MCP's final spec drops the persistent connection requirement

MCP finalized its July 28 spec with a rewritten core, replacing the bidirectional stateful connection with plain stateless request/response, per the MCP blog post announcing the release.

A persistent connection means the server must stay alive for the whole session, ruling out serverless functions and most edge runtimes. Drop that requirement and an MCP server looks like any other HTTP endpoint, deployable anywhere an API route runs.

The spec spent ten weeks as a release candidate, dated May 21, before finalizing on July 28. That's a real validation window for a change this structural.

What moved to extensions

Instead of adding capability to the core, the spec pushed the two biggest additions into a new, versioned Extensions framework. MCP Apps lets a server render HTML inside a sandboxed iframe. Templates get declared upfront, so clients can prefetch them and review them for security before anything executes. Tasks, contributed by AWS, handles long-running work that doesn't fit a quick request/response cycle. Both ship as optional layers on the stateless core, not requirements every server must implement.

The rest of the release is smaller plumbing: header-based routing, cacheable list results, and tighter authorization rules. It also adds a formal deprecation policy, so future breaking changes come with a defined off-ramp instead of a surprise.