While research on AI agents focuses on enabling them to operate graphical user interfaces, the most effective and widely adopted agent tools in practice are terminal-based. We argue that this convergence is not coincidental. It reflects three design properties central to effective human-AI-UI collaboration: representational compatibility between agent and interface, transparency of agent actions within the interaction medium, and low barriers to entry for human participants. We ground each property in established HCI theory, show how terminal-based tools satisfy them by default, and argue that any modality, including graphical and spatial interfaces, must be deliberately engineered to achieve them. Rather than a legacy artifact, the terminal serves as a design exemplar whose properties any agent-facing modality must replicate.

翻译：尽管关于人工智能体的研究主要聚焦于使其能够操作图形用户界面，但在实践中最为有效且广泛采用的智能体工具却是基于终端的。我们认为这种趋同并非偶然。它反映了有效人机智能体-用户界面协作的三个核心设计特性：智能体与界面之间的表征兼容性、交互媒介中智能体行为的透明度，以及人类参与者的低准入门槛。我们将每个特性根植于既定的人机交互理论，展示基于终端的工具如何默认满足这些特性，并论证包括图形界面和空间界面在内的任何交互模态都必须经过精心设计才能实现这些特性。终端并非遗留产物，而是作为设计典范，其特性必须被所有面向智能体的交互模态所复现。