Wit-Coder-4B

An English coding-agent fine-tune of Qwen3.5-4B, focused on completing solvable tasks, breaking repetitive actions, and explaining blockers. This release candidate uses DPO-2.

Results

Project measurements of the base model and DPO-2:

Benchmark Qwen3.5-4B Wit-Coder-4B
MMLU, 5-shot 69.67% 70.16%
GSM8K, 8-shot CoT, strict 84.08% 82.64%
HumanEval plus tests, modified bounded protocol 81.10% (133/164) 87.20% (143/164)
MATH-500, first 100 problems 65/100 82/100

GSM8K decreased. MBPP results are unavailable. HumanEval scores are not official EvalPlus results: two tasks were chunked, resetting candidate state; no HumanEval inputs were omitted. Canonical HumanEval/32 also failed validation in this environment. Benchmark scores do not measure the quantized GGUF files. See evaluation details for settings and limitations.

Coding-agent panel

42 tasks ร— 3 seeds, including 90 solvable and 36 blocked episodes:

Outcome Base Wit
Task success, including successful escalation 40/126 71/126
Blocked tasks successfully escalated 0/36 11/36
Protected-file integrity failures 28/126 25/126

This small panel informed later experiments and model selection; it is a development comparison, not an independent final test. False completion remains a problem: 15/36 blocked episodes ended with a non-escalating submit. Use external tests and tool permissions. Only English text-based coding-agent use was evaluated; no broad chat, vision or long-context claim is made.

Training

Approximately 138M SFT tokens, then two sandbox-graded DPO rounds of 877 and 404 turn-level pairs. Round 2 used self-check-guided candidate sampling. GRPO checkpoints were not selected for release because the conservative run showed no clear improvement over DPO-2. A more aggressive run increased looping and reduced escalation on the monitoring set, so it was stopped.

Usage

vllm serve /path/to/Wit-Coder-4B --max-model-len 32768 --reasoning-parser qwen3

The training harness used one bash tool with Qwen-style XML calls and task-specific submit/escalation markers; see details. Adapt tool handling to your application.

GGUF

Format File Size
BF16 Download 8.67 GB
Q8_0 Download 4.61 GB
Q4_K_M Download 2.78 GB

Available formats: BF16, Q8_0 and Q4_K_M. Checksums/settings: gguf/manifest.json. Structure and hashes were checked; GGUF inference and quantized quality were not evaluated. No image projector is supplied.

Support

I research alignment, internal representations, and behavioral fine-tuning of small language models. I am preparing for military service; optional Buy Me a Coffee support helps fund future independent projects when I return. Wit remains free under Apache-2.0.

License

Apache-2.0, following the base model.

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