What Remains When the Coordinates Disappear?

What remains of orientation when coordinates are no longer sufficient? This interdisciplinary research note develops a question arising within ψ-Architecture™: what is the minimum difference that must remain for distinct histories — and distinct possible futures — not to collapse into indistinguishability? The work introduces the problem through the formal language of future-equivalence, future-null information, the minimal retentive state \mathcal H_R=\mathcal H/N_\infty, and a filtration of distinguishability. These constructions are placed in conceptual continuity with earlier work on retentive architecture for navigation without coordinates. The formal argument is accompanied by Retentive Lantern, a visual research translation exploring the same question through light, boundary, orientation, and retained difference. The visual work is explicitly not presented as experimental evidence for the mathematical framework; rather, it functions as an interdisciplinary translation of the underlying research question. The resulting work occupies the boundary between mathematical formalization, conceptual navigation, and visual research: not asking how completely a system can reconstruct its world, but how much it may lose before different futures cease to remain distinguishable.