UkrQualBench

Benchmark for evaluating Ukrainian language quality in Large Language Models (LLMs)

UkrQualBench evaluates linguistic quality (nativeness) of Ukrainian language in LLMs, not cognitive abilities. Unlike existing benchmarks measuring knowledge and reasoning, UkrQualBench focuses on how naturally and correctly models use Ukrainian.

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Leaderboard (June 2026)

ELO Rating (Pairwise Comparisons)

Rank	Model	ELO
1	gemini-3.5-flash	1792.4
2	gemini-3.1-flash-lite-preview	1696.2
3	gemini-3-flash-preview	1680.5
4	gemini-3-pro-preview	1593.0
5	openrouter:google/gemma-4-31b-it	1571.9
6	claude-opus-4-5	1565.7
7	openrouter:openai/gpt-5.2	1563.1
8	claude-sonnet-4-5	1553.3
9	claude-opus-4-7	1543.8
10	openrouter:deepseek/deepseek-v4-flash	1532.8
11	gpt-5.5	1508.2
12	mamaylm-gemma-3-12b-it-v1.0	1503.1
13	google/gemma-4-26b-a4b	1491.2
14	google/gemma-3-27b-it-fast	1421.8
15	lapa-v0.1.2-instruct	1392.7
16	gpt-5-nano	1343.8
17	openai/gpt-oss-20b	1304.6
18	Qwen/Qwen3-32B-fast	1236.3
19	claude-haiku-4-5	1132.3

Detailed Metrics

Model	MC Acc	GEC F1	Fertility	Russisms	Markers
gemini-3.5-flash	86.0%	80.3%	1.48	0.2	10.3
gemini-3.1-flash-lite-preview	87.0%	66.2%	1.49	0.2	8.1
gemini-3-flash-preview	90.0%	77.2%	1.44	2.3	13.0
gemini-3-pro-preview	89.1%	84.2%	1.46	1.6	9.3
openrouter:google/gemma-4-31b-it	78.0%	69.7%	1.49	0.2	11.2
claude-opus-4-5	90.0%	73.0%	1.49	0.0	6.0
openrouter:openai/gpt-5.2	-	-	-	-	-
claude-sonnet-4-5	67.0%	75.0%	1.41	1.8	6.3
claude-opus-4-7	100.0%	82.2%	1.47	0.0	6.9
openrouter:deepseek/deepseek-v4-flash	87.9%	80.6%	1.52	0.0	8.8
gpt-5.5	82.0%	73.7%	1.48	0.0	8.3
mamaylm-gemma-3-12b-it-v1.0	74.0%	64.3%	1.40	1.6	7.3
google/gemma-4-26b-a4b	83.1%	74.3%	1.48	0.2	10.1
google/gemma-3-27b-it-fast	83.0%	78.4%	1.41	1.0	4.5
lapa-v0.1.2-instruct	54.0%	71.0%	1.40	7.0	4.8
gpt-5-nano	75.0%	60.1%	1.47	0.0	3.0
openai/gpt-oss-20b	60.0%	60.5%	1.50	1.9	4.4
Qwen/Qwen3-32B-fast	78.0%	69.7%	1.47	3.9	13.7
claude-haiku-4-5	62.0%	74.0%	1.43	1.7	9.9

Note: mamaylm-gemma-3-12b-it-v1.0 and lapa-v0.1.2-instruct were used with quantization (Q4_K_S)

Metrics Explanation

• ELO Rating: Swiss-system tournament rating (baseline 1500, K=32)
• MC Acc: Multiple choice accuracy (orthography, punctuation, russisms)
• GEC F1: Grammar error correction quality
• Fertility: Tokens per word ratio (optimal ~1.4-1.5 for Ukrainian)
• Russisms: Russian calques per 1000 tokens detected by LLM judge (lower = better)
• Markers: Native positive markers per 1000 tokens (higher = more natural)

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Key Principles

Principle	Description
Pairwise over Absolute	Compare models against each other, not absolute scores
Positive over Negative	Reward native markers, not just penalize errors
Real over Synthetic	Real corpus data over synthetic examples
Calibrated Judges	LLM judges calibrated against gold standard
Reproducible	Deterministic results with temperature=0

Installation

# Using uv (recommended)
uv sync

# With development dependencies
uv sync --extra dev

# With local model support
uv sync --extra local

Quick Start

All commands should be run with uv run prefix:

# Show configuration and API key status
uv run ukrqualbench info

# Calibrate a judge model
uv run ukrqualbench calibrate --judge claude-3-5-haiku-latest

# Evaluate a single model (lite benchmark ~30min)
uv run ukrqualbench evaluate --model gpt-5.2 --benchmark lite

# Compare multiple models
uv run ukrqualbench compare --models gpt-5.2,claude-opus-4-5-20251101 --benchmark base

# Generate leaderboard
uv run ukrqualbench leaderboard --results-dir results/ --format html

CLI Commands

Command	Description
info	Show configuration, API keys, and benchmark sizes
calibrate	Calibrate a judge model against gold standards
evaluate	Evaluate a single model on the benchmark
compare	Compare multiple models using Swiss-system tournament
leaderboard	Generate leaderboard from evaluation results

Command Options

# Calibrate with custom output
uv run ukrqualbench calibrate --judge claude-3-5-haiku-latest --output results/calibration --verbose

# Evaluate with budget limit
uv run ukrqualbench evaluate --model gpt-5.2 --benchmark lite --max-cost 10.0 --resume

# Compare with specific round count
uv run ukrqualbench compare --models gpt-5.2,gemini-3-flash-preview --rounds 5 --judge claude-3-5-haiku-latest

# Leaderboard in different formats
uv run ukrqualbench leaderboard --results-dir results/ --format json  # or csv, markdown, html

Benchmark Architecture

Block A: Calibration Tests (with reference answers)

• A1: Multiple Choice (400 tasks) — ZNO Ukrainian, error detection
• A2: GEC (400 tasks) — Grammar error correction from UA-GEC
• A3: Translation (200 tasks) — EN→UK and RU→UK with COMET scoring
• A4: False Positives (50 tasks) — Ensure judges don't "correct" valid classic literature
• A5: Positive Markers (50 tasks) — Test for native language markers

Block B: Generation Tests (pairwise evaluation)

• B1: Free generation (300 prompts) — explanations, advice, creative, technical
• B2: Adversarial (100 prompts) — test resistance to mimicking bad Ukrainian
• B3: Long context (50 prompts) — check language degradation over long contexts

Block V: Objective Metrics (automatic)

• Fertility rate (tokens/word ratio)
• Positive markers detection (regex-based)
• Calque detection (LLM judge-based for lexical, syntactic, morphological calques)
• Anglicism auto-detection (regex-based)

Benchmark Versions

Version	Block A	Block B	Est. Time	Use Case
lite	200	100	~30 min	Quick screening
base	550	250	~2 hr	Standard evaluation
large	1100	450	~5 hr	Full research

Supported Models

Cloud Providers

Provider	Models	Env Variable
OpenAI	gpt-5.2, gpt-5.2-pro, gpt-5-mini	UKRQUALBENCH_OPENAI_API_KEY
Anthropic	claude-opus-4-5-, claude-sonnet-4-, claude-haiku-4	UKRQUALBENCH_ANTHROPIC_API_KEY
Google	gemini-3-pro-preview, gemini-3-flash-preview	UKRQUALBENCH_GOOGLE_API_KEY

Local Models

Provider	Configuration
LM Studio (and any OpenAI-compatible server)	UKRQUALBENCH_LOCAL_BASE_URL (default: http://localhost:1234/v1)
Ollama	UKRQUALBENCH_OLLAMA_BASE_URL (default: http://localhost:11434)
vLLM	UKRQUALBENCH_VLLM_BASE_URL (default: http://localhost:8000)

Any model id containing gemma (e.g. google/gemma-4-26b-a4b) is routed to the local OpenAI-compatible endpoint — load the model in LM Studio and run ukrqualbench eval --model google/gemma-4-26b-a4b.

Judge Calibration

Before using a judge model, it must pass calibration:

Metric	Threshold
MC Accuracy	> 85%
GEC F1	> 80%
Russism Detection F1	> 85%
False Positive Rate	< 15%
Pairwise Consistency	> 90%
Position Bias	< 5%
Length Bias
Final Score	> 0.80

Quality Badges

Badge	ELO	Russism Rate	Positive Markers	Fertility
🥇 Gold	≥ 1650	< 1.0	≥ 5.0	< 1.5
🥈 Silver	≥ 1550	< 3.0	≥ 3.0	< 1.8
🥉 Bronze	≥ 1450	< 5.0	≥ 1.0	< 2.0
⚠️ Caution	≥ 1350	< 10.0	≥ 0.0	< 2.5
🚫 Not Recommended	< 1350	≥ 10.0	—	—

Configuration

Configuration via environment variables (prefix: UKRQUALBENCH_):

# API Keys
UKRQUALBENCH_OPENAI_API_KEY=sk-...
UKRQUALBENCH_ANTHROPIC_API_KEY=sk-ant-...
UKRQUALBENCH_GOOGLE_API_KEY=...

# Local models (LM Studio, Ollama, vLLM, etc.)
UKRQUALBENCH_LOCAL_BASE_URL=http://localhost:1234/v1

# Settings
UKRQUALBENCH_BENCHMARK_VERSION=base
UKRQUALBENCH_DEFAULT_JUDGE=claude-3-5-haiku-latest
UKRQUALBENCH_MAX_COST_USD=50.0
UKRQUALBENCH_TEMPERATURE=0.0

# ELO Settings
UKRQUALBENCH_ELO_INITIAL_RATING=1500
UKRQUALBENCH_ELO_K_FACTOR=32

# Execution
UKRQUALBENCH_MAX_CONCURRENT_REQUESTS=10
UKRQUALBENCH_REQUEST_TIMEOUT=60
UKRQUALBENCH_CHECKPOINT_INTERVAL=100

See .env.example for all options.

Methodology

What We Measure

UkrQualBench evaluates linguistic nativeness, not cognitive abilities:

Aspect	What We Check	Example
Russisms	Calques from Russian	"прийняти участь" → "взяти участь"
Orthography	Correct spelling rules	"пів'яблука" vs "півяблука"
Vocative Case	Native address forms	"Пане Андрію" vs "Пан Андрій"
Particles	Ukrainian expressiveness	же, бо, адже, хіба, невже
False Corrections	Not "fixing" correct text	Classic literature should stay unchanged

Test Examples

Multiple Choice (Block A1)

Виберіть правильний варіант:
A) пів'яблука  ← correct (apostrophe before я)
B) півяблука
C) пів яблука

Яке слово є русизмом?
A) захід
B) міроприємство  ← russism (correct: захід)
C) подія

Grammar Error Correction (Block A2)

Input:  "Треба прийняти участь у заході."
Output: "Треба взяти участь у заході."
        ↑ "прийняти участь" is a russism

Input:  "На протязі року ми працювали."
Output: "Протягом року ми працювали."
        ↑ "на протязі" is a calque from Russian

Positive Markers Detection (Block V)

Good: "Друже, як справи? Адже ми ж домовлялися!"
       ↑       ↑        ↑    ↑
    vocative particle particle particle

Bad:  "Друг, как дела? Мы ведь договаривались!"
      (no Ukrainian markers, sounds translated)

Critical Russisms to Detect

Russism	Correct Form	Severity
прийняти участь	взяти участь	Critical
міроприємство	захід	Critical
на протязі	протягом	Critical
являється	є	Critical
слідуючий	наступний	Critical
отримати досвід	здобути досвід	High

Data Sources

• UA-GEC 2.0: Grammar error correction (CC BY 4.0)
• ZNO Dataset: Multiple choice from Ukrainian standardized tests (MIT)
• FLORES-200: Translation benchmark (CC BY-SA 4.0)
• Brown-UK: Validation corpus (CC BY 4.0)

Project Structure

ukrqualbench/
├── src/ukrqualbench/
│   ├── cli.py              # Command-line interface
│   ├── core/               # Evaluator, ELO, schemas, config
│   ├── datasets/           # Data loaders (UA-GEC, ZNO, FLORES, Brown-UK)
│   ├── detectors/          # Russism, anglicism, markers, fertility
│   ├── judges/             # LLM judge system, calibration
│   ├── models/             # API clients (OpenAI, Anthropic, Google, local OpenAI-compatible)
│   └── reports/            # Leaderboard, HTML, analysis
├── data/
│   ├── benchmarks/         # lite.json, base.json, large.json
│   ├── gold/               # Calibration datasets
│   └── dictionaries/       # Russism/anglicism patterns
└── tests/                  # 382 tests

Development

# Install dev dependencies
uv sync --extra dev

# Run tests
uv run pytest

# Run with coverage
uv run pytest --cov=ukrqualbench

# Linting
uv run ruff check .
uv run ruff format .

# Type checking
uv run mypy src/

Key Findings

Model Comparison Insights

1. GPT-5.2 and Claude Opus tied at top ELO (~1720) with best MC accuracy (90-93%)
2. Claude Opus 4.5 is the only model with zero calques detected — cleanest Ukrainian
3. Gemini-3-Pro has best GEC performance (84% F1) and highest PM score (0.9)
4. Qwen3/Gemini-Flash generate most "native" Ukrainian (13+ positive markers/1K tokens)
5. GPT-5.2 and Lapa have highest calque rates (6-7 per 1K), despite strong ELO scores
6. Open models (Gemma, MamaLyM) competitive with proprietary in linguistic quality

Correlation Analysis

ELO Rating strongly correlates with MC Accuracy (r ≈ 0.7)
ELO Rating moderately correlates with GEC F1 (r ≈ 0.4)
Positive Markers inversely correlate with model size (smaller models use more native forms)

Observations

• Claude Opus 4.5 is the only model with 0.0 calque rate — cleanest Ukrainian among tested models
• GPT-5.2 and Lapa show highest calque rates (6.0-7.0 per 1K tokens), indicating more Russian influence
• Fertility rate is consistent across models (~1.4-1.5), indicating similar tokenization efficiency
• Qwen3 has most positive markers (13.7/1K) but also elevated calque rate (3.9), suggesting mixed quality
• Claude models have lower positive markers than Gemini, suggesting more "formal" language style

License

MIT License. See LICENSE for details.

Citation

If you use UkrQualBench in your research, please cite:

@software{ukrqualbench2026,
  title = {UkrQualBench: Benchmark for Ukrainian Language Quality in LLMs},
  year = {2026},
  url = {https://github.com/ukrqualbench/ukrqualbench}
}