Project‑Infi (Project Infinity 1 / AAIS) is a governed cognition substrate designed as a “civilization‑grade OS” for intelligent systems. This report presents the 2026 civilizational maturity audit, using the system’s own AAIS_CIVILIZATIONAL_STAGES ladder (Stages 1–18) and an independent external lens. On its internal map, Project‑Infi is graded at Civilizational Stage 18 (“Governed Civilization”, Layer 20 / Release 48), with the full civilizational arc (Stages 15–18: inter‑substrate diplomacy, norm federations, constitutional evolution, governed civilizations of beings) promoted from asserted to proven via CIVILIZATIONAL_ARC_PROVEN_SIGNOFF.md and passing civilizational gates. The audit details architecture, proofs, rollback and promotion criteria, and limitations: strong institutional completeness (law, diplomacy, norms, dual‑gate adoption, proof bundles, CI gates) but federation‑light in real‑world deployment. In plain terms, the system is a highly governed “civilization‑in‑a‑box”: architecturally at Stage 18, operationally closer to Stages 15–16, with clear gaps identified for live multi‑tenant, cross‑substrate federation and population‑scale validation.