Anthropic announced yesterday (July 28) the release of the fifth version of the Model Context Protocol (MCP) specification. Officially, the company described this update as the largest and most systematic overhaul since the protocol was introduced.
Note: MCP (Model Context Protocol) is an open standard and open-source protocol introduced by Anthropic in late November 2024, designed to standardize communication between large language models (LLMs) and external data sources and tools.
Compared with the previous specification (the currently mainstream 2025-11-25 version), the most significant change in the 2026-07-28 version of the MCP protocol is its complete shift from “bidirectional stateful connections” to a “stateless core,” along with the introduction of an independent extension ecosystem.
Handshake removal: Protocol-level initialization handshakes have been completely removed. The new server / discover capability allows prior exploration, but is not mandatory.
Session ID dependency: Sessions are fixed through the Mcp-Session-Id request header. Servers must maintain connection state in memory or Redis.
The new version also introduces a versioned extension framework, formally incorporating the MCP Apps and Tasks extensions. Developers can use these extensions to add capabilities such as interactive interfaces and long-running tasks without modifying the core protocol.
Regarding authorization, the new specification strengthens support for OAuth 2.0 and OIDC deployments in production environments. MCP servers no longer need workarounds and can connect to enterprise identity systems such as Entra (Microsoft’s enterprise identity and access management service) or Okta (an identity management platform).
