This looks like a PyTorch error. Check your PyTorch Version

python -c "import torch; print(torch.__version__)"
Could you share more on the issue? vllm version and how this occurred?

This undefined symbol error is a classic ABI mismatch!

Root cause:
The vLLM binary was compiled with a different PyTorch version than what's currently installed.

Fixes:

1. Reinstall vLLM with matching PyTorch

pip uninstall vllm
pip install vllm --no-cache-dir

2. Check PyTorch version

import torch
print(torch.__version__)
print(torch.version.cuda)

vLLM needs specific CUDA + PyTorch combos.

3. Full clean install

pip uninstall vllm torch
pip cache purge
pip install torch==2.2.0+cu121 -f https://download.pytorch.org/whl/torch_stable.html
pip install vllm

4. Build from source (if weird setup)

git clone https://github.com/vllm-project/vllm.git
cd vllm
pip install -e .

Common causes:

• Installing vLLM before PyTorch
• Conda/pip environment mixing
• Multiple CUDA versions on system

We've debugged these ABI issues at RevolutionAI many times. The clean reinstall usually fixes it.

What's your pip list | grep torch output?