Your current environment

The output of python collect_env.py

VERL’s vLLM rollout fails to initialize with vLLM 0.8.4 (the version listed in VERL’s requirements.txt).

The file vllm_rollout_spmd.py imports:

from vllm.model_executor.model_loader.utils import process_weights_after_loading

And I get this error:

ImportError: cannot import name 'process_weights_after_loading' from 'vllm.model_executor.model_loader.utils’

File "/verl/verl/workers/rollout/vllm_rollout/vllm_rollout_spmd.py", line 54, in
from vllm.model_executor.model_loader.utils import process_weights_after_loading
ImportError: cannot import name 'process_weights_after_loading' from 'vllm.model_executor.model_loader.utils' (/verl/.venv/lib/python3.10/site-packages/vllm/model_executor/model_loader/utils.py)

I saw this function is indeed in vllm.model_executor.model_loader.utils so don't know why the import failed. Is it version problem?

I've attached my script. I'm using 2.6.0+cu124.

run_qwen3-0.6b.sh

🐛 Describe the bug

.

Before submitting a new issue...

• Make sure you already searched for relevant issues, and asked the chatbot living at the bottom right corner of the documentation page, which can answer lots of frequently asked questions.