---
license: apache-2.0
language:
- en
- zh
base_model:
- Qwen/Qwen3-8B
library_name: transformers
tags:
- rm
- cr
---

# SWE-CARE-RM

This model is a custom reward model built on top of **Qwen3-8B** with:

- a merged **LoRA** adapter
- an additional **projector head**
- a scalar reward output in **[0, 1]**

The model is designed to score the quality of a review conditioned on:

1. an issue / problem statement
2. a code patch
3. a candidate review

A higher score means the model considers the review better under the given issue and patch.

## Model Architecture

The model consists of:

- base model: **Qwen3-8B**
- adaptation: **LoRA**
- reward head: a custom **MLP projector**
- final score: `sigmoid(projector(last_hidden_state[:, -1]))`

This repository contains the **merged decoder weights** together with `projector.pth`.

## Input Format

The model expects three text fields:

- `issue`
- `patch`
- `review`

During inference, the input is formatted as:

```latex
<issue>{issue}</issue><patch>{patch}</patch><review>{review}<review>
```

The score is computed from the last token hidden state.

## Quick Start

```latex
from pathlib import Path
import json

import torch
import torch.nn as nn
from transformers import AutoModelForCausalLM, AutoTokenizer


MODEL_DIR = "codefuse-ai/SWE-CARE-RM"
MAX_SEQ_LEN = 51200
MIN_REVIEW_LEN = 4096
TRUST_REMOTE_CODE = True

with open(f"{MODEL_DIR}/data_sample.jsonl", "r") as fr:
    for line in fr:
        json_data = json.loads(line)
        break

SAMPLE = {
    "issue": json_data['problem_statement'],
    "patch": json_data['patch_to_review'],
    "review": json_data['pos_review'][0]
}

class Projector(nn.Module):
    def __init__(self, arch, input_size, hidden_size, use_bf16):
        super().__init__()
        depth = int(arch[len("mlp"): arch.index("x_relu")])
        layers = [nn.Linear(input_size, hidden_size).bfloat16() if use_bf16 else
nn.Linear(input_size, hidden_size)]
        for _ in range(1, depth):
            layers.append(nn.ReLU())
            layers.append(nn.Linear(hidden_size, 1).bfloat16() if use_bf16 else
nn.Linear(hidden_size, 1))
        self.model = nn.Sequential(*layers)

    def forward(self, x):
        return self.model(x)


def resolve_dtype(dtype_name):
    if dtype_name in {"bf16", "bfloat16"}:
        return torch.bfloat16
    if dtype_name in {"fp16", "float16"}:
        return torch.float16
    return torch.float32


def infer_proj_arch(projector_state_dict):
    linear_weight_keys = [k for k in projector_state_dict if k.startswith("model.")
and k.endswith(".weight")]
    return f"mlp{len(linear_weight_keys)}x_relu"


def process_one(issue_ids, issue_masks, patch_ids, patch_masks, review_ids,
review_masks, max_len, min_review_len):
    review_keep = min(min_review_len, len(review_ids))
    remain_for_patch = max(max_len - len(issue_ids) - review_keep, 0)
    patch_keep = min(len(patch_ids), remain_for_patch)

    ids_all = issue_ids + patch_ids[:patch_keep] + review_ids[-review_keep:]
    masks_all = issue_masks + patch_masks[:patch_keep] + review_masks[-review_keep:]

    if len(ids_all) < max_len:
        pad_len = max_len - len(ids_all)
        ids_all = [0] * pad_len + ids_all
        masks_all = [0] * pad_len + masks_all

    return ids_all[:max_len], masks_all[:max_len]


reward_config = {}
reward_config_path = Path(MODEL_DIR) / "reward_config.json"
if reward_config_path.exists():
    reward_config = json.load(open(reward_config_path, "r", encoding="utf-8"))

projector_path = Path(MODEL_DIR) / "projector.pth"
projector_state_dict = torch.load(projector_path, map_location="cpu")
proj_arch = reward_config.get("proj_arch") or infer_proj_arch(projector_state_dict)
torch_dtype = resolve_dtype(reward_config.get("torch_dtype") or "bfloat16")
attn_implementation = reward_config.get("attn_implementation")

tokenizer = AutoTokenizer.from_pretrained(MODEL_DIR,
trust_remote_code=TRUST_REMOTE_CODE, padding_side="left")

model_kwargs = {"trust_remote_code": TRUST_REMOTE_CODE, "torch_dtype": torch_dtype}
if attn_implementation:
    model_kwargs["attn_implementation"] = attn_implementation
decoder = AutoModelForCausalLM.from_pretrained(MODEL_DIR, **model_kwargs)

projector = Projector(proj_arch, decoder.config.hidden_size,
decoder.config.hidden_size, torch_dtype == torch.bfloat16)
projector.load_state_dict(projector_state_dict)

device = torch.device("cuda" if torch.cuda.is_available() else "cpu")
decoder.to(device).eval()
projector.to(device).eval()

issue_inputs = tokenizer(f"<issue>{SAMPLE['issue']}</issue>", padding=False,
truncation="longest_first")
patch_inputs = tokenizer(f"<patch>{SAMPLE['patch']}</patch>", padding=False,
truncation="longest_first")
review_inputs = tokenizer(SAMPLE["review"], padding=False, truncation="longest_first")

input_ids, attention_mask = process_one(
    issue_inputs["input_ids"],
    issue_inputs["attention_mask"],
    patch_inputs["input_ids"],
    patch_inputs["attention_mask"],
    review_inputs["input_ids"],
    review_inputs["attention_mask"],
    max_len=MAX_SEQ_LEN,
    min_review_len=MIN_REVIEW_LEN,
)

inputs = {
    "input_ids": torch.tensor([input_ids], dtype=torch.long, device=device),
    "attention_mask": torch.tensor([attention_mask], dtype=torch.long, device=device),
}

with torch.no_grad():
    hidden_state = decoder(**inputs, output_hidden_states=True).hidden_states[-1]
    reward = torch.sigmoid(projector(hidden_state).squeeze(-1)[:, -1]).item()

print(reward)
```

## Output

The model outputs a single scalar reward score in [0, 1].

Typical interpretation:

- higher score: better review quality
- lower score: worse review quality

This score is best used for:

- ranking candidate reviews
- pairwise comparison
- reward modeling in downstream training or reranking

## Intended Use

This model is intended for:

- code review quality scoring
- reward modeling for review generation
- reranking multiple candidate reviews for the same issue and patch

## Limitations

- The score is relative, not an absolute guarantee of correctness.
- Long-input truncation may affect results.
- The model should not be used as the only signal for production-critical review
  decisions.

## Citation

If you use this model, please cite SWE-CARE as appropriate.

```
@misc{guo2025codefusecrbenchcomprehensivenessawarebenchmarkendtoend,
      title={CodeFuse-CR-Bench: A Comprehensiveness-aware Benchmark for End-to-End Code Review Evaluation in Python Projects}, 
      author={Hanyang Guo and Xunjin Zheng and Zihan Liao and Hang Yu and Peng DI and Ziyin Zhang and Hong-Ning Dai},
      year={2025},
      eprint={2509.14856},
      archivePrefix={arXiv},
      primaryClass={cs.SE},
      url={https://arxiv.org/abs/2509.14856}, 
}
```

