This work examines the possibility that the geometric constant π, the cosmological constant Λ, and Newton’s gravitational constant G admit a common boundary geometric origin. The construction begins with a spherical radiative boundary whose topology, flux projection, phase space organization, and harmonic spectral summation combine into the dimensionless invariant π³/15. Under the boundary projection adopted here, this invariant is related to the cosmological horizon through ΛR_H² = π³/15 and, in corresponding form, Ω_Λ = π³/45. If the horizon is further resolved holographically through N = A_H / l_P² with l_P² = ħG / c³, then G appears as the Planck scale closure parameter associated with that same horizon geometry. In this picture, π encodes the spherical boundary structure, Λ its cosmological projection, and G its microscopic holographic closure. The construction is geometric rather than dynamical, and suggests that part of the normalization of cosmological and gravitational parameters may be traced to a common radiative boundary structure.