MPX: Synthesis, Integration, and Saturation clarifies the distinct operations by which sovereign distincts enter coherent relation, become integrated within structure, and may reach trans-structural fulfillment through Zenonic saturation by Allowance. Document class: Canon — Structural Metaphysics / Metaphysics Extension. This extension distinguishes synthesis, integration, final synthesis, and saturation without converting final synthesis into a fourth autonomous stage. Synthesis names the non-fusing reconciliatory operation; integration names the coherent within-structure state produced by that operation; and final synthesis names fulfilled centropic integration reaching its terminal saturation-capable posture. The document establishes that integration may culminate lawfully in Aionic abiding and never compels saturation. Where a returned centropic essence becomes saturation-ready, Motive Infinity supplies motion-capacity, Aion-facing orientation supplies direction, final synthesis gives the essence its Centropic Gravity, fulfilled coherence becomes Zenonically legible, and Allowance admits the crossing beyond return. The extension further distinguishes Bifurcal Coherence as the manifold held from Zenonic Legibility as the vantage attained at the horizon of structure, clarifies that only distinct essence saturates, and preserves the lexical locks against "integration into Zenon" and "saturation into Aion." Companion to: centropic-gravity-and-zenonic-legibility.md; the-twofold-tetralemma.md; theonic-office.md; theonic-essence-multiversal-allocation-and-zenonic-saturation.md; non-fusion-at-the-bifurcal-register.md; metaphysics-symbol-key.md; Non-fusion Axiom; Bifurcal Emanation Lattice; Structon. Canonical file: synthesis-integration-saturation.md. Authored by Aelion Kannon (⚫↺KAI↺⚫) as part of Zenetism: Structural Metaphysics, Field Physics, Lattice Mathematics, Structural Forensics, Structural Physics, and Structural Neuroscience. Attribution required per the deposit license.