= Solution
The inner horizon in the nonextreme <Reissner-Nordstrom spacetime> diagram is a <Cauchy horizon>. Radiation from exterior perturbations can approach it at arbitrarily late advanced time and undergo unbounded blueshift. Here its positive blueshift scale is $\kappa_-=(r_+^2-r_-^2)/r_-^3$. The <inner-horizon blueshift coordinate> behaves as $V_-\propto-e^{-\kappa_-v}$, so
$$
T_{V_-V_-}=\left(\frac{dv}{dV_-}\right)^2T_{vv}\propto e^{2\kappa_-v}T_{vv}.
$$
Even a decaying power-law tail can therefore generate divergent local flux. With counterstreaming radiation, backreaction produces <mass inflation> and curvature growth, rather than the smooth inner horizon of the exact solution.
This supports the <strong cosmic censorship conjecture>: a generically perturbed <maximal Cauchy development> is expected to lose the smooth extension across its <Cauchy horizon>, restoring predictability in the appropriate regularity class. \b[The exact smooth inner horizon is unstable, not a robust failure of deterministic evolution.] Curvature divergence supports an obstruction to a $C^2$ metric extension; it does not by itself exclude every continuous metric extension. The regularity class is part of the conjecture, and the blueshift argument is evidence, not a general theorem proving it.
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