arXiv · 2605.25846
On the Limits of Model Merging for Multilinguality in Pre-Training
Abstract
Endowing models with consistent multilingual performance can be achieved by mixing pre-training data, or post-training approaches such as language-specific model merging. In this work, we test whether merging can be applied to monolingually pre-trained models. We conduct a controlled study on the efficacy of mixed, merged, and monolingual pre-training setups. We find that while monolingual pre-training results in strong in-language performance, merging any combination of monolingual models leads to performance collapse due to interference. Our analysis suggests representational similarity is a prerequisite for model merging. We therefore conclude that the flexibility of merging in fine-tuning does not extend trivially to language-specific pre-training.
Explore related subjects
Keep this discovery
Seth Aycock, Fedor Vitiugin, Aleksandr Umnov, Christof Monz, Khalil Sima'an. 2026-05-25. On the Limits of Model Merging for Multilinguality in Pre-Training. https://arxiv.org/abs/2605.25846
Cite the original work for its findings. Save a collection to share your selection of sources.