How to use from
vLLM
Install from pip and serve model
# Install vLLM from pip:
pip install vllm
# Start the vLLM server:
vllm serve "McGill-NLP/A3-Qwen3.5-9B"
# Call the server using curl (OpenAI-compatible API):
curl -X POST "http://localhost:8000/v1/chat/completions" \
	-H "Content-Type: application/json" \
	--data '{
		"model": "McGill-NLP/A3-Qwen3.5-9B",
		"messages": [
			{
				"role": "user",
				"content": [
					{
						"type": "text",
						"text": "Describe this image in one sentence."
					},
					{
						"type": "image_url",
						"image_url": {
							"url": "https://cdn.britannica.com/61/93061-050-99147DCE/Statue-of-Liberty-Island-New-York-Bay.jpg"
						}
					}
				]
			}
		]
	}'
Use Docker
docker model run hf.co/McGill-NLP/A3-Qwen3.5-9B
Quick Links

A3-Qwen3.5-9B is a 9B multimodal web agent fine-tuned from Qwen/Qwen3.5-9B on A3-Synth, a synthetic dataset generated using the Agent-as-Annotators (A3) framework.

The model achieves 41.5% on WebArena, surpassing closed-source models such as Claude 3.5 Sonnet (36.0%) and GPT-4o (31.5%) under the same evaluation protocol.

Usage

Serve with vLLM:

vllm serve McGill-NLP/A3-Qwen3.5-9B --tensor-parallel-size 2 --max-model-len 65536 --enforce-eager --dtype bfloat16

Training

  • Base model: Qwen/Qwen3.5-9B
  • Data: A3-Synth (16k examples from Gemini 3 Pro trajectories)
  • Method: SFT with FSDP
  • Max sequence length: 16,384
  • Learning rate: 1e-5
  • Epochs: 2
  • Batch size: 1 per GPU, gradient accumulation 4

Model Variants

Model Parameters Link
A3-Qwen3.5-9B 9B McGill-NLP/A3-Qwen3.5-9B
A3-Qwen3.5-4B 4B McGill-NLP/A3-Qwen3.5-4B
A3-Qwen3.5-2B 2B McGill-NLP/A3-Qwen3.5-2B

Citation

@misc{lu2026structured,
      title={Structured Distillation of Web Agent Capabilities Enables Generalization}, 
      author={Xing Han Lù and Siva Reddy},
      year={2026},
      eprint={2604.07776},
      archivePrefix={arXiv},
      primaryClass={cs.LG},
      url={https://arxiv.org/abs/2604.07776}, 
}
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