Lux-V2-Pro

Lux-V2-Pro is a Korean-enhanced, fully fine-tuned LLM built on top of google/gemma-4-31B-it by PoSTMEDIA AI Lab, succeeding Lux-V1-Pro.

It is produced with the second generation of PoSTMEDIA's in-house Capability-Preserving Full Fine-Tuning research — a training methodology designed so that deep domain adaptation does not erode the reasoning, instruction-following, and multilingual abilities of the base model. As the maximum-capability tier of the Lux line, V2-Pro improves on Lux-V1-Pro across the board while adding substantial Korean domain knowledge.


Highlights

  • Upgrade over Lux-V1-Pro on 16 of 18 internal benchmarks — including AIME 2024 93.3 (+13.3) and AIME 2025 +13.4
  • Korean domain knowledge built in — trained on PoSTMEDIA's in-house Korean synthetic datasets spanning seven domains: general conversation, coding, instruction following, law, cultural heritage, tourism, and mathematics, plus the PoSTMEDIA identity dataset
  • Base capability preserved and improved — general knowledge (MMLU 86.6) and instruction following (IFEval 93.7) end above the V1-Pro level
  • Dense 31B — the strongest reasoning tier of the Lux family
  • Verified training data — synthetic datasets produced with execution- and rule-based verification pipelines

Model Overview

Specification Details
Base Model google/gemma-4-31B-it
Parameters 31B (dense)
Architecture Decoder-only Transformer (dense)
Training Precision BF16
Inference Precision BF16
Context Length Inherits from Gemma-4 base
Fine-Tuning Method Full-parameter SFT (Capability-Preserving recipe, 2nd gen)
Languages Korean, English

What's New vs Lux-V1-Pro

All results below were measured in-house under a single unified protocol (identical prompts, sampling, and generation budgets for both models).

Benchmark gemma-4-31B-it (base) Lux-V1-Pro Lux-V2-Pro
MMLU 86.6 85.9 86.6
AIME 2024 83.3 80.0 93.3
AIME 2025 66.7 63.3 76.7
HMMT 2025 70.0 60.0 63.3
IFEval 93.2 92.4 93.7
KMMLU 76.6 74.8 76.9
KMMLU-Pro 78.2 77.0 77.4
CLIcK 85.1 84.8 85.5
KoBALT 73.4 71.9 73.9
HAE-RAE Bench 82.0 80.6 83.1
HRM8K 85.8 84.7 85.8
KoSimpleQA 91.2 90.0 90.8
KoSQA-EM 38.0 36.1 38.5
Average (17 common benchmarks) 76.6 75.5 78.2

The full 18-benchmark suite shows 16 wins, 1 tie (GPQA), and 2 minor regressions (GSM8K −1.2, IFBench −0.2) versus Lux-V1-Pro. Averaged over the 17 benchmarks measured for all three models, Lux-V2-Pro scores 78.2 — above both the original Gemma-4 base (76.6) and Lux-V1-Pro (75.5). (MMLU-Pro was not measured for the base model due to generation-budget constraints.)


Training Data

The V2 generation is trained on PoSTMEDIA's in-house Korean synthetic data assets, generated and quality-controlled by our internal data factory:

  • General conversation — natural Korean multi-topic dialogue
  • Coding — execution-verified code generation and explanation
  • Instruction following — rule-verifiable Korean constraint-following tasks
  • Law — source-grounded Korean legal knowledge QA
  • Cultural heritage — source-grounded Korean heritage knowledge QA
  • Tourism — source-grounded Korean tourism knowledge QA
  • Mathematics — symbolically verified Korean math reasoning
  • PoSTMEDIA identity — hand-curated identity dataset

Correctness of the synthetic data is enforced by verification gates (code execution, symbolic math equivalence, rule checkers, and source-grounding checks) rather than by model self-judgment.

The exact training procedure — schedule, module selection, and the post-training consolidation step that preserves base capability — is an internal research method and is not disclosed in detail.


Quick Start

pip install transformers accelerate
from transformers import AutoModelForCausalLM, AutoTokenizer
import torch

model_name = "PoSTMEDIA/Lux-V2-Pro"
tokenizer = AutoTokenizer.from_pretrained(model_name)
model = AutoModelForCausalLM.from_pretrained(
    model_name,
    torch_dtype=torch.bfloat16,
    device_map="auto",
)

messages = [{"role": "user", "content": "문화재보호법의 목적을 두 문장으로 설명해줘."}]
inputs = tokenizer.apply_chat_template(
    messages, add_generation_prompt=True, return_tensors="pt"
).to(model.device)
outputs = model.generate(inputs, max_new_tokens=512)
print(tokenizer.decode(outputs[0][inputs.shape[1]:], skip_special_tokens=True))

Use Cases

  • The most demanding Korean reasoning and generation workloads in the Lux line
  • Korean domain QA (law, cultural heritage, tourism) with source-grounded knowledge
  • Competition-level mathematical assistance
  • Drop-in upgrade for existing Lux-V1-Pro deployments

Safety & Limitations

  • The model can generate incorrect or outdated information; verify high-stakes outputs.
  • Korean domain knowledge reflects the training data snapshot and may not cover recent changes (e.g., amended laws).
  • Inherits the general limitations and usage considerations of the Gemma-4 base model.

Citation

@misc{lux2026pro,
  title  = {Lux-V2-Pro: Capability-Preserving Korean Domain Adaptation of Gemma-4},
  author = {{PoSTMEDIA AI Lab}},
  year   = {2026},
  url    = {https://huggingface.co/PoSTMEDIA/Lux-V2-Pro}
}

Contact

Questions and feedback — please open a discussion on the model page.

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