Alpha) — Ray 2.9.1

import torch
from pprint import pprint

from ray.rllib.algorithms.ppo import PPOConfig

config = (

algorithm = config.build()

# run for 2 training steps
for _ in range(2):
    result = algorithm.train()

Error: experimental() got an unexpected keyword argument ‘_enable_new_api_stack’

I found that _enable_new_api_stack is not called in experimental function

@hung_trinh_medium Thanks for raising this issue here. Can you check, if you are indeed running on ray==2.9.1?. I can not reproduce this issue with ray=2.9.1.

Thank you for your quick reply.
I can not run this code with ray = 2.9.1.
I tried with other versions, but it didn’t work.