Kept BERT's pretrained weights mostly frozen (or used a very small LR).

Kept BERT's pretrained weights mostly frozen (or used a very small LR). Added a classification head on top of the [CLS] token: linear → dropout → linear → softmax over 2 classes. Also tested adding a Bi-LSTM layer on top of BERT's token outputs before classification. Fine-tuned with AdamW, warmup scheduler, and early stopping on validation F1.