Multilingual large language models (LLMs) often exhibit emergent 'shadow' capabilities in languages without official support, yet their performance on these languages remains uneven and under-measured. This is particularly acute for morphosyntactically rich minority languages such as Scottish Gaelic, where translation benchmarks fail to capture structural competence. We introduce GaelEval, the first multi-dimensional benchmark for Gaelic, comprising: (i) an expert-authored morphosyntactic MCQA task; (ii) a culturally grounded translation benchmark and (iii) a large-scale cultural knowledge Q&A task. Evaluating 19 LLMs against a fluent-speaker human baseline (n=30), we find that Gemini 3 Pro Preview achieves 83.3% accuracy on the linguistic task, surpassing the human baseline (78.1%). Proprietary models consistently outperform open-weight systems, and in-language (Gaelic) prompting yields a small but stable advantage (+2.4%). On the cultural task, leading models exceed 90% accuracy, though most systems perform worse under Gaelic prompting and absolute scores are inflated relative to the manual benchmark. Overall, GaelEval reveals that frontier models achieve above-human performance on several dimensions of Gaelic grammar, demonstrates the effect of Gaelic prompting and shows a consistent performance gap favouring proprietary over open-weight models.
Figures & tables
Category
N
Nominal morphology
17
Adjectives
11
Verbal noun cores
12
Formulaic expressions
10
Questions and tags
10
Prepositions
9
Table 1: Distribution of MCQs across principal grammatical categories.
FLUENT
NON-FLUENT
Onset
Near-/Native
Adv
Upp-Int
Int
Sum
0–4
12
0
0
0
12
12–18
2
2
1
0
5
18–30
7
5
3
1
16
30+
2
0
0
0
2
Total
23
7
4
1
35
Table 2: Participant distribution by age of first exposure to Gaelic (Onset), self-reported proficiency level ( N=35 ) and fluency grouping. ‘Fluent’ combines near-/native and advanced.
Closed-weight: Claude Haiku 4.5, Claude Opus 4.6, Gemini 2.5 Flash, Gemini 3 Flash Preview, Gemini 3 Pro Preview, GPT-4.1, GPT-4.1 Mini, GPT-4.1 Nano, GPT-4o, GPT-4o Mini, GPT-5, GPT-5 Mini, GPT-5 Nano, GPT-5.2
Table 3: Models evaluated in GaelEval.
Figure 1: Linguistic competence accuracy by grammatical category for the human baseline and the top nine most-performant models (0–1 scale; darker = higher accuracy). ADJ = adjectives; ADV = adverbials; CFE = clefts and focussing expressions; COL = colours; CONJ = conjunctions and particles; DET = determiners; FORM = formulaic expressions; IPAS = impersonals and passives; NOM = nominal morphology; NUM = numerals; PREP = prepositions; PRO = pronouns and anaphor resolution; QUES = questions and tags; REL = relative clauses; TAM = Tense-Aspect-Modality system; VNC = verbal noun cores. Means are cross-category and so differ from those in Table 4 . English prompting conditions used.
Model / Group
Gaelic
English
Δ G-E
Gemini 3 Pro Prev
83.3
80.0
3.3
Gemini 3 Flash Prev
79.2
77.5
1.7
Humans (Fluent)
n/a
78.1
–
GPT-5
69.2
71.7
-2.5
Gemini 2.5 Flash
61.7
62.5
-0.8
Claude Opus 4.6
59.2
50.8
8.3
Table 4: MCQA accuracy (%) under Gaelic and English prompting. Δ indicates Gaelic minus English performance. Human baseline shown for fluent speakers (n=30).
Level
N
Mean
Max
Min
Near-/Native
23
76.7
98.3
53.3
Native only
12
70.9
85.0
53.3
Advanced
7
82.6
97.5
63.3
Upper Intermediate
4
73.1
79.2
67.5
Intermediate
1
41.7
41.7
41.7
Fluent
30
78.1
98.3
53.3
Table 5: Human accuracy (%) on the 120-item MCQA by self-reported proficiency. ‘Fluent’ includes near-/native and advanced speakers.
en → gd
gd → en
BLEU
chrF
BLEU
chrF
Gemini 3 Flash Preview
71.47
79.07
71.75
77.38
Gemini 3 Pro Preview
65.56
78.57
73.41
78.20
Gemini 2.5 Flash
65.53
74.72
74.36
77.58
GPT-4.1
65.41
74.62
66.60
72.77
Deepseek R1
62.12
71.84
75.28
77.73
Table 6: BLEU and chrF scores for both English to Gaelic (en → gd) and Gaelic to English (gd → en) translation tasks.
Model
Gaelic
English
Δ G-E
Gemini 3 Flash Prev
91.35
91.63
-0.28
Gemini 3 Pro Prev
91.17
90.98
0.19
GPT-5
85.28
88.50
-3.22
Gemini 2.5 Flash
79.85
83.44
-3.59
Claude Opus 4.6
79.48
83.53
-4.05
GPT-5 Mini
71.48
80.04
-8.56
Table 7: Accuracy (%) on the cultural knowledge Q&A task under Gaelic and English prompting. Δ indicates Gaelic minus English performance.
Multilingual LLM benchmarks omit Slovak, a morphologically rich West Slavic language of five million speakers, or cover it only by machine translation. We present sk-bench, a native-first Slovak benchmark with 30 datasets (33 scored task variants) across ten skill categories. Eleven resources are introduced or first packaged for generative-LLM evaluation, including IFEval-SK with Slovak-adapted instruction checkers and native Chiby/SKJ1 resources for Slovak grammar and morphology. We evaluate 55 open- and closed-weights models under one harness. The best open model trails proprietary APIs by 12.6 points. Model rankings are similar for native and translated closed-form data (ρ≥0.98), though translation separates the strongest models less well. By contrast, human-authored and LLM-generated QA questions rank models differently (ρ=0.72). For Qwen3-14B, continued Slovak pretraining lowers the overall score by 13.9 points. A small instruction set restores three quarters of that loss. Test-time reasoning improves scores by 8.5 to 12.5 points for models of 9B and above. Together, these findings suggest four design lessons for other under-resourced languages: use native data where translation fails, plan instruction repair after language adaptation, enable test-time reasoning before scaling up, and avoid overinvesting in target-language prompts. We release the data and code at https://github.com/slovak-nlp/sk-bench
Marek Šuppa, Ivan Vykopal, Andrej Ridzik +9
Comenius University in Bratislava, Slovakia · Cisco Systems · Kempelen Institute of Intelligent Technologies, Bratislava, Slovakia +2
Evaluating large language models (LLMs) across languages remains challenging, as most multilingual benchmarks rely on translated English datasets, often obscuring linguistic and cultural specificity in the target language. This issue is particularly pronounced for less-resourced languages such as Kyrgyz, where reliable natively authored evaluation data are scarce. Building on previously introduced Kyrgyz-language evaluation datasets, this work reports the first systematic and large-scale evaluation of LLMs in Kyrgyz using the KyrgyzLLM-Bench benchmark suite. KyrgyzLLM-Bench comprises two natively authored datasets−KyrgyzMMLU and KyrgyzRC−together with carefully translated and manually post-edited versions of WinoGrande, HellaSwag, BoolQ, and TruthfulQA. We evaluate 26 open- and closed-source LLMs under zero-shot and few-shot settings, analyzing model performance, cross-lingual transfer, and the impact of translation artifacts on evaluation reliability. Across families and tasks, model rankings transfer broadly from English to Kyrgyz on WinoGrande and BoolQ, and to a lesser extent on MMLU, while HellaSwag exhibits a substantial English-Kyrgyz performance gap consistent with translation-induced plausibility shifts. Few-shot prompting improves several open-source models on reading comprehension but behaves inconsistently for proprietary models on translated tasks. We publicly release all datasets, evaluation code, and per-model results, and integrate the Kyrgyz tasks into a widely used multilingual evaluation framework to support future research on Kyrgyz NLP.
Timur Turatali, Aida Turdubaeva, Rustem Izmailov +2
1The Cramer Project · Institute of IT, Kyrgyz State Technical University named after I. Razzakov · School of Computer Science, University of Windsor +2
Large language models (LLMs) have demonstrated impressive multilingual capabilities for well-resourced languages, yet their performance on low-resource African languages remains poorly understood and largely unevaluated. This paper presents Nsanku, a systematic benchmark that evaluates the zero-shot machine translation performance of 19 open-weight and proprietary LLMs across 43 Ghanaian languages paired with English. Evaluation sentences were sourced from the YouVersion Bible platform, providing 300 sentence pairs per language. Two complementary automatic metrics are employed: Bilingual Evaluation Understudy (BLEU) and Character n-gram F-Score (chrF), alongside an average accuracy score and a cross-language consistency dimension. Nsanku represents the most comprehensive LLM translation evaluation for Ghanaian languages conducted to date. Results show that gemini-2.5-flash achieves the highest overall average score of 26.88 (BLEU: 24.60, chrF: 29.16), followed by claude-sonnet-4-5 at 24.87 (BLEU: 22.46, chrF: 27.28) and gpt-4.1 at 23.20 (BLEU: 21.15, chrF: 25.24). Among open-weight models, kimi-k2-instruct-0905 leads at an average score of 20.87. A critical finding from the consistency analysis is that no model and no language reached the Leaders quadrant of high performance and high consistency simultaneously, indicating that current LLMs are not yet reliably usable for Ghanaian language translation at scale. Siwu achieved the highest per-language average score at 25.73 while Nkonya scored lowest at 11.65. Nsanku establishes a publicly available, community-extensible evaluation infrastructure for African language NLP research.
Stephen E. Moore, Mich-Seth Owusu, Akwasi Asare +13
Department of Mathematics, University of Cape Coast, Cape Coast, Ghana · Ghana Natural Language Processing, Cape Coast, Cape Coast, Ghana · Khaya AI LTD Ghana