Early Galaxy Timescales under Boundary-Constrained Closure

Massive, dusty star-forming galaxies at z >= 7 intensify the early assembly timescale problem. In standard hierarchical treatments, halo assembly and virial relaxation reduce the interval available for star formation, forcing high effective efficiencies to reach stellar masses above 10^10 solar masses. This Letter examines a boundary-constrained closure in which macroscopic capacity is evaluated at a radiative decoupling surface rather than through a bulk volume parametrization. With Stefan-Boltzmann emission and Newtonian surface gravity, the dimensionless boundary ratio reduces to I = pi^3/15 after explicit bulk dependence cancels. This reduction is used here only as an alternative closure for timescale accounting. Within that accounting, the critical bottleneck shifts from extended pre-star-formation virialization to baryonic collapse, which enlarges the effective star-forming window and reduces the implied efficiency requirement. Detailed radiative transfer, stellar mass systematics, and full halo phenomenology are not modeled.