# MetricX-25 and GemSpanEval: Google Translate Submissions to the WMT25 Evaluation Shared Task

arXiv: https://arxiv.org/abs/2510.24707 · HTML: https://mlsanity.com/paper/2510.24707/

## Key facts

- Cited by 10 papers in the map (data through 14 Oct 2026).
- Builds on 22 of its 43 references that are in the map.
- First posted on arXiv 28 Oct 2025.

## Builds on (most cited first, 22 of 22)

- [Unsupervised Cross-lingual Representation Learning at Scale](https://mlsanity.com/paper/1911.02116/) (2019)
- [mT5: A massively multilingual pre-trained text-to-text transformer](https://mlsanity.com/paper/2010.11934/) (2020)
- [BLEURT: Learning Robust Metrics for Text Generation](https://mlsanity.com/paper/2004.04696/) (2020)
- [COMET: A Neural Framework for MT Evaluation](https://mlsanity.com/paper/2009.09025/) (2020)
- [Adafactor: Adaptive Learning Rates with Sublinear Memory Cost](https://mlsanity.com/paper/1804.04235/) (2018)
- [Large Language Models Are State-of-the-Art Evaluators of Translation Quality](https://mlsanity.com/paper/2302.14520/) (2023)
- [Experts, Errors, and Context: A Large-Scale Study of Human Evaluation for Machine Translation](https://mlsanity.com/paper/2104.14478/) (2021)
- [xCOMET: Transparent Machine Translation Evaluation through Fine-grained Error Detection](https://mlsanity.com/paper/2310.10482/) (2023)
- [Tower: An Open Multilingual Large Language Model for Translation-Related Tasks](https://mlsanity.com/paper/2402.17733/) (2024)
- [GEMBA-MQM: Detecting Translation Quality Error Spans with GPT-4](https://mlsanity.com/paper/2310.13988/) (2023)
- [The Devil is in the Errors: Leveraging Large Language Models for Fine-grained Machine Translation Evaluation](https://mlsanity.com/paper/2308.07286/) (2023)
- [Learning Compact Metrics for MT](https://mlsanity.com/paper/2110.06341/) (2021)
- [MetricX-24: The Google Submission to the WMT 2024 Metrics Shared Task](https://mlsanity.com/paper/2410.03983/) (2024)
- [Scaling up COMETKIWI: Unbabel-IST 2023 Submission for the Quality Estimation Shared Task](https://mlsanity.com/paper/2309.11925/) (2023)
- [Ties Matter: Meta-Evaluating Modern Metrics with Pairwise Accuracy and Tie Calibration](https://mlsanity.com/paper/2305.14324/) (2023)
- [Error Span Annotation: A Balanced Approach for Human Evaluation of Machine Translation](https://mlsanity.com/paper/2406.11580/) (2024)
- [Tower+: Bridging Generality and Translation Specialization in Multilingual LLMs](https://mlsanity.com/paper/2506.17080/) (2025)
- [Improving Statistical Significance in Human Evaluation of Automatic Metrics via Soft Pairwise Accuracy](https://mlsanity.com/paper/2409.09598/) (2024)
- [The Eval4NLP 2023 Shared Task on Prompting Large Language Models as Explainable Metrics](https://mlsanity.com/paper/2310.19792/) (2023)
- [PrExMe! Large Scale Prompt Exploration of Open Source LLMs for Machine Translation and Summarization Evaluation](https://mlsanity.com/paper/2406.18528/) (2024)
- [Adapting Decoder-Based Language Models for Diverse Encoder Downstream Tasks](https://mlsanity.com/paper/2503.02656/) (2025)
- [From Jack of All Trades to Master of One: Specializing LLM-based Autoraters to a Test Set](https://mlsanity.com/paper/2411.15387/) (2024)

## Built on by (most cited first, 10 of 10)

- [BERT-as-a-Judge: A Robust Alternative to Lexical Methods for Efficient Reference-Based LLM Evaluation](https://mlsanity.com/paper/2604.09497/) (2026)
- [OmnilingualGAIA2: Evaluating the Multilingual Gap in Frontier AI Agents](https://mlsanity.com/paper/2608.08775/) (2026)
- [What Are We Measuring in NLG? A Meta-Analysis of Evaluation Trends 2020-2025](https://mlsanity.com/paper/2601.07648/) (2026)
- [PEAR: Pairwise Evaluation for Automatic Relative Scoring in Machine Translation](https://mlsanity.com/paper/2601.18006/) (2026)
- [Dynamically Allocating Evaluation Effort for Model Ranking](https://mlsanity.com/paper/2608.03437/) (2026)
- [LuxMT Technical Report](https://mlsanity.com/paper/2602.15506/) (2026)
- [Is Human Annotation Necessary? Iterative MBR Distillation for Error Span Detection in Machine Translation](https://mlsanity.com/paper/2603.12983/) (2026)
- [Span-Level Machine Translation Meta-Evaluation](https://mlsanity.com/paper/2603.19921/) (2026)
- [CompactQE: Interpretable Translation Quality Estimation via Small Open-Weight LLMs](https://mlsanity.com/paper/2605.15763/) (2026)
- [Ouvia: A User-centered Framework for Measuring Usability of Speech Translation in Real-World Communication Scenarios](https://mlsanity.com/paper/2606.06177/) (2026)

## Abstract (arXiv)

In this paper, we present our submissions to the unified WMT25 Translation Evaluation Shared Task. For the Quality Score Prediction subtask, we create a new generation of MetricX with improvements in the input format and the training protocol, while for the Error Span Detection subtask we develop a new model, GemSpanEval, trained to predict error spans along with their severities and categories. Both systems are based on the state-of-the-art multilingual open-weights model Gemma 3, fine-tuned on publicly available WMT data. We demonstrate that MetricX-25, adapting Gemma 3 to an encoder-only architecture with a regression head on top, can be trained to effectively predict both MQM and ESA quality scores, and significantly outperforms its predecessor. Our decoder-only GemSpanEval model, on the other hand, we show to be competitive in error span detection with xCOMET, a strong encoder-only sequence-tagging baseline. With error span detection formulated as a generative task, we instruct the model to also output the context for each predicted error span, thus ensuring that error spans are identified unambiguously.