# Bug report multi\_agent configuration

**URL:** <https://discuss.ray.io/t/bug-report-multi-agent-configuration/23118>\
**Category:** RLlib\
**Created:** [September 18, 2025, 3:04pm UTC](https://discuss.ray.io/t/bug-report-multi-agent-configuration/23118 "2025-09-18T15:04:41Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![sunghyun.chung](https://avatars.discourse-cdn.com/v4/letter/s/41988e/32.png) [@sunghyun.chung](https://discuss.ray.io/u/sunghyun.chung)\
**Post date:** [September 18, 2025, 3:04pm UTC](https://discuss.ray.io/t/bug-report-multi-agent-configuration/23118/1 "2025-09-18T15:04:41Z")

</div>

**1. Severity of the issue: (select one)**  
 None: I’m just curious or want clarification.  
 Low: Annoying but doesn’t hinder my work.  
 Medium: Significantly affects my productivity but can find a workaround.  
 High: Completely blocks me.

**2. Environment:**

- Ray version: 2.44
- Python version: 3.12
- OS: windows
- Cloud/Infrastructure:
- Other libs/tools (if relevant):

**3. What happened vs. what you expected:**

- Expected:
- Actual:

env = gym.make(“CartPole-v1”)  
cfg = (  
PPOConfig()  
.environment(env=“CartPole-v1”)  
.multi\_agent(  
policies={  
“asdf”: (  
(  
None,  
env.observation\_space,  
env.action\_space,  
{“model”: [128, 128]},  
)  
)  
},  
policy\_mapping\_fn=lambda agent\_id, episode, \*\*kwargs: “asdf”  
)  
.debugging(log\_level=“INFO”)  
)  
cfg.build\_algo()

output:  
2025-09-18 10:00:23,712 ERROR actor\_manager.py:873 – Ray error (The actor died because of an error raised in its creation task, ray::MultiAgentEnvRunner.\__init_\_() (pid=29440, ip=127.0.0.1, actor\_id=3a3bb3179ad29cccc9eae6cc01000000, repr=\<ray.rllib.env.multi\_agent\_env\_runner.MultiAgentEnvRunner object at 0x000002250DE38250\>) File “python\\ray\\_raylet.pyx”, line 1895, in ray.\_raylet.execute\_task File “python\\ray\\_raylet.pyx”, line 1835, in ray.\_raylet.execute\_task.function\_executor File “c:\DEC\am\.venv\lib\site-packages\ray\_private\function\_manager.py”, line 689, in actor\_method\_executor return method(\_\_ray\_actor, \*args, \*\*kwargs) File “c:\DEC\am\.venv\lib\site-packages\ray\util\tracing\tracing\_helper.py”, line 463, in \_resume\_span return method(self, \*\_args, \*\*\_kwargs) File “c:\DEC\am\.venv\lib\site-packages\ray\rllib\env\multi\_agent\_env\_runner.py”, line 107, in \__init_\_ self.make\_env() File “c:\DEC\am\.venv\lib\site-packages\ray\util\tracing\tracing\_helper.py”, line 463, in \_resume\_span return method(self, \*\_args, \*\*\_kwargs) File “c:\DEC\am\.venv\lib\site-packages\ray\rllib\env\multi\_agent\_env\_runner.py”, line 795, in make\_env self.env = make\_vec( File “c:\DEC\am\.venv\lib\site-packages\ray\rllib\env\vector\registration.py”, line 69, in make\_vec env = SyncVectorMultiAgentEnv( File “c:\DEC\am\.venv\lib\site-packages\ray\rllib\env\vector\sync\_vector\_multi\_agent\_env.py”, line 37, in \__init_\_ self.single\_action\_spaces = self.envs[0].unwrapped.action\_spaces or dict( AttributeError: ‘CartPoleEnv’ object has no attribute ‘action\_spaces’), taking actor 1 out of service. 2025-09-18 10:00:23,714 ERROR actor\_manager.py:873 – Ray error (The actor died because of an error raised in its creation task, ray::MultiAgentEnvRunner.\__init_\_() (pid=46112, ip=127.0.0.1, actor\_id=172503951d93979676e46d9901000000, repr=\<ray.rllib.env.multi\_agent\_env\_runner.MultiAgentEnvRunner object at 0x000001E90DC78280\>) File “python\\ray\\_raylet.pyx”, line 1895, in ray.\_raylet.execute\_task File “python\\ray\\_raylet.pyx”, line 1835, in ray.\_raylet.execute\_task.function\_executor File “c:\DEC\am\.venv\lib\site-packages\ray\_private\function\_manager.py”, line 689, in actor\_method\_executor return method(\_\_ray\_actor, \*args, \*\*kwargs) File “c:\DEC\am\.venv\lib\site-packages\ray\util\tracing\tracing\_helper.py”, line 463, in \_resume\_span return method(self, \*\_args, \*\*\_kwargs)

…

```
env = SyncVectorMultiAgentEnv( File "c:\\DEC\\am\\.venv\\lib\\site-packages\\ray\\rllib\\env\\vector\\sync_vector_multi_agent_env.py", line 37, in \__init_\_ self.single_action_spaces = self.envs\[0\].unwrapped.action_spaces or dict( AttributeError: 'CartPoleEnv' object has no attribute 'action_spaces' 

```

I looked at the source code of `SyncVectorMultiAgentEnv` and line 37 probably needs to be fixed, or a include a warning that environment that is passed in (which is CartPole here) is a single-agent environment.