Amazon Web Services shipped same-day Bedrock AgentCore Gateway support for the Model Context Protocol 2026-07-28 specification, the largest protocol revision since MCP launched, according to an AWS Machine Learning Blog post by Sean Eichenberger and Luca Chang published July 28. Customers can enable the new version with a single UpdateGateway API call while keeping existing 2025-11-25 clients operational. Nothing breaks on upgrade.

What Changed in MCP 2026-07-28

The core change is architectural: MCP is now stateless. Previous versions required a handshake (initialize/initialized) that pinned each client to the server that issued its session ID. Scaling horizontally meant sticky sessions at the load balancer or a shared session store behind the fleet. The new version eliminates both.

Every request now carries protocol version, client info, and client capabilities inside its _meta parameter, according to the AWS blog. A single tool call is fully self-contained: no prior session context, routable to any server instance. Clients needing continuity across calls pass an explicit ID as a tool parameter, following standard HTTP request patterns rather than protocol-level session management.

Routing, Caching, and Tracing

Three additional changes target infrastructure operators. MCP requests now surface intent in standard headers (Mcp-Method and Mcp-Name), giving load balancers and API gateways the information to route, throttle, and meter without parsing JSON-RPC bodies. List and resource-read responses include explicit freshness metadata (ttlMs and cacheScope), borrowed from HTTP Cache-Control semantics. The spec also reserves W3C Trace Context keys (traceparent, tracestate, baggage) inside _meta, formalizing distributed tracing across agent-to-tool call chains in OpenTelemetry-compatible collectors.

Adoption Path

Tier 1 SDKs including LangChain, the OpenAI SDK, and Anthropic SDK shipped 2026-07-28 support during the ten-week release candidate window, according to the blog post. AgentCore Gateway advertises supported protocol versions through a configuration field. Clients select a version on every request. Adding 2026-07-28 to a gateway still advertising 2025-11-25 does not affect existing clients. Only requests that explicitly specify the new version get stateless behavior.

Infrastructure Consolidation Signal

AWS shipping same-day support signals that the protocol has reached production readiness across the major cloud providers. Combined with NVIDIA’s Open Secure AI Alliance announced July 27 (which includes MCP-aligned governance frameworks), the agent infrastructure layer is consolidating around open standards rather than vendor-specific protocols. For teams building production agent systems, the question of which protocol to standardize on has a clearer answer than it did a week ago.