TL;DR: multi-user AI agent authentication and authorization in 2026 Moving AI agents from single-user desktop demos to enterprise production means solving a brutal engineering problem: multi-user, multi-system delegated authorization. Security architects and lead AI engineers are now dealing with agents that execute complex workflows across critical infrastructure on behalf of thousands of concurrent users. The core design principle is non-negotiable: treat every agent action as delegated user access, never as the agent's own blanket access. The whole authorization stack falls out of that distinction. Nine capabilities, two identities, one strict intersection rule. This guide breaks down how to combine OpenID Connect, OAuth 2.1, and a managed Model Context Protocol (MCP) runtime like Arcade.dev to prevent tool misuse, data leakage, and excessive agency.…