Reinforcement Learning for Long-Horizon Multi-Turn Search Agents

Abstract

Large Language Model (LLM) agents can leverage multiple turns and tools to solve complex tasks, with prompt-based approaches achieving strong performance. This work demonstrates that Reinforcement Learning (RL) can push capabilities significantly further by learning from experience. Through experiments on a legal document search benchmark, we show that our RL-trained 14 Billion parameter model outperforms frontier class models (85% vs 78% accuracy). In addition, we explore turn-restricted regimes, during training and at test-time, that show these agents achieve better results if allowed to operate over longer multi-turn horizons.

4 pages plus references and appendices. Accepted into the First Workshop on Multi-Turn Interactions in Large Language Models at NeurIPS 2025