  A large primordial lepton asymmetry can lead to successful baryogenesis by
preventing the restoration of electroweak symmetry at high temperatures,
thereby suppressing the sphaleron rate. This asymmetry can also lead to a
first-order cosmic QCD transition, accompanied by detectable gravitational wave
(GW) signals. By employing next-to-leading order dimensional reduction we
determine that the necessary lepton asymmetry is approximately one order of
magnitude smaller than previously estimated. Incorporating an updated QCD
equation of state that harmonizes lattice and functional QCD outcomes, we
pinpoint the range of lepton flavor asymmetries capable of inducing a
first-order cosmic QCD transition. To maintain consistency with observational
constraints from the Cosmic Microwave Background and Big Bang Nucleosynthesis,
achieving the correct baryon asymmetry requires entropy dilution by
approximately a factor of ten. However, the first-order QCD transition itself
can occur independently of entropy dilution. We propose that the sphaleron
freeze-in mechanism can be investigated through forthcoming GW experiments such
as $\mu$Ares.
