ESTS at WMT26: Routing-Informed Expert Pruning for Model Compression

Liu Martin, Lucas Bandarkar, Nanyun Peng


Abstract
We describe six submissions under the team name ESTS to the unconstrained WMT26 Model Compression Shared Task for English–Simplified Chinese and English–Egyptian Arabic. We submit three compression operating points per translation direction, all derived from GPT-OSS-20B. We use task-specific routing mass to rank experts and cross-lingual routing divergence to allocate retained capacity across layers, then physically remove low-importance experts. The resulting specialists are recovery-tuned on GPT-5.1-generated synthetic translation data and further compressed by applying MXFP4 quantization to the retained expert projection weights. We additionally implement a robust inference system for the instruction-conditioned WMT26 setting, including category inference, output validation, retries, segmented fallback, and source-owned JSON reconstruction. Across our six submissions, parameter counts range from 4.186B to 7.770B and packed artifact sizes from 4.55 to 6.33~GiB. Internal xCOMET-XL evaluation using GPT-5.1 pseudo-references provides an internal comparison across the submitted compression operating points.
Anthology ID:
2026.wmt-main.138
Volume:
Proceedings of the Eleventh Conference on Machine Translation
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Barry Haddow, Tom Kocmi, Philipp Koehn, Christof Monz
Venues:
WMT | WS
SIG:
SIGMT
Publisher:
Association for Computational Linguistics
Note:
Pages:
2009–2016
Language:
URL:
https://aclanthology.org/2026.wmt-main.138/
DOI:
Bibkey:
Cite (ACL):
Liu Martin, Lucas Bandarkar, and Nanyun Peng. 2026. ESTS at WMT26: Routing-Informed Expert Pruning for Model Compression. In Proceedings of the Eleventh Conference on Machine Translation, pages 2009–2016, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
ESTS at WMT26: Routing-Informed Expert Pruning for Model Compression (Martin et al., WMT 2026)
Copy Citation:
PDF:
https://aclanthology.org/2026.wmt-main.138.pdf