verl: Volcano Engine Reinforcement Learning for LLMs verl is a flexible, efficient, and production-ready RL training library for large language models from ByteDance's Seed team. It implements the HybridFlow framework (EuroSys 2025) and powers models like Doubao-1.5-pro achieving O1-level performance on math benchmarks. When to Use verl Choose verl when you need: - Production-ready RL training at scale (tested up to 671B parameters) - Flexibility to swap backends (FSDP ↔ Megatron-LM ↔ vLLM ↔ SGLang) - Support for multiple RL algorithms (PPO, GRPO, RLOO, REINFORCE++, DAPO) - Multi-turn rollout…