Substrate-Mediated Coordination Across the Inter-Self Perimeter: Extending the Coordination Knowledge Substrate Pattern to Cross-Organizational Coordination and Population Scope under Unified Human Governance

Paper 1 (Li, 2026a) defended the Coordination Knowledge Substrate (CKS) as a design pattern at the coordination and decision layer, with the substrate handling coordination and governance, the LLM handling high-dimensional reasoning, and the division drawn at the governance boundary at cell scope. Paper 2 (Li, 2026b) extended CKS to AI Self scope and toward the enterprise brain Self with the foundational separation of fast-pattern instinct from deliberate reasoning into independently-evolving layers under unified human governance. This paper extends substrate-mediated coordination one further step — across the inter-Self perimeter and at population scope — defending six architectural commitments.

The first establishes the shared substrate as the architectural object through which two or more CKS-governed Selves coordinate — temporarily constructed for an interaction, perimeter-spanning across distinct Selves' home governance perimeters, with all six Paper 1 commitments holding within scope. The second commits Full Aspect Integration (FAI) as the canonical operation over the shared substrate — n-ary aspect-level merge with full-merge as architectural default, exchange bounded to reasoning-layer content per Paper 2's instinct/reasoning separation extended at the inter-Self boundary. The third commits three-tier conflict handling within the shared substrate — preserve as substrate-level state by default; resolve via orchestration with rules as inspectable substrate content under explicit human authority; escalate to humans across joint authority of participating Selves' governance. The fourth commits a four-locus evolution-feed mechanism connecting inter-Self events to home-perimeter Paper 2 evolution machinery — hand-off at FAI dissolution, per-mechanism feed structure, a three-case layer-routing rule sending DNA-layer content to DNA evolution and action-layer content to action-feedback evolution while instinct evolution takes no FAI input by architectural commitment, and asymmetric ingestion sourced from per-perimeter governance. The fifth commits configuration as substrate content with recursive applicability — every dimension of the FAI mechanism is itself substrate content under all six Paper 1 commitments, with the recursion bottoming at human-authored governance authority. The sixth offers the extension claim that population-scale collective evolution is the architectural object Paper 3's five preceding claims compose into at population register when accumulated FAI events across many CKS-governed Selves operate under joint authority across population-level governance perimeters. Population-scale CKS-governed Self deployments do not yet exist; the architectural commitment is to what the inheritance produces at population scope through composition, with specific population-scale dynamics awaiting empirical observation — the architectural commitment rendered confidently, the empirical-verification status of the population-scale extension rendered with calibrated humility.

The contribution is a design pattern, not an empirical evaluation. The unifying architectural move across all six claims is the extension of substrate-mediated coordination across the inter-Self perimeter under unified human governance, composed at population scope through accumulated FAI events under joint authority across population-level governance perimeters — Paper 1's outside-the-model vs. inside-the-model spine extended through the inter-Self perimeter and into population-scale collective evolution. Paper 3 inherits Papers 1 and 2's architectural commitments and extends them one further step at trilogy completion, sitting at the intersection of multi-agent systems and inter-agent coordination, federated learning and cross-organizational ML, governance-as-code and policy-as-substrate work, multi-coordinator and joint-authority architectures, substrate-as-content and recursive-governance literature, and trilogy continuity with Papers 1 and 2 — articulating a design pattern available to be adopted, varied, composed with adjacent patterns, or argued against. Empirical validation through real-world cross-organizational deployment at scale is downstream work.