In this work we investigate the stability and instability properties of a
    class of naked singularity spacetimes. The first rigorous study of naked
    singularity formation in the spherically symmetric Einstein-scalar field system
    was due to Christodoulou, who constructed a family $(\overline{g}_k,
    \overline{\phi}_k)$ of $k$-self-similar solutions, for any $k^2 \in
    (0,\frac{1}{3})$. We extend the construction to produce examples of interior
    and exterior regions of naked singularity spacetimes locally modeled on the
    $(\overline{g}_k, \overline{\phi}_k)$, without requiring exact self-similarity.

    The main result is a global stability statement under fine-tuned data
    perturbations, for a class of naked singularity spacetimes satisfying
    self-similar bounds. Given the well-known blueshift instability for suitably
    regular naked singularities in the Einstein-scalar field model, we require
    non-generic conditions on the data perturbations. In particular, the scalar
    field perturbation along the past lightcone of the singular point $\mathcal{O}$
    vanishes to high order near $\mathcal{O}$. Technical difficulties arise from
    the singular behavior of the background solution, as well as regularity
    considerations at the axis and past lightcone of the singularity. The interior
    region is constructed via a backwards stability argument, thereby avoiding
    activating the blueshift instability. The extension to the exterior region is
    treated as a global existence problem to the future of $\mathcal{O}$, adapting
    techniques of Rodnianski and Shlapentokh-Rothman for vacuum spacetimes.

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