Large language model assistants have shifted the primary locus of brand visibility from retrieval surfaces to reasoning and recommendation layers. Existing input-side metrics no longer capture this shift. The Answer Space Occupancy Score (ASOS) is a reproducible probe-based metric that quantifies the fraction of the observable answer surface occupied by a specified entity under controlled repetition. This article publishes the complete alpha specification, scoring rules, and the first fully redacted thirty-run dataset.