AgentCore Gateway Gains Full Stateful MCP Session Support with Streaming and Elicitation

Full analysis

AWS AgentCore Gateway received a suite of stateful MCP (Model Context Protocol) capabilities in May 2026. Clients now receive a unique session ID on initialization, enabling the gateway to track state including downstream MCP server sessions and pending interactions. New features built on this foundation include Server-Sent-Events (SSE) streaming for real-time tool output, elicitation pass-through allowing MCP servers to request user input mid-execution (via forms or OAuth consent URLs), sampling messages enabling MCP servers to request LLM completions from the client mid-flight, and real-time progress and logging notifications. Together these make AgentCore Gateway a managed hub for sophisticated human-in-the-loop and model-in-the-loop agentic workflows.