Dg-separable dg-extensions

We define and characterise completely dg-separable dg-extensions $\phi :(A,d_A)\to (B,d_B)$. We completely characterise the case of graded commutative dg-division algebras in characteristic different from $2$. We prove that for a dg-separable extension a short exact sequence of dg-modules over $(B,d_B)$ splits if and only if the restriction to $(A,d_A)$ splits.