Model Context Protocol released version 2026-07-28 with a transition to a stateless architecture
MCP has published specification 2026-07-28, the largest revision of the protocol since its inception – it is becoming stateless and scales on standard HTTP infrastructure. According to AWS, Amazon Bedrock AgentCore Gateway supports it through an opt-in upgrade, and existing clients work without changes.
Model Context Protocol has published the specification for version 2026-07-28, which the AWS blog describes as the largest and most significant revision of the protocol since its inception. According to the article, the protocol is changing from stateful to stateless and now scales on standard HTTP infrastructure. It also introduces a governed extension system (extensions), strengthens authorization by aligning it with enterprise practices around OAuth 2.0 and OpenID Connect, and establishes lifecycle guarantees intended to limit future breaking changes.
The key technical change concerns sessions. Previously, every interaction over Streamable HTTP began with an initialize/initialized handshake, after which the server issued a Mcp-Session-Id header required for all subsequent requests – this required sticky sessions on the load balancer or shared session storage across the server fleet. In the new version, each request carries information about the protocol version, the client and its capabilities directly in the _meta parameter, eliminating the initial handshake and allowing the client to discover server capabilities at any time using the new server/discover method. Each tool call is therefore self-contained and can be routed to any server instance. Stateful applications remain possible, but continuity between calls is handled through an explicit identifier passed as a tool parameter, rather than by the protocol itself.
According to AWS, the new protocol version can be activated on AgentCore Gateway (part of Amazon Bedrock AgentCore) by calling UpdateGateway with a list of supported versions. The upgrade is described as opt-in and backward compatible – existing clients work without changes, and nothing changes until both the gateway operator and the client actively select the version. The gateway handles a request according to the Mcp-Protocol-Version header if that version is supported; otherwise, it returns an HTTP 400 error with a list of supported versions. Requests without this header are processed as version 2025-03-26 by default.
You can find details in the source article.
Why it matters
Removing sessions at the protocol level means MCP servers can operate as standard stateless HTTPS endpoints without the need for sticky load balancing or shared session storage, simplifying horizontal scaling in enterprise deployments. According to AWS, the upgrade is opt-in and backward compatible, so existing integrations are not at risk, but teams operating MCP servers or AgentCore Gateway must plan when and how to activate the new version and rework any stateful scenarios (e.g. an order cart) using their own identifiers passed as tool parameters.
Relevant practical impact
What this means
For a business
Companies operating MCP servers and gateways (e.g. Amazon Bedrock AgentCore Gateway) can now scale traffic like standard stateless HTTPS endpoints without sticky sessions or shared session storage, but must plan an opt-in upgrade and, if needed, rework stateful scenarios using their own tool parameters.
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