python -m verl.model_merger merge \
    --backend fsdp \
    --local_dir /xxx/verl/grpo_model/qwen3-8b-tools-0714-grpo-multi-node/global_step_140/actor \
    --target_dir /xxx/verl/grpo_model/qwen3-8b-tools-0714-grpo-multi-node/global_step_140/actor/huggingface