If you’re running a production MCP server with sticky sessions, a shared session store, or Mcp-Session-Id header handling — pay attention. The MCP 2026-07-28 release candidate is the largest revision to the protocol since its launch, and the headline change is a breaking one: sessions are gone entirely.

The final specification ships July 28, 2026. If you haven’t started preparing your MCP server implementations, you have less than a month.

The Core Change: Stateless HTTP

The old MCP protocol required:

  • An initialize handshake before any other requests
  • Mcp-Session-Id headers to maintain server-side session state
  • Sticky sessions or a shared session store at the load balancer layer
  • Deep packet inspection at the gateway to route requests to the right server instance

All of that is gone.

In the new stateless model:

  • Every request is self-contained — protocol version and capabilities are carried in _meta, not negotiated in a prior handshake
  • No Mcp-Session-Id — headers that previously identified a session no longer exist in the spec
  • No initialize handshake — clients don’t need to establish a session before making requests
  • Plain round-robin load balancing works — no more sticky sessions or shared stores needed
  • Traffic routes on Mcp-Method header — enabling standard HTTP routing infrastructure
  • Clients can cache tools/list responses — using the server’s ttlMs value

The practical infrastructure effect is immediate. A remote MCP server that previously needed specialized gateway configuration can now run behind standard HTTP infrastructure. This is a major operational win for teams running MCP servers at scale.

Source: MCP Blog — The 2026-07-28 MCP Specification Release Candidate

New Features in This RC

The stateless architecture isn’t the only change. This RC introduces several new capabilities:

server/discover RPC

A new server/discover endpoint allows clients to discover what an MCP server exposes without prior knowledge. This is foundational for directory services and programmatic MCP ecosystem navigation.

MCP Apps: Server-Rendered UIs

MCP Apps allows MCP servers to serve user interface components directly. This is a significant extension of what MCP can do — moving from a pure data/tool protocol toward one that can also deliver interactive experiences to MCP clients.

Tasks Extension

Long-running operations are now handled by the Tasks extension, which graduates from experimental to a first-class extension. Tasks enables agent workflows that span minutes or hours rather than requiring single-request completion.

Authorization Hardening

The RC aligns authorization more closely with OAuth and OpenID Connect deployments. For enterprise MCP deployments with strict identity requirements, this closes some of the gaps between MCP’s previous auth model and standard enterprise identity infrastructure.

Deprecations

Several protocol features are formally deprecated in this RC:

  • Roots — deprecated
  • Sampling — deprecated
  • Logging — deprecated

These were part of the original MCP spec but are being replaced by more structured approaches. Check the full spec for migration guidance on each.

Full JSON Schema 2020-12 for Tools

Tool definitions now support the full JSON Schema 2020-12 specification. This significantly increases the expressiveness available for tool parameter validation.

What You Need to Update

If you’re maintaining an MCP server, here’s a practical checklist of what needs to change before July 28:

Remove:

  • Session management code and session stores
  • Mcp-Session-Id header handling (send and receive)
  • The initialize request/response handler
  • Sticky session configuration at your load balancer

Add or update:

  • Protocol version in every request via _meta field
  • Capabilities negotiation moved to per-request _meta (check the official spec for exact format)
  • server/discover endpoint if you want discoverability
  • Mcp-Method header support for routing (confirm exact header name in the spec)
  • Cache-control handling for tools/list if your server supports ttlMs

Review deprecation:

  • If using Roots, Sampling, or Logging — migrate to replacement patterns per the spec

⚠️ Important: This is a breaking change. The final spec is July 28 — after that, clients built against the new spec will not be compatible with servers still using the old session-based approach. Review the full release candidate at blog.modelcontextprotocol.io before making changes.

Why Stateless Matters for Agents

For agent developers, this change matters beyond infrastructure: stateless HTTP is the foundation for truly scalable, composable agent systems.

With the old stateful model, MCP servers were inherently sticky — you couldn’t easily run multiple instances, failover gracefully, or distribute load. An agent that needed to switch MCP server instances mid-workflow would lose its session context.

Stateless requests break that constraint. Each request carries everything the server needs. That means:

  • Horizontal scaling with no coordination overhead
  • Graceful failover — if a server instance dies mid-agent-run, the next request goes to a healthy instance with no special handling
  • Simpler deployments — standard reverse proxies work without modification
  • Better caching — tool lists can be cached at the HTTP layer

The trade-off is that any state your MCP server was managing in sessions now needs to live somewhere else — in the client, in a database, or in the request payload itself. For most MCP server implementations, this means auditing what session state you were tracking and deciding where it belongs in a stateless model.

Timeline

  • Now: Release candidate available, breaking changes documented
  • July 28, 2026: Final specification ships
  • After July 28: Clients built against the new spec will expect stateless servers

The maintainers — David Soria Parra and Den Delimarsky — have also announced a formal deprecation policy as part of this release. Future protocol changes will follow a defined timeline rather than happening without warning. That’s a significant commitment for teams building on MCP infrastructure.

Sources

  1. MCP Blog: The 2026-07-28 MCP Specification Release Candidate — official announcement with full spec details
  2. Model Context Protocol Documentation — specification reference

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