What problem does it solve? Fine-tuning language models to follow strict output formats or solve verifiable tasks is difficult with supervised methods alone, and GRPO training involves subtle pitfalls like misread loss curves, mode collapse, and poorly designed reward functions. ## Core Features & Use Cases - Complete GRPO Workflow: Step-by-step guidance covering dataset preparation, reward function design, training configuration, and deployment with TRL. - Reward Function Library: Over 20 ready-to-adapt reward functions for correctness, format, length, and style objectives, plus presets for math, code, summarization, and Q&A tasks. - Production Template: A runnable training script using Qwen 2.5 1.5B with LoRA, three reward functions, and memory-optimized hyperparameters. - Use Case: Train a model to answer math problems in a strict <reasoning>/<answer> XML format by combining an incremental format reward with an exact-match correctness reward. ## Quick Start Use the grpo-rl-training skill to set up a GRPO training run with TRL that teaches my model to output reasoning and answers in XML tags.