Enable wight-free export for VLM

[quic-amitraj]

Summary

This PR enables the VLM weight-free export path for Qwen/Qwen3-VL-30B-A3B-Instruct, a Qwen3-VL-MoE image-text-to-text model.

Model validated:

Qwen/Qwen3-VL-30B-A3B-Instruct

Validation script:

examples/dynamo/image_text_to_text/qwen3_vl_moe_dynamo_inference.py

Performance Comparison

Measured with the full-layer model using:

python examples/dynamo/image_text_to_text/qwen3_vl_moe_dynamo_inference.py

Legacy means no weight-free export. Weight-free uses the Dynamo/torch.export path because weight-free export is implemented on top of Dynamo export.

Export Time

Component	Legacy	Weight-Free Dynamo	Saved	Improvement
Vision export	28.685 sec	17.584 sec	11.101 sec	1.63x faster, 38.70% lower
Decoder export	1352.880 sec	86.967 sec	1265.913 sec	15.56x faster, 93.57% lower
Total export	1381.565 sec	104.551 sec	1277.014 sec	13.21x faster, 92.43% lower

Compile Time

Component	Legacy	Weight-Free Dynamo	Saved	Improvement
Vision compile	19.051 sec	18.644 sec	0.407 sec	1.02x faster, 2.14% lower
Decoder compile	1705.522 sec	366.976 sec	1338.546 sec	4.65x faster, 78.48% lower
Total compile	1724.573 sec	385.620 sec	1338.953 sec	4.47x faster, 77.64% lower

Artifact Size Comparison

For ONNX size, this table uses the complete wrapper export directory excluding QPC, because legacy export stores large external tensor files beside the small .onnx protobuf.

ONNX Export Artifact Size

Component	Legacy	Weight-Free Dynamo	Reduction
Vision ONNX artifact	2.01 GiB	1.48 MiB	1386.14x smaller, 99.928% lower
Decoder ONNX artifact	113.81 GiB	76.92 MiB	1515.12x smaller, 99.934% lower
Total ONNX artifact	115.82 GiB	78.40 MiB	1512.68x smaller, 99.934% lower

QPC Size

Component	Legacy	Weight-Free Dynamo	Delta
Vision QPC	1.04 GiB	1.04 GiB	97.65 KiB smaller
Decoder QPC	44.55 GiB	44.55 GiB	2.25 MiB larger
Total QPC	45.59 GiB	45.59 GiB	2.15 MiB larger

The QPC size is effectively unchanged, as expected. The major storage improvement is in the exported ONNX artifact before compile.

Runtime Comparison

Metric	Legacy	Weight-Free Dynamo	Delta
Average prefill / TTFT	1.03 sec	1.03 sec	no change
Decode throughput	66.49 tok/sec	65.60 tok/sec	-1.34%
Total throughput	39.59 tok/sec	39.30 tok/sec	-0.73%
Total E2E inference time	2.50 sec	2.52 sec	+0.80%

Runtime is effectively at parity while export, compile, and pre-compile artifact size improve substantially.

[quic-amitraj]

Legacy output:

['Based on the image provided, the following colors are visible:\n\n- Black: This is the dominant color, seen in the fur of the puppy.\n- Brown: The wooden surface has various shades of brown, from light tan to darker, weathered brown.\n- Gray: There are significant gray tones in the wood, particularly in the shadows and the weathered parts of the planks.\n- White: The highlights in the puppy's eyes appear as bright white or"']

Weight-free output:

['Based on the image provided, the following colors are visible:\n\n- Black: This is the dominant color, seen in the fur of the puppy.\n- Brown: The wooden surface has various shades of brown, from light tan to darker, weathered brown, creating a rustic appearance.\n- Gray: There are noticeable gray tones in the wood, particularly in the shadows and the weathered parts of the planks.\n- White: The highlights in the puppy's eyes"']