HC3 AI-Generated Text Detector (HW1)

sentence-transformers/all-MiniLM-L6-v2 (22.7M params) fine-tuned for binary classification of English answers: 0 = human, 1 = ChatGPT. Built for a course homework; not a production detector.

Results

Accuracy on the 4,668-answer HC3 test split:

Model Accuracy
Frozen embeddings + logistic regression 84.49%
Fine-tuned, lr 2e-5, 5 epochs (the model in this repo) 99.64%
Side run: lr 1e-5 98.71%
Side run: 7 epochs 98.86%

Confusion matrix for the model in this repo (rows = true human / ChatGPT): [[2322, 12], [5, 2329]], i.e. 17 mistakes out of 4,668. The baseline made 724.

The side runs were single runs with one seed and differ by only a few answers

How it was trained

Full fine-tuning with AdamW, lr 2e-5, 5 epochs, batch size 32, max length 256, seed 42, on the provided HC3 split (37,334 train / 4,666 validation / 4,668 test, split by question). Input is the answer text only.

Usage

from transformers import pipeline
clf = pipeline("text-classification", model="Aishkrish/hw1-hc3-detector")
clf("Your text here")
```​
```
The output labels appear as `LABEL_0` (human) and `LABEL_1` (ChatGPT).
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