  We consider the $q$-nonabelianization map, which maps links $L$ in a
3-manifold $M$ to links $\widetilde{L}$ in a branched $N$-fold cover
$\widetilde{M}$. In quantum field theory terms, $q$-nonabelianization is the
UV-IR map relating two different sorts of defect: in the UV we have the
six-dimensional $(2,0)$ superconformal field theory of type $\mathfrak{gl}(N)$
on $M \times \mathbb{R}^{2,1}$, and we consider surface defects placed on $L
\times \{x^4 = x^5 = 0\}$; in the IR we have the $(2,0)$ theory of type
$\mathfrak{gl}(1)$ on $\widetilde{M} \times \mathbb{R}^{2,1}$, and put the
defects on $\widetilde{L} \times \{x^4 = x^5 = 0\}$. In the case $M =
\mathbb{R}^3$, $q$-nonabelianization computes the Jones polynomial of a link,
or its analogue associated to the group $U(N)$. In the case $M = C \times
\mathbb{R}$, when the projection of $L$ to $C$ is a simple non-contractible
loop, $q$-nonabelianization computes the protected spin character for framed
BPS states in 4d $\mathcal{N}=2$ theories of class $S$. In the case $N=2$ and
$M = C \times \mathbb{R}$, we give a concrete construction of the
$q$-nonabelianization map. The construction uses the data of the WKB foliations
associated to a holomorphic covering $\widetilde{C} \to C$.
