  Charge symmetry breaking (CSB) is particularly strong in the A=4 mirror
hypernuclei $_{\Lambda}^4$H--$_{\Lambda}^4$He. Recent four-body no-core shell
model calculations that confront this CSB by introducing $\Lambda$-$\Sigma^0$
mixing to leading-order chiral effective field theory hyperon-nucleon
potentials are reviewed, and a shell-model approach to CSB in p-shell $\Lambda$
hypernuclei is outlined.
