The one wire-to-resident memory model the byte budgets share.

A fetched metadata document costs far more resident than its wire size: the parsed structure, the retained raw Value, and their spines expand a compact-encoded document by a near-constant factor. Every consumer that budgets bytes against that expansion must use the same factor, or the budgets drift against each other (historically the cache weigher assumed 7.5x while the memory budget assumed 4x, so the admission arithmetic under-counted what the cache accounting would charge for the very same document). This module is that single model: the cache weigher (Ecluse.Core.Server.Cache) and the composition root's memory plan both read it, so they can never disagree again.

The factor sits at the high end of the measured resident-to-encoded ratio, so estimates upper-bound resident bytes and a budget never systematically under-counts (a leaner document is over-estimated, which only over-evicts). A measurement pass refining it is deliberately deferred to the architect's load bench; until then the conservative bound stands.