This work is a non-normative, non-operational interpretive companion governing how institutional authority is read, framed, and relied upon when actorhood integrity has collapsed. Actor Stewardship does not address why actorhood fails, nor does it define the conditions under which actorhood would be constitutionally sufficient. Those functions are performed by The Actor Before Sovereigns and the Institutional Actor Integrity Framework (IAIF), respectively. This book occupies the stewardship layer: it governs interpretive reliance when those conditions are absent. The work examines how institutions continue to exercise authority under actor deficit, and how reliance on that authority must remain provisional, explicit, and contestable. It distinguishes reliance from legitimacy, rejects proxy substitution for absent actors, and prohibits the silent normalization of degraded authority. Stewardship is treated as an interpretive discipline, not as governance, policy, or remediation. This book does not propose solutions, safeguards, controls, governance models, metrics, or implementation guidance. It does not define compliance requirements, certify systems, or authorize action. Its purpose is boundary-preserving: to ensure that institutional claims of authority remain constrained and honest when no bindable actor can be produced. The publication is jurisdiction-neutral and does not constitute legal advice. It forms the interpretive (HOW) layer of a closed constitutional corpus on institutional authority in the digital era and is intended for courts, regulators, institutional reviewers, and constitutional advisors concerned with reliance on authority under conditions of actor deficit.