---
license: apache-2.0
base_model: answerdotai/ModernBERT-base
pipeline_tag: text-classification
tags: [code, bug-detection, python, java, cpp]
---

# BugAgent bug localizer

A binary classifier (clean or buggy) over single functions in Python, Java and C/C++, used by
[BugAgent](https://github.com/haaardikkk/BugAgent). Built on answerdotai/ModernBERT-base, with 512 tokens per function.

## Results

AUC: 0.50 is chance and 1.00 is perfect.

| Test | Held-out projects | Benchmarks never used in training or selection |
|---|---|---|
| Buggy vs its own fix | 0.49 | 0.50 |
| Buggy vs fixed and unchanged code | 0.67 | 0.55 |
| Buggy vs unchanged code | 0.75 | 0.58 |
| Buggy ranked above its fix | 42% of pairs | 47% of pairs |

**This model can't tell a bug from its own fix: that score is chance level.** BugAgent gives its scores zero weight
when ranking problems. Don't rely on it to decide whether code is correct.

## Data

Trained on: nebius/SWE-rebench, princeton-nlp/SWE-bench (train), nebius/SWE-bench-extra, SWE-Gym/SWE-Gym, ByteDance-Seed/Multi-SWE-RL, bigcode/commitpackft, ASSERT-KTH/megadiff-single-function, bstee615/bigvul.

Benchmarks: princeton-nlp/SWE-bench_Verified, ByteDance-Seed/Multi-SWE-bench.