LLMs as Layout Designers: A Spatial Reasoning Perspective

While Large Language Models (LLMs) have demonstrated impressive reasoning and planning abilities in textual domains and can effectively follow instructions for complex tasks, their capacity for spatial understanding and reasoning remains limited. Such capabilities, however, are critical for applications like content-aware graphic layout design, which demands precise placement, alignment, and structural organization of multiple elements within constrained visual spaces. To address this gap, we propose LaySPA, a reinforcement learning-based framework that augments LLM agents with explicit spatial reasoning capabilities. LaySPA leverages hybrid reward signals that capture geometric validity, structural fidelity, and visual quality, enabling agents to model inter-element relationships, navigate the canvas, and optimize spatial arrangements. Through iterative self-exploration and adaptive policy optimization, LaySPA produces both interpretable reasoning traces and structured layouts. Experimental results demonstrate that LaySPA generates structurally sound and visually appealing layouts, outperforming larger general-purpose LLMs and achieving results on par with state-of-the-art specialized layout models.