GEPA: Reflective Prompt Evolution Can Outperform Reinforcement Learning

ICLR 2026 Conference Submission21539 Authors

Keywords: prompt optimization, natural language, reflection, large language models, agent design, agent discovery, code optimization, compound AI systems, genetic, language based learning, evolutionary algorithms

TL;DR: GEPA uses natural language reflection to optimize prompts, outperforming GRPO and MIPROv2 while needing far fewer rollouts.

Abstract:

Large language models (LLMs) are increasingly adapted to downstream tasks via reinforcement learning (RL) methods like Group Relative Policy Optimization (GRPO), which often require thousands of rollouts to learn new tasks. We argue that the interpretable nature of language often provides a much richer learning medium for LLMs, compared to policy gradients derived from sparse, scalar rewards. To test this, we introduce GEPA (Genetic-Pareto), a prompt optimizer that thoroughly incorporates natural language reflection to learn high-level rules from trial and error.
Given any AI system containing one or more LLM prompts, GEPA samples trajectories (e.g., reasoning, tool calls, and tool outputs) and reflects on them in natural language to diagnose problems, propose and test prompt updates, and combine complementary lessons from the Pareto frontier of its own attempts. As a result of GEPA's design, it can often turn even just a few rollouts into a large quality gain.
Across four tasks, GEPA outperforms GRPO by 10% on average and by up to 20%, while using up to 35x fewer rollouts. GEPA also outperforms the leading prompt optimizer, MIPROv2, by over 10% (e.g., +10% accuracy on AIME-2025).

Primary Area: foundation or frontier models, including LLMs

Submission Number: 21539