Multimodal AI

UniWeTok: An Unified Binary Tokenizer with Codebook Size 2^{128} for Unified Multimodal Large Language Model

SShaobin ZhuangYYuang AiJJiaming HanWWeijia MaoXXiaohui LiFFangyikang WangXXiao WangYYan LiSShanchuan LinKKun XuZZhenheng YangHHuaibo HuangXXiangyu YueHHao ChenYYali Wang
Published
February 15, 2026
Authors
15
Word Count
15,419

UniWeTok unifies multimodal AI with a 2^128 codebook enabling both image understanding and generation.

Abstract

Unified Multimodal Large Language Models (MLLMs) require a visual representation that simultaneously supports high-fidelity reconstruction, complex semantic extraction, and generative suitability. However, existing visual tokenizers typically struggle to satisfy these conflicting objectives within a single framework. In this paper, we introduce UniWeTok, a unified discrete tokenizer designed to bridge this gap using a massive binary codebook (2^{128}). For training framework, we introduce Pre-Post Distillation and a Generative-Aware Prior to enhance the semantic extraction and generative prior of the discrete tokens. In terms of model architecture, we propose a convolution-attention hybrid architecture with the SigLu activation function. SigLu activation not only bounds the encoder output and stabilizes the semantic distillation process but also effectively addresses the optimization conflict between token entropy loss and commitment loss. We further propose a three-stage training framework designed to enhance UniWeTok's adaptability cross various image resolutions and perception-sensitive scenarios, such as those involving human faces and textual content. On ImageNet, UniWeTok achieves state-of-the-art image generation performance (FID: UniWeTok 1.38 vs. REPA 1.42) while requiring a remarkably low training compute (Training Tokens: UniWeTok 33B vs. REPA 262B). On general-domain, UniWeTok demonstrates highly competitive capabilities across a broad range of tasks, including multimodal understanding, image generation (DPG Score: UniWeTok 86.63 vs. FLUX.1 [Dev] 83.84), and editing (GEdit Overall Score: UniWeTok 5.09 vs. OmniGen 5.06). We release code and models to facilitate community exploration of unified tokenizer and MLLM.

Key Takeaways

  • 1

    UniWeTok uses a massive 2^128 codebook with binary quantization to unify image understanding and generation.

  • 2

    Pre-Post Distillation aligns both pre and post-quantized features to preserve semantic information through quantization.

  • 3

    SigLu activation resolves optimization conflicts between commitment loss and token entropy loss in semantic learning.

Limitations

  • Previous tokenizers struggled with unified performance across reconstruction, semantic understanding, and generation tasks simultaneously.

  • Traditional vector quantization creates computational overhead that binary quantization approaches aim to eliminate.

Keywords

visual tokenizersdiscrete tokenizerbinary codebookPre-Post DistillationGenerative-Aware Priorconvolution-attention hybrid architectureSigLu activation functiontoken entropy losscommitment lossthree-stage training frameworkmultimodal understandingimage generationDPG ScoreGEdit Overall Score

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UniWeTok: An Unified Binary Tokenizer with Codebook Size 2^{128} for Unified Multimodal Large Language Model | Paperchime