---
license: apache-2.0
base_model: Qwen/Qwen3-4B-Base
tags:
- code
- livecodebench
- sft
- lora-merged
- nothink
library_name: transformers
---

# code-nothink-q4b-20260908

Formerly `Qwen3-4B-Base-code-v4-nothink` (HF redirect).

**Arm ID:** `Q4B-NOTHINK`  
**Run ID:** `t30b2507-q4b-nothink-v4-tail151643`

Merged full bf16 weights used for the official DEV256 NoThink evaluation. Tokenizer files in this repo are the **eval-caliber** bundle (`qwen3-v4-tail151643`); they overlay any tokenizer files that were present in the merge directory (the merge tree's `tokenizer.json` was a different, larger file).

**Single-seed exploratory result, not a preregistered confirmatory claim.**

## Base model

- Hugging Face: [`Qwen/Qwen3-4B-Base`](https://huggingface.co/Qwen/Qwen3-4B-Base)
- Revision: `906bfd4b4dc7f14ee4320094d8b41684abff8539`

## Training

- Method: LoRA r64 / α128 on seven projections (`q_proj`, `k_proj`, `v_proj`, `o_proj`, `gate_proj`, `up_proj`, `down_proj`), then merged into full-model bf16 safetensors
- Data: NoThink code SFT (paired V4, physical 2-epoch concat)
- Endpoint (score): **step 142**, **9,455,736** assistant tokens — endpoint-as-score, no checkpoint picking
- Train seed 42; LR `1e-4`; context 8192; AdamW; cosine by assistant-token dose
- Host: mathbox; eval tokenizer renderer `qwen3-v4-tail151643`

## Evaluation

- Suite: official LiveCodeBench **DEV256**
- Seed **3407**, mode **NoThink**, `max_model_len` **8192**, vLLM **0.28.0**
- Metric: sandbox pass@1 = passed / 256
- This arm: **67/256 (26.2%)**, caps **99**
- Base (`Qwen/Qwen3-4B-Base`, same NoThink protocol): **36/256 (14.1%)**, caps **48**
- McNemar exact p = **7.8e-07**

## Inference notes

- Use **this repository's** tokenizer and `chat_template.jinja`.
- NoThink: do not prefill `<think>`; if the template accepts `enable_thinking`, keep it false.
- Stop token ids: **151643** (`<|endoftext|>`) and **151645** (`<|im_end|>`).
- Eval sampling used temperature 0.7, top_p 0.8, top_k 20.

## Weight checksum

- `model.safetensors` (8,822,894,520 bytes): `sha256:4309b112b8635695282a1c18f7d9e301862ef028c83e2b000a34caa08b47ef1f`

`OFFICIAL_MERGE_RECEIPT.json` is included for merge provenance. LoRA adapter checkpoints are **not** in this repo.