Predict and Fix: A Unified Model for Translation Quality Estimation and Post-Editing
Summary
In localization pipelines, quality estimation (QE) and automatic post-editing (APE) usually run as two separate models. This means the error signals found by the QE model are discarded before correction begins, and each segment needs two expensive inference passes. The authors merge both tasks into one small decoder-only model, Qwen2.5-0.5B. They add a special <QE> token whose final hidden state feeds a two-layer sigmoid regression head. The head predicts a quality score defined as one minus the normalized edit distance between the MT output and the linguist's correction. The standard language-modeling head then emits a PE/No PE decision and, when needed, a revised translation. Both objectives are trained together with uncertainty-weighted multi-task loss. Training uses proprietary, manually post-edited data for eight English-source language pairs at three scales. The largest model gives far better quality scores and edit decisions than zero-shot GPT-5.4 and Gemini 3.1 Pro, and it edits good translations less often. This suggests that task-specific joint training matters more than raw model size for QE-guided post-editing.
Key points
- Training data: three sets of about 100K, 1M and 1.84M segments covering eight pairs (EN→Canadian French, Japanese, Spanish, Korean, Simplified Chinese, German, Polish, European French).
- The 1.84M set is rebalanced to roughly 250K segments per pair, except European French (93,364).
- The test set has 9,048 segments.
- Main results:
- The 1.84M model reaches Pearson r = 0.907, MAE 0.054 and PE decision accuracy of 88.4%.
- The 1M model reaches r = 0.863 and 87.7% accuracy.
- GPT-5.4 scores r = 0.236 with 65.8% accuracy; Gemini 3.1 Pro scores r = 0.310 with 61.3%.
- Ablation baseline: an autoregressive Qwen variant that outputs the score as text, without the regression head, isolates the head's contribution. It was trained only on the 100K split.
- Over-editing remains a problem:
- EN→Spanish and EN→European French show negative ΔBLEU and ΔCOMET for every system, because the original MT is already strong (BLEU 82.56 and 61.15).
- Accuracy on No-PE segments is only 77.7%.
- Limitations:
- The data is proprietary and cannot be released.
- The comparison with commercial LLMs is asymmetric, since they ran zero-shot without in-domain data.
- Future work proposes few-shot baselines and MQM-style error-span prediction.
Cite
@inproceedings{modrzejewski2026predict,
title = {{Predict and Fix: A Unified Model for Translation Quality Estimation and Post-Editing}},
author = {Modrzejewski, Maciej and Bhaskar, Yash and Pateria, Chinmay},
booktitle = {Proceedings of the 17th Conference of the Association for Machine Translation in the Americas (Volume 1: Research Track)},
year = {2026},
url = {https://aclanthology.org/2026.amta-research.5/}
}References
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