Thermochemically consistent realization of a stochastic autocatalytic exporter: chemical completion, inherited operating certificates, cycle affinities and a necessary initiation scale

A quantitative stochastic reaction model is physically informative only if its chemical completion preserves the propensities and the meaning of its output and resource counters. We exhibit such a completion for a maintained autocatalytic exporter whose finite-time operating, output and supply guarantees were proved in a companion paper as statements about a twenty-channel labelled count process. Six reversible chemical pairs on eight species admit positive elemental compositions and a single standard-potential assignment throughout a two-parameter rectangle of paired release and cleavage speeds; at unit fuel and waste activities their mass-action count propensities, stoichiometric updates, export marks and service marks coincide label by label with the certified source. Consequently every inherited estimate transfers without a change of constants: outward interval evaluation of the proved error budget gives success probabilities of at least $0.923849$, $0.994201$ and $0.999558$ for one hundred observation windows at copy scales $10^8$, $2\times10^8$ and $3\times10^8$, while deleting only the templated ligation pair, with every other chemical specification retained, bounds the probability of the same output schedule below $10^{-21699}$ at the first scale. We then extract three consequences of the completed chemistry. The internal stoichiometric cycles are exactly a passive cycle of zero affinity and one emergent fuel-to-waste cycle of affinity $\log(8\times10^{10})$; local detailed balance holds for the count propensities at neighbouring states with the falling-factorial convention; and, because the preparation contains food only, the first template can arise only through two channels, which yields the necessary initiation bound $V\ge(4\times10^8/401)\log(1/\varepsilon_0)$ for any operating guarantee with failure probability at most $\varepsilon_0$, about $4.59\times10^6$ at $99\%$. Dimensional examples make the eight-hour startup allowance, the gross chemical service and the mixed-species character of the exported product explicit, and a conditional stock-sizing relation delimits the remaining extension to autonomous finite reservoirs. The algebraic and finite marked-kernel statements are verified in Lean 4; the identification with a nonexplosive count process and the initiation argument are conventional proofs, and every printed decimal is an interval-certified evaluation of a proved bound rather than a simulation.