Mitigating Task Drift in Long-Horizon GUI Agents

While coding agents have advanced rapidly, progress in GUI agent harnesses has lagged, especially for long-horizon tasks. In such tasks, a GUI agent can carry an incorrect or outdated completion judgment into later decisions and overlook unmet user requirements. We define task drift as this persistent mismatch between the agent’s believed progress and the actual satisfaction of the original task requirements. The root cause is that progress judgments detach from the original requirements and lack requirement-specific environmental evidence. To address this, we introduce a framework that separates persistent user requirements from revisable plans and progress judgments, and grounds each judgment in concrete environmental evidence. Its controller distinguishes missing evidence from evidence of an unmet requirement: the former triggers inspection, the latter triggers correction, and invalidated support triggers revalidation only for affected requirements. On OSWorld, our framework improves the mean task score from 73.3 to 82.1 with Qwen3.7-Plus as the backbone.