SkillDroid: Compile Once, Reuse Forever
Qijia Chen, Andrea Bellucci, Zhida Sun, Giulio Jacucci
Stop treating every mobile automation task as a fresh reasoning problem. Compile successful trajectories into reusable skills. Best for repetitive workflows where reliability compounds—the system gets better with use while your baseline degrades.
LLM-based mobile agents re-derive every task from scratch, burning inference costs and never improving. A task that worked yesterday gets the full reasoning treatment today—no memory, no speed gain, no reliability improvement.
Method: SkillDroid compiles successful LLM trajectories into parameterized skill templates—sequences of UI actions with weighted element locators and typed parameter slots—then replays them without LLM calls. Over 150 rounds with instruction variation and controlled perturbations, it hit 85.3% success (23 points above the stateless baseline) using 49% fewer LLM calls. Skill replay achieved 100% success across 79 rounds at 2.4x speed. Most critically: success rate converged upward from 87% to 91%, while the baseline degraded from 80% to 44%.
Caveats: Tested on controlled mobile GUI tasks. Real-world app updates and UI redesigns may break skill templates faster than the study captured.
Reflections: How frequently do real-world app updates invalidate compiled skills, and can update detection trigger preemptive recompilation? · Can skill templates transfer across similar apps (e.g., different email clients) or do UI variations require per-app compilation? · What's the minimum number of successful executions needed to compile a reliable skill template?