What problem does it solve? Data leakage from preprocessing steps (imputation, scaling, SMOTE) applied globally before cross-validation splits silently inflates model metrics, leading to invalid conclusions in Kaggle-style machine learning experiments. This Skill detects and quantifies that leakage. ## Core Features & Use Cases - Leakage Variant Comparison: Benchmarks a correct baseline (all preprocessing inside CV folds) against leakage variants (ImputeLeak, SMOTELeak, SevereLeak) and reports F1 differences in a leakage kill table. - Imbalance and Complexity Analysis: Correlates class imbalance ratio and model complexity (RandomForest/XGBoost) with leakage severity, identifying global SMOTE as the primary leakage source. - Extreme Imbalance Handling: For datasets with positive class below 1%, forbids F1-only conclusions and requires precision/recall/AUC supplementary metrics. - Use Case: Given an imbalanced binary classification dataset, run the audit script to compare fold-internal preprocessing against global SMOTE variants and produce a report showing how much F1 inflation the leakage caused. ## Quick Start Audit my imbalanced Kaggle dataset for preprocessing leakage by comparing fold-internal preprocessing against global SMOTE, impute, and scale variants with RandomForest and XGBoost models.