# Stable training — DistilBERT + TF-IDF LR + hybrid ensemble
# Goals: Test F1 > 0.80, |Train F1 - Test/Val F1| < 0.05 (5 pp)

pipeline:
  random_state: 42
  test_size: 0.2
  val_size: 0.15  # fraction of remaining train after test split
  cv_folds: 5
  max_train_test_gap: 0.05  # |train F1 - test/val F1| rubric (5 pp)

data:
  raw_path: data/raw/youtoxic_english_1000.csv
  target_binary: IsToxic
  text_column: Text

augmentation:
  enabled: true
  strategy: back_translation  # toxic class only
  source_lang: en
  pivot_lang: es
  min_words: 3
  max_words: 60
  rate_limit_every: 50
  rate_limit_sleep_sec: 1.0
  dedup:
    enabled: true
    cosine_threshold: 0.95
    embedding_model: sentence-transformers/all-MiniLM-L6-v2

distilbert:
  model_id: distilbert-base-uncased
  max_length: 128
  num_layers: 6
  freeze_first_n_layers: 4  # layers 0-3 frozen; layers 4-5 + head trainable
  learning_rate: 1.0e-5
  weight_decay: 0.01
  max_epochs: 15
  batch_size: 8
  warmup_ratio: 0.1
  head_dropout: 0.5
  label_smoothing: 0.1
  early_stopping:
    patience: 3
    metric: f1_toxic  # val F1 for patience-based stop
    gap_stop_enabled: false  # production: patience on val F1 only
    max_train_val_gap: 0.045
    gap_check_min_epoch: 2
  metric_for_best: f1_toxic

logistic_regression:
  C: 0.05
  max_iter: 2000
  class_weight: balanced
  solver: lbfgs
  gap_search:
    enabled: true
    max_gap: 0.05
    use_original_train_for_gap: true
    param_grid:
      - {C: 0.05, max_features: 800, min_df: 3}
      - {C: 0.05, max_features: 500, min_df: 5}
      - {C: 0.03, max_features: 800, min_df: 5}
      - {C: 0.02, max_features: 400, min_df: 5}
      - {C: 0.01, max_features: 400, min_df: 8}
      - {C: 0.005, max_features: 300, min_df: 10}
  tfidf:
    max_features: 800
    ngram_range: [1, 2]
    sublinear_tf: true
    min_df: 3

ensemble:
  method: soft_vote  # soft_vote | stacking
  bert_weight: 0.5
  lr_weight: 0.5

output:
  distilbert_dir: models/stable_distilbert
  lr_path: models/stable_lr_tfidf.joblib
  ensemble_meta_path: models/stable_ensemble_meta.json
  reports_dir: reports/stable