Evolution of the binary period (blue) and eccentricity (purple) of the binary that forms a reported HR 6819 inner-binary-like system in the isolated binary evolution framework. The CE phase (red) takes place at ∼8.2 Myr and was initiated by the primary star, which collapses shortly thereafter into a BH. A BH-MS system (similar to HR 6819) phase is noted for ∼40 Myr (∼10 − 50 Myr after ZAMS). We also show the evolution of this binary beyond the BH-MS phase with two stable RLOF events (at ∼49 Myr and ∼61 Myr since ZAMS) initiated by an expanding secondary.