2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/221475The Bost conjecture with C*-algebra coefficients for locally compact Hausdorff groups passes to open subgroups. We also prove that if a locally compact Hausdorff group acts on a tree, then the Bost conjecture with C*-coefficients is true for the group if and only if it is true for the stabilisers of the vertices.17 pages; to be published in the Journal of K-TheoryK-Theory and HomologyOperator Algebras19K35 (Primary) 46L80, 22A22, 43A20 (Secondary)text