Protocol Signal | Monday
MCP RC Published on Official Blog Today: Eight Days to the Stateless Spec
2026-07-20 · Source
The Model Context Protocol team published the official release candidate post on blog.modelcontextprotocol.io on July 20, 2026, eight days ahead of the July 28 final specification ship date. The RC formalizes the complete stateless rewrite: the session handshake is gone, every request is now self-contained with protocol version, client info, and capabilities traveling inline. The practical effect is immediate for production deployments. A remote MCP server that previously required sticky sessions, a shared session store, and connection management can now run as a pure stateless HTTP endpoint behind any load balancer. The RC also ships the Extensions framework, which includes MCP Apps (SEP-1865: server-rendered UIs in sandboxed iframes), the Tasks extension for long-running work, and an authorization layer that aligns with OAuth and OpenID Connect. Roots, Sampling, and Logging are formally deprecated with the RC. The specification contains breaking changes; the RC blog post includes a migration guide and validation checklist. Final spec ships July 28.
Why it matters: The RC publishing on the official blog is the last signal before the July 28 hard ship date. Builders have eight days to validate against the stateless transport before it becomes the canonical protocol version. For the agentic commerce stack specifically, the stateless rewrite removes the last architectural reason to avoid MCP for payment-critical server-to-server calls. A paid API endpoint built on the new spec can run on standard HTTP infrastructure without session management overhead, making x402 + MCP the natural stack for machine-native commerce. The formal deprecation of Sampling in the same release is the spec choosing a side on who owns the rendering surface — MCP Apps take that role through the host client's sandboxed iframe, not through the model.
Brief Items
NSA and CISA Joint Guidance Targets MCP Security Gaps: OAuth, Least-Privilege, and Tool Authorization
Three government security documents converged on MCP in May-July 2026. CISA published Careful Adoption of Agentic AI Services on May 1 alongside five allied cyber agencies. The NSA's AI Security Center followed with Model Context Protocol: Security Design Considerations for AI-Driven Automation, naming specific authentication and authorization gaps in MCP deployments. The MCP 2026-07-28 RC arrived one day later with the largest security rewrite in the protocol's history, addressing the exact weaknesses the NSA document identified. Together the documents establish a clear production baseline: strong OAuth, least-privilege tool access, detailed logging, and explicit authorization scopes. Teams running MCP in production now have external audit criteria for the first time. Read more
MCP Apps Explained: The Official Interactive UI Extension Ships With the RC
SEP-1865, the MCP Apps extension, is included in the July 28 RC as a first-class spec feature. MCP Apps lets an MCP server return a ui:// resource that the host client renders as a sandboxed iframe. The model never touches the server's rendering context — the server owns the UI surface, the host client owns the sandbox boundary, and the user sees a rich interactive component without leaving the agent session. The extension formalizes what was previously a workaround: developers were shipping Sampling-based UI flows that the spec never formally supported. With Sampling deprecated in the same RC, MCP Apps is now the only sanctioned path for server-rendered interactive UI in an MCP session. Read more
Agent Commerce Weekly · agentcommerceweekly.com