The harmonic between the modules.
NEXUS coordinates between the modules of the living ecosystem. Where GENESIS conducts the brain, NEXUS carries the harmonic between systems, the inter-module recursion that lets the ecosystem act as one rather than as parts.
NEXUS sits at the inter-module tier of the living ecosystem, in the harmonic triad recursion with LYRA at the meta tier. Layer L4.
NEXUS coordinates module to module. It is one voice in the harmonic triad: local, inter-module, meta. It carries the signal between systems so they stay in phase.