Carlos Escolano Peinado
Author directory2026
Task-Preserving Multilingual Instruction Tuning for Open-Ended QA at WMT 2026 MIST
Aleix Sant | Jordi Luque Serrano | Carlos Escolano Peinado
Proceedings of the Eleventh Conference on Machine Translation
Aleix Sant | Jordi Luque Serrano | Carlos Escolano Peinado
Proceedings of the Eleventh Conference on Machine Translation
We describe our submission to the WMT 2026 Multilingual Instruction Shared Task. We adapt Qwen3-8B with LoRA using organiser-provided data, EuroAlpaca, a multilingual instruction dataset created through task-preserving localisation, and CrossEuroAlpaca, a cross-lingual augmentation that assigns different source and target languages to instructions, contexts and responses. Our system targets open-ended question answering (QA-OEG) in ten shared-task languages represented in the auxiliary data. Under matched decoding, adaptation improves the mean automatic Gemma-4 judge score on target-language QA-OEG by 7.8% relative to the base model. On the 27-language Aya Evaluation Suite, it yields relative gains of 41.5% in macro-averaged ROUGE-L and 2.9% in BERTScore-F1, with larger improvements in the target languages. However, these gains are task- and language-specific. Gemma-4 scores improve for QA-OEG and summarisation in the target languages but decline for context-grounded QA within this set and across all three tasks outside it.