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Basic Information

ART (Agent Reinforcement Trainer) is an open-source reinforcement learning framework designed to train multi-step, LLM-based agents to perform real-world tasks by letting models learn from experience. The repository provides tooling to integrate GRPO training into Python applications via an OpenAI-compatible client and a separate server that runs inference and training on GPU-enabled machines. ART includes example notebooks and end-to-end workflows for tasks such as MCP•RL (specializing models to use Model Context Protocol servers), email search (ART•E), and game-playing examples like 2048 and Tic Tac Toe. The project supplies ergonomic wrappers, training loop orchestration, RULER-based reward scoring, and support for saving and loading LoRA checkpoints into vLLM during iterative training. Installation is available via pip and the code is published under the Apache-2.0 license.

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Features
ART provides modular client-server orchestration for RL training with GRPO and a clear training loop that collects trajectories, assigns rewards, groups rollouts, and updates LoRA checkpoints loaded into vLLM. MCP•RL automates discovery of MCP server tools, generates training scenarios, and trains models to use those tools without labeled data. RULER is integrated for relative scoring of trajectories. The project offers ready-made notebooks and benchmarks for tasks including MCP•RL, ART•E email agent, 2048, Codenames, Tic Tac Toe, and Temporal Clue. Integrations with observability platforms such as W&B, Langfuse, and OpenPipe are supported. ART targets most vLLM/HuggingFace-compatible causal models, supports running the server on local or ephemeral GPU environments, and exposes configurable intelligent defaults to simplify setup.
Use Cases
For developers building agentic systems, ART reduces the engineering burden of training LLM agents by providing a reusable RL trainer, example pipelines, and evaluation tooling. It enables zero- or low-data workflows by generating training scenarios and applying RULER to produce reward signals, which is useful for adapting models to specific tool sets like MCP servers. The client-server split lets you run the client from a laptop while the server handles GPU training and inference, producing LoRA artifacts that are hot-loaded into vLLM so agents improve iteratively. Observability integrations and notebooks help validate performance and reproduce benchmarks. ART is intended to be drop-in friendly for Python projects and includes guidance for supported models and contributing to the project.

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