From: Rabbi Moshe Sofer
To: Rabbi Ber
The Chasam Sofer analyzes the precise scope of halachic agency (shelucho shel adam kemoso), arguing it applies only to mitzvos, aveiros, and kinyanim. He concludes that since Shabbos is fundamentally a prohibition 'upon the body' requiring bodily rest, the entire framework of shlichus is conceptually inapplicable to Shabbos violations.
Source: Shu"t Chasam Sofer OC §201