Top: mass fraction profiles without overshooting (NOV) during the CHeB phase. Left: mass fraction profiles after core helium depletion, terminated prior to the first thermal pulse at ﹩\mathrm{log}(L/{L}_{\odot })\gt 3.0﹩. Middle: mass fraction profiles at the first wd_builder model step. These profiles have been shaved of their excess hydrogen envelope prior to running on the WD cooling track. These are the initial hot WD profiles. Right: mass fraction profiles when the models have cooled to T _eff = 10,000 K. The smoothness in the profiles reflects the element diffusion processes included in the calculation. Bottom: mass fraction profiles with core overshooting (OV) during the CHeB phase, in the same format as above. Green curves represent positive σ _i ¹²C(α, γ)¹⁶O reaction rates, gray curves represent negative σ _i ¹²C(α, γ)¹⁶O reaction rates. For both positive and negative σ _i , the shading grows fainter the further σ is from the standard rate (σ = 0; black curve).