Code as Agent Harness

Hugging Face Daily Papers Papers

Summary

This survey paper presents a unified view of code as the operational substrate for agent reasoning and execution in agentic systems, organizing the discussion around three layers: harness interface, mechanisms, and scaling.

Recent large language models (LLMs) have demonstrated strong capabilities in understanding and generating code, from competitive programming to repository-level software engineering. In emerging agentic systems, code is no longer only a target output. It increasingly serves as an operational substrate for agent reasoning, acting, environment modeling, and execution-based verification. We frame this shift through the lens of agent harnesses and introduce code as agent harness: a unified view that centers code as the basis for agent infrastructure. To systematically study this perspective, we organize the survey around three connected layers. First, we study the harness interface, where code connects agents to reasoning, action, and environment modeling. Second, we examine harness mechanisms: planning, memory, and tool use for long-horizon execution, together with feedback-driven control and optimization that make harness reliable and adaptive. Third, we discuss scaling the harness from single-agent systems to multi-agent settings, where shared code artifacts support multi-agent coordination, review, and verification. Across these layers, we summarize representative methods and practical applications of code as agent harness, spanning coding assistants, GUI/OS automation, embodied agents, scientific discovery, personalization and recommendation, DevOps, and enterprise workflows. We further outline open challenges for harness engineering, including evaluation beyond final task success, verification under incomplete feedback, regression-free harness improvement, consistent shared state across multiple agents, human oversight for safety-critical actions, and extensions to multimodal environments. By centering code as the harness of agentic AI, this survey provides a unified roadmap toward executable, verifiable, and stateful AI agent systems.
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Source: https://huggingface.co/papers/2605.18747 Authors:

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Abstract

Large language models are increasingly used as operational substrates for agent reasoning and execution in agentic systems, with code serving as a unified infrastructure layer across multiple domains and applications.

Recentlarge language models(LLMs) have demonstrated strong capabilities in understanding and generating code, from competitive programming to repository-level software engineering. In emergingagentic systems, code is no longer only a target output. It increasingly serves as an operational substrate for agentreasoning, acting,environment modeling, and execution-based verification. We frame this shift through the lens ofagent harnesses and introducecode as agent harness: a unified view that centers code as the basis foragent infrastructure. To systematically study this perspective, we organize the survey around three connected layers. First, we study the harness interface, where code connects agents toreasoning,action, andenvironment modeling. Second, we examine harness mechanisms:planning,memory, andtool usefor long-horizon execution, together withfeedback-driven controlandoptimizationthat make harness reliable and adaptive. Third, we discuss scaling the harness from single-agent systems to multi-agent settings, where shared code artifacts supportmulti-agent coordination, review, and verification. Across these layers, we summarize representative methods and practical applications ofcode as agent harness, spanning coding assistants, GUI/OS automation, embodied agents, scientific discovery, personalization and recommendation,DevOps, andenterprise workflows. We further outline open challenges for harness engineering, including evaluation beyond final task success, verification under incomplete feedback, regression-free harness improvement, consistent shared state across multiple agents, human oversight for safety-criticalactions, and extensions to multimodal environments. By centering code as the harness of agentic AI, this survey provides a unified roadmap toward executable, verifiable, and stateful AI agent systems.

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