---
license: apache-2.0
base_model: Qwen/Qwen3.5-9B
tags:
  - qwen3.5
  - code
  - tool-calling
  - lora
  - sft
  - dpo
  - unsloth
  - reasoning
  - chain-of-thought
datasets:
  - nohurry/Opus-4.6-Reasoning-3000x-filtered
  - Roman1111111/claude-opus-4.6-10000x
  - TeichAI/claude-4.5-opus-high-reasoning-250x
  - Jackrong/Qwen3.5-reasoning-700x
  - togethercomputer/CoderForge-Preview
  - TIGER-Lab/AceCode-V2-122K
language:
  - en
pipeline_tag: text-generation
---

# Qwen3.5-DeltaCoder-9B

> Reliable tool-calling for agentic coding — LoRA fine-tune of Qwen3.5-9B
> **v1.1-DPO released** — DPO alignment improves code correctness and self-verification.
> If you downloaded before March 28, 2026, please re-pull to get v1.1-DPO.

[![License: Apache 2.0](https://img.shields.io/badge/License-Apache_2.0-blue.svg)](https://opensource.org/licenses/Apache-2.0)
[![Base Model](https://img.shields.io/badge/Base-Qwen3.5--9B-purple)](https://huggingface.co/Qwen/Qwen3.5-9B)
[![HuggingFace](https://img.shields.io/badge/HuggingFace-GGUF-yellow)](https://huggingface.co/danielcherubini/Qwen3.5-DeltaCoder-9B-GGUF)
[![LoRA](https://img.shields.io/badge/HuggingFace-LoRA-orange)](https://huggingface.co/danielcherubini/Qwen3.5-DeltaCoder-9B)

Small language models can reason about code, but they struggle to **call tools reliably**. DeltaCoder takes a strong reasoning base and teaches it to produce correctly-formatted JSON tool calls — the kind that coding agents like [OpenCode](https://github.com/opencode-ai/opencode), [Pi](https://github.com/badlogic/pi-mono), and [Cline](https://github.com/cline/cline) depend on.

v1.1-DPO adds **Direct Preference Optimization** to further improve code correctness — the model now self-corrects its own bugs rather than submitting wrong answers.

## Downloads

| Format | Link | Size |
|--------|------|------|
| GGUF Q4_K_M (recommended) | [HuggingFace](https://huggingface.co/danielcherubini/Qwen3.5-DeltaCoder-9B-GGUF) | ~5.5 GB |
| GGUF Q5_K_M | [HuggingFace](https://huggingface.co/danielcherubini/Qwen3.5-DeltaCoder-9B-GGUF) | ~6.5 GB |
| GGUF BF16 | [HuggingFace](https://huggingface.co/danielcherubini/Qwen3.5-DeltaCoder-9B-GGUF) | ~17.9 GB |
| DPO LoRA adapter | [HuggingFace](https://huggingface.co/danielcherubini/Qwen3.5-DeltaCoder-9B) | ~700 MB |

## The Problem

[Jackrong's Qwen3.5-9B reasoning distill](https://huggingface.co/Jackrong/Qwen3.5-9B-Claude-4.6-Opus-Reasoning-Distilled-v2) scores **53.7% on HumanEval** — best-in-class at 9B. But when used as a coding agent, it frequently produces malformed JSON tool calls:

```
tool=edit, error=JSON Parse error: Property name must be a string literal
tool=bash, error=JSON Parse error: Expected '}'
```

**DeltaCoder fixes this**, and v1.1-DPO further improves code correctness through preference learning.

## What's New in v1.1-DPO

- **Self-correcting behavior** — detects and fixes its own bugs during agentic tasks
- **Improved code correctness** — trained on 4,519 preference pairs from AceCode-V2-122K
- **Two-stage merge** — v1 SFT tool-calling improvements + DPO code quality improvements combined
- **13 GGUF quants** — from Q2_K to BF16, covering all VRAM configurations

## Training Details

### v1 — SFT (Tool-Call Reliability)

| Parameter | Value |
|-----------|-------|
| Base model | Qwen3.5-9B (hybrid GDN architecture) |
| Method | LoRA (r=64, alpha=32) |
| Dataset | [CoderForge-Preview](https://huggingface.co/datasets/togethercomputer/CoderForge-Preview) `filtered_reward1` (50K subset) |
| Sequence length | 4096 |
| Effective batch size | 16 |
| Learning rate | 1e-4 (cosine) |
| Epochs | 1 |
| Hardware | NVIDIA H200 140GB (Vast.ai) |
| Training time | ~10 hours |
| Final loss | ~0.94 |

### v1.1 — DPO (Code Correctness)

| Parameter | Value |
|-----------|-------|
| Method | DPO (Direct Preference Optimization) |
| Dataset | [AceCode-V2-122K](https://huggingface.co/datasets/TIGER-Lab/AceCode-V2-122K) — 4,519 preference pairs |
| Pair generation | 10K problems × 8 samples, keep if ≥1 pass AND ≥1 fail (45% keep rate) |
| Beta | 0.1 |
| Loss type | sigmoid |
| Learning rate | 5e-6 (cosine) |
| Effective batch size | 16 |
| Hardware | NVIDIA H100 80GB (Vast.ai) |
| Training time | ~3.7 hours |
| Final loss | 0.538 |
| Rewards/margins (final) | ~1.0 |
| Rewards/accuracies (final) | ~80% |

### LoRA Target Modules

All major weight matrices adapted across the hybrid architecture:

- **Full Attention** (8/32 layers): `q_proj`, `k_proj`, `v_proj`, `o_proj`
- **Gated Delta Net** (24/32 layers): `in_proj_qkv`, `in_proj_z`, `in_proj_b`, `in_proj_a`, `out_proj`
- **MLP** (all 32 layers): `gate_proj`, `up_proj`, `down_proj`

## Usage

### Ollama

```bash
ollama create deltacoder -f Modelfile
```

### llama.cpp / ik_llama.cpp

```bash
./llama-server -m DeltaCoder-9B-v1.1-DPO-Q5_K_M.gguf -ngl 999 -c 131072 -ctk f16 -ctv q4_0 -fa 1 --jinja
```

### With PEFT (Python)

```python
from transformers import AutoModelForCausalLM, AutoTokenizer
from peft import PeftModel
import torch

base = AutoModelForCausalLM.from_pretrained(
    "Jackrong/Qwen3.5-9B-Claude-4.6-Opus-Reasoning-Distilled-v2",
    torch_dtype=torch.bfloat16,
    trust_remote_code=True,
)
model = PeftModel.from_pretrained(base, "danielcherubini/Qwen3.5-DeltaCoder-9B")
tokenizer = AutoTokenizer.from_pretrained("danielcherubini/Qwen3.5-DeltaCoder-9B")
```

## Benchmarks

| Model | HumanEval | HumanEval+ | Terminal-Bench Easy |
|-------|-----------|------------|-------------------|
| Jackrong Qwen3.5-9B-v2 (base) | 53.7% | — | — |
| DeltaCoder-9B v1 (temp=0.6) | 50.6% | 49.4% | 2/4 (50%) |
| **DeltaCoder-9B v1.1-DPO** (temp=0.6) | TBD | TBD | 2/4 (50%)* |

*v1.1-DPO timed out on 2 tasks that v1 answered incorrectly — behavioral improvement confirmed, re-evaluating with extended timeout.

## Recommended Sampling Settings

| Parameter | Value |
|-----------|-------|
| temperature | 0.6 |
| top_k | 20 |
| top_p | 0.95 |
| min_p | 0.0 |
| presence_penalty | 0.0 |
| repeat_penalty | 1.0 |

> [!WARNING]
> **Do not use temperature below 0.5** — low temperatures cause deterministic looping in multi-turn agentic use.

### KV Cache Quantization

| Context Length | KV Cache | VRAM (Q4_K_M) | Generation Speed |
|---------------|----------|---------------|-----------------|
| 102,400 | f16/q4_0 | ~8.5 GB | ~111 tok/s |
| 131,072 | f16/q4_0 | ~9.1 GB | ~110 tok/s |

## Key Findings

> [!NOTE]
> **Qwen3.5 is a VLM** — Unsloth treats it as a vision model. For text-only DPO training, use standard HuggingFace + PEFT + TRL directly (no Unsloth DPOTrainer).

> [!WARNING]
> **Do not use `flash_attention_2` with sample packing on Qwen3.5** — training loss goes to 0. Use `attn_implementation="eager"` instead.

- Qwen3.5 uses **Gated Delta Networks** — include `in_proj_qkv`, `in_proj_z`, `in_proj_b`, `in_proj_a`, `out_proj` in LoRA target modules or 75% of attention layers are untrained
- DPO pairs generated on-policy using `Qwen/Qwen3.5-9B` base with vLLM async inference (32 concurrent requests)
- Keep rate of 45.2% from 10K AceCode problems (4,519 pairs used for training)

## Project Structure

```
scripts/
  train_unsloth.py          # v1 SFT training
  train_dpo.py              # v1.1 DPO training (HF + PEFT + TRL)
  generate_dpo_pairs.py     # Async on-policy pair generation
  merge_and_export_dpo.py   # Two-stage merge + GGUF export
```

## Status

- [x] v1 SFT fine-tune (CoderForge, H200, ~10hrs)
- [x] GGUF export (all quants Q2_K → BF16)
- [x] HumanEval benchmarking (50.6% / 49.4%)
- [x] Terminal-Bench evaluation (2/4 easy tasks)
- [x] DPO pair generation (4,519 pairs from AceCode-V2-122K)
- [x] v1.1-DPO training (H100, ~3.7hrs)
- [x] v1.1-DPO GGUF export + HuggingFace release
- [ ] v1.1-DPO HumanEval benchmarking
- [ ] v1.1-DPO Terminal-Bench extended timeout evaluation

## Acknowledgements

- [Unsloth](https://unsloth.ai) for Qwen3.5 SFT training support
- [Together AI](https://together.ai) for the CoderForge dataset
- [TIGER Lab](https://huggingface.co/TIGER-Lab) for AceCode-V2-122K
- [Jackrong](https://huggingface.co/Jackrong) for the reasoning distillation
- [Qwen](https://huggingface.co/Qwen) for the base model