llm-compressor pins transformers<=4.57.6, can't load Qwen3.6. AutoRound (Intel) works with transformers 5.x and is already installed as an llmcompressor dependency. Produces vLLM-compatible INT4 output.
Merged model has tokenizer_class=TokenizersBackend (transformers 5.x) which is unknown to transformers 4.57.6 in the quant venv.