Hybrid Token Compression for Vision-Language Models

Vision-language models (VLMs) rely on hundreds of visual tokens, leading to high computational and memory costs. Existing compression methods face a trade-off: continuous compression can weaken high-level semantics, while discrete quantization may lose fine-grained appearance details. We introduce HTC-VLM, a hybrid visual token compression framework that disentangles semantics and appearance through two complementary pathways. A continuous pathway preserves detailed ViT patch features, while a discrete pathway provides semantic anchors using MGVQ quantization represented by four tokens. The two pathways are fused into a 580-token hybrid sequence and compressed into a single token using a disentanglement attention mask and a <voco> bottleneck. Under the same one-token output budget, HTC-VLM achieves 87.2% average performance retention across seven benchmarks (GQA, VQAv2, MMBench, MME, POPE, SEED-Bench, and ScienceQA-Image), outperforming the leading continuous baseline at 81.0%. Attention analysis shows that the compressed token prioritizes discrete anchors, supporting their role as semantic guidance. We further study token-budget scaling, cross-architecture generalization, inference efficiency, robustness to codebook and masking variations, and the information-theoretic properties of the hybrid bottleneck. These results show that combining continuous appearance features with discrete semantic anchors enables effective extreme visual token compression for efficient VLMs.