FullStackArena: Evaluating Browser Agents in Dynamic and Temporally Evolving Full-Stack Environments

Existing browser-use benchmarks largely assume a classical, static web architecture. In contrast, today's web relies heavily on dynamic, stateful, and temporal behaviours driven by asynchronous requests, persistent server communications, and real-time user interactions. Consequently, current agents struggle to handle the non-deterministic, partially observable nature of modern web applications. This exposes fundamental flaws not just in the models themselves, but in current agent architectures and prompting strategies. To address these deficiencies, we introduce FullStackArena, a novel browser-use benchmark that challenges web agents with complex, full-stack environments. FullStackArena encompasses six diverse, fully operational websites spanning online bidding, stock trading, ride-hailing, maps, social media, and video. While emulating the dynamic impact of time-sensitive events, the benchmark remains entirely self-hosted, deterministic, and reproducible. Across all 781 tasks, the four baseline models pass only 16–18% of attempts on average across our evaluation settings.