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

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.

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

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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).

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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

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

Evaluation dataset (not used for gradient updates)

Downloaded but not used in this SFT mix

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)

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).

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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.

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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

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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

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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

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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.

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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

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Maintainers

• @dylanjkl — Comulative Limited (United Kingdom)
• Organization: Comulative

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