Summary: Asymptotic symmetries of \(\mathrm{AdS}_{4}\) quantum gravity and gauge theory are derived by coupling the holographically dual \(\mathrm{CFT}_{3}\) to Chern-Simons gauge theory and 3D gravity in a “probe” (large-level) limit. Despite the fact that the three-dimensional \(\mathrm{AdS}_{4}\) boundary as a whole is consistent with only finite-dimensional asymptotic symmetries, given by AdS isometries, infinite-dimensional symmetries are shown to arise in circumstances where one is restricted to boundary subspaces with effectively two-dimensional geometry. A canonical example of such a restriction occurs within the 4D subregion described by a Wheeler-DeWitt wavefunctional of \(\mathrm{AdS}_{4}\) quantum gravity. An \(\mathrm{AdS}_{4}\) analog of Minkowski “super-rotation” asymptotic symmetry is probed by 3D Einstein gravity, yielding \(\mathrm{CFT}_{2}\) structure (in a large central charge limit), via \(\mathrm{AdS}_{3}\) foliation of \(\mathrm{AdS}_{4}\) and the \(\mathrm{AdS}_{3}/\mathrm{CFT}_{2}\) correspondence. The maximal asymptotic symmetry is however probed by 3D conformal gravity. Both 3D gravities have Chern-Simons formulation, manifesting their topological character. Chern-Simons structure is also shown to be emergent in the Poincare patch of \(\mathrm{AdS}_{4}\), as soft/boundary limits of 4D gauge theory, rather than “put in by hand” as an external probe. This results in a finite effective Chern-Simons level. Several of the considerations of asymptotic symmetry structure are found to be simpler for \(\mathrm{AdS}_{4}\) than for \(Mink_{4}\), such as non-zero 4D particle masses, 4D non-perturbative “hard” effects, and consistency with unitarity. The last of these in particular is greatly simplified because in some set-ups the time dimension is explicitly shared by each level of description: Lorentzian \(\mathrm{AdS}_{4}\), \(\mathrm{CFT}_{3}\) and \(\mathrm{CFT}_{2}\). Relatedly, the \(\mathrm{CFT}_{2}\) structure clarifies the sense in which the infinite asymptotic charges constitute a useful form of “hair” for black holes and other complex 4D states. An \(\mathrm{AdS}_{4}\) analog of Minkowski “memory” effects is derived, but with late-time memory of earlier events being replaced by (holographic) “shadow” effects. Lessons from \(\mathrm{AdS}_{4}\) provide hints for better understanding Minkowski asymptotic symmetries, the 3D structure of its soft limits, and Minkowski holography.