This is a Spanish (es) language-specific base language model trained by the HiTZ Research Center, starting from Qwen3-8B-Base and further pretrained on curated Spanish data.

This model is released as a base model, intended for further fine-tuning or adaptation (e.g., instruction tuning, domain adaptation).

To train language-specific base LLMs, we followed the methodology proposed by Etxaniz et al. (2024), originally developed for Basque, and extended it to other low-resource languages. To enable fair comparisons across languages, we limited the corpus size for each language to roughly the same number of tokens. We also included a small English subset to mitigate catastrophic forgetting.

Token counts vary slightly depending on the tokenizer, but remain comparable in overall size.

Spanish data was extracted from the multilingual CulturaX corpus. Given the substantially larger size of CulturaX compared to the Basque and Galician resources, we applied targeted filtering to obtain a more representative subset. Specifically, we retained only documents whose URLs indicate origin in Spain (i.e., containing the top-level domains .es, .eus, .cat, or .gal).
In addition, the Spanish data was filtered using the Dolma toolkit with the Gopher and C4 heuristics.
The English subset was sampled from the FineWeb corpus.

Training was conducted on the CINECA Leonardo high-performance computing cluster using Fully Sharded Data Parallel (FSDP) across 32 nodes, each equipped with 4 NVIDIA A100 GPUs (64 GB).

This work has been partially supported by the Basque Government (Research group funding IT1570-22 and IKER-GAITU project), the Spanish Ministry for Digital Transformation and of Civil Service, and the EU-funded NextGenerationEU Recovery, Transformation and Resilience Plan (ILENIA project, 2022/TL22/00215335; and ALIA project).