cs.SEOct 2, 2026

Engineering Sustainable Agents: A Systematic Comparison of Agentic LLMs for Developer Workflows

Authors: Merve Astekin, Yan Naing Tun, Arda Goknil, Erik Johannes Husom, Lwin Khin Shar, Hasan Sözer, Ratnadira Widyasari, Hui Song

Organizations: SINTEF, Oslo, Norway · Singapore Management University, Singapore, Singapore · Ozyegin University, Istanbul, Turkiye

Abstract

Large language models (LLMs) are increasingly used in software engineering, including agentic systems that coordinate multiple agents, but impose higher computational and environmental costs. In this paper, we present a comprehensive empirical study of agentic LLM systems across five software engineering tasks: code generation, technical debt identification, code vulnerability detection, log parsing, and log analysis. For each task, we compare LLM configurations that range from a non-agentic single-query baseline to multi-agent workflows, using six open-weight LLMs, two prompt strategies, and three hardware platforms. We assess each configuration in terms of accuracy, inference latency, and energy consumption. Our results reveal substantial trade-offs between agentic complexity and energy efficiency: multi-agent designs consume on average 6.36×\times as much energy and run 6.07×\times as long as the non-agentic baseline, with worst-case slowdowns of up to 160×\times for individual task--hardware pairs. Accuracy gains from additional agents are limited and task-specific: multi-agent improves average vulnerability-detection accuracy, but lightweight non-agentic and single-agent configurations still dominate the Pareto front, accounting for 59 of 66 Pareto-optimal configurations. Model and prompt choice act as task-specific levers whose effective direction varies between tasks rather than as global defaults. We translate these findings into design guidelines for sustainable, task-aware LLM-based development tools.

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