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KAT-Coder-V2.5_JKL-Luau-NVFP4

Roblox Luau–specialized fine-tune of Kwaipilot/KAT-Coder-V2.5-Dev, released as NVFP4 (W4A4 compressed-tensors) for efficient inference on NVIDIA Blackwell GPUs.

Base model Kwaipilot/KAT-Coder-V2.5-Dev (~35B-A3B Qwen3.5-MoE, text/language release)
Fine-tune Supervised LoRA SFT on a Roblox / Luau mix (1 epoch)
This artifact Merged bf16 weights → NVFP4 post-training quantization
Trained by @dylanjkl at Comulative Limited (UK)
Hardware 1× NVIDIA RTX PRO 6000 Blackwell 96GB (sm_120)

This is not an official Kwaipilot release. It is an independent specialty fine-tune and quant by Comulative Limited.


Intended uses

Primary: local / self-hosted Roblox Luau coding assistant and task executor:

  • Idiomatic Luau modules (--!strict, services, remotes, DataStore patterns)
  • Roblox client/server split, RemoteEvents / RemoteFunctions, replication-aware snippets
  • Code completion / continuation on existing Luau scripts
  • Roblox engine Q&A grounded in specialty SFT data

Recommended deployment pattern: use a stronger planning / review model for architecture and security, and this model as a fast local executor for Luau implementation (low latency, private weights, Blackwell-friendly NVFP4).

Not intended for: unsupervised production game economy / anti-cheat design without human review; non-Roblox general agenting as a drop-in frontier replacement; vision/multimodal tasks (language-only lineage).


What we did (training pipeline)

1. Base

Started from KAT-Coder-V2.5-Dev (Qwen3.5 MoE coding model, language-only open weights; vision tower declared in config but not shipped upstream).

2. Domain SFT data mix

Built a chat-formatted SFT mix (42,302 train rows after filtering/dedup; ~57M tokens) from public Hugging Face datasets (local mirror under data/).

Hugging Face datasets used in training

Hub dataset Role in mix Approx. SFT rows (source tag)
TorpedoSoftware/Roblox-Luau-Reasoning-v1.0 Prompt → CoT + Luau code + explanation (train) 14,840 luau-reasoning
Pinkstack/luaucoder-instructions-v3-SFT Instruction SFT (filtered; cap ~8k quality rows) 7,927 pinkstack-sft
khtsly/luau-stack-hq Curated Luau corpus → fill-in / continuation tasks 5,944 stackhq-completion
TorpedoSoftware/RobloxQA-v2.0 Engine/API knowledge from train (MCQ + direct QA variants) 4,573 robloxqa2-mcq + 2,290 robloxqa2-direct
TorpedoSoftware/LuauLeetcode Algorithmic Luau problems (train) 2,336 luau-leetcode
TorpedoSoftware/RobloxQA-v1.0 Older QA; deduped against RobloxQA-v2 test 2,281 robloxqa1-mcq
Roblox/luau_corpus Official Luau Data Sharing fragments → continuation (train) 2,111 luaucorpus-completion

Total train examples: 42,302 (plus 400 held-out mix rows for training-time val).

Evaluation dataset (not used for gradient updates)

Hub dataset Use
TorpedoSoftware/RobloxQA-v2.0 test (3,000 MCQ) Held out for baseline / future eval only

Downloaded but not used in this SFT mix

Hub dataset Notes
TorpedoSoftware/roblox-info-dump Roblox/Luau docs scrape present under data/; not mixed into the epoch-1 SFT JSONL

Formatting used the base model chat template, with prompt tokens masked (train on completions). Optional system prompts mixed in (~30% Roblox-assistant style). Decompiled-looking completion snippets filtered out. Pinkstack rows required code fences + minimum reasoning length.

3. LoRA fine-tune (1 epoch)

Hyperparameter Value
Method LoRA (PEFT), bf16 base
Rank / alpha r=64, α=128, dropout 0.05
Targets Attention (q/k/v/o), linear-attn projections, shared-expert MLP; not per-routed experts
Context 4096
Effective batch 16 (microbatch 2 × grad accum 8)
Epochs shipped here 1 (stopped at step 2642 / 5284 of a 2-epoch schedule)
Optim AdamW fused, LR 1e-4 cosine, warmup 40
Hardware 1× RTX PRO 6000 96GB, Windows 11 + WSL2 Ubuntu

A full Trainer checkpoint (adapter + optimizer) was frozen at epoch 1 so a second epoch can be resumed later if desired. This Hub repo is the merged + NVFP4 product of that epoch-1 adapter, not the raw LoRA.

4. Merge & cleanup

  • Merged LoRA into base bf16 weights
  • Stripped randomly initialized visual.* keys so the checkpoint matches the language-only upstream release

5. NVFP4 quantization

  • Tooling: llm-compressor oneshot PTQ
  • Scheme: NVFP4 (W4A4, nvfp4-pack-quantized)
  • Calibration: 256 samples @ 4096 from the Luau SFT mix
  • moe_calibrate_all_experts=True
  • Ignores: lm_head, visual towers, router gates, embeddings, linear-attn (see recipe.yaml)

Why NVFP4: native-friendly 4-bit float path for Blackwell inference stacks (e.g. vLLM on modern NVIDIA data-center / pro GPUs). Smaller footprint (22GB weights here) vs full bf16 (70GB class).


Base model evaluation note

Unmodified base KAT-Coder-V2.5-Dev on RobloxQA-v2.0 test (3000 questions), MMLU-style log-prob forced choice, bf16, HF Transformers:

Baseline: 87.60% (2628 / 3000) — measured 2026-08-01.

Post–fine-tune / post-NVFP4 RobloxQA numbers for this checkpoint may be published later; treat the above as the starting point the specialty run was designed to preserve or beat on knowledge while improving Luau generation.


How to use

Transformers / llm-compressor compressed load

Follow current llm-compressor / Transformers docs for NVFP4 compressed-tensors checkpoints. Ensure a stack that understands quantization_config with format nvfp4-pack-quantized.

vLLM (Blackwell)

Prefer a recent vLLM build with NVFP4 + Qwen3.5 MoE support. Language-only serving flags may still apply (upstream was language-only; config may still mention vision). Example pattern (versions change quickly—check your vLLM release notes):

vllm serve Comulative/KAT-Coder-V2.5_JKL-Luau-NVFP4 \
  --quantization modelopt_fp4 \
  # plus whatever your vLLM build requires for NVFP4 / Qwen3.5 MoE

Use the model’s chat template (chat_template.jinja / tokenizer config). For agentic coding UIs, Qwen-style reasoning / tool parsers may apply depending on runtime.

Prompting tips

  • Prefer narrow tasks: one module, one bugfix, one remote contract
  • State client vs server, remote names, and data shapes
  • Ask for --!strict Luau when you want typed modules
  • Review security (RemoteEvent trust, DataStore races) with a stronger planner model before shipping

Training summary card

Base:     Kwaipilot/KAT-Coder-V2.5-Dev (Qwen3.5-MoE ~35B-A3B)
SFT:      LoRA r=64, 1 epoch, Luau/Roblox mix ~42k examples
Merge:    bf16 merge + strip visual.*
Quant:    NVFP4 (llm-compressor), 256 calib samples, all MoE experts
Trainer:  @dylanjkl / Comulative Limited (UK)
GPU:      1× NVIDIA RTX PRO 6000 Blackwell 96GB

Limitations & risks

  • Domain SFT can narrow style; may be weaker than base on non-Roblox agentic coding
  • 1 epoch only in this release; second epoch optional, not included
  • NVFP4 is a lossy quant vs bf16 merge—validate on your tasks
  • No Studio execution loop in training—always test Luau in Roblox
  • May produce insecure remote/DataStore patterns; do not deploy unreviewed
  • MoE + hybrid linear attention runtimes are still evolving—pin tested engine versions

License

Weights are a derivative of Kwaipilot/KAT-Coder-V2.5-Dev. Unless otherwise required by the base model license, this distribution is provided under Apache-2.0. Review the base model card and license for any additional terms.


Citation / attribution

Base model: Kwaipilot/KAT-Coder-V2.5-Dev
Fine-tune & NVFP4 release: Comulative Limited (UK) / @dylanjkl
Hub: Comulative/KAT-Coder-V2.5_JKL-Luau-NVFP4
Hardware: 1× NVIDIA RTX PRO 6000 Blackwell 96GB

Maintainers

For issues with this fine-tune/quant, contact the Comulative maintainers—not Kwaipilot—unless the bug is reproducible on the unmodified base.

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