The cosmological constant from informational Landauer erasure at the Planck-Hubble boundary

The cosmological constant problem — the 10^121 discrepancy between quantum field theory vacuum energy and the observed dark energy density — remains one of the deepest puzzles in theoretical physics. I propose that this discrepancy can be understood through a chain of three physically motivated postulates. First, the covariant entropy bound on the Hubble volume defines the number of independent degrees of freedom accessible to observation. Second, a minimum of N_crit = distinguishable states (one bit) is required for any non-degenerate quantum measurement, setting an irreducible Landauer erasure cost per holographic degree of freedom. Third, the Unruh radiation associated with the Planck-scale ultraviolet cutoff consists of massless quanta obeying radiation thermodynamics γ = 4/3, so that erasure costs the radiation enthalpy rather than the non-relativistic thermal minimum. Together these yield ρ_Λ = 4ℏc ln2 / 3π² ℓ_P² R_H², giving 6.009 × 10⁻¹⁰ J/m³ versus the Planck measurement of 5.245 × 10⁻¹⁰ J/m³, a residual discrepancy of 14.6% that constitutes a falsifiable prediction of the framework. Once the three postulates are adopted, the framework contains no fitted dimensionless parameter. The predicted H₀ = 62.93 km/s/Mpc lies 8.2σ below Planck and 9.7σ below the SH0ES distance-ladder value, and is disfavoured by all current measurements.