Four root causes of GUI agent loops and a screenshot-hash fix

On November 7, 2026, a Juejin post titled "GUI Agent 打转死循环的四个根因与画面哈希解法" examined why GUI Agents that operate computers end up in looping cycles. The author argues that the problem is not the model's capability, but that existing anti-loop mechanisms are bypassed by four blind spots. First, actions report mechanical success: mouse moves and key presses all return ok=True, so failure-triggered stop logic never activates. Second, loop detection relies on identifying identical actions, yet the model's target descriptions and coordinates differ slightly each time, so they never match. Third, the model lacks screenshot comparison: it cannot perceive that the screen has stayed the same and keeps trying more clicks. Fourth, a low reasoning tier further weakens its ability to break out of the cycle. Instead of raising thresholds, the post proposes judging progress from the screen itself. A screenshot hash detects whether an action actually changes the display, treating no change as a failure signal. This is combined with a wait-screenshot-verify rule, coordinate drift detection, and an iteration cap. The author also provides runnable code. So far only this one source has been reported, and the effectiveness of the approach in other GUI Agent settings remains unverified.