MCP ships 2026-07-28 spec, going stateless in largest overhaul since launch
The Model Context Protocol's 2026-07-28 revision finalizes today, removing protocol-level sessions and the initialize handshake, formalizing an Extensions framework, and hardening OAuth 2.1 authorization.
The Model Context Protocol’s 2026-07-28 specification finalizes today, and it drops the two things that most defined MCP’s original shape: the initialize/initialized handshake (SEP-2575) and the protocol-level session, including the Mcp-Session-Id header (SEP-2567). Lead maintainer David Soria Parra, an Anthropic technical staff member, called it the “most substantial changes we have made to the specification, probably since adding authorization” on a July 23 livestream, adding that “a lot of things that made MCP are gone.”
In place of negotiation, every request now carries a _meta field describing protocol version, client identity, and capabilities. A new server/discover method lets clients pull capabilities on demand. The operational payoff is the point of the exercise: a stateless MCP server sits behind an ordinary round-robin load balancer and routes on an Mcp-Method header, retiring sticky routing, shared session stores, and the deep packet inspection that stateful MCP demanded at scale.
Sampling, which let servers request completions from the client’s model, is deprecated. Soria Parra attributed the removal to confused semantics and thin real-world adoption.
The revision also formalizes an Extensions framework (SEP-2133), shipping with two official extensions: MCP Apps (SEP-1865), which lets servers deliver interactive HTML rendered in a sandboxed iframe by the host, and a redesigned Tasks extension (SEP-2663) built around handle-based state. Six SEPs tighten alignment with OAuth 2.0 and OpenID Connect, and a new lifecycle policy guarantees at least 12 months between deprecation and removal.
That window is narrower than it sounds. Stacklok, in an enterprise-readiness guide, notes that servers on 2026-07-28 may not speak to older clients without deliberate fallback. Akamai analysts flagged in SecurityWeek that while several vulnerability classes disappear with sessions, new risk areas “depend heavily on implementation choices.”
The trajectory is legible. Anthropic donated MCP to the Linux Foundation’s AAIF in 2025, when SDKs were being pulled more than 97 million times a month. Today’s spec is what happens when a hobbyist-shaped protocol has to answer to load balancers, security teams, and a governance body. The pieces that made MCP recognizable were, by that measure, the pieces that had to go.
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