Highlights
- Competition math significantly improved — AIME 2024/2025/2026 and HMMT 2025 average up strongly over the base model, measured across 3 sampling seeds
- Base capability preserved — general knowledge (MMLU/MMLU-Pro), GPQA, and instruction following stay at or near base level
- Korean-first tuning — trained on PoSTMEDIA's in-house verified Korean synthetic datasets
- Non-thinking product — fast direct answers; no
<think> traces
- Hybrid-attention 27B — 16 full-attention + 48 linear-attention layers, efficient long-context serving
Model Overview
Table with columns: Specification, Details| Specification | Details |
|---|
| Base Model | Qwen/Qwen3.8-27B |
| Parameters | 27B (hybrid attention: 16 full + 48 linear layers) |
| Training Precision | BF16 |
| Inference Precision | BF16 |
| Context Length | Inherits from Qwen3.8 base |
| Fine-Tuning Method | Full-parameter SFT (Capability-Preserving recipe) |
| Mode | Non-thinking (direct answer) |
| Languages | Korean, English |
Benchmarks vs Base
All results measured in-house under a single unified protocol (identical prompts, official non-thinking sampling — temperature 0.7, top-p 0.8, top-k 20, presence penalty 1.5 — and identical generation budgets). Competition-math rows (AIME/HMMT) are the mean of 3 sampling seeds for both models to suppress small-sample noise.
Table with columns: Benchmark, Qwen3.8-27B (base), Xin-V1| Benchmark | Qwen3.8-27B (base) | Xin-V1 |
|---|
| MMLU | 84.5 | 83.5 |
| MMLU-Pro | 82.1 | 82.0 |
| GPQA | 80.3 | 81.3 |
| GSM8K | 86.1 | 86.8 |
| AIME 2024† | 77.8 | 83.3 |
| AIME 2025† |
† Competition-math rows are the mean of 3 sampling seeds for both models.
‡ Judge-scored short-answer QA; Xin-V1's more direct answer style contributes to this gain (exact-match on the same set is comparable to base).
Training Data
Xin-V1 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
- 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) 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, AutoTokenizerimport torch model_name = "PoSTMEDIA/Xin-V1"tokenizer = AutoTokenizer.from_pretrained(model_name)model = AutoModelForCausalLM.from_pretrained( model_name, torch_dtype=torch.bfloat16, device_map="auto",) messages = [{"role": "user", "content": "한국의 전통 명절 세 가지를 소개해줘."}]inputs = tokenizer.apply_chat_template( messages, add_generation_prompt=True, enable_thinking=False, return_tensors="pt",).to(model.device)outputs = model.generate( inputs, max_new_tokens=512, do_sample=True, temperature=0.7, top_p=0.8, top_k=20,)print(tokenizer.decode(outputs[0][inputs.shape[1]:], skip_special_tokens=True))
Note: Xin-V1 is tuned for non-thinking use. Pass enable_thinking=False to apply_chat_template (as above) and use the official non-thinking sampling parameters (temperature 0.7, top-p 0.8, top-k 20, presence penalty 1.5).
Use Cases
- Korean-first assistants requiring fast, direct answers
- Mathematical and coding assistance in Korean and English
- General Korean instruction-following workloads
Safety & Limitations
- The model can generate incorrect or outdated information; verify high-stakes outputs.
- Inherits the general limitations and usage considerations of the Qwen3.8 base model.
Citation
@misc{xin2026, title = {Xin-V1: Capability-Preserving Korean Fine-Tuning of Qwen3.8}, author = {{PoSTMEDIA AI Lab}}, year = {2026}, url = {https://huggingface.co/PoSTMEDIA/Xin-V1}}
Questions and feedback — please open a discussion on the model page.