Diploid Saccharomyces cerevisiae cells undergo meiosis and sporulation during nutritional deprivation. Unlike many other fungi, S. cerevisiae spores remain encased in the ascus, a sac-like structure derived from the vegetative cell wall of the pre-meiotic mother cell, unless environmental conditions degrade the ascus and promote spore dispersal. Upon exposure to nutrients, spores germinate (i.e., partially break down the spore wall) and either begin mitotic proliferation immediately, or mate with other cells and then proliferate mitotically. Homothallic spores have the additional option of mating-type switching after the first haploid budding event and then mating with the bud or its progeny. If the original diploid cells are heterozygous at important loci, these three options (mate, bud, or bud/switch/mate) have drastically different consequences for the possible allelic combinations following germination and, thus, for fitness. Although this basic question has been considered from a genetic perspective for many decades, the basic cell biology of germination is surprisingly understudied. It is widely assumed in the literature that the act of budding reflects or induces “global” breakdown of the ascus wall that liberates all constituent spores simultaneously. Strikingly, we find, instead, that budding and mating reflect “local” remodeling of the ascus, such that individual spores can bud or mate “out” of the ascus without liberating their sisters. To address the influence of ascus persistence during germination on the bud-vs-mate decision, we developed three independent assays: (i) the Sex with Sister Selection (SwiSS), which allows colony growth only when a spore mates with its sister; (ii) the Germination Abstinence eNforcer (GermAN), which allows colony growth only when a spore avoids mating; and (iii) appropriate colony color markers to visualize mating between sister spores as half-sectored colonies. These approaches demonstrate that an intact ascus promotes mating as the first post-germination event. Together with our observations of ascus perdurance after budding, these findings uncover a hitherto unappreciated role for the ascus in the control of genetic stability through the yeast life cycle. As vegetative conditions influence cell wall durability, ascal control of post-germination events may create a regulatory circuit in which environmental conditions prior to sporulation dictate the duration of ascus persistence and, consequently, the extent of intra-ascus mating. In addition to the poorly understood S. cerevisiae ecological niches, these mechanisms are likely at play in certain industrial settings, such as vinification.