In this talk, we will describe how to construct a basis of Bott-Samelson bimodules, called singular light leaves. Bott-Samelson bimodules are algebraic objects that correspond geometrically to resolutions of singularities of Schubert varieties. In the nonsingular case, that is for Schubert varieties in full flag varieties, Libedinsky introduced a basis (called light leaves) between Bott-Samelson bimodules which has been extensively used to compute the decomposition behavior in the Hecke category, for example enabling the discovery of counterexamples to Lusztig's conjecture on representations in characteristic p. We will thoroughly extend Libedinsky's result to the singular setting. To do this, we will employ the language of diagrammatic calculus associated with Frobenius extensions. Our construction has concrete applications in computing intersection forms, as well as more theoretical implications pointing towards a diagrammatic definition of the Hecke category. This is a joint project with B. Elias, H. Ko, and N. Libedinsky.