On the non-generic part of cohomology of compact unitary Shimura varieties of signature $(1,n)$

In this short note, we prove a result about the non-generic part of the cohomology of certain compact unitary Shimura varieties for good $p$, partially extending a result of Boyer in the case of Harris–Taylor unitary Shimura varieties. Our arguments are different to those of Boyer – we work in the context of the work of Fargues–Scholze, using ideas introduced by Koshikawa to study the generic part of cohomology.