Large-scale engineering organizations struggle with centralized architecture becoming a bottleneck. A practical framework for decentralizing architecture is presented, built around clear decision boundaries aligned to C4 abstraction levels, shared architectural principles, Architecture Decision Records (ADRs), Architecture Governance Forums as alignment mechanisms rather than approval gates, platform teams as enablers, and fitness functions embedded in CI/CD pipelines for continuous validation. The architect's role evolves from gatekeeper to Socratic coach, building distributed judgment across teams. AI's primary value in this model is drift detection—scanning code, infrastructure, and ADRs to surface misalignments early—rather than code generation. The framework progresses organizations from centralized 'infancy' through 'adolescence' to decentralized 'adulthood,' where autonomy is sustainable because guardrails are structural, observable, and continuously enforced.
