English

Languages are Modalities: Cross-Lingual Alignment via Encoder Injection

Computation and Language 2025-11-03 v1 Artificial Intelligence Machine Learning

Abstract

Instruction-tuned Large Language Models (LLMs) underperform on low resource, non-Latin scripts due to tokenizer fragmentation and weak cross-lingual coupling. We present LLINK (Latent Language Injection for Non-English Knowledge), a compute efficient language-as-modality method that conditions an instruction-tuned decoder without changing the tokenizer or retraining the decoder. First, we align sentence embeddings from a frozen multilingual encoder to the decoder's latent embedding space at a reserved position via a lightweight contrastive projector. Second, the vector is expanded into K soft slots and trained with minimal adapters so the frozen decoder consumes the signal. LLINK substantially improves bilingual retrieval and achieves 81.3% preference over the base model and 63.6% over direct fine-tuning in LLM-judged Q&A evaluations. We further find that improvements can be attributed to reduced tokenization inflation and a stronger cross lingual alignment, despite the model having residual weaknesses in numeric fidelity. Treating low resource languages as a modality offers a practical path to stronger cross-lingual alignment in lightweight LLMs.

Keywords

Cite

@article{arxiv.2510.27254,
  title  = {Languages are Modalities: Cross-Lingual Alignment via Encoder Injection},
  author = {Rajan Agarwal and Aarush Gupta},
  journal= {arXiv preprint arXiv:2510.27254},
  year   = {2025}
}

Comments

14 pages, 3 Figures

R2 v1 2026-07-01T07:15:14.478Z