What problem does it solve? Machine learning teams lose track of experiments, hyperparameters, and model versions when training runs are scattered across notebooks and scripts. This Skill provides complete guidance for using Weights & Biases (W&B) to log metrics, compare runs, optimize hyperparameters, and version datasets and models with full lineage. ## Core Features & Use Cases - Experiment Tracking: Log metrics, configs, media, and system stats from PyTorch, TensorFlow, Keras, HuggingFace, and PyTorch Lightning training loops. - Hyperparameter Sweeps: Run grid, random, or Bayesian optimization searches with early termination and parallel agents across multiple GPUs. - Artifacts & Model Registry: Version datasets and models with automatic lineage tracking, aliases for deployment stages, and a central model registry. - Use Case: A data scientist fine-tuning a BERT model can initialize a W&B run, launch a Bayesian sweep over learning rate and batch size, compare 50 trials in a real-time dashboard, and promote the best checkpoint to a production model registry. ## Quick Start Set up a W&B experiment tracking run for my PyTorch training script that logs loss and accuracy each epoch and saves the final model as an artifact.