Persona skills leak identity across three frontier agents

AntiSkillBench found that persona skills leak private details across unrelated conversations in all three frontier agents tested, per the paper posted to arXiv. That's a risk for anyone building products that compress a user into a reusable artifact. The leakage went beyond explicit attributes into communication style and personality traits, drawn from 7,500 dialogue traces built off 50 profiles.

The researchers tested four defenses meant to stop the leak. All four were distillation-dependent, and none held up once the underlying model changed. The paper doesn't say how the compression step decides what to keep, which is the exact point where the leakage starts.

Persona portability and privacy protection are pulling in opposite directions. A file compact enough to carry someone's history between agents is compact enough to carry the parts you didn't mean to hand over. Nothing tested here stops that once you swap in a different model. Watch for a defense that survives a model swap. None does yet, on this evidence.