I Built Multi-Agent Systems Before NEXT '26 — Here's What the New ADK, MCP & A2A Stack Actually Changes

The author shares firsthand experience building multi-agent systems on Google Cloud before the NEXT '26 announcements, highlighting past challenges. They detail issues with manual tool integration, hardcoded agent-to-agent communication, and imperfect MCP tool integration. The recent NEXT '26 updates, specifically the Agent Development Kit (ADK), Universal MCP, and Agent-to-Agent (A2A) Protocol, are presented as significant improvements. The new ADK formalizes previously custom patterns, offering a platform for managing agent lifecycles and scaling. Universal MCP support means Google Cloud services are now accessible without custom adapters, simplifying integrations. The A2A Protocol and Agent Registry introduce dynamic discovery, eliminating the need for hardcoded routing between agents. The Memory Bank feature addresses agent persistence across sessions, moving beyond simple in-memory storage. While acknowledging these advancements, the author expresses caution regarding agent identity, IAM integration, and potential cold starts. They also note the organizational aspect of managing registered agents. The author concludes by presenting a unified stack view and recommending resources for developers to explore the new capabilities.