  Let $X$ be a Nakajima quiver variety and $X'$ its $3d$-mirror. We consider
the action of the Picard torus $\mathsf{K}=\mathrm{Pic}(X)\otimes
\mathbb{C}^{\times}$ on $X'$. Assuming that $(X')^{\mathsf{K}}$ is finite, we
propose a formula for the $\mathsf{K}$-character of the tangent spaces at the
fixed points in terms of certain enumerative invariants of $X$ known as vertex
functions.
