A Fixed-Point Derivation of the Observed Vacuum Energy from Moduli Stabilization in Type IIB String Theory

<div> The cosmological constant problem — why the observed vacuum energy density is so small and positive —remains unresolved in conventional string theory, though it has been constructively addressed in the QuEST framework via symbolic causal geometry. A derivation of the observed value&nbsp;rho_Lambda ~ 10^-122 * M_Pl^4 is presented by embedding three independently derived structural&nbsp;mechanisms—fixed-point stabilization, a bulk informational constraint, and a universal suppression&nbsp;law—into a Type IIB compactification background. Building on the Kachru-Kallosh-Linde-Trivedi (KKLT) framework, the analysis imposes three structural mechanisms: (1) fixed-point stabilization,&nbsp;(2) a bulk informational constraint, and (3) a symbolic suppression law. The resulting scalar potential exhibits a double-exponential suppression of vacuum energy after canonical normalization,&nbsp;and the uplift mechanism is shown to emerge from flux quantization and warped throat geometry&nbsp;rather than parameter fitting. The theory yields a modulus mass that ensures radiative stability&nbsp;and a Hubble constant consistent with current cosmological observations. The derivation is self-contained, requires no external tuning, and identifies structural selection mechanisms that, while&nbsp;expressed within string theory, originate from symbolic causal geometry&nbsp; external to it. </div>