@inproceedings{park-etal-2026-boundary,
title = "Boundary-Aware Expert Ordering Preservation with Next-Router Supervision for {M}o{E} Quantization",
author = "Park, Hancheol and
Lee, Geonho and
Kim, Tae-Ho",
editor = "Lee, Hung-Yi and
Dev, Sunipa and
Li, Jessy and
Elliott, Desmond",
booktitle = "Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing",
month = oct,
year = "2026",
address = "Budapest, Hungary",
publisher = "Association for Computational Linguistics",
url = "https://aclanthology.org/2026.emnlp-main.2041/",
pages = "46537--46548",
ISBN = "979-8-89176-459-0",
abstract = "Mixture-of-Experts (MoE) language models scale model capacity through sparse expert activation, but their large parameter footprint remains costly to deploy. Post-training quantization (PTQ) offers a practical compression strategy; however, quantization errors can alter router decisions and cause the quantized model to activate experts different from those selected by its full-precision counterpart. Prior router-aware PTQ objectives mitigate such expert-shift by aligning router outputs or preserving top-$k$ expert orderings and margins at a given router. Yet sequential block-wise PTQ introduces an additional failure mode: quantizing a decoder block changes the representations received by the next MoE router, potentially causing downstream expert-shift that is not directly optimized by existing objectives. To address this issue, we propose MENDS-MoE (Margin-Preserving Expert Orderings with Next-Router Decision Supervision), an auxiliary calibration objective that supervises current-block quantization using routing decisions at the next MoE router. MENDS-MoE further introduces a boundary-aware margin loss that preserves orderings among selected experts while maintaining their separation from unselected experts near the top-$k$ boundary. It is applied only during calibration and adds no inference-time computation. Across three MoE language models under 4-bit and 3-bit-average weight-only quantization, MENDS-MoE achieves the best average downstream accuracy and the lowest perplexity in most evaluated model{--}bit settings. Ablation studies further support the contributions of both next-router supervision and boundary-aware margin preservation."
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<abstract>Mixture-of-Experts (MoE) language models scale model capacity through sparse expert activation, but their large parameter footprint remains costly to deploy. Post-training quantization (PTQ) offers a practical compression strategy; however, quantization errors can alter router decisions and cause the quantized model to activate experts different from those selected by its full-precision counterpart. Prior router-aware PTQ objectives mitigate such expert-shift by aligning router outputs or preserving top-k expert orderings and margins at a given router. Yet sequential block-wise PTQ introduces an additional failure mode: quantizing a decoder block changes the representations received by the next MoE router, potentially causing downstream expert-shift that is not directly optimized by existing objectives. To address this issue, we propose MENDS-MoE (Margin-Preserving Expert Orderings with Next-Router Decision Supervision), an auxiliary calibration objective that supervises current-block quantization using routing decisions at the next MoE router. MENDS-MoE further introduces a boundary-aware margin loss that preserves orderings among selected experts while maintaining their separation from unselected experts near the top-k boundary. It is applied only during calibration and adds no inference-time computation. Across three MoE language models under 4-bit and 3-bit-average weight-only quantization, MENDS-MoE achieves the best average downstream accuracy and the lowest perplexity in most evaluated model–bit settings. Ablation studies further support the contributions of both next-router supervision and boundary-aware margin preservation.</abstract>
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%0 Conference Proceedings
%T Boundary-Aware Expert Ordering Preservation with Next-Router Supervision for MoE Quantization
%A Park, Hancheol
%A Lee, Geonho
%A Kim, Tae-Ho
%Y Lee, Hung-Yi
%Y Dev, Sunipa
%Y Li, Jessy
%Y Elliott, Desmond
%S Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
%D 2026
%8 October
%I Association for Computational Linguistics
%C Budapest, Hungary
%@ 979-8-89176-459-0
%F park-etal-2026-boundary
%X Mixture-of-Experts (MoE) language models scale model capacity through sparse expert activation, but their large parameter footprint remains costly to deploy. Post-training quantization (PTQ) offers a practical compression strategy; however, quantization errors can alter router decisions and cause the quantized model to activate experts different from those selected by its full-precision counterpart. Prior router-aware PTQ objectives mitigate such expert-shift by aligning router outputs or preserving top-k expert orderings and margins at a given router. Yet sequential block-wise PTQ introduces an additional failure mode: quantizing a decoder block changes the representations received by the next MoE router, potentially causing downstream expert-shift that is not directly optimized by existing objectives. To address this issue, we propose MENDS-MoE (Margin-Preserving Expert Orderings with Next-Router Decision Supervision), an auxiliary calibration objective that supervises current-block quantization using routing decisions at the next MoE router. MENDS-MoE further introduces a boundary-aware margin loss that preserves orderings among selected experts while maintaining their separation from unselected experts near the top-k boundary. It is applied only during calibration and adds no inference-time computation. Across three MoE language models under 4-bit and 3-bit-average weight-only quantization, MENDS-MoE achieves the best average downstream accuracy and the lowest perplexity in most evaluated model–bit settings. Ablation studies further support the contributions of both next-router supervision and boundary-aware margin preservation.
%U https://aclanthology.org/2026.emnlp-main.2041/
%P 46537-46548
Markdown (Informal)
[Boundary-Aware Expert Ordering Preservation with Next-Router Supervision for MoE Quantization](https://aclanthology.org/2026.emnlp-main.2041/) (Park et al., EMNLP 2026)
ACL