A Rational Target for Dynamical Dark Energy: w0=-27/28, wa=-1/28

A Rational Target for Dynamical Dark Energy: w0=-27/28, wa=-1/28. A short, dated pre-registration note freezing a single falsifiable dark-energy target from the finite-QEC substrate programme before the next generation of constraints arrives. In the Chevallier-Polarski-Linder (CPL) parameterisation w(a)=w_0+w_a(1-a), the framework predicts w(a)=-1+a/28, i.e. w_0=-27/28=-0.96429 and w_a=-1/28=-0.03571, with w_0+w_a=-1 (a non-phantom, late-time thawing-like branch returning to a cosmological constant at early times; w(z=1)=-55/56; the dark-energy density rises only to exp(3/28)=1.113 times today's value at high redshift). The number 27/28 is not fitted to DESI, Euclid, Planck, or supernova data; it is a fixed rational target from the same 28-channel service clock that gives the scalar tilt n_s=27/28. Planck's Omega_Lambda=12pi/55 and n_s are postdictions in this context; the live prediction is the slight non-phantom departure w_0>-1, w_a<0. The deviation is mild - gentler than current DESI central values - so the rational point sits between LambdaCDM and the stronger evolving-dark-energy fits and is falsifiable from either side: a flat-CPL BAO+CMB+supernova/weak-lensing reconstruction that excludes the point at high significance would falsify this dark-energy branch (it would not, by itself, prove the wider programme). Companion to the finite-QEC substrate cosmology work. This record is part of the finite-QEC substrate / It-from-Bit publication refresh. Version 2 / outcome addendum (2026-07-02): The registered flat-CPL dark-energy line w(a)=-1+a/28, equivalently (w0, wa)=(-27/28,-1/28), is recorded as killed at the framework-internal tier by the framework-pinned H0 acoustic-scale test. The as-registered external flat-CPL falsifier has not yet fired. The uploaded outcome addendum records the evidence, the frozen-form rule, and the pre-registered reopen/confirm-kill conditions. The concept DOI remains 10.5281/zenodo.21049001. 2026-07-08 canon refresh: This version incorporates the 2026-07-08 ANCHOR/DRIFT/PTMS canon refresh and rebuilt local PDF.