# KAT‑Coder‑V2.5‑Dev‑MTP (int4 + MTP, vLLM‑ready)

[![Quantization](https://img.shields.io/badge/Quantization-int4_AutoRound-blue)]()
[![MTP](https://img.shields.io/badge/MTP-speculative_decoding-green)]()
[![vLLM](https://img.shields.io/badge/vLLM-%E2%89%A50.19.0-orange)]()

---

**This is a quantized, vLLM‑optimised version of [KAT‑Coder‑V2.5‑Dev](https://huggingface.co/Kwaipilot/KAT‑Coder‑V2.5‑Dev).**  
The model was post‑trained with **int4 AutoRound** (W4A16) and enhanced with a **Multi‑Token Prediction (MTP) head** from Qwen3.6‑35B‑A3B to enable speculative decoding in vLLM. It is designed for high‑throughput agentic coding workloads on hardware with 128 GiB unified memory (e.g. NVIDIA GB10).

> [!IMPORTANT]  
> **All benchmark scores reported in the KAT‑Coder‑V2.5 technical paper refer to the full BF16 model.**  
> This int4 quantisation has **not been re‑evaluated** on standard benchmarks. It is expected to closely match the original quality, but individual results may vary.

---

## Model Overview

| Property | Value |
|----------|-------|
| Base model | [KAT‑Coder‑V2.5‑Dev](https://huggingface.co/Kwaipilot/KAT‑Coder‑V2.5‑Dev) (35 B total, 3 B active MoE) |
| Quantisation | int4 AutoRound (W4A16), group size 128 |
| MTP head | Added from Qwen3.6‑35B‑A3B (Apache 2.0) for speculative decoding |
| Calibration data | OpenCode Instruct (512 samples, sequence length 2048) |
| Quantisation tool | [Spark Auto Round](https://github.com/whpthomas/spark-auto-round) – an optimised fork of Intel® AutoRound |
| Deployment target | vLLM ≥ 0.19.0 with FlashInfer on GB10‑class hardware |
| Hugging Face Hub | [slopops/KAT-Coder-V2.5-Dev-MTP-int4-AutoRound-SAR](https://huggingface.co/slopops/KAT-Coder-V2.5-Dev-MTP-int4-AutoRound-SAR) |

---

## Key Features

- **Built on a highly efficient agentic coder** – the original KAT‑Coder‑V2.5‑Dev was RL‑tuned to produce concise traces with fewer tool calls and reasoning tokens compared to its base model.
- **Speculative decoding with MTP** – the added MTP head enables up to 3‑token lookahead. On GB10 hardware we observe throughput around **65–77 tokens/second** under vLLM.
- **Reduced abnormal outputs** – the original model reported tool‑label errors dropping from 9.34 % to 0.28 %, and single‑turn repetition nearly eliminated. These improvements are expected to carry over to the quantised version, though your mileage may vary.
- **Memory‑efficient int4 format** – fits comfortably within 128 GiB unified memory, leaving headroom for large batch sizes and long contexts.

---

## Deployment (vLLM)

This model is intended for use with **vLLM only**.  
We recommend using a recent official image (≥ 0.19.0) with FlashInfer support.

```bash
docker run --rm --gpus all --net=host --ipc=host \
  vllm/vllm-openai:latest \
  vllm serve slopops/KAT-Coder-V2.5-Dev-MTP-int4-AutoRound-SAR \
    --port 8001 \
    --host 0.0.0.0 \
    --max-model-len 262144 \
    --gpu-memory-utilization 0.55 \
    --max-num-batched-tokens 16384 \
    --max-num-seqs 8 \
    --attention-backend flashinfer \
    --enable-prefix-caching \
    --enable-chunked-prefill \
    --speculative-config '{"method":"mtp","num_speculative_tokens":3}' \
    --tool-call-parser qwen3_coder \
    --reasoning-parser qwen3 \
    --enable-auto-tool-choice \
    --chat-template-kwargs '{"preserve_thinking":true}' \
    --generation-config '{"temperature":0.6,"top_p":0.95,"top_k":-1,"min_p":0.0,"presence_penalty":0.0,"repetition_penalty":1.0}'
```

> [!NOTE]  
> The server will be available at `http://localhost:8001/v1`.

### Flag Reference

| Flag | Purpose |
|------|---------|
| `--attention-backend flashinfer` | Fast attention kernel, recommended for GB10 |
| `--speculative-config` | Activates MTP with 3 speculative tokens |
| `--enable-auto-tool-choice` + `--tool-call-parser` | Required for agentic tool‑use |
| `--chat-template-kwargs '{"preserve_thinking":true}'` | Keeps thinking traces from previous turns |
| `--generation-config` | Safe defaults for deterministic outputs |

---

## Quantisation Details

- **Spark Auto Round** – a GB10‑tuned fork of Intel® AutoRound that respects a 96 GiB memory budget during calibration.
- **Stateful resume** – interrupted runs can be restarted from the last completed block.
- **ASAQ (Adaptive Sensitivity‑Aware Quantisation)** – sensitive layers are identified via cosine similarity, PSNR, and router Jaccard similarity and kept in FP16 to preserve accuracy.
- The MTP head was added **after** quantisation as a separate adapter; the core architecture remains the standard Qwen3.6‑35B‑A3B. vLLM handles speculative decoding via the `--speculative-config` flag.

---

## Why This Model Exists

- The original KAT‑Coder‑V2.5‑Dev was trained with hierarchical rewards that penalised excessive tool calls, empty blocks, and repetition – leading to **more concise and reliable agentic traces**.
- The int4 quantisation makes it practical to run on hardware with 128 GiB unified memory **without a separate GPU**.
- Adding the MTP head brings speculative decoding, which is especially beneficial for agentic loops where the model often emits multiple tokens in one step.

> [!WARNING]  
> Performance claims (throughput, token savings, error reduction) refer to the **original BF16 model** as reported in the technical paper, or to our internal tests on a GB10 system. They are **not guaranteed** for every deployment. Always validate with your own workload.

---

## Citation

If you use this quantised release, please cite the original KAT‑Coder work:

```bibtex
@misc{katcoder_v25_2026,
  title={{KAT-Coder-V2.5 Technical Report}},
  author={{KwaiKAT Team}},
  year={2026},
  month={July},
  eprint={2607.05471},
  archivePrefix={arXiv},
  primaryClass={cs.AI},
  url={https://arxiv.org/pdf/2607.05471}
}
```

---

## Disclaimer

- **Language‑model only** – vision/multimodal components are **not included**.
- All benchmark scores cited from the KAT‑Coder‑V2.5 paper are for the **full BF16 model**; this int4 version has **not been re‑evaluated**.
- Throughput figures are observed on a specific hardware configuration (GB10 with 128 GiB unified memory) and may differ in other environments.
- This model is provided “as‑is” for research and development purposes. Always test thoroughly before production use.