Topological defects and tensionless holography

We study topological defect lines in the symmetric-product orbifolds ${\mathrm{S}\mathrm{y}\mathrm{m}}^N(X)$ for a generic seed CFT $X$. We focus on the defects which preserve the maximum of the $S_N$ symmetry. When $X$ is taken to describe the free theory of four fermions and four bosons on a ${\mathbb{T}}^4$, we construct holographically dual backgrounds describing propagation of tensionless closed strings in the presence of spacetime defects wrapping the conformal boundary. We find a precise match between the spectra of local on-shell closed-string vertex operators in the bulk and the spectra of non-local disorder fields in the spacetime theory.